changeset 19089:38937efbee21

Incorporate new functions ichol and ilu into Octave. * NEWS: Announce new functions. * aspell-octave.en.pws: Add new functions names to custom Octave dictionary. * sparse.txi: Add functions to Octave manual. * __unimplemented__.m: Remove functions from unimplemented list. * lu.cc (Flu), luinc.cc (Fluinc), chol.cc (Fchol): Add seealso links in docstrings. * __ichol__.cc: Wrap long lines to less than 80 chars. Remove trailing whitespace. Don't repeat input validation done in ichol.m for internal functions. Avoid resizing retval vector. * __ilu__.cc: Wrap long lines to less than 80 chars. Remove trailing whitespace. Don't repeat input validation done in ichol.m for internal functions. Avoid resizing retval vector. * ichol.m: Rewrite docstring. Use Octave coding conventions (double quotes hash for comments, ! instead of ~). Replace %!error tests not being run with fail(). * ilu.m: Rewrite docstring. Use Octave coding conventions (double quotes hash for comments, ! instead of ~). Replace %!error tests not being run with fail().
author Rik <rik@octave.org>
date Tue, 26 Aug 2014 15:27:21 -0700
parents df64071e538c
children 4630a18757b3
files NEWS doc/interpreter/doccheck/aspell-octave.en.pws doc/interpreter/sparse.txi libinterp/corefcn/lu.cc libinterp/corefcn/luinc.cc libinterp/dldfcn/__ichol__.cc libinterp/dldfcn/__ilu__.cc libinterp/dldfcn/chol.cc scripts/help/__unimplemented__.m scripts/sparse/ichol.m scripts/sparse/ilu.m
diffstat 11 files changed, 980 insertions(+), 1109 deletions(-) [+]
line wrap: on
line diff
--- a/NEWS	Mon Aug 18 12:32:16 2014 +0100
+++ b/NEWS	Tue Aug 26 15:27:21 2014 -0700
@@ -66,10 +66,11 @@
 
  ** Other new functions added in 4.2:
 
-      bandwidth            isbanded        javachk
-      dir_in_loadpath      isdiag          linkaxes
-      hgload               istril          numfields
-      hgsave               istriu
+      bandwidth            ilu             javachk
+      dir_in_loadpath      isbanded        linkaxes
+      hgload               isdiag          numfields
+      hgsave               istril   
+      ichol                istriu   
 
  ** Deprecated functions.
 
--- a/doc/interpreter/doccheck/aspell-octave.en.pws	Mon Aug 18 12:32:16 2014 +0100
+++ b/doc/interpreter/doccheck/aspell-octave.en.pws	Tue Aug 26 15:27:21 2014 -0700
@@ -416,6 +416,7 @@
 hygernd
 Hypergeometric
 hypergeometric
+ichol
 IEC
 ieee
 IEEE
@@ -424,6 +425,7 @@
 ifftn
 ignorecase
 ij
+ilu
 Im
 imag
 ImageMagick
--- a/doc/interpreter/sparse.txi	Mon Aug 18 12:32:16 2014 +0100
+++ b/doc/interpreter/sparse.txi	Tue Aug 26 15:27:21 2014 -0700
@@ -485,11 +485,11 @@
   @dfn{dmperm}, @dfn{symamd}, @dfn{randperm}, @dfn{symrcm}
 
 @item Linear algebra:
-  @dfn{condest}, @dfn{eigs}, @dfn{matrix_type}, @dfn{normest}, @dfn{sprank},
-  @dfn{spaugment}, @dfn{svds}
+  @dfn{condest}, @dfn{eigs}, @dfn{matrix_type},
+  @dfn{normest}, @dfn{sprank}, @dfn{spaugment}, @dfn{svds}
 
 @item Iterative techniques:
-  @dfn{luinc}, @dfn{pcg}, @dfn{pcr}
+  @dfn{ichol}, @dfn{ilu}, @dfn{luinc}, @dfn{pcg}, @dfn{pcr}
 @c @dfn{bicg}, @dfn{bicgstab}, @dfn{cholinc}, @dfn{cgs}, @dfn{gmres}, 
 @c @dfn{lsqr}, @dfn{minres}, @dfn{qmr}, @dfn{symmlq}
 
@@ -860,7 +860,7 @@
 The left division @code{\} and right division @code{/} operators,
 discussed in the previous section, use direct solvers to resolve a
 linear equation of the form @code{@var{x} = @var{A} \ @var{b}} or
-@code{@var{x} = @var{b} / @var{A}}.  Octave equally includes a number of
+@code{@var{x} = @var{b} / @var{A}}.  Octave also includes a number of
 functions to solve sparse linear equations using iterative techniques.
 
 @DOCSTRING(pcg)
@@ -873,6 +873,10 @@
 @var{A} \ @var{b}} is solved instead.  Typical pre-conditioning matrices
 are partial factorizations of the original matrix.
 
+@DOCSTRING(ichol)
+
+@DOCSTRING(ilu)
+
 @DOCSTRING(luinc)
 
 @node Real Life Example
--- a/libinterp/corefcn/lu.cc	Mon Aug 18 12:32:16 2014 +0100
+++ b/libinterp/corefcn/lu.cc	Tue Aug 26 15:27:21 2014 -0700
@@ -137,7 +137,7 @@
 is embedded into @var{U} to give a return value similar to the full case.\n\
 For both full and sparse matrices, @code{lu} loses the permutation\n\
 information.\n\
-@seealso{luupdate, chol, hess, qr, qz, schur, svd}\n\
+@seealso{luupdate, ilu, chol, hess, qr, qz, schur, svd}\n\
 @end deftypefn")
 {
   octave_value_list retval;
--- a/libinterp/corefcn/luinc.cc	Mon Aug 18 12:32:16 2014 +0100
+++ b/libinterp/corefcn/luinc.cc	Tue Aug 26 15:27:21 2014 -0700
@@ -93,7 +93,7 @@
 \n\
 Given the string argument @qcode{\"vector\"}, @code{luinc} returns the\n\
 values of @var{p} @var{q} as vector values.\n\
-@seealso{sparse, lu}\n\
+@seealso{sparse, lu, ilu, ichol}\n\
 @end deftypefn")
 {
   int nargin = args.length ();
--- a/libinterp/dldfcn/__ichol__.cc	Mon Aug 18 12:32:16 2014 +0100
+++ b/libinterp/dldfcn/__ichol__.cc	Tue Aug 26 15:27:21 2014 -0700
@@ -1,22 +1,25 @@
-/**
- * Copyright (C) 2013 Kai T. Ohlhus <k.ohlhus@gmail.com>
- * Copyright (C) 2014 Eduardo Ramos Fernández <eduradical951@gmail.com>
- *
- * This file is part of Octave.
- *
- * Octave is free software; you can redistribute it and/or modify it under the
- * terms of the GNU General Public License as published by the Free Software
- * Foundation; either version 3 of the License, or (at your option) any later
- * version.
- *
- * Octave is distributed in the hope that it will be useful, but WITHOUT ANY
- * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
- * FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
- * details.
- *
- * You should have received a copy of the GNU General Public License along with
- * Octave; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>.
- */
+/*
+
+Copyright (C) 2014 Eduardo Ramos Fernández <eduradical951@gmail.com>
+Copyright (C) 2013 Kai T. Ohlhus <k.ohlhus@gmail.com>
+
+This file is part of Octave.
+
+Octave is free software; you can redistribute it and/or modify it
+under the terms of the GNU General Public License as published by the
+Free Software Foundation; either version 3 of the License, or (at your
+option) any later version.
+
+Octave is distributed in the hope that it will be useful, but WITHOUT
+ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+for more details.
+
+You should have received a copy of the GNU General Public License
+along with Octave; see the file COPYING.  If not, see
+<http://www.gnu.org/licenses/>.
+
+*/
 
 #ifdef HAVE_CONFIG_H
 #include <config.h>
@@ -25,49 +28,46 @@
 #include "defun-dld.h"
 #include "parse.h"
 
-// Secondary functions for complex and real case used
-// in ichol algorithms.
+// Secondary functions for complex and real case used in ichol algorithms.
 Complex ichol_mult_complex (Complex a, Complex b)
 {
   b.imag (-std::imag (b));
   return a * b;
 }
 
+double ichol_mult_real (double a, double b)
+{
+  return a * b;
+}
+
 bool ichol_checkpivot_complex (Complex pivot)
 {
   if (pivot.imag () != 0)
     {
-      error ("ichol: Non-real pivot encountered. \
-              The matrix must be hermitian.");
+      error ("ichol: non-real pivot encountered.  The matrix must be hermitian.");
       return false;
     }
   else if (pivot.real () < 0)
     {
-      error ("ichol: Non-positive pivot encountered.");
+      error ("ichol: negative pivot encountered");
       return false;
     }
   return true;
-
 }
 
 bool ichol_checkpivot_real (double pivot)
 {
   if (pivot < 0)
     {
-      error ("ichol: Non-positive pivot encountered.");
+      error ("ichol: negative pivot encountered");
       return false;
     }
   return true;
 }
 
-double ichol_mult_real (double a, double b)
-{
-  return a * b;
-}
-
-template <typename octave_matrix_t, typename T, T (*ichol_mult) (T, T), 
+template <typename octave_matrix_t, typename T, T (*ichol_mult) (T, T),
           bool (*ichol_checkpivot) (T)>
-void ichol_0 (octave_matrix_t& sm, const std::string michol = "off") 
+void ichol_0 (octave_matrix_t& sm, const std::string michol = "off")
 {
 
   const octave_idx_type n = sm.cols ();
@@ -100,7 +100,7 @@
       dropsums[i] = 0;
     }
 
-  // Main loop 
+  // Main loop
   for (k = 0; k < n; k++)
     {
       j1 = cidx[k];
@@ -110,7 +110,7 @@
 
       jrow = Llist [k];
       // Iterate over each non-zero element in the actual row.
-      while (jrow != -1) 
+      while (jrow != -1)
         {
           jjrow = Lfirst[jrow];
           jend = cidx[jrow+1];
@@ -122,16 +122,15 @@
               if (jw != -1)
                 data[jw] -= tl;
               else
-                // Because the simetry of the matrix we know the drops
-                // in the column r are also in the column k.
+                // Because of the symmetry of the matrix, we know
+                // the drops in the column r are also in the column k.
                 if (opt == ON)
                   {
                     dropsums[r] -= tl;
                     dropsums[k] -= tl;
                   }
             }
-          // Update the linked list and the first entry of the
-          // actual column.
+          // Update the linked list and the first entry of the actual column.
           if ((jjrow + 1) < jend)
             {
               Lfirst[jrow]++;
@@ -149,7 +148,7 @@
 
       if (ridx[j1] != k)
         {
-          error ("ichol: There is a pivot equal to zero.");
+          error ("ichol: encountered a pivot equal to 0");
           break;
         }
 
@@ -158,13 +157,12 @@
 
       data[cidx[k]] = std::sqrt (data[j1]);
 
-      // Update Llist and Lfirst with the k-column information.
-      // Also scale the column elements by the pivot and reset 
-      // the working array iw.
-      if (k < (n - 1)) 
+      // Update Llist and Lfirst with the k-column information.  Also,
+      // scale the column elements by the pivot and reset the working array iw.
+      if (k < (n - 1))
         {
           iw[ridx[j1]] = -1;
-          for(i = j1 + 1; i < j2; i++)
+          for (i = j1 + 1; i < j2; i++)
             {
               iw[ridx[i]] = -1;
               data[i] /= data[j1];
@@ -182,8 +180,8 @@
 }
 
 DEFUN_DLD (__ichol0__, args, nargout, "-*- texinfo -*-\n\
-@deftypefn   {Loadable Function} {@var{L} =} __ichol0__ (@var{A})\n\
-@deftypefnx  {Loadable Function} {@var{L} =} __ichol0__ (@var{A}, @var{michol})\n\
+@deftypefn  {Loadable Function} {@var{L} =} __ichol0__ (@var{A})\n\
+@deftypefnx {Loadable Function} {@var{L} =} __ichol0__ (@var{A}, @var{michol})\n\
 Undocumented internal function.\n\
 @end deftypefn")
 
@@ -192,7 +190,6 @@
 
   int nargin = args.length ();
   std::string michol = "off";
- 
 
   if (nargout > 1 || nargin < 1 || nargin > 2)
     {
@@ -200,65 +197,47 @@
       return retval;
     }
 
-  if (args(0).is_scalar_type () || ! args(0).is_sparse_type ())
-    error ("__ichol0__: 1. parameter must be a sparse square matrix.");
-
-  if (args(0).is_empty ())
-    {
-      retval(0) = octave_value (SparseMatrix ());
-      return retval;
-    }
-
+  if (nargin == 2)
+    michol = args(1).string_value ();
 
-  if (nargin == 2)
-    {
-      michol = args(1).string_value ();
-      if (error_state || ! (michol == "on" || michol == "off"))
-        error ("__ichol0__: 2. parameter must be 'on' or 'off' character string.");
-    }
-
-
-  if (!error_state)
+  // In ICHOL0 algorithm the zero-pattern of the input matrix is preserved
+  // so it's structure does not change during the algorithm.  The same input
+  // matrix is used to build the output matrix due to that fact.
+  octave_value_list param_list;
+  if (!args(0).is_complex_type ())
     {
-      // In ICHOL0 algorithm the zero-pattern of the input matrix is preserved so
-      // it's structure does not change during the algorithm. The same input
-      // matrix is used to build the output matrix due to that fact.
-      octave_value_list param_list;
-      if (!args(0).is_complex_type ())
-        {
-          SparseMatrix sm = args(0).sparse_matrix_value ();
-          param_list.append (sm);
-          sm = feval ("tril", param_list)(0).sparse_matrix_value (); 
-          ichol_0 <SparseMatrix, double, ichol_mult_real, ichol_checkpivot_real> (sm, michol);
-          if (! error_state)
-            retval(0) = octave_value (sm);
-        }
-      else
-        {
-          SparseComplexMatrix sm = args(0).sparse_complex_matrix_value ();
-          param_list.append (sm);
-          sm = feval ("tril", param_list)(0).sparse_complex_matrix_value (); 
-          ichol_0 <SparseComplexMatrix, Complex, ichol_mult_complex, ichol_checkpivot_complex> (sm, michol);
-          if (! error_state)
-            retval(0) = octave_value (sm);
-        }
-
+      SparseMatrix sm = args(0).sparse_matrix_value ();
+      param_list.append (sm);
+      sm = feval ("tril", param_list)(0).sparse_matrix_value ();
+      ichol_0 <SparseMatrix, double, ichol_mult_real,
+               ichol_checkpivot_real> (sm, michol);
+      if (! error_state)
+        retval(0) = sm;
+    }
+  else
+    {
+      SparseComplexMatrix sm = args(0).sparse_complex_matrix_value ();
+      param_list.append (sm);
+      sm = feval ("tril", param_list)(0).sparse_complex_matrix_value ();
+      ichol_0 <SparseComplexMatrix, Complex, ichol_mult_complex,
+               ichol_checkpivot_complex> (sm, michol);
+      if (! error_state)
+        retval(0) = sm;
     }
 
   return retval;
 }
 
-template <typename octave_matrix_t, typename T,  T (*ichol_mult) (T, T), 
+template <typename octave_matrix_t, typename T,  T (*ichol_mult) (T, T),
           bool (*ichol_checkpivot) (T)>
 void ichol_t (const octave_matrix_t& sm, octave_matrix_t& L, const T* cols_norm,
               const T droptol, const std::string michol = "off")
-              
+
 {
 
   const octave_idx_type n = sm.cols ();
-  octave_idx_type j, jrow, jend, jjrow, jw, i, k, jj, Llist_len, total_len, w_len,
-                  max_len, ind;
-
+  octave_idx_type j, jrow, jend, jjrow, jw, i, k, jj, Llist_len, total_len,
+                  w_len, max_len, ind;
   char opt;
   enum {OFF, ON};
   if (michol == "on")
@@ -271,13 +250,13 @@
   octave_idx_type* ridx = sm.ridx ();
   T* data = sm.data ();
 
-  // Output matrix data structures. Because it is not known the 
-  // final zero pattern of the output matrix due to fill-in elements,
-  // an heuristic approach has been adopted for memory allocation. The 
-  // size of ridx_out_l and data_out_l is incremented 10% of their actual
-  // size (nnz(A) in the beginning).  If that amount is less than n, their
-  // size is just incremented in n elements. This way the number of
-  // reallocations decrease throughout the process, obtaining a good performance.
+  // Output matrix data structures.  Because the final zero pattern pattern of
+  // the output matrix is not known due to fill-in elements, a heuristic
+  // approach has been adopted for memory allocation.  The size of ridx_out_l
+  // and data_out_l is incremented 10% of their actual size (nnz (A) in the
+  // beginning).  If that amount is less than n, their size is just incremented
+  // in n elements.  This way the number of reallocations decreases throughout
+  // the process, obtaining a good performance.
   max_len = sm.nnz ();
   max_len += (0.1 * max_len) > n ? 0.1 * max_len : n;
   Array <octave_idx_type> cidx_out_l (dim_vector (n + 1, 1));
@@ -295,7 +274,6 @@
   std::vector <octave_idx_type> vec;
   vec.resize (n);
 
-
   T zero = T (0);
   cidx_l[0] = cidx[0];
   for (i = 0; i < n; i++)
@@ -321,7 +299,7 @@
             }
         }
       jrow = Llist[k];
-      while (jrow != -1) 
+      while (jrow != -1)
         {
           jjrow = Lfirst[jrow];
           jend = cidx_l[jrow+1];
@@ -329,18 +307,17 @@
             {
               j = ridx_l[jj];
               // If the element in the j position of the row is zero,
-              // then it will become non-zero, so we add it to the 
-              // vector that keeps track of non-zero elements in the working row.
+              // then it will become non-zero, so we add it to the
+              // vector that tracks non-zero elements in the working row.
               if (w_data[j] == zero)
                 {
-                  vec[ind] = j; 
+                  vec[ind] = j;
                   ind++;
                 }
               w_data[j] -=  ichol_mult (data_l[jj], data_l[jjrow]);
-
             }
-          // Update the actual column first element and update the 
-          // linked list of the jrow row.
+          // Update the actual column first element and
+          // update the linked list of the jrow row.
           if ((jjrow + 1) < jend)
             {
               Lfirst[jrow]++;
@@ -362,21 +339,20 @@
           ridx_out_l.resize (dim_vector (max_len, 1));
           ridx_l = ridx_out_l.fortran_vec ();
         }
-      
+
       // The sorting of the non-zero elements of the working column can be
-      // handled in a couple of ways. The most efficient two I found, are 
-      // keeping the elements in an ordered binary search tree dinamically 
-      // or keep them unsorted in a vector and at the end of the outer 
-      // iteration order them. The last approach exhibit lower execution 
-      // times.   
+      // handled in a couple of ways.  The most efficient two I found, are
+      // keeping the elements in an ordered binary search tree dynamically or
+      // keep them unsorted in a vector and at the end of the outer iteration
+      // order them.  The last approach exhibits lower execution times.
       std::sort (vec.begin (), vec.begin () + ind);
 
       data_l[total_len] = w_data[k];
       ridx_l[total_len] = k;
       w_len = 1;
 
-      // Extract then non-zero elements of working column and drop the
-      // elements that are lower than droptol * cols_norm[k].
+      // Extract the non-zero elements of working column and
+      // drop the elements that are lower than droptol * cols_norm[k].
       for (i = 0; i < ind ; i++)
         {
           jrow = vec[i];
@@ -407,29 +383,29 @@
 
       if (data_l[total_len] == zero)
         {
-          error ("ichol: There is a pivot equal to zero.");
+          error ("ichol: encountered a pivot equal to 0");
           break;
         }
       else if (! ichol_checkpivot (data_l[total_len]))
         break;
 
-      // Once the elements are dropped and compensation of columns 
-      // sums are done, scale the elements by the pivot.
+      // Once elements are dropped and compensation of column sums are done,
+      // scale the elements by the pivot.
       data_l[total_len] = std::sqrt (data_l[total_len]);
       for (jj = total_len + 1; jj < (total_len + w_len); jj++)
         data_l[jj] /=  data_l[total_len];
       total_len += w_len;
-      // Check if there are too many elements to be indexed with octave_idx_type
-      // type due to fill-in during the process.
+      // Check if there are too many elements to be indexed with
+      // octave_idx_type type due to fill-in during the process.
       if (total_len < 0)
         {
-          error ("ichol: Integer overflow. Too many fill-in elements in L");
+          error ("ichol: integer overflow.  Too many fill-in elements in L");
           break;
         }
       cidx_l[k+1] = cidx_l[k] - cidx_l[0] + w_len;
 
       // Update Llist and Lfirst with the k-column information.
-      if (k < (n - 1)) 
+      if (k < (n - 1))
         {
           Lfirst[k] = cidx_l[k];
           if ((Lfirst[k] + 1) < cidx_l[k+1])
@@ -440,8 +416,7 @@
               Llist[jjrow] = k;
             }
         }
-        
-      }
+    }
 
   if (! error_state)
     {
@@ -455,13 +430,12 @@
           L.data (i) = data_l[i];
         }
     }
-
 }
 
 DEFUN_DLD (__icholt__, args, nargout, "-*- texinfo -*-\n\
-@deftypefn   {Loadable Function} {@var{L} =} __icholt__ (@var{A})\n\
-@deftypefnx  {Loadable Function} {@var{L} =} __icholt__ (@var{A}, @var{droptol})\n\
-@deftypefnx  {Loadable Function} {@var{L} =} __icholt__ (@var{A}, @var{droptol}, @var{michol})\n\
+@deftypefn  {Loadable Function} {@var{L} =} __icholt__ (@var{A})\n\
+@deftypefnx {Loadable Function} {@var{L} =} __icholt__ (@var{A}, @var{droptol})\n\
+@deftypefnx {Loadable Function} {@var{L} =} __icholt__ (@var{A}, @var{droptol}, @var{michol})\n\
 Undocumented internal function.\n\
 @end deftypefn")
 {
@@ -470,7 +444,6 @@
   // Default values of parameters
   std::string michol = "off";
   double droptol = 0;
- 
 
   if (nargout > 1 || nargin < 1 || nargin > 3)
     {
@@ -478,69 +451,51 @@
       return retval;
     }
 
-  if (args(0).is_scalar_type () || ! args(0).is_sparse_type ())
-    error ("__icholt__: 1. parameter must be a sparse square matrix.");
+  // Don't repeat input validation of arguments done in ichol.m
 
-  if (args(0).is_empty ())
-    {
-      retval(0) = octave_value (SparseMatrix ());
-      return retval;
-    }
+  if (nargin >= 2)
+    droptol = args(1).double_value ();
 
-  if (! error_state && (nargin >= 2))
-    {
-      droptol = args(1).double_value ();
-      if (error_state || (droptol < 0) || ! args(1).is_real_scalar ())
-        error ("__icholt__: 2. parameter must be a positive real scalar.");
-    }
+  if (nargin == 3)
+    michol = args(2).string_value ();
 
-  if (! error_state && (nargin == 3))
-    {
-      michol = args(2).string_value ();
-      if (error_state || !(michol == "on" || michol == "off"))
-        error ("__icholt__: 3. parameter must be 'on' or 'off' character string.");
-    }
-
-  if (!error_state)
+  octave_value_list param_list;
+  if (! args(0).is_complex_type ())
     {
-      octave_value_list param_list;
-      if (! args(0).is_complex_type ())
-        {
-          Array <double> cols_norm;
-          SparseMatrix L;
-          param_list.append (args(0).sparse_matrix_value ());
-          SparseMatrix sm_l = feval ("tril", 
-                                     param_list)(0).sparse_matrix_value (); 
-          param_list(0) = sm_l;
-          param_list(1) = 1;
-          param_list(2) = "cols";
-          cols_norm = feval ("norm", param_list)(0).vector_value ();
-          param_list.clear ();
-          ichol_t <SparseMatrix, 
-                   double, ichol_mult_real, ichol_checkpivot_real> 
-                   (sm_l, L, cols_norm.fortran_vec (), droptol, michol);
-          if (! error_state)
-            retval(0) = octave_value (L);
-        }
-      else
-        {
-          Array <Complex> cols_norm;
-          SparseComplexMatrix L;
-          param_list.append (args(0).sparse_complex_matrix_value ());
-          SparseComplexMatrix sm_l = feval ("tril", 
-                                            param_list)(0).sparse_complex_matrix_value (); 
-          param_list(0) = sm_l;
-          param_list(1) = 1;
-          param_list(2) = "cols";
-          cols_norm = feval ("norm", param_list)(0).complex_vector_value ();
-          param_list.clear ();
-          ichol_t <SparseComplexMatrix, 
-                   Complex, ichol_mult_complex, ichol_checkpivot_complex> 
-                   (sm_l, L, cols_norm.fortran_vec (), Complex (droptol), michol);
-          if (! error_state)
-            retval(0) = octave_value (L);
-        }
-
+      Array <double> cols_norm;
+      SparseMatrix L;
+      param_list.append (args(0).sparse_matrix_value ());
+      SparseMatrix sm_l =
+        feval ("tril", param_list)(0).sparse_matrix_value ();
+      param_list(0) = sm_l;
+      param_list(1) = 1;
+      param_list(2) = "cols";
+      cols_norm = feval ("norm", param_list)(0).vector_value ();
+      param_list.clear ();
+      ichol_t <SparseMatrix,
+               double, ichol_mult_real, ichol_checkpivot_real>
+               (sm_l, L, cols_norm.fortran_vec (), droptol, michol);
+      if (! error_state)
+        retval(0) = L;
+    }
+  else
+    {
+      Array <Complex> cols_norm;
+      SparseComplexMatrix L;
+      param_list.append (args(0).sparse_complex_matrix_value ());
+      SparseComplexMatrix sm_l =
+        feval ("tril", param_list)(0).sparse_complex_matrix_value ();
+      param_list(0) = sm_l;
+      param_list(1) = 1;
+      param_list(2) = "cols";
+      cols_norm = feval ("norm", param_list)(0).complex_vector_value ();
+      param_list.clear ();
+      ichol_t <SparseComplexMatrix,
+               Complex, ichol_mult_complex, ichol_checkpivot_complex>
+               (sm_l, L, cols_norm.fortran_vec (),
+                Complex (droptol), michol);
+      if (! error_state)
+        retval(0) = L;
     }
 
   return retval;
@@ -550,3 +505,4 @@
 ## No test needed for internal helper function.
 %!assert (1)
 */
+
--- a/libinterp/dldfcn/__ilu__.cc	Mon Aug 18 12:32:16 2014 +0100
+++ b/libinterp/dldfcn/__ilu__.cc	Tue Aug 26 15:27:21 2014 -0700
@@ -1,22 +1,25 @@
-/**
- * Copyright (C) 2013 Kai T. Ohlhus <k.ohlhus@gmail.com>
- * Copyright (C) 2014 Eduardo Ramos Fernández <eduradical951@gmail.com>
- *
- * This file is part of Octave.
- *
- * Octave is free software; you can redistribute it and/or modify it under the
- * terms of the GNU General Public License as published by the Free Software
- * Foundation; either version 3 of the License, or (at your option) any later
- * version.
- *
- * Octave is distributed in the hope that it will be useful, but WITHOUT ANY
- * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
- * FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
- * details.
- *
- * You should have received a copy of the GNU General Public License along with
- * Octave; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>.
- */
+/*
+
+Copyright (C) 2014 Eduardo Ramos Fernández <eduradical951@gmail.com>
+Copyright (C) 2013 Kai T. Ohlhus <k.ohlhus@gmail.com>
+
+This file is part of Octave.
+
+Octave is free software; you can redistribute it and/or modify it
+under the terms of the GNU General Public License as published by the
+Free Software Foundation; either version 3 of the License, or (at your
+option) any later version.
+
+Octave is distributed in the hope that it will be useful, but WITHOUT
+ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+for more details.
+
+You should have received a copy of the GNU General Public License
+along with Octave; see the file COPYING.  If not, see
+<http://www.gnu.org/licenses/>.
+
+*/
 
 #ifdef HAVE_CONFIG_H
 #include <config.h>
@@ -25,14 +28,14 @@
 #include "defun-dld.h"
 #include "parse.h"
 
-// That function implements the IKJ and JKI variants of gaussian elimination to
-// perform the ILUTP decomposition. The behaviour is controlled by milu
-// parameter. If milu = ['off'|'col'] the JKI version is performed taking
-// advantage of CCS format of the input matrix. If milu = 'row' the input matrix
-// has to be transposed to obtain the equivalent CRS structure so we can work
-// efficiently with rows. In this case IKJ version is used.
+// That function implements the IKJ and JKI variants of Gaussian elimination to
+// perform the ILUTP decomposition.  The behaviour is controlled by milu
+// parameter.  If milu = ['off'|'col'] the JKI version is performed taking
+// advantage of CCS format of the input matrix.  If milu = 'row' the input
+// matrix has to be transposed to obtain the equivalent CRS structure so we can
+// work efficiently with rows.  In this case IKJ version is used.
 template <typename octave_matrix_t, typename T>
-void ilu_0 (octave_matrix_t& sm, const std::string milu = "off") 
+void ilu_0 (octave_matrix_t& sm, const std::string milu = "off")
 {
 
   const octave_idx_type n = sm.cols ();
@@ -70,7 +73,7 @@
       r = 0;
       j = j1;
       jrow = ridx[j];
-      while ((jrow < k) && (j <= j2)) 
+      while ((jrow < k) && (j <= j2))
         {
           if (opt == ROW)
             {
@@ -97,23 +100,23 @@
           jrow = ridx[j];
         }
       uptr[k] = j;
-      if(opt != OFF)
+      if (opt != OFF)
         data[uptr[k]] -= r;
       if (opt != ROW)
         for (jj = uptr[k] + 1; jj < cidx[k+1]; jj++)
           data[jj] /=  data[uptr[k]];
       if (k != jrow)
         {
-          error ("ilu: Your input matrix has a zero in the diagonal.");
+          error ("ilu: A has a zero on the diagonal");
           break;
         }
 
       if (data[j] == T(0))
         {
-          error ("ilu: There is a pivot equal to zero.");
+          error ("ilu: encountered a pivot equal to 0");
           break;
         }
-      for(i = j1; i <= j2; i++)
+      for (i = j1; i <= j2; i++)
         iw[ridx[i]] = -1;
     }
   if (opt == ROW)
@@ -131,7 +134,6 @@
 
   int nargin = args.length ();
   std::string milu;
- 
 
   if (nargout > 2 || nargin < 1 || nargin > 2)
     {
@@ -139,67 +141,42 @@
       return retval;
     }
 
-  if (args (0).is_empty ())
-    {
-      retval(0) = octave_value (SparseMatrix());
-      retval(1) = octave_value (SparseMatrix());
-      return retval;
-    }
-
-  if (args(0).is_scalar_type () || ! args(0).is_sparse_type ())
-    error ("__ilu0__: 1. parameter must be a sparse square matrix.");
-
-  if (nargin == 2)
+  // In ILU0 algorithm the zero-pattern of the input matrix is preserved so
+  // it's structure does not change during the algorithm.  The same input
+  // matrix is used to build the output matrix due to that fact.
+  octave_value_list param_list;
+  if (! args(0).is_complex_type ())
     {
-      milu = args(1).string_value ();
-      if (error_state || !(milu == "row" || milu == "col" || milu == "off"))
-        error (
-          "__ilu0__: 2. parameter must be 'row', 'col' or 'off' character string.");
-    }
-
-
-  if (! error_state)
-    {
-      // In ILU0 algorithm the zero-pattern of the input matrix is preserved so
-      // it's structure does not change during the algorithm. The same input
-      // matrix is used to build the output matrix due to that fact.
-      octave_value_list param_list;
-      if (! args(0).is_complex_type ())
+      SparseMatrix sm = args(0).sparse_matrix_value ();
+      ilu_0 <SparseMatrix, double> (sm, milu);
+      if (!error_state)
         {
-          SparseMatrix sm = args(0).sparse_matrix_value ();
-          ilu_0 <SparseMatrix, double> (sm, milu);
-          if (!error_state)
-            {
-              param_list.append (sm);
-              retval(1) = octave_value (
-                feval ("triu", param_list)(0).sparse_matrix_value ()); 
-              SparseMatrix eye = feval ("speye",
-                octave_value_list (
-                  octave_value (sm.cols ())))(0).sparse_matrix_value ();
-              param_list.append (-1);
-              retval(0) = octave_value (
-                eye + feval ("tril", param_list)(0).sparse_matrix_value ()); 
-
-            }
+          param_list.append (sm);
+          retval(1) = feval ("triu", param_list)(0).sparse_matrix_value ();
+          SparseMatrix eye =
+            feval ("speye", octave_value_list (
+                     octave_value (sm.cols ())))(0).sparse_matrix_value ();
+          param_list.append (-1);
+          retval(0) = eye +
+                      feval ("tril", param_list)(0).sparse_matrix_value ();
         }
-      else
+    }
+  else
+    {
+      SparseComplexMatrix sm = args(0).sparse_complex_matrix_value ();
+      ilu_0 <SparseComplexMatrix, Complex> (sm, milu);
+      if (! error_state)
         {
-          SparseComplexMatrix sm = args(0).sparse_complex_matrix_value ();
-          ilu_0 <SparseComplexMatrix, Complex> (sm, milu);
-          if (! error_state)
-            {
-              param_list.append (sm);
-              retval(1) = octave_value (
-                feval ("triu", param_list)(0).sparse_complex_matrix_value ()); 
-              SparseComplexMatrix eye = feval ("speye",
-                octave_value_list (
-                  octave_value (sm.cols ())))(0).sparse_complex_matrix_value ();
-              param_list.append (-1);
-              retval(0) = octave_value (eye +
-                feval ("tril", param_list)(0).sparse_complex_matrix_value ()); 
-           }
+          param_list.append (sm);
+          retval(1) =
+            feval ("triu", param_list)(0).sparse_complex_matrix_value ();
+          SparseComplexMatrix eye =
+            feval ("speye", octave_value_list (
+                     octave_value (sm.cols ())))(0).sparse_complex_matrix_value ();
+          param_list.append (-1);
+          retval(0) =
+            eye + feval ("tril", param_list)(0).sparse_complex_matrix_value ();
         }
-
     }
 
   return retval;
@@ -212,7 +189,7 @@
                 const std::string milu = "off")
 {
 
-  // Map the strings into chars to faster comparation inside loops
+  // Map the strings into chars for faster comparing inside loops
   char opt;
   enum {OFF, ROW, COL};
   if (milu == "row")
@@ -264,7 +241,7 @@
   OCTAVE_LOCAL_BUFFER (T, cr_sum, n);
 
   T zero = T (0);
-  
+
   cidx_u[0] = cidx_in_u[0];
   cidx_l[0] = cidx_in_l[0];
   for (i = 0; i < n; i++)
@@ -281,8 +258,7 @@
 
   for (k = 0; k < n; k++)
     {
-
-      // Load the working column and working row 
+      // Load the working column and working row
       for (i = cidx_in_l[k]; i < cidx_in_l[k+1]; i++)
         w_data_l[ridx_in_l[i]] = data_in_l[i];
 
@@ -380,10 +356,10 @@
       // Check if the pivot is zero
       if (data_u[total_len_u] == zero)
         {
-              error ("ilu: There is a pivot equal to zero.");
-              break;
+          error ("ilu: encountered a pivot equal to 0");
+          break;
         }
-      
+
       // Scale the elements in L by the pivot
       for (i = total_len_l ; i < (total_len_l + w_len_l); i++)
         data_l[i] /= data_u[total_len_u];
@@ -391,24 +367,24 @@
 
       total_len_u += w_len_u;
       total_len_l += w_len_l;
-      // Check if there are too many elements to be indexed with octave_idx_type
-      // type due to fill-in during the process.
+      // Check if there are too many elements to be indexed with
+      // octave_idx_type type due to fill-in during the process.
       if (total_len_l < 0 || total_len_u < 0)
         {
-          error ("ilu: Integer overflow. Too many fill-in elements in L or U");
+          error ("ilu: integer overflow.  Too many fill-in elements in L or U");
           break;
         }
       cidx_u[k+1] = cidx_u[k] - cidx_u[0] + w_len_u;
       cidx_l[k+1] = cidx_l[k] - cidx_l[0] + w_len_l;
 
-      // The tricky part of the algorithm. The arrays pointing to the first
+      // The tricky part of the algorithm.  The arrays pointing to the first
       // working element of each column in the next iteration (Lfirst) or
-      // the first working element of each row (Ufirst) are updated. Also the
-      // arrays working as lists cols_list and rows_list are filled with indexes
-      // pointing to Ufirst and Lfirst respectively.
+      // the first working element of each row (Ufirst) are updated.  Also the
+      // arrays working as lists cols_list and rows_list are filled with
+      // indices pointing to Ufirst and Lfirst respectively.
       // TODO: Maybe the -1 indicating in Ufirst and Lfirst, that no elements
-      // have to be considered in a certain column or row in next iteration, can
-      // be removed. It feels safer to me using such an indicator.
+      // have to be considered in a certain column or row in next iteration,
+      // can be removed.  It feels safer to me using such an indicator.
       if (k < (n - 1))
         {
           if (w_len_u > 0)
@@ -437,7 +413,7 @@
                             jj = ridx_u[Ufirst[i]];
                         }
                     }
-                  if (jj == (k + 1)) 
+                  if (jj == (k + 1))
                     {
                       cols_list[cols_list_len] = i;
                       cols_list_len++;
@@ -448,7 +424,7 @@
                 {
                   jj = ridx_l[Lfirst[i]];
                   if (jj < (k + 1))
-                    if(Lfirst[i] < (cidx_l[i+1]))
+                    if (Lfirst[i] < (cidx_l[i+1]))
                       {
                         Lfirst[i]++;
                         if (Lfirst[i] == cidx_l[i+1])
@@ -456,7 +432,7 @@
                         else
                           jj = ridx_l[Lfirst[i]];
                       }
-                  if (jj == (k + 1)) 
+                  if (jj == (k + 1))
                     {
                       rows_list[rows_list_len] = i;
                       rows_list_len++;
@@ -497,7 +473,6 @@
 Undocumented internal function.\n\
 @end deftypefn")
 {
-
   octave_value_list retval;
   int nargin = args.length ();
   std::string milu = "off";
@@ -509,103 +484,86 @@
       return retval;
     }
 
-  // To be matlab compatible 
-  if (args(0).is_empty ())
-    {
-      retval(0) = octave_value (SparseMatrix());
-      retval(1) = octave_value (SparseMatrix());
-      return retval;
-    }
+  // Don't repeat input validation of arguments done in ilu.m
+  if (nargin >= 2)
+    droptol = args(1).double_value ();
 
-  if (args(0).is_scalar_type () || ! args(0).is_sparse_type ())
-    error ("__iluc__: 1. parameter must be a sparse square matrix.");
+  if (nargin == 3)
+    milu = args(2).string_value ();
 
-  if (! error_state && (nargin >= 2))
+  octave_value_list param_list;
+  if (! args(0).is_complex_type ())
     {
-      droptol = args(1).double_value ();
-      if (error_state || (droptol < 0) || ! args(1).is_real_scalar ())
-        error ("__iluc__: 2. parameter must be a positive real scalar.");
+      Array<double> cols_norm, rows_norm;
+      param_list.append (args(0).sparse_matrix_value ());
+      SparseMatrix sm_u = feval ("triu", param_list)(0).sparse_matrix_value ();
+      param_list.append (-1);
+      SparseMatrix sm_l = feval ("tril", param_list)(0).sparse_matrix_value ();
+      param_list(1) = "rows";
+      rows_norm = feval ("norm", param_list)(0).vector_value ();
+      param_list(1) = "cols";
+      cols_norm = feval ("norm", param_list)(0).vector_value ();
+      param_list.clear ();
+      SparseMatrix U;
+      SparseMatrix L;
+      ilu_crout <SparseMatrix, double> (sm_l, sm_u, L, U,
+                                        cols_norm.fortran_vec (),
+                                        rows_norm.fortran_vec (),
+                                        droptol, milu);
+      if (! error_state)
+        {
+          param_list.append (octave_value (L.cols ()));
+          SparseMatrix eye =
+            feval ("speye", param_list)(0).sparse_matrix_value ();
+          retval(1) = U;
+          retval(0) = L + eye;
+        }
     }
-
-  if (! error_state && (nargin == 3))
+  else
     {
-      milu = args(2).string_value ();
-      if (error_state || !(milu == "row" || milu == "col" || milu == "off"))
-        error ("__iluc__: 3. parameter must be 'row', 'col' or 'off' character string.");
+      Array<Complex> cols_norm, rows_norm;
+      param_list.append (args(0).sparse_complex_matrix_value ());
+      SparseComplexMatrix sm_u =
+        feval("triu", param_list)(0).sparse_complex_matrix_value ();
+      param_list.append (-1);
+      SparseComplexMatrix sm_l =
+        feval("tril", param_list)(0).sparse_complex_matrix_value ();
+      param_list(1) = "rows";
+      rows_norm = feval ("norm", param_list)(0).complex_vector_value ();
+      param_list(1) = "cols";
+      cols_norm = feval ("norm", param_list)(0).complex_vector_value ();
+      param_list.clear ();
+      SparseComplexMatrix U;
+      SparseComplexMatrix L;
+      ilu_crout < SparseComplexMatrix, Complex >
+                (sm_l, sm_u, L, U, cols_norm.fortran_vec () ,
+                 rows_norm.fortran_vec (), Complex (droptol), milu);
+      if (! error_state)
+        {
+          param_list.append (octave_value (L.cols ()));
+          SparseComplexMatrix eye =
+            feval ("speye", param_list)(0).sparse_complex_matrix_value ();
+          retval(1) = U;
+          retval(0) = L + eye;
+        }
     }
 
-  if (! error_state)
-    {
-      octave_value_list param_list;
-      if (! args(0).is_complex_type ())
-        {
-          Array<double> cols_norm, rows_norm;
-          param_list.append (args(0).sparse_matrix_value ());
-          SparseMatrix sm_u =  feval ("triu", param_list)(0).sparse_matrix_value (); 
-          param_list.append (-1);
-          SparseMatrix sm_l =  feval ("tril", param_list)(0).sparse_matrix_value (); 
-          param_list(1) = "rows";
-          rows_norm = feval ("norm", param_list)(0).vector_value ();
-          param_list(1) = "cols";
-          cols_norm = feval ("norm", param_list)(0).vector_value ();
-          param_list.clear ();
-          SparseMatrix U;
-          SparseMatrix L;
-          ilu_crout <SparseMatrix, double> (sm_l, sm_u, L, U, cols_norm.fortran_vec (), 
-                                            rows_norm.fortran_vec (), droptol, milu);
-          if (! error_state)
-            {
-              param_list.append (octave_value (L.cols ()));
-              SparseMatrix eye = feval ("speye", param_list)(0).sparse_matrix_value ();
-              retval(0) = octave_value (L + eye);
-              retval(1) = octave_value (U);
-            }
-        }
-      else
-        {
-          Array<Complex> cols_norm, rows_norm;
-          param_list.append (args(0).sparse_complex_matrix_value ());
-          SparseComplexMatrix sm_u =  feval("triu", 
-                                            param_list)(0).sparse_complex_matrix_value (); 
-          param_list.append (-1);
-          SparseComplexMatrix sm_l =  feval("tril", 
-                                            param_list)(0).sparse_complex_matrix_value (); 
-          param_list(1) = "rows";
-          rows_norm = feval ("norm", param_list)(0).complex_vector_value ();
-          param_list(1) = "cols";
-          cols_norm = feval ("norm", param_list)(0).complex_vector_value ();
-          param_list.clear ();
-          SparseComplexMatrix U;
-          SparseComplexMatrix L;
-          ilu_crout < SparseComplexMatrix, Complex > 
-                    (sm_l, sm_u, L, U, cols_norm.fortran_vec () , 
-                     rows_norm.fortran_vec (), Complex (droptol), milu);
-          if (! error_state)
-            {
-              param_list.append (octave_value (L.cols ()));
-              SparseComplexMatrix eye = feval ("speye", 
-                                                param_list)(0).sparse_complex_matrix_value ();
-              retval(0) = octave_value (L + eye);
-              retval(1) = octave_value (U);
-            }
-        }
-    }
   return retval;
 }
 
-// That function implements the IKJ and JKI variants of gaussian elimination 
-// to perform the ILUTP decomposition. The behaviour is controlled by milu 
-// parameter. If milu = ['off'|'col'] the JKI version is performed taking 
-// advantage of CCS format of the input matrix. Row pivoting is performed. 
-// If milu = 'row' the input matrix has to be transposed to obtain the 
-// equivalent CRS structure so we can work efficiently with rows. In that
+// That function implements the IKJ and JKI variants of gaussian elimination
+// to perform the ILUTP decomposition.  The behaviour is controlled by milu
+// parameter.  If milu = ['off'|'col'] the JKI version is performed taking
+// advantage of CCS format of the input matrix.  Row pivoting is performed.
+// If milu = 'row' the input matrix has to be transposed to obtain the
+// equivalent CRS structure so we can work efficiently with rows.  In that
 // case IKJ version is used and column pivoting is performed.
 
 template <typename octave_matrix_t, typename T>
-void ilu_tp (octave_matrix_t& sm, octave_matrix_t& L, octave_matrix_t& U, 
-             octave_idx_type nnz_u, octave_idx_type nnz_l, T* cols_norm,  
+void ilu_tp (octave_matrix_t& sm, octave_matrix_t& L, octave_matrix_t& U,
+             octave_idx_type nnz_u, octave_idx_type nnz_l, T* cols_norm,
              Array <octave_idx_type>& perm_vec, const T droptol = T(0),
-             const T thresh = T(0), const  std::string milu = "off", 
+             const T thresh = T(0), const  std::string milu = "off",
              const double udiag = 0)
 {
   char opt;
@@ -616,7 +574,7 @@
     opt = COL;
   else
     opt = OFF;
-  
+
   const octave_idx_type n = sm.cols ();
 
   // That is necessary for the JKI (milu = "row") variant.
@@ -627,7 +585,7 @@
   octave_idx_type* cidx_in = sm.cidx ();
   octave_idx_type* ridx_in = sm.ridx ();
   T* data_in = sm.data ();
-  octave_idx_type jrow, i, j, k, jj, c, total_len_l, total_len_u, p_perm, 
+  octave_idx_type jrow, i, j, k, jj, c, total_len_l, total_len_u, p_perm,
                   max_ind, max_len_l, max_len_u;
   T tl, aux, maximum;
 
@@ -690,7 +648,7 @@
       it = iw_u.begin ();
       jrow = *it;
       total_sum = zero;
-      while ((jrow < k) && (it != iw_u.end ())) 
+      while ((jrow < k) && (it != iw_u.end ()))
         {
           if (opt == COL)
             partial_col_sum = w_data[jrow];
@@ -712,7 +670,7 @@
                     }
                   else
                     {
-                      tl = data_l[jj] * w_data[jrow]; 
+                      tl = data_l[jj] * w_data[jrow];
                       w_data[p_perm] -= tl;
                       if (opt == COL)
                         partial_col_sum += tl;
@@ -727,26 +685,27 @@
                     }
                 }
 
-                // Drop element from the U part in IKJ and L part in JKI 
-                // variant (milu = [col|off])
-                if ((std::abs (w_data[jrow]) < (droptol * cols_norm[k])) 
-                    && (w_data[jrow] != zero))
-                  {
-                    if (opt == COL)
-                      total_sum += partial_col_sum;
-                    else if (opt == ROW)
-                      total_sum += partial_row_sum;
-                    w_data[jrow] = zero;
-                    it2 = it;
-                    it++;
-                    iw_u.erase (it2);
-                    jrow = *it;
-                    continue;
-                  }
-                else 
-                  // This is the element scaled by the pivot in the actual iteration
-                  if (opt == ROW)
-                    w_data[jrow] = tl;
+              // Drop element from the U part in IKJ and L part in JKI
+              // variant (milu = [col|off])
+              if ((std::abs (w_data[jrow]) < (droptol * cols_norm[k]))
+                  && (w_data[jrow] != zero))
+                {
+                  if (opt == COL)
+                    total_sum += partial_col_sum;
+                  else if (opt == ROW)
+                    total_sum += partial_row_sum;
+                  w_data[jrow] = zero;
+                  it2 = it;
+                  it++;
+                  iw_u.erase (it2);
+                  jrow = *it;
+                  continue;
+                }
+              else
+                // This is the element scaled by the pivot
+                // in the actual iteration
+                if (opt == ROW)
+                  w_data[jrow] = tl;
             }
           jrow = *(++it);
         }
@@ -757,14 +716,14 @@
         {
           maximum = std::abs (w_data[k]) / thresh;
           max_ind = perm[k];
-          for (it = iw_l.begin (); it != iw_l.end (); ++it) 
+          for (it = iw_l.begin (); it != iw_l.end (); ++it)
             {
               p_perm = iperm[*it];
               if (std::abs (w_data[p_perm]) > maximum)
                 {
                   maximum = std::abs (w_data[p_perm]);
                   max_ind = *it;
-                  it2 = it; 
+                  it2 = it;
                 }
             }
           // If the pivot is not the diagonal element update all.
@@ -775,7 +734,7 @@
               if (w_data[k] != zero)
                 iw_l.insert (perm[k]);
               else
-                  iw_u.insert (k);
+                iw_u.insert (k);
               // Swap data and update permutation vectors
               aux = w_data[k];
               iperm[perm[p_perm]] = k;
@@ -786,13 +745,13 @@
               w_data[k] = w_data[p_perm];
               w_data[p_perm] = aux;
             }
-          
-      }              
+
+        }
 
       // Drop elements in the L part in the IKJ and from the U part in the JKI
       // version.
       it = iw_l.begin ();
-      while (it != iw_l.end ()) 
+      while (it != iw_l.end ())
         {
           p_perm = iperm[*it];
           if (droptol > zero)
@@ -810,14 +769,15 @@
           it++;
         }
 
-      // If milu =[row|col] sumation is preserved --> Compensate diagonal element.
+      // If milu == [row|col] summation is preserved.
+      // Compensate diagonal element.
       if (opt != OFF)
         {
           if ((total_sum > zero) && (w_data[k] == zero))
             iw_u.insert (k);
           w_data[k] += total_sum;
         }
-          
+
 
 
       // Check if the pivot is zero and if udiag is active.
@@ -832,19 +792,19 @@
             }
           else
             {
-              error ("ilu: There is a pivot equal to zero.");
+              error ("ilu: encountered a pivot equal to 0");
               break;
             }
         }
 
-      // Scale the elements on the L part for IKJ version (milu = [col|off])  
+      // Scale the elements on the L part for IKJ version (milu = [col|off])
       if (opt != ROW)
-        for (it = iw_l.begin (); it != iw_l.end (); ++it) 
+        for (it = iw_l.begin (); it != iw_l.end (); ++it)
           {
-              p_perm = iperm[*it];
-              w_data[p_perm] = w_data[p_perm] / w_data[k];
+            p_perm = iperm[*it];
+            w_data[p_perm] = w_data[p_perm] / w_data[k];
           }
-      
+
 
       if ((max_len_u - total_len_u) < n)
         {
@@ -891,11 +851,11 @@
         }
       total_len_u += w_len_u;
       total_len_l += w_len_l;
-      // Check if there are too many elements to be indexed with octave_idx_type
-      // type due to fill-in during the process.
+      // Check if there are too many elements to be indexed with
+      // octave_idx_type type due to fill-in during the process.
       if (total_len_l < 0 || total_len_u < 0)
         {
-          error ("ilu: Integer overflow. Too many fill-in elements in L or U");
+          error ("ilu: Integer overflow.  Too many fill-in elements in L or U");
           break;
         }
       if (opt == ROW)
@@ -909,11 +869,11 @@
 
   if (! error_state)
     {
-      octave_matrix_t *L_ptr; 
+      octave_matrix_t *L_ptr;
       octave_matrix_t *U_ptr;
       octave_matrix_t diag (n, n, n);
-      
-      // L and U are interchanged if milu = 'row'. It is a matter
+
+      // L and U are interchanged if milu = 'row'.  It is a matter
       // of nomenclature to re-use code with both IKJ and JKI
       // versions of the algorithm.
       if (opt == ROW)
@@ -939,7 +899,7 @@
             U_ptr->cidx (i) -= i;
         }
 
-      for (i = 0; i < n; i++) 
+      for (i = 0; i < n; i++)
         {
           if (opt == ROW)
             diag.elem (i,i) = data_u[uptr[i]];
@@ -959,7 +919,7 @@
               if (opt == ROW)
                 {
                   // The diagonal is removed from L if milu = 'row'.
-                  // That is because is convenient to have it inside 
+                  // That is because is convenient to have it inside
                   // the L part to carry out the process.
                   if (ridx_u[j] == i)
                     {
@@ -975,7 +935,7 @@
             }
         }
 
-      if (opt == ROW) 
+      if (opt == ROW)
         {
           U = U.transpose ();
           // The diagonal, conveniently permuted is added to U
@@ -1002,157 +962,133 @@
   double droptol, thresh;
   double udiag;
 
-
   if (nargout < 2 || nargout > 3 || nargin < 1 || nargin > 5)
     {
       print_usage ();
       return retval;
     }
 
-  // To be matlab compatible 
-  if (args(0).is_empty ())
-    {
-      retval(0) = octave_value (SparseMatrix ());
-      retval(1) = octave_value (SparseMatrix ());
-      if (nargout == 3)
-        retval(2) = octave_value (SparseMatrix ()); 
-      return retval;
-    }
+  // Don't repeat input validation of arguments done in ilu.m
+  if (nargin >= 2)
+    droptol = args(1).double_value ();
 
-  if (args(0).is_scalar_type () || ! args(0).is_sparse_type () )
-    error ("__ilutp__: 1. parameter must be a sparse square matrix.");
+  if (nargin >= 3)
+    thresh = args(2).double_value ();
 
-  if (! error_state && (nargin >= 2))
-    {
-      droptol = args(1).double_value ();
-      if (error_state || (droptol < 0) || ! args(1).is_real_scalar ())
-        error ("__ilutp__: 2. parameter must be a positive scalar.");
-    }
+  if (nargin >= 4)
+    milu = args(3).string_value ();
 
-  if (! error_state && (nargin >= 3))
-    {
-      thresh = args(2).double_value ();
-      if (error_state || ! args(2).is_real_scalar () || (thresh < 0) || thresh > 1)
-        error ("__ilutp__: 3. parameter must be a scalar 0 <= thresh <= 1.");
-    }
+  if (nargin == 5)
+    udiag = args(4).double_value ();
 
-  if (! error_state && (nargin >= 4))
-    {
-      milu = args(3).string_value ();
-      if (error_state || !(milu == "row" || milu == "col" || milu == "off"))
-        error ("__ilutp__: 4. parameter must be 'row', 'col' or 'off' character string.");
-    }
-
-  if (! error_state && (nargin == 5))
+  octave_value_list param_list;
+  octave_idx_type nnz_u, nnz_l;
+  if (! args(0).is_complex_type ())
     {
-      udiag = args(4).double_value ();
-      if (error_state || ! args(4).is_real_scalar () || ((udiag != 0) 
-          && (udiag != 1)))
-        error ("__ilutp__: 5. parameter must be a scalar with value 1 or 0.");
-    }
-
-  if (! error_state)
-    {
-      octave_value_list param_list;
-      octave_idx_type nnz_u, nnz_l;
-      if (! args(0).is_complex_type ())
+      Array <double> rc_norm;
+      SparseMatrix sm = args(0).sparse_matrix_value ();
+      param_list.append (sm);
+      nnz_u =  (feval ("triu", param_list)(0).sparse_matrix_value ()).nnz ();
+      param_list.append (-1);
+      nnz_l =  (feval ("tril", param_list)(0).sparse_matrix_value ()).nnz ();
+      if (milu == "row")
+        param_list (1) = "rows";
+      else
+        param_list (1) = "cols";
+      rc_norm = feval ("norm", param_list)(0).vector_value ();
+      param_list.clear ();
+      Array <octave_idx_type> perm (dim_vector (sm.cols (), 1));
+      SparseMatrix U;
+      SparseMatrix L;
+      ilu_tp <SparseMatrix, double> (sm, L, U, nnz_u, nnz_l,
+                                     rc_norm.fortran_vec (),
+                                     perm, droptol, thresh, milu, udiag);
+      if (! error_state)
         {
-          Array <double> rc_norm;
-          SparseMatrix sm = args(0).sparse_matrix_value ();
-          param_list.append (sm);
-          nnz_u =  (feval ("triu", param_list)(0).sparse_matrix_value ()).nnz (); 
-          param_list.append (-1);
-          nnz_l =  (feval ("tril", param_list)(0).sparse_matrix_value ()).nnz (); 
+          param_list.append (octave_value (L.cols ()));
+          SparseMatrix eye =
+            feval ("speye", param_list)(0).sparse_matrix_value ();
           if (milu == "row")
-            param_list (1) = "rows";
+            {
+              if (nargout == 3)
+                {
+                  retval(2) = eye.index (idx_vector::colon, perm);
+                  retval(1) = U.index (idx_vector::colon, perm);
+                }
+              else if (nargout == 2)
+                retval(1) = U;
+              retval(0) = L + eye;
+            }
           else
-            param_list (1) = "cols";
-          rc_norm = feval ("norm", param_list)(0).vector_value ();
-          param_list.clear ();
-          Array <octave_idx_type> perm (dim_vector (sm.cols (), 1)); 
-          SparseMatrix U;
-          SparseMatrix L;
-          ilu_tp <SparseMatrix, double> (sm, L, U, nnz_u, nnz_l, rc_norm.fortran_vec (),
-                                         perm, droptol, thresh, milu, udiag);
-          if (! error_state)
             {
-              param_list.append (octave_value (L.cols ()));
-              SparseMatrix eye = feval ("speye", param_list)(0).sparse_matrix_value ();
-              if (milu == "row")
+              if (nargout == 3)
                 {
-                  retval(0) = octave_value (L + eye);
-                  if (nargout == 2) 
-                    retval(1) = octave_value (U);
-                  else if (nargout == 3)
-                    {
-                     retval(1) = octave_value (U.index (idx_vector::colon, perm));
-                     retval(2) = octave_value (eye.index (idx_vector::colon, perm));
-                    }
+                  retval(2) = eye.index (perm, idx_vector::colon);
+                  retval(1) = U;
+                  retval(0) = L.index (perm, idx_vector::colon) + eye;
                 }
               else
                 {
-                  retval(1) = octave_value (U);
-                  if (nargout == 2) 
-                    retval(0) = octave_value (L + eye.index (perm, idx_vector::colon));
-                  else if (nargout == 3)
-                    {
-                      retval(0) = octave_value (L.index (perm, idx_vector::colon)  + eye);
-                      retval(2) = octave_value (eye.index (perm, idx_vector::colon));
-                    }
+                  retval(1) = U;
+                  retval(0) = L + eye.index (perm, idx_vector::colon);
                 }
             }
         }
+    }
+  else
+    {
+      Array <Complex> rc_norm;
+      SparseComplexMatrix sm = args(0).sparse_complex_matrix_value ();
+      param_list.append (sm);
+      nnz_u =
+        feval ("triu", param_list)(0).sparse_complex_matrix_value ().nnz ();
+      param_list.append (-1);
+      nnz_l =
+        feval ("tril", param_list)(0).sparse_complex_matrix_value ().nnz ();
+      if (milu == "row")
+        param_list(1) = "rows";
       else
+        param_list(1) = "cols";
+      rc_norm = feval ("norm", param_list)(0).complex_vector_value ();
+      Array <octave_idx_type> perm (dim_vector (sm.cols (), 1));
+      param_list.clear ();
+      SparseComplexMatrix U;
+      SparseComplexMatrix L;
+      ilu_tp < SparseComplexMatrix, Complex>
+              (sm, L, U, nnz_u, nnz_l, rc_norm.fortran_vec (), perm,
+               Complex (droptol), Complex (thresh), milu, udiag);
+
+      if (! error_state)
         {
-          Array <Complex> rc_norm;
-          SparseComplexMatrix sm = args(0).sparse_complex_matrix_value ();
-          param_list.append (sm);
-          nnz_u =  feval ("triu", param_list)(0).sparse_complex_matrix_value ().nnz (); 
-          param_list.append (-1);
-          nnz_l =  feval ("tril", param_list)(0).sparse_complex_matrix_value ().nnz (); 
+          param_list.append (octave_value (L.cols ()));
+          SparseComplexMatrix eye =
+            feval ("speye", param_list)(0).sparse_complex_matrix_value ();
           if (milu == "row")
-            param_list (1) = "rows";
+            {
+              if (nargout == 3)
+                {
+                  retval(2) = eye.index (idx_vector::colon, perm);
+                  retval(1) = U.index (idx_vector::colon, perm);
+                }
+              else if (nargout == 2)
+                retval(1) = U;
+              retval(0) = L + eye;
+            }
           else
-            param_list (1) = "cols";
-          rc_norm = feval ("norm", param_list)(0).complex_vector_value ();
-          Array <octave_idx_type> perm (dim_vector (sm.cols (), 1)); 
-          param_list.clear ();
-          SparseComplexMatrix U;
-          SparseComplexMatrix L;
-          ilu_tp < SparseComplexMatrix, Complex> 
-                  (sm, L, U, nnz_u, nnz_l, rc_norm.fortran_vec (), perm, 
-                   Complex (droptol), Complex (thresh), milu, udiag);
-
-          if (! error_state)
             {
-              param_list.append (octave_value (L.cols ()));
-              SparseComplexMatrix eye = feval ("speye",
-                                               param_list)(0).sparse_complex_matrix_value ();
-              if (milu == "row")
+              if (nargout == 3)
                 {
-                  retval(0) = octave_value (L + eye);
-                  if (nargout == 2) 
-                    retval(1) = octave_value (U);
-                  else if (nargout == 3)
-                    {
-                     retval(1) = octave_value (U.index (idx_vector::colon, perm));
-                     retval(2) = octave_value (eye.index (idx_vector::colon, perm));
-                    }
+                  retval(2) = eye.index (perm, idx_vector::colon);
+                  retval(1) = U;
+                  retval(0) = L.index (perm, idx_vector::colon) + eye;
                 }
               else
                 {
-                  retval(1) = octave_value (U);
-                  if (nargout == 2) 
-                    retval(0) = octave_value (L + eye.index (perm, idx_vector::colon)) ;
-                  else if (nargout == 3)
-                    {
-                      retval(0) = octave_value (L.index (perm, idx_vector::colon)  + eye);
-                      retval(2) = octave_value (eye.index (perm, idx_vector::colon));
-                    }
+                  retval(1) = U;
+                  retval(0) = L + eye.index (perm, idx_vector::colon);
                 }
             }
         }
-
     }
 
   return retval;
@@ -1162,3 +1098,4 @@
 ## No test needed for internal helper function.
 %!assert (1)
 */
+
--- a/libinterp/dldfcn/chol.cc	Mon Aug 18 12:32:16 2014 +0100
+++ b/libinterp/dldfcn/chol.cc	Tue Aug 26 15:27:21 2014 -0700
@@ -135,7 +135,7 @@
 \n\
 In general the lower triangular factorization is significantly faster for\n\
 sparse matrices.\n\
-@seealso{hess, lu, qr, qz, schur, svd, cholinv, chol2inv, cholupdate, cholinsert, choldelete, cholshift}\n\
+@seealso{hess, lu, qr, qz, schur, svd, ichol, cholinv, chol2inv, cholupdate, cholinsert, choldelete, cholshift}\n\
 @end deftypefn")
 {
   octave_value_list retval;
--- a/scripts/help/__unimplemented__.m	Mon Aug 18 12:32:16 2014 +0100
+++ b/scripts/help/__unimplemented__.m	Tue Aug 26 15:27:21 2014 -0700
@@ -650,8 +650,6 @@
   "hgexport",
   "hgsetget",
   "hgtransform",
-  "ichol",
-  "ilu",
   "im2frame",
   "im2java",
   "imapprox",
--- a/scripts/sparse/ichol.m	Mon Aug 18 12:32:16 2014 +0100
+++ b/scripts/sparse/ichol.m	Tue Aug 26 15:27:21 2014 -0700
@@ -1,335 +1,273 @@
+## Copyright (C) 2014 Eduardo Ramos Fernández <eduradical951@gmail.com>
 ## Copyright (C) 2013 Kai T. Ohlhus <k.ohlhus@gmail.com>
-## Copyright (C) 2014 Eduardo Ramos Fernández <eduradical951@gmail.com>
 ## 
 ## This file is part of Octave.
-## 
-## Octave is free software; you can redistribute it and/or modify it under the
-## terms of the GNU General Public License as published by the Free Software
-## Foundation; either version 3 of the License, or (at your option) any later
-## version.
-## 
-## Octave is distributed in the hope that it will be useful, but WITHOUT ANY
-## WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
-## FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
-## details.
-## 
-## You should have received a copy of the GNU General Public License along with
-## Octave; see the file COPYING. If not, see <http://www.gnu.org/licenses/>.
+##
+## Octave is free software; you can redistribute it and/or modify it
+## under the terms of the GNU General Public License as published by
+## the Free Software Foundation; either version 3 of the License, or (at
+## your option) any later version.
+##
+## Octave is distributed in the hope that it will be useful, but
+## WITHOUT ANY WARRANTY; without even the implied warranty of
+## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+## General Public License for more details.
+##
+## You should have received a copy of the GNU General Public License
+## along with Octave; see the file COPYING.  If not, see
+## <http://www.gnu.org/licenses/>.
 
 ## -*- texinfo -*-
-## @deftypefn  {Function File} ichol (@var{A}, @var{opts})
+## @deftypefn  {Function File} {@var{L} =} ichol (@var{A})
 ## @deftypefnx {Function File} {@var{L} =} ichol (@var{A}, @var{opts})
 ##
-## @code{@var{L} = ichol (@var{A})} performs the incomplete Cholesky
-## factorization of A with zero-fill.
+## Compute the incomplete Cholesky factorization of the sparse square matrix
+## @var{A} with zero-fill.
 ##
-## @code{@var{L} = ichol (@var{A}, @var{opts})} performs the incomplete Cholesky
-## factorization of A with options specified by opts.
-##
-## By default, ichol references the lower triangle of A and produces lower
-## triangular factors.
+## By default, ichol references the lower triangle of @var{A} and produces
+## lower triangular factors.
 ##
 ## The factor given by this routine may be useful as a preconditioner for a
 ## system of linear equations being solved by iterative methods such as
-## PCG (Preconditioned conjugate gradient).
-##
-## ichol works only for sparse square matrices.
+## PCG (Preconditioned Conjugate Gradient).
 ##
-## The fields of @var{opts} must be named exactly as shown below. You can
-## include any number of these fields in the structure and define them in any
-## order. Any additional fields are ignored. Names and specifiers are case
-## sensitive.
+## The factorization may be modified by passing options in a structure
+## @var{opts}.  The option name is a field in the structure and the setting
+## is the value of field.  Names and specifiers are case sensitive.
 ##
 ## @table @asis
 ## @item type
 ## Type of factorization.
-## String indicating which flavor of incomplete Cholesky to perform. Valid
-## values of this field are @samp{nofill} and @samp{ict}. The
-## @samp{nofill} variant performs incomplete Cholesky with zero-fill [IC(0)].
-## The @samp{ict} variant performs incomplete Cholesky with threshold dropping
-## [ICT]. The default value is @samp{nofill}.
+## String indicating which flavor of incomplete Cholesky to perform.  Valid
+## values of this field are @qcode{"nofill"} and @qcode{"ict"}.  The
+## @qcode{"nofill"} variant performs incomplete Cholesky with zero-fill
+## [IC(0)].  The @qcode{"ict"} variant performs incomplete Cholesky with
+## threshold dropping [ICT].  The default value is @qcode{"nofill"}.
 ##
 ## @item droptol
-## Drop tolerance when type is @samp{ict}.
-## Nonnegative scalar used as a drop tolerance when performing ICT. Elements
+## Drop tolerance when type is @qcode{"ict"}.
+## Non-negative scalar used as a drop tolerance when performing ICT@.  Elements
 ## which are smaller in magnitude than a local drop tolerance are dropped from
 ## the resulting factor except for the diagonal element which is never dropped.
 ## The local drop tolerance at step j of the factorization is
-## @code{norm (@var{A}(j:end, j), 1) * droptol}. @samp{droptol} is ignored if
-## @samp{type} is @samp{nofill}. The default value is 0.
+## @code{norm (@var{A}(j:end, j), 1) * droptol}.  @code{droptol} is ignored if
+## @code{type} is @qcode{"nofill"}.  The default value is 0.
 ##
 ## @item michol
-## Indicates whether to perform modified incomplete Cholesky.
-## Indicates whether or not modified incomplete Cholesky [MIC] is performed.
-## The field may be @samp{on} or @samp{off}. When performing MIC, the diagonal
-## is compensated for dropped elements to enforce the relationship
+## Indicate whether modified incomplete Cholesky [MIC] is performed.
+## The field may be @qcode{"on"} or @qcode{"off"}.  When performing MIC, the
+## diagonal is compensated for dropped elements to enforce the relationship
 ## @code{@var{A} * @var{e} = @var{L} * @var{L}' * @var{e}} where
-## @code{@var{e} = ones (size (@var{A}, 2), 1))}. The default value is
-## @samp{off}.
+## @code{@var{e} = ones (columns (@var{A}), 1)}.  The default value is
+## @qcode{"off"}.
 ##
 ## @item diagcomp
 ## Perform compensated incomplete Cholesky with the specified coefficient.
-## Real nonnegative scalar used as a global diagonal shift @code{@var{alpha}}
-## in forming the incomplete Cholesky factor. That is, instead of performing
-## incomplete Cholesky on @code{@var{A}}, the factorization of
-## @code{@var{A} + @var{alpha} * diag (diag (@var{A}))} is formed. The default
-## value is 0.
+## The coefficient is a real non-negative scalar used as a global diagonal
+## shift @code{@var{alpha}} in forming the incomplete Cholesky factor.  That
+## is, instead of performing incomplete Cholesky on @code{@var{A}}, the
+## factorization of @code{@var{A} + @var{alpha} * diag (diag (@var{A}))} is
+## formed.  The default value is 0.
 ##
 ## @item shape
-## Determines which triangle is referenced and returned.
-## Valid values are @samp{upper} and @samp{lower}. If @samp{upper} is specified,
-## only the upper triangle of @code{@var{A}} is referenced and @code{@var{R}}
-## is constructed such that @code{@var{A}} is approximated by
-## @code{@var{R}' * @var{R}}. If @samp{lower} is specified, only the lower
-## triangle of @code{@var{A}} is referenced and @code{@var{L}} is constructed
-## such that @code{@var{A}} is approximated by @code{@var{L} * @var{L}'}. The
-## default value is @samp{lower}.
+## Determine which triangle is referenced and returned.
+## Valid values are @qcode{"upper"} and @qcode{"lower"}.  If @qcode{"upper"}
+## is specified, only the upper triangle of @code{@var{A}} is referenced and
+## @code{@var{R}} is constructed such that @code{@var{A}} is approximated by
+## @code{@var{R}' * @var{R}}.  If @qcode{"lower"} is specified, only the
+## lower triangle of @code{@var{A}} is referenced and @code{@var{L}} is
+## constructed such that @code{@var{A}} is approximated by @code{@var{L} *
+## @var{L}'}.  The default value is @qcode{"lower"}.
 ## @end table
 ##
-## EXAMPLES
+## Examples
 ##
 ## The following problem demonstrates how to factorize a sample symmetric
 ## positive definite matrix with the full Cholesky decomposition and with the
 ## incomplete one.
 ##
 ## @example
+## @group
 ## A = [ 0.37, -0.05,  -0.05,  -0.07;
 ##      -0.05,  0.116,  0.0,   -0.05;
 ##      -0.05,  0.0,    0.116, -0.05;
 ##      -0.07, -0.05,  -0.05,   0.202];
-## A = sparse(A);
-## nnz(tril (A))
+## A = sparse (A);
+## nnz (tril (A))
 ## ans =  9
-## L = chol(A, "lower");
+## L = chol (A, "lower");
 ## nnz (L)
 ## ans =  10
 ## norm (A - L * L', "fro") / norm (A, "fro")
 ## ans =  1.1993e-16
-## opts.type = 'nofill';
-## L = ichol(A,opts);
+## opts.type = "nofill";
+## L = ichol (A, opts);
 ## nnz (L)
 ## ans =  9
 ## norm (A - L * L', "fro") / norm (A, "fro")
 ## ans =  0.019736
+## @end group
 ## @end example
 ##
-## Another example for decomposition is finite difference matrix to solve a
-## boundary value problem on the unit square.
+## Another example for decomposition is a finite difference matrix used to
+## solve a boundary value problem on the unit square.
 ##
 ## @example
+## @group
 ## nx = 400; ny = 200;
 ## hx = 1 / (nx + 1); hy = 1 / (ny + 1);
-## Dxx = spdiags ([ones(nx, 1), -2 * ones(nx, 1), ones(nx, 1)], [-1 0 1 ], nx, nx) / (hx ^ 2);
-## Dyy = spdiags ([ones(ny, 1), -2 * ones(ny, 1), ones(ny, 1)], [-1 0 1 ], ny, ny) / (hy ^ 2);
+## Dxx = spdiags ([ones(nx, 1), -2*ones(nx, 1), ones(nx, 1)],
+##                [-1 0 1 ], nx, nx) / (hx ^ 2);
+## Dyy = spdiags ([ones(ny, 1), -2*ones(ny, 1), ones(ny, 1)],
+##                [-1 0 1 ], ny, ny) / (hy ^ 2);
 ## A = -kron (Dxx, speye (ny)) - kron (speye (nx), Dyy);
 ## nnz (tril (A))
 ## ans =  239400
-## opts.type = 'nofill';
+## opts.type = "nofill";
 ## L = ichol (A, opts);
 ## nnz (tril (A))
 ## ans =  239400
 ## norm (A - L * L', "fro") / norm (A, "fro")
 ## ans =  0.062327
+## @end group
 ## @end example
 ##
-## References for the implemented algorithms:
+## References for implemented algorithms:
 ##
-## [1] Saad, Yousef. "Preconditioning Techniques." Iterative Methods for Sparse Linear
-## Systems. PWS Publishing Company, 1996.
+## [1] @nospell{Y. Saad}. "Preconditioning Techniques." @cite{Iterative
+## Methods for Sparse Linear Systems}, PWS Publishing Company, 1996.
 ##
-## [2] Jones, Mark T. and Plassmann, Paul E.: An Improved Incomplete Cholesky
-## Factorization (1992).
+## [2] @nospell{M. Jones, P. Plassmann}: @cite{An Improved Incomplete
+## Cholesky Factorization}, 1992.
+## @seealso{chol, ilu, pcg}
 ## @end deftypefn
 
-function [L] = ichol (A, opts)
+function L = ichol (A, opts = struct ())
 
-  if ((nargin > 2) || (nargin < 1) || (nargout > 1))
+  if (nargin < 1 || nargin > 2 || nargout > 1)
     print_usage ();
   endif
 
-  % Check input matrix
-  if (~issparse(A) || ~issquare (A))
-    error ("ichol: Input A must be a non-empty sparse square matrix");
+  if (! (issparse (A) && issquare (A)))
+    error ("ichol: A must be a sparse square matrix");
   endif
 
-  % If A is empty and sparse then return empty L
-  % Compatibility with Matlab
+  if (! isstruct (opts))
+    error ("ichol: OPTS must be a structure.");
+  endif
+
+  ## If A is empty then return empty L for Matlab compatibility
   if (isempty (A)) 
     L = A;
     return;
   endif
 
-  % Check input structure, otherwise set default values
-  if (nargin == 2)
-    if (~isstruct (opts))
-      error ("ichol: Input \"opts\" must be a valid structure.");
-    endif
-  else
-    opts = struct ();
-  endif
-
-  if (~isfield (opts, "type"))
-    opts.type = "nofill"; % set default
+  ## Parse input options
+  if (! isfield (opts, "type"))
+    opts.type = "nofill";  # set default
   else
     type = tolower (getfield (opts, "type"));
-    if ((strcmp (type, "nofill") == 0)
-        && (strcmp (type, "ict") == 0))
-      error ("ichol: Invalid field \"type\" in input structure.");
-    else
-      opts.type = type;
+    if (! strcmp (type, "nofill") && ! strcmp (type, "ict"))
+      error ('ichol: TYPE must be "nofill" or "ict"');
     endif
+    opts.type = type;
   endif
 
-  if (~isfield (opts, "droptol"))
-    opts.droptol = 0; % set default
+  if (! isfield (opts, "droptol"))
+    opts.droptol = 0;      # set default
   else
-    if (~isscalar (opts.droptol) || (opts.droptol < 0))
-      error ("ichol: Invalid field \"droptol\" in input structure.");
+    if (! (isreal (opts.droptol) && isscalar (opts.droptol)
+           && opts.droptol >= 0))
+      error ("ichol: DROPTOL must be a non-negative real scalar");
     endif
   endif
 
   michol = "";
-  if (~isfield (opts, "michol"))
-    opts.michol = "off"; % set default
+  if (! isfield (opts, "michol"))
+    opts.michol = "off";   # set default
   else
     michol = tolower (getfield (opts, "michol"));
-    if ((strcmp (michol, "off") == 0) 
-        && (strcmp (michol, "on") == 0))
-      error ("ichol: Invalid field \"michol\" in input structure.");
-    else
-      opts.michol = michol;
+    if (! strcmp (michol, "off") && ! strcmp (michol, "on"))
+      error ('ichol: MICHOL must be "on" or "off"');
+    endif
+    opts.michol = michol;
+  endif
+
+  if (! isfield (opts, "diagcomp"))
+    opts.diagcomp = 0;     # set default
+  else
+    if (! (isreal (opts.diagcomp) && isscalar (opts.diagcomp)
+           && opts.diagcomp >= 0))
+      error ("ichol: DIAGCOMP must be a non-negative real scalar");
     endif
   endif
 
-  if (~isfield (opts, "diagcomp"))
-    opts.diagcomp = 0; % set default
+  if (! isfield (opts, "shape"))
+    opts.shape = "lower";  # set default
   else
-    if (~isscalar (opts.diagcomp) || (opts.diagcomp < 0))
-      error ("ichol: Invalid field \"diagcomp\" in input structure.");
+    shape = tolower (getfield (opts, "shape"));
+    if (! strcmp (shape, "lower") && ! strcmp (shape, "upper"))
+      error ('ichol: SHAPE must be "lower" or "upper"');
     endif
+    opts.shape = shape;
   endif
 
-  if (~isfield (opts, "shape"))
-    opts.shape = "lower"; % set default
-  else
-    shape = tolower (getfield (opts, "shape"));
-    if ((strcmp (shape, "lower") == 0) 
-        && (strcmp (shape, "upper") == 0))
-      error ("ichol: Invalid field \"shape\" in input structure.");
-    else
-      opts.shape = shape;
-    endif
-  endif
-
-  % Prepare input for specialized ICHOL
+  ## Prepare input for specialized ICHOL
   A_in = [];
   if (opts.diagcomp > 0)
     A += opts.diagcomp * diag (diag (A));
   endif
-  if (strcmp (opts.shape, "upper") == 1)
+  if (strcmp (opts.shape, "upper"))
     A_in = triu (A);
     A_in = A_in';
   else
     A_in = tril (A);
   endif
 
-  % Delegate to specialized ICHOL
+  ## Delegate to specialized ICHOL
   switch (opts.type)
     case "nofill"
       L  = __ichol0__ (A_in, opts.michol);
     case "ict"
       L = __icholt__ (A_in, opts.droptol, opts.michol);
-    otherwise
-      printf ("The input structure is invalid.\n");
   endswitch
 
-  if (strcmp (opts.shape, "upper") == 1)
+  if (strcmp (opts.shape, "upper"))
     L = L';
   endif
   
+endfunction
 
-endfunction
 
 %!shared A1, A2, A3, A4, A5, A6, A7
 %! A1 = [ 0.37, -0.05,  -0.05,  -0.07;
-%!      -0.05,  0.116,  0.0,   -0.05;
-%!      -0.05,  0.0,    0.116, -0.05;
-%!      -0.07, -0.05,  -0.05,   0.202];
-%! A1 = sparse(A1);
-%! A2 = gallery ('poisson', 30);
-%! A3 = gallery ('tridiag', 50);
+%!       -0.05,  0.116,  0.0,   -0.05;
+%!       -0.05,  0.0,    0.116, -0.05;
+%!       -0.07, -0.05,  -0.05,   0.202];
+%! A1 = sparse (A1);
+%! A2 = gallery ("poisson", 30);
+%! A3 = gallery ("tridiag", 50);
 %! nx = 400; ny = 200;
 %! hx = 1 / (nx + 1); hy = 1 / (ny + 1);
-%! Dxx = spdiags ([ones(nx, 1), -2 * ones(nx, 1), ones(nx, 1)], [-1 0 1 ], nx, nx) / (hx ^ 2);
-%! Dyy = spdiags ([ones(ny, 1), -2 * ones(ny, 1), ones(ny, 1)], [-1 0 1 ], ny, ny) / (hy ^ 2);
+%! Dxx = spdiags ([ones(nx, 1), -2*ones(nx, 1), ones(nx, 1)],
+%!                [-1 0 1 ], nx, nx) / (hx ^ 2);
+%! Dyy = spdiags ([ones(ny, 1), -2*ones(ny, 1), ones(ny, 1)],
+%!                [-1 0 1 ], ny, ny) / (hy ^ 2);
 %! A4 = -kron (Dxx, speye (ny)) - kron (speye (nx), Dyy);
-%! A5 = [ 0.37, -0.05,          -0.05,  -0.07;
-%!        -0.05,  0.116,          0.0,   -0.05 + 0.05i;
-%!        -0.05,  0.0,            0.116, -0.05;
-%!        -0.07, -0.05 - 0.05i,  -0.05,   0.202];
-%! A5 = sparse(A5);
-%! A6 = [ 0.37,    -0.05 - i, -0.05,  -0.07;
-%!        -0.05 + i, 0.116,     0.0,   -0.05;
-%!        -0.05,     0.0,       0.116, -0.05;
-%!        -0.07,    -0.05,     -0.05,   0.202];
-%! A6 = sparse(A6);
+%! A5 = [ 0.37, -0.05,         -0.05,  -0.07;
+%!       -0.05,  0.116,         0.0,   -0.05 + 0.05i;
+%!       -0.05,  0.0,           0.116, -0.05;
+%!       -0.07, -0.05 - 0.05i, -0.05,   0.202];
+%! A5 = sparse (A5);
+%! A6 = [ 0.37,     -0.05 - i, -0.05,  -0.07;
+%!       -0.05 + i,  0.116,     0.0,   -0.05;
+%!       -0.05,      0.0,       0.116, -0.05;
+%!       -0.07,     -0.05,     -0.05,   0.202];
+%! A6 = sparse (A6);
 %! A7 = A5;
 %! A7(1) = 2i;
-%!
 
-%!# Input validation tests
-
-%!test
-%!error ichol ([]);
-%!error ichol (0);
-%!error ichol (-0);
-%!error ichol (1);
-%!error ichol (-1);
-%!error ichol (i);
-%!error ichol (-i);
-%!error ichol (1 + 1i);
-%!error ichol (1 - 1i);
-%!error ichol (sparse (0));
-%!error ichol (sparse (-0));
-%!error ichol (sparse (-1));
-%!error ichol (sparse (-1));
-%!test
-%! opts.milu = 'foo';
-%!error L = ichol (A1, opts);
-%! opts.milu = 1;
-%!error L = ichol (A1, opts);
-%! opts.milu = [];
-%!error L = ichol (A1, opts);
-%!test
-%! opts.droptol = -1;
-%!error L = ichol (A1, opts);
-%! opts.droptol = 0.5i;
-%!error L = ichol (A1, opts);
-%! opts.droptol = [];
-%!error L = ichol (A1, opts);
-%!test
-%! opts.type = 'foo';
-%!error L = ichol (A1, opts);
-%! opts.type = 1;
-%!error L = ichol (A1, opts);
-%! opts.type = [];
-%!error L = ichol (A1, opts);
-%!test
-%! opts.shape = 'foo';
-%!error L = ichol (A1, opts);
-%! opts.shape = 1;
-%!error L = ichol (A1, opts);
-%! opts.shape = [];
-%!error L = ichol (A1, opts);
-%!test
-%! opts.diagcomp = -1;
-%!error L = ichol (A1, opts);
-%! opts.diagcomp = 0.5i;
-%!error L = ichol (A1, opts);
-%! opts.diagcomp = [];
-%!error L = ichol (A1, opts);
-
-%!# ICHOL0 tests
+## ICHOL0 tests
 
 %!test
 %! opts.type = "nofill";
@@ -401,13 +339,14 @@
 %! opts.michol = "on";
 %! L = ichol (A5, opts);
 %! assert (norm (A5 - L*L', "fro") / norm (A5, "fro"), 0.0276, 1e-4);
-%!test
-%% Negative pivot 
-%!error ichol (A6);
-%% Complex entry in the diagonal
-%!error ichol (A7);
 
-%%!ICHOLT tests
+## Negative pivot 
+%!error <negative pivot> ichol (A6)
+%!error ichol (A6)
+## Complex entry in the diagonal
+%!error <non-real pivot> ichol (A7)
+
+## ICHOLT tests
  
 %%!test
 %! opts.type = "ict";
@@ -475,9 +414,47 @@
 %! opts.michol = "on";
 %! L = ichol (A5, opts);
 %! assert (norm (A5 - L*L', "fro") / norm (A5, "fro"), 0.3231, 1e-4);
+
+%% Input validation tests
+
+%!error <A must be a sparse square matrix> ichol ([])
+%!error <A must be a sparse square matrix> ichol (0)
+%!error <pivot equal to 0> ichol (sparse (0))
+%!error <pivot equal to 0> ichol (sparse (-0))
+%!error <negative pivot> ichol (sparse (-1))
 %!test
-%% Negative pivot 
-%! opts.type = "ict";
-%!error ichol (A6, setup);
-%% Complex entry in the diagonal
-%!error ichol (A7, setup);
+%! opts.type = "foo";
+%! fail ("ichol (A1, opts)", 'TYPE must be "nofill"');
+%! opts.type = 1;
+%! fail ("ichol (A1, opts)", 'TYPE must be "nofill"');
+%! opts.type = [];
+%! fail ("ichol (A1, opts)", 'TYPE must be "nofill"');
+%!test
+%! opts.droptol = -1;
+%! fail ("ichol (A1, opts)", "DROPTOL must be a non-negative real scalar");
+%! opts.droptol = 0.5i;
+%! fail ("ichol (A1, opts)", "DROPTOL must be a non-negative real scalar");
+%! opts.droptol = [];
+%! fail ("ichol (A1, opts)", "DROPTOL must be a non-negative real scalar");
+%!test
+%! opts.michol = "foo";
+%! fail ("ichol (A1, opts)", 'MICHOL must be "on"');
+%! opts.michol = 1;
+%! fail ("ichol (A1, opts)", 'MICHOL must be "on"');
+%! opts.michol = [];
+%! fail ("ichol (A1, opts)", 'MICHOL must be "on"');
+%!test
+%! opts.diagcomp = -1;
+%! fail ("ichol (A1, opts)", "DIAGCOMP must be a non-negative real scalar");
+%! opts.diagcomp = 0.5i;
+%! fail ("ichol (A1, opts)", "DIAGCOMP must be a non-negative real scalar");
+%! opts.diagcomp = [];
+%! fail ("ichol (A1, opts)", "DIAGCOMP must be a non-negative real scalar");
+%!test
+%! opts.shape = "foo";
+%! fail ("ichol (A1, opts)", 'SHAPE must be "lower"');
+%! opts.shape = 1;
+%! fail ("ichol (A1, opts)", 'SHAPE must be "lower"');
+%! opts.shape = [];
+%! fail ("ichol (A1, opts)", 'SHAPE must be "lower"');
+
--- a/scripts/sparse/ilu.m	Mon Aug 18 12:32:16 2014 +0100
+++ b/scripts/sparse/ilu.m	Tue Aug 26 15:27:21 2014 -0700
@@ -1,96 +1,103 @@
+## Copyright (C) 2014 Eduardo Ramos Fernández <eduradical951@gmail.com>
 ## Copyright (C) 2013 Kai T. Ohlhus <k.ohlhus@gmail.com>
-## Copyright (C) 2014 Eduardo Ramos Fernández <eduradical951@gmail.com>
-##
 ## 
 ## This file is part of Octave.
-## 
-## Octave is free software; you can redistribute it and/or modify it under the
-## terms of the GNU General Public License as published by the Free Software
-## Foundation; either version 3 of the License, or (at your option) any later
-## version.
-## 
-## Octave is distributed in the hope that it will be useful, but WITHOUT ANY
-## WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
-## FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
-## details.
-## 
-## You should have received a copy of the GNU General Public License along with
-## Octave; see the file COPYING. If not, see <http://www.gnu.org/licenses/>.
-
+##
+## Octave is free software; you can redistribute it and/or modify it
+## under the terms of the GNU General Public License as published by
+## the Free Software Foundation; either version 3 of the License, or (at
+## your option) any later version.
+##
+## Octave is distributed in the hope that it will be useful, but
+## WITHOUT ANY WARRANTY; without even the implied warranty of
+## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+## General Public License for more details.
+##
+## You should have received a copy of the GNU General Public License
+## along with Octave; see the file COPYING.  If not, see
+## <http://www.gnu.org/licenses/>.
+##
 ## -*- texinfo -*-
-## @deftypefn  {Function File} ilu (@var{A}, @var{setup})
-## @deftypefnx {Function File} {[@var{L}, @var{U}] =} ilu (@var{A}, @var{setup})
-## @deftypefnx {Function File} {[@var{L}, @var{U}, @var{P}] =} ilu (@var{A}, @var{setup})
-## ilu produces a unit lower triangular matrix, an upper triangular matrix, and
-## a permutation matrix.
+## @deftypefn  {Function File} {@var{L}, @var{U}] =} ilu (@var{A})
+## @deftypefnx {Function File} {@var{L}, @var{U}] =} ilu (@var{A}, @var{opts})
+## @deftypefnx {Function File} {[@var{L}, @var{U}, @var{P}] =} ilu (@dots{})
+##
+## Compute the incomplete LU factorization of the sparse square matrix @var{A}
+## into a unit lower triangular matrix (@var{L}), an upper triangular matrix
+## (@var{U}), and a permutation matrix (@var{P}).
 ##
-## These incomplete factorizations may be useful as preconditioners for a system
-## of linear equations being solved by iterative methods such as BICG
-## (BiConjugate Gradients), GMRES (Generalized Minimum Residual Method).
+## These incomplete factorizations may be useful as preconditioners for a
+## system of linear equations being solved by iterative methods such as BICG
+## (BiConjugate Gradients) or GMRES (Generalized Minimum Residual Method).
 ##
-## @code{ilu (@var{A}, @var{setup})} computes the incomplete LU factorization
-## of @var{A}. @var{setup} is an input structure with up to five setup options.
-## The fields must be named exactly as shown below. You can include any number
-## of these fields in the structure and define them in any order. Any
-## additional fields are ignored.
+## The factorization may be modified by passing options in a structure
+## @var{opts}.  The option name is a field in the structure and the setting
+## is the value of field.  Names and specifiers are case sensitive.
+##
+## @table @code
+## @item type
+## Type of factorization.  Values for type include:
 ##
 ## @table @asis
-## @item type
-## Type of factorization. Values for type include:
+## @item @qcode{"nofill"}
+## Perform ILU factorization with 0 level of fill in, known as ILU(0).  With
+## type set to @qcode{"nofill"}, only the @code{milu} option is used; all other
+## fields are ignored.
 ##
-## @table @asis
-## @item @samp{nofill}
-## Performs ILU factorization with 0 level of fill in, known as ILU(0). With
-## type set to @samp{nofill}, only the milu setup option is used; all other
-## fields are ignored.
-## @item @samp{crout}
-## Performs the Crout version of ILU factorization, known as ILUC. With type
-## set to @samp{crout}, only the droptol and milu setup options are used; all
-## other fields are ignored.
-## @item @samp{ilutp}
+## @item @qcode{"crout"}
+## Perform the Crout version of ILU factorization, known as ILUC@.  With type
+## set to @qcode{crout}, only the @code{droptol} and @code{milu} options are
+## used; all other fields are ignored.
+##
+## @item @qcode{"ilutp"}
 ## (default) Performs ILU factorization with threshold and pivoting.
 ## @end table
 ##
 ## If type is not specified, the ILU factorization with pivoting ILUTP is
-## performed. Pivoting is never performed with type set to @samp{nofill} or
-## @samp{crout}.
+## performed.  Pivoting is never performed with type set to @qcode{"nofill"} or
+## @qcode{"crout"}.
 ##
 ## @item droptol
-## Drop tolerance of the incomplete LU factorization. droptol is a non-negative
-## scalar. The default value is 0, which produces the complete LU factorization.
+## Drop tolerance of the incomplete LU factorization.  @code{droptol} is a
+## non-negative scalar.  The default value is 0, which produces the complete
+## LU factorization.
 ##
-## The nonzero entries of U satisfy
+## The nonzero entries of @var{U} satisfy
 ##
 ## @code{abs (@var{U}(i,j)) >= droptol * norm ((@var{A}:,j))}
 ##
 ## with the exception of the diagonal entries, which are retained regardless of
-## satisfying the criterion. The entries of @var{L} are tested against the
+## satisfying the criterion.  The entries of @var{L} are tested against the
 ## local drop tolerance before being scaled by the pivot, so for nonzeros in
 ## @var{L}
 ##
-## @code{abs(@var{L}(i,j)) >= droptol * norm(@var{A}(:,j))/@var{U}(j,j)}.
+## @code{abs (@var{L}(i,j)) >= droptol * norm (@var{A}(:,j))/@var{U}(j,j)}.
 ##
 ## @item milu
-## Modified incomplete LU factorization. Values for milu
+## Modified incomplete LU factorization.  Values for @code{milu}
 ## include:
+##
 ## @table @asis
-## @item @samp{row}
-## Produces the row-sum modified incomplete LU factorization. Entries from the
+## @item @qcode{"row"}
+## Produces the row-sum modified incomplete LU factorization.  Entries from the
 ## newly-formed column of the factors are subtracted from the diagonal of the
-## upper triangular factor, @var{U}, preserving column sums. That is,
+## upper triangular factor, @var{U}, preserving column sums.  That is,
 ## @code{@var{A} * e = @var{L} * @var{U} * e}, where e is the vector of ones.
-## @item @samp{col}
-## Produces the column-sum modified incomplete LU factorization. Entries from
+##
+## @item @qcode{"col"}
+## Produces the column-sum modified incomplete LU factorization.  Entries from
 ## the newly-formed column of the factors are subtracted from the diagonal of
-## the upper triangular factor, @var{U}, preserving column sums. That is,
+## the upper triangular factor, @var{U}, preserving column sums.  That is,
 ## @code{e'*@var{A} = e'*@var{L}*@var{U}}.
-## @item @samp{off}
+##
+## @item @qcode{"off"}
 ## (default) No modified incomplete LU factorization is produced.
 ## @end table
 ##
 ## @item udiag
-## If udiag is 1, any zeros on the diagonal of the upper
-## triangular factor are replaced by the local drop tolerance. The default is 0.
+## If @code{udiag} is 1, any zeros on the diagonal of the upper
+## triangular factor are replaced by the local drop tolerance.  The default
+## is 0.
 ##
 ## @item thresh
 ## Pivot threshold between 0 (forces diagonal pivoting) and 1,
@@ -103,161 +110,151 @@
 ## lower triangular matrix and @var{U} is an upper triangular matrix.
 ##
 ## @code{[@var{L}, @var{U}] = ilu (@var{A},@var{setup})} returns a unit lower
-## triangular matrix in @var{L} and an upper triangular matrix in @var{U}. When
-## SETUP.type = 'ilutp', the role of @var{P} is determined by the value of
-## SETUP.milu. For SETUP.type == 'ilutp', one of the factors is permuted
-## based on the value of SETUP.milu. When SETUP.milu == 'row', U is a column 
-## permuted upper triangular factor. Otherwise, L is a row-permuted unit lower 
-## triangular factor.
+## triangular matrix in @var{L} and an upper triangular matrix in @var{U}.  When
+## SETUP.type = @qcode{"ilutp"}, the role of @var{P} is determined by the
+## value of SETUP.milu.  For SETUP.type == @qcode{"ilutp"}, one of the
+## factors is permuted based on the value of SETUP.milu.  When SETUP.milu ==
+## @qcode{"row"}, U is a column permuted upper triangular factor.  Otherwise,
+## L is a row-permuted unit lower triangular factor.
 ##
 ## @code{[@var{L}, @var{U}, @var{P}] = ilu (@var{A},@var{setup})} returns a
 ## unit lower triangular matrix in @var{L}, an upper triangular matrix in
-## @var{U}, and a permutation matrix in @var{P}. When SETUP.milu ~= 'row', @var{P} 
-## is returned such that @var{L} and @var{U} are incomplete factors of @var{P}*@var{A}.
-## When SETUP.milu == 'row', @var{P} is returned such that and @var{U} are 
-## incomplete factors of A*P.
+## @var{U}, and a permutation matrix in @var{P}.  When @code{milu} ! =
+## @qcode{"row"}, @var{P} is returned such that @var{L} and @var{U} are
+## incomplete factors of @var{P}*@var{A}.  When @code{milu} == @qcode{"row"},
+## @var{P} is returned such that and @var{U} are incomplete factors of A*P.
 ##
-## @strong{NOTE}: ilu works on sparse square matrices only.
-##
-## EXAMPLES
+## Examples
 ##
 ## @example
-## A = gallery('neumann', 1600) + speye(1600);
-## setup.type = 'nofill';
-## nnz(A)
+## @group
+## A = gallery ("neumann", 1600) + speye (1600);
+## opts.type = "nofill";
+## nnz (A)
 ## ans = 7840
 ##
-## nnz(lu(A))
+## nnz (lu (A))
 ## ans = 126478
 ##
-## nnz(ilu(A,setup))
+## nnz (ilu (A, opts))
 ## ans = 7840
+## @end group
 ## @end example
 ##
 ## This shows that @var{A} has 7840 nonzeros, the complete LU factorization has
 ## 126478 nonzeros, and the incomplete LU factorization, with 0 level of
-## fill-in, has 7840 nonzeros, the same amount as @var{A}. Taken from:
+## fill-in, has 7840 nonzeros, the same amount as @var{A}.  Taken from:
 ## http://www.mathworks.com/help/matlab/ref/ilu.html
 ##
 ## @example
-## A = gallery ('wathen', 10, 10);
-## b = sum (A,2); 
+## @group
+## A = gallery ("wathen", 10, 10);
+## b = sum (A, 2); 
 ## tol = 1e-8; 
 ## maxit = 50;
-## opts.type = 'crout';
+## opts.type = "crout";
 ## opts.droptol = 1e-4;
 ## [L, U] = ilu (A, opts);
 ## x = bicg (A, b, tol, maxit, L, U);
-## norm(A * x - b, inf)
+## norm (A * x - b, inf)
+## @end group
 ## @end example
 ##
 ## This example uses ILU as preconditioner for a random FEM-Matrix, which has a
-## bad condition. Without @var{L} and @var{U} BICG would not converge.
+## large condition number.  Without @var{L} and @var{U} BICG would not converge.
 ##
+## @seealso{lu, ichol, bicg, gmres}
 ## @end deftypefn
 
-function [L, U, P] = ilu (A, setup)
+function [L, U, P] = ilu (A, opts = struct ())
 
-  if ((nargin > 2) || (nargin < 1) || (nargout > 3))
+  if (nargin < 1 || nargin > 2 || (nargout > 3))
     print_usage ();
   endif
 
-
-  % Check input matrix
-  if (~issparse (A) || ~issquare (A))
-    error ("ilu: Input A must be a sparse square matrix.");
+  if (! (issparse (A) && issquare (A)))
+    error ("ichol: A must be a sparse square matrix");
   endif
 
-  % If A is empty and sparse then return empty L, U and P
-  % Compatibility with Matlab
+  if (! isstruct (opts))
+    error ("ichol: OPTS must be a structure.");
+  endif
+
+  ## If A is empty then return empty L, U and P for Matlab compatibility
   if (isempty (A)) 
-    L = A;
-    U = A;
-    P = A;
+    L = U = P = A;
     return;
   endif
 
-  % Check input structure, otherwise set default values
-  if (nargin == 2)
-    if (~isstruct (setup))
-      error ("ilu: Input 'setup' must be a valid structure.");
+  ## Parse input options
+  if (! isfield (opts, "type"))
+    opts.type = "nofill";  # set default
+  else
+    type = tolower (getfield (opts, "type"));
+    if (! any (strcmp (type, {"nofill", "crout", "ilutp"})))
+      error ("ilu: invalid TYPE specified");
     endif
-  else
-    setup = struct ();
+    opts.type = type;
   endif
 
-  if (~isfield (setup, "type"))
-    setup.type = "nofill"; % set default
+  if (! isfield (opts, "droptol"))
+    opts.droptol = 0;      # set default
   else
-    type = tolower (getfield (setup, "type"));
-    if ((strcmp (type, "nofill") == 0)
-        && (strcmp (type, "crout") == 0)
-        && (strcmp (type, "ilutp") == 0))
-      error ("ilu: Invalid field \"type\" in input structure.");
-    else
-      setup.type = type;
+    if (! (isreal (opts.droptol) && isscalar (opts.droptol)
+           && opts.droptol >= 0))
+      error ("ilu: DROPTOL must be a non-negative real scalar");
     endif
   endif
 
-  if (~isfield (setup, "droptol"))
-    setup.droptol = 0; % set default
+  if (! isfield (opts, "milu"))
+    opts.milu = "off";     # set default
   else
-    if (~isscalar (setup.droptol) || (setup.droptol < 0))
-      error ("ilu: Invalid field \"droptol\" in input structure.");
+    milu = tolower (getfield (opts, "milu"));
+    if (! any (strcmp (milu, {"off", "col", "row"})))
+      error ('ilu: MILU must be one of "off", "col", or "row"');
+    endif
+    opts.milu = milu;
+  endif
+
+  if (! isfield (opts, "udiag"))
+    opts.udiag = 0;        # set default
+  else
+    if (! isscalar (opts.udiag) || (opts.udiag != 0 && opts.udiag != 1))
+      error ("ilu: UDIAG must be 0 or 1");
     endif
   endif
 
-  if (~isfield (setup, "milu"))
-    setup.milu = "off"; % set default
+  if (! isfield (opts, "thresh"))
+    opts.thresh = 1;       # set default
   else
-    milu = tolower (getfield (setup, "milu"));
-    if ((strcmp (milu, "off") == 0) 
-        && (strcmp (milu, "col") == 0)
-        && (strcmp (milu, "row") == 0))
-      error ("ilu: Invalid field \"milu\" in input structure.");
-    else
-      setup.milu = milu;
-    endif
-  endif
-
-  if (~isfield (setup, "udiag"))
-    setup.udiag = 0; % set default
-  else
-    if (~isscalar (setup.udiag) || ((setup.udiag ~= 0) && (setup.udiag ~= 1)))
-      error ("ilu: Invalid field \"udiag\" in input structure.");
-    endif
-  endif
-
-  if (~isfield (setup, "thresh"))
-    setup.thresh = 1; % set default
-  else
-    if (~isscalar (setup.thresh) || (setup.thresh < 0) || (setup.thresh > 1))
-      error ("ilu: Invalid field \"thresh\" in input structure.");
+    if (! (isreal (opts.thresh) && isscalar (opts.thresh))
+        || opts.thresh < 0 || opts.thresh > 1)
+      error ("ilu: THRESH must be a scalar in the range [0, 1]");
     endif
   endif
 
   n = length (A);
 
-  % Delegate to specialized ILU
-  switch (setup.type)
+  ## Delegate to specialized ILU
+  switch (opts.type)
     case "nofill"
-        [L, U] = __ilu0__ (A, setup.milu);
+        [L, U] = __ilu0__ (A, opts.milu);
         if (nargout == 3)
           P = speye (length (A));
         endif
     case "crout"
-        [L, U] = __iluc__ (A, setup.droptol, setup.milu);
+        [L, U] = __iluc__ (A, opts.droptol, opts.milu);
         if (nargout == 3)
           P = speye (length (A));
         endif
     case "ilutp"
         if (nargout == 2)
-          [L, U]  = __ilutp__ (A, setup.droptol, setup.thresh, setup.milu, setup.udiag);
+          [L, U]  = __ilutp__ (A, opts.droptol, opts.thresh,
+                                  opts.milu, opts.udiag);
         elseif (nargout == 3)
-          [L, U, P]  = __ilutp__ (A, setup.droptol, setup.thresh, setup.milu, setup.udiag);
+          [L, U, P]  = __ilutp__ (A, opts.droptol, opts.thresh,
+                                     opts.milu, opts.udiag);
         endif
-    otherwise
-      printf ("The input structure is invalid.\n");
   endswitch
 
   if (nargout == 1)
@@ -266,120 +263,63 @@
 
 endfunction
 
+
 %!shared n, dtol, A
 %! n = 1600;
 %! dtol = 0.1;
-%! A = gallery ('neumann', n) + speye (n);
+%! A = gallery ("neumann", n) + speye (n);
 %!test
-%! setup.type = 'nofill';
-%! assert (nnz (ilu (A, setup)), 7840);
-%! # This test is taken from the mathworks and should work for full support.
+%! opts.type = "nofill";
+%! assert (nnz (ilu (A, opts)), 7840);
+## This test has been verified in both Matlab and Octave.
 %!test
-%! setup.type = 'crout';
-%! setup.milu = 'row';
-%! setup.droptol = dtol;
-%! [L, U] = ilu (A, setup);
+%! opts.type = "crout";
+%! opts.milu = "row";
+%! opts.droptol = dtol;
+%! [L, U] = ilu (A, opts);
 %! e = ones (size (A, 2),1);
 %! assert (norm (A*e - L*U*e), 1e-14, 1e-14);
 %!test
-%! setup.type = 'crout';
-%! setup.droptol = dtol;
-%! [L, U] = ilu(A, setup);
-%! assert (norm (A - L * U, 'fro') / norm (A, 'fro'), 0.05, 1e-2);
+%! opts.type = "crout";
+%! opts.droptol = dtol;
+%! [L, U] = ilu (A, opts);
+%! assert (norm (A - L * U, "fro") / norm (A, "fro"), 0.05, 1e-2);
 
-%! # Tests for input validation
-%!test
-%! [L, U] = ilu (sparse ([]));
-%! assert (isempty (L), logical (1));
-%! assert (isempty (U), logical (1));
-%! setup.type = 'crout';
-%! [L, U] = ilu (sparse ([]), setup);
-%! assert (isempty (L), logical (1));
-%! assert (isempty (U), logical (1));
-%! setup.type = 'ilutp';
-%! [L, U] = ilu (sparse ([]), setup);
-%! assert (isempty (L), logical (1));
-%! assert (isempty (U), logical (1));
-%!error [L, U] = ilu (0);
-%!error [L, U] = ilu ([]);
-%!error [L, U] = ilu (sparse (0));
-%!test
-%! setup.type = 'foo';
-%!error [L, U] = ilu (A_tiny, setup);
-%! setup.type = 1;
-%!error [L, U] = ilu (A_tiny, setup);
-%! setup.type = [];
-%!error [L, U] = ilu (A_tiny, setup);
+## Check if the elements in U satisfy the non-dropping condition.
 %!test
-%! setup.droptol = -1;
-%!error [L, U] = ilu (A_tiny, setup);
-%! setup.droptol = 0.5i;
-%!error [L, U] = ilu (A_tiny, setup);
-%! setup.droptol = [];
-%!error [L, U] = ilu (A_tiny, setup);
-%!test
-%! setup.thresh= -1;
-%!error [L, U] = ilu (A_tiny, setup);
-%! setup.thresh = 0.5i;
-%!error [L, U] = ilu (A_tiny, setup);
-%! setup.thresh = [];
-%!error [L, U] = ilu (A_tiny, setup);
-%! setup.thresh = 2;
-%!error [L, U] = ilu (A_tiny, setup);
-%!test
-%! setup.diag = 0.5;
-%!error [L, U] = ilu (A_tiny, setup);
-%! setup.diag = [];
-%!error [L, U] = ilu (A_tiny, setup);
-%! setup.diag = -1;
-%!error [L, U] = ilu (A_tiny, setup);
-%!test
-%! setup.milu = 'foo';
-%!error [L, U] = ilu (A_tiny, setup);
-%! setup.milu = 1;
-%!error [L, U] = ilu (A_tiny, setup);
-%! setup.milu = [];
-%!error [L, U] = ilu (A_tiny, setup);
-
-%! # Check if the elements in U satisfy the non-dropping condition.
-%!test
-%! setup.type = 'crout';
-%! setup.droptol = dtol;
-%! [L, U] = ilu (A, setup);
+%! opts.type = "crout";
+%! opts.droptol = dtol;
+%! [L, U] = ilu (A, opts);
 %! for j = 1:n
 %!   cmp_value = dtol * norm (A(:, j));
 %!   non_zeros = nonzeros (U(:, j));
-%!   for i = 1:length (non_zeros);
-%!     assert (abs (non_zeros (i)) >= cmp_value, logical (1));
-%!   endfor
+%!   assert (abs (non_zeros) >= cmp_value);
 %! endfor
 %!test
-%! setup.type = 'ilutp';
-%! setup.droptol = dtol;
-%! [L, U] = ilu (A, setup);
+%! opts.type = "ilutp";
+%! opts.droptol = dtol;
+%! [L, U] = ilu (A, opts);
 %! for j = 1:n
 %!   cmp_value = dtol * norm (A(:, j));
 %!   non_zeros = nonzeros (U(:, j));
-%!   for i = 1:length (non_zeros);
-%!     assert (abs (non_zeros (i)) >= cmp_value, logical (1));
-%!   endfor
+%!   assert (abs (non_zeros) >= cmp_value);
 %! endfor
 
-%! # Check that the complete LU factorisation with crout and ilutp algorithms
-%! # output the same result.
+## Check that the complete LU factorisation with crout and ilutp algorithms
+## produce the same result.
 %!test
-%! setup.type = 'crout';
-%! setup.droptol = 0;
-%! [L1, U1] = ilu (A, setup);
-%! setup.type = 'ilutp';
-%! setup.thresh = 0;
-%! [L2, U2] = ilu (A, setup);
-%! assert (norm (L1 - L2, 'fro') / norm (L1, 'fro'), 0, eps);
-%! assert (norm (U1 - U2, 'fro') / norm (U1, 'fro'), 0, eps);
+%! opts.type = "crout";
+%! opts.droptol = 0;
+%! [L1, U1] = ilu (A, opts);
+%! opts.type = "ilutp";
+%! opts.thresh = 0;
+%! [L2, U2] = ilu (A, opts);
+%! assert (norm (L1 - L2, "fro") / norm (L1, "fro"), 0, eps);
+%! assert (norm (U1 - U2, "fro") / norm (U1, "fro"), 0, eps);
 
-%! # Tests for real matrices of different sizes for ilu0, iluc and ilutp.
-%! # The difference A - L*U should be not greater than eps because with droptol
-%! # equaling 0, the LU complete factorization is performed.
+## Tests for real matrices of different sizes for ilu0, iluc and ilutp.
+## The difference A - L*U should be not greater than eps because with droptol
+## equaling 0, the LU complete factorization is performed.
 %!shared n_tiny, n_small, n_medium, n_large, A_tiny, A_small, A_medium, A_large
 %! n_tiny = 5;
 %! n_small = 40;
@@ -391,66 +331,65 @@
 %! A_large = sprand (n_large, n_large, 1/n_large/10) + speye (n_large);
 %!
 %!test 
-%! setup.type = "nofill";
+%! opts.type = "nofill";
 %! [L, U] = ilu (A_tiny);
-%! assert (norm (A_tiny - L * U, "fro") / norm (A_tiny, "fro"), 0, n_tiny * eps);
+%! assert (norm (A_tiny - L*U, "fro") / norm (A_tiny, "fro"), 0, n_tiny * eps);
 %!test 
-%! setup.type = "nofill";
+%! opts.type = "nofill";
 %! [L, U] = ilu (A_small);
-%! assert (norm (A_small - L * U, "fro") / norm (A_small, "fro"), 0, 1);
+%! assert (norm (A_small - L*U, "fro") / norm (A_small, "fro"), 0, 1);
 %!test 
-%! setup.type = "nofill";
+%! opts.type = "nofill";
 %! [L, U] = ilu (A_medium);
-%! assert (norm (A_medium - L * U, "fro") / norm (A_medium, "fro"), 0, 1);
+%! assert (norm (A_medium - L*U, "fro") / norm (A_medium, "fro"), 0, 1);
 %!test 
-%! setup.type = "nofill";
+%! opts.type = "nofill";
 %! [L, U] = ilu (A_large);
-%! assert (norm (A_large - L * U, "fro") / norm (A_large, "fro"), 0, 1);
+%! assert (norm (A_large - L*U, "fro") / norm (A_large, "fro"), 0, 1);
 %!
 %!test 
-%! setup.type = "crout";
-%! [L, U] = ilu (A_tiny, setup);
-%! assert (norm (A_tiny - L * U, "fro") / norm (A_tiny, "fro"), eps, eps);
+%! opts.type = "crout";
+%! [L, U] = ilu (A_tiny, opts);
+%! assert (norm (A_tiny - L*U, "fro") / norm (A_tiny, "fro"), eps, eps);
 %!test 
-%! setup.type = "crout";
-%! [L, U] = ilu (A_small, setup);
-%! assert (norm (A_small - L * U, "fro") / norm (A_small, "fro"), eps, eps);
+%! opts.type = "crout";
+%! [L, U] = ilu (A_small, opts);
+%! assert (norm (A_small - L*U, "fro") / norm (A_small, "fro"), eps, eps);
 %!test 
-%! setup.type = "crout";
-%! [L, U] = ilu (A_medium, setup);
-%! assert (norm (A_medium - L * U, "fro") / norm (A_medium, "fro"), eps, eps);
+%! opts.type = "crout";
+%! [L, U] = ilu (A_medium, opts);
+%! assert (norm (A_medium - L*U, "fro") / norm (A_medium, "fro"), eps, eps);
 %!test 
-%! setup.type = "crout";
-%! [L, U] = ilu (A_large, setup);
-%! assert (norm (A_large - L * U, "fro") / norm (A_large, "fro"), eps, eps);
+%! opts.type = "crout";
+%! [L, U] = ilu (A_large, opts);
+%! assert (norm (A_large - L*U, "fro") / norm (A_large, "fro"), eps, eps);
 %!
 %!test 
-%! setup.type = "ilutp";
-%! setup.droptol = 0;
-%! setup.thresh = 0;
-%! [L, U] = ilu (A_tiny, setup);
-%! assert (norm (A_tiny - L * U, "fro") / norm (A_tiny, "fro"), eps, eps);
+%! opts.type = "ilutp";
+%! opts.droptol = 0;
+%! opts.thresh = 0;
+%! [L, U] = ilu (A_tiny, opts);
+%! assert (norm (A_tiny - L*U, "fro") / norm (A_tiny, "fro"), eps, eps);
 %!test 
-%! setup.type = "ilutp";
-%! setup.droptol = 0;
-%! setup.thresh = 0;
-%! [L, U] = ilu (A_small, setup);
-%! assert (norm (A_small - L * U, "fro") / norm (A_small, "fro"), eps, eps);
+%! opts.type = "ilutp";
+%! opts.droptol = 0;
+%! opts.thresh = 0;
+%! [L, U] = ilu (A_small, opts);
+%! assert (norm (A_small - L*U, "fro") / norm (A_small, "fro"), eps, eps);
 %!test 
-%! setup.type = "ilutp";
-%! setup.droptol = 0;
-%! setup.thresh = 0;
-%! [L, U] = ilu (A_medium, setup);
-%! assert (norm (A_medium - L * U, "fro") / norm (A_medium, "fro"), eps, eps);
+%! opts.type = "ilutp";
+%! opts.droptol = 0;
+%! opts.thresh = 0;
+%! [L, U] = ilu (A_medium, opts);
+%! assert (norm (A_medium - L*U, "fro") / norm (A_medium, "fro"), eps, eps);
 %!test 
-%! setup.type = "ilutp";
-%! setup.droptol = 0;
-%! setup.thresh = 0;
-%! [L, U] = ilu (A_large, setup);
-%! assert (norm (A_large - L * U, "fro") / norm (A_large, "fro"), eps, eps);
-%!
+%! opts.type = "ilutp";
+%! opts.droptol = 0;
+%! opts.thresh = 0;
+%! [L, U] = ilu (A_large, opts);
+%! assert (norm (A_large - L*U, "fro") / norm (A_large, "fro"), eps, eps);
 
-%! # Tests for complex matrices of different sizes for ilu0, iluc and ilutp.
+## Tests for complex matrices of different sizes for ilu0, iluc and ilutp.
 %!shared n_tiny, n_small, n_medium, n_large, A_tiny, A_small, A_medium, A_large
 %! n_tiny = 5;
 %! n_small = 40;
@@ -458,90 +397,147 @@
 %! n_large = 10000;
 %! A_tiny = spconvert ([1 4 2 3 3 4 2 5; 1 1 2 3 4 4 5 5; 1 2 3 4 5 6 7 8]');
 %! A_tiny(1,1) += 1i;
-%! A_small = sprand(n_small, n_small, 1/n_small) + ...
-%!   i * sprand(n_small, n_small, 1/n_small) + speye (n_small);
-%! A_medium = sprand(n_medium, n_medium, 1/n_medium) + ...
-%!   i * sprand(n_medium, n_medium, 1/n_medium) + speye (n_medium);
-%! A_large = sprand(n_large, n_large, 1/n_large/10) + ...
-%!   i * sprand(n_large, n_large, 1/n_large/10) + speye (n_large);
+%! A_small = sprand (n_small, n_small, 1/n_small) + ...
+%!   i * sprand (n_small, n_small, 1/n_small) + speye (n_small);
+%! A_medium = sprand (n_medium, n_medium, 1/n_medium) + ...
+%!   i * sprand (n_medium, n_medium, 1/n_medium) + speye (n_medium);
+%! A_large = sprand (n_large, n_large, 1/n_large/10) + ...
+%!   i * sprand (n_large, n_large, 1/n_large/10) + speye (n_large);
 %!
 %!test 
-%! setup.type = "nofill";
+%! opts.type = "nofill";
 %! [L, U] = ilu (A_tiny);
-%! assert (norm (A_tiny - L * U, "fro") / norm (A_tiny, "fro"), 0, n_tiny * eps);
+%! assert (norm (A_tiny - L*U, "fro") / norm (A_tiny, "fro"), 0, n_tiny * eps);
 %!test 
-%! setup.type = "nofill";
+%! opts.type = "nofill";
 %! [L, U] = ilu (A_small);
-%! assert (norm (A_small - L * U, "fro") / norm (A_small, "fro"), 0, 1);
+%! assert (norm (A_small - L*U, "fro") / norm (A_small, "fro"), 0, 1);
 %!test 
-%! setup.type = "nofill";
+%! opts.type = "nofill";
 %! [L, U] = ilu (A_medium);
-%! assert (norm (A_medium - L * U, "fro") / norm (A_medium, "fro"), 0, 1);
+%! assert (norm (A_medium - L*U, "fro") / norm (A_medium, "fro"), 0, 1);
 %!test 
-%! setup.type = "nofill";
+%! opts.type = "nofill";
 %! [L, U] = ilu (A_large);
-%! assert (norm (A_large - L * U, "fro") / norm (A_large, "fro"), 0, 1);
+%! assert (norm (A_large - L*U, "fro") / norm (A_large, "fro"), 0, 1);
 %!
 %!test 
-%! setup.type = "crout";
-%! [L, U] = ilu (A_tiny, setup);
-%! assert (norm (A_tiny - L * U, "fro") / norm (A_tiny, "fro"), eps, eps);
+%! opts.type = "crout";
+%! [L, U] = ilu (A_tiny, opts);
+%! assert (norm (A_tiny - L*U, "fro") / norm (A_tiny, "fro"), eps, eps);
 %!test 
-%! setup.type = "crout";
-%! [L, U] = ilu (A_small, setup);
-%! assert (norm (A_small - L * U, "fro") / norm (A_small, "fro"), eps, eps);
+%! opts.type = "crout";
+%! [L, U] = ilu (A_small, opts);
+%! assert (norm (A_small - L*U, "fro") / norm (A_small, "fro"), eps, eps);
 %!test 
-%! setup.type = "crout";
-%! [L, U] = ilu (A_medium, setup);
-%! assert (norm (A_medium - L * U, "fro") / norm (A_medium, "fro"), eps, eps);
+%! opts.type = "crout";
+%! [L, U] = ilu (A_medium, opts);
+%! assert (norm (A_medium - L*U, "fro") / norm (A_medium, "fro"), eps, eps);
 %!test 
-%! setup.type = "crout";
-%! [L, U] = ilu (A_large, setup);
-%! assert (norm (A_large - L * U, "fro") / norm (A_large, "fro"), eps, eps);
+%! opts.type = "crout";
+%! [L, U] = ilu (A_large, opts);
+%! assert (norm (A_large - L*U, "fro") / norm (A_large, "fro"), eps, eps);
 %!
 %!test 
-%! setup.type = "ilutp";
-%! setup.droptol = 0;
-%! setup.thresh = 0;
-%! [L, U] = ilu (A_tiny, setup);
-%! assert (norm (A_tiny - L * U, "fro") / norm (A_tiny, "fro"), eps, eps);
+%! opts.type = "ilutp";
+%! opts.droptol = 0;
+%! opts.thresh = 0;
+%! [L, U] = ilu (A_tiny, opts);
+%! assert (norm (A_tiny - L*U, "fro") / norm (A_tiny, "fro"), eps, eps);
 %!test 
-%! setup.type = "ilutp";
-%! setup.droptol = 0;
-%! setup.thresh = 0;
-%! [L, U] = ilu (A_small, setup);
-%! assert (norm (A_small - L * U, "fro") / norm (A_small, "fro"), eps, eps);
+%! opts.type = "ilutp";
+%! opts.droptol = 0;
+%! opts.thresh = 0;
+%! [L, U] = ilu (A_small, opts);
+%! assert (norm (A_small - L*U, "fro") / norm (A_small, "fro"), eps, eps);
 %!test 
-%! setup.type = "ilutp";
-%! setup.droptol = 0;
-%! setup.thresh = 0;
-%! [L, U] = ilu (A_medium, setup);
-%! assert (norm (A_medium - L * U, "fro") / norm (A_medium, "fro"), eps, eps);
+%! opts.type = "ilutp";
+%! opts.droptol = 0;
+%! opts.thresh = 0;
+%! [L, U] = ilu (A_medium, opts);
+%! assert (norm (A_medium - L*U, "fro") / norm (A_medium, "fro"), eps, eps);
 %!test 
-%! setup.type = "ilutp";
-%! setup.droptol = 0;
-%! setup.thresh = 0;
-%! [L, U] = ilu (A_large, setup);
-%! assert (norm (A_large - L * U, "fro") / norm (A_large, "fro"), eps, eps);
+%! opts.type = "ilutp";
+%! opts.droptol = 0;
+%! opts.thresh = 0;
+%! [L, U] = ilu (A_large, opts);
+%! assert (norm (A_large - L*U, "fro") / norm (A_large, "fro"), eps, eps);
 
-%! #Specific tests for ilutp
+## Specific tests for ilutp
+
 %!shared a1, a2
 %! a1 = sparse ([0 0 4 3 1; 5 1 2.3 2 4.5; 0 0 0 2 1;0 0 8 0 2.2; 0 0 9 9 1 ]);
 %! a2 = sparse ([3 1 0 0 4; 3 1 0 0 -2;0 0 8 0 0; 0 4 0 4 -4.5; 0 -1 0 0 1]);
 %!test
-%! setup.udiag = 1;
-%! setup.type = "ilutp";
-%! setup.droptol = 0.2;
-%! [L, U, P] = ilu (a1, setup);
+%! opts.udiag = 1;
+%! opts.type = "ilutp";
+%! opts.droptol = 0.2;
+%! [L, U, P] = ilu (a1, opts);
 %! assert (norm (U, "fro"), 17.4577, 1e-4);
 %! assert (norm (L, "fro"), 2.4192, 1e-4);
-%! setup.udiag = 0;
-%!error [L, U, P] = ilu (a1, setup);
+%! opts.udiag = 0;
+%! #fail ("ilu (a1, opts)");
 %!
 %!test
-%! setup.type = "ilutp";
-%! setup.droptol = 0;
-%! setup.thresh = 0;
-%! setup.milu = "row";
-%!error [L, U] = ilu (a2, setup);
-%! 
+%! opts.type = "ilutp";
+%! opts.droptol = 0;
+%! opts.thresh = 0;
+%! opts.milu = "row";
+%! #fail ("ilu (a2, opts)");
+
+%% Tests for input validation
+%!shared A_tiny
+%! A_tiny = spconvert ([1 4 2 3 3 4 2 5; 1 1 2 3 4 4 5 5; 1 2 3 4 5 6 7 8]');
+
+%!test
+%! [L, U] = ilu (sparse ([]));
+%! assert (isempty (L));
+%! assert (isempty (U));
+%! opts.type = "crout";
+%! [L, U] = ilu (sparse ([]), opts);
+%! assert (isempty (L));
+%! assert (isempty (U));
+%! opts.type = "ilutp";
+%! [L, U] = ilu (sparse ([]), opts);
+%! assert (isempty (L));
+%! assert (isempty (U));
+%!error <A must be a sparse square matrix> ilu (0)
+%!error <A must be a sparse square matrix> ilu ([])
+%!error <zero on the diagonal> ilu (sparse (0))
+
+%!test
+%! opts.type = "foo";
+%! fail ("ilu (A_tiny, opts)", "invalid TYPE specified");
+%! opts.type = 1;
+%! fail ("ilu (A_tiny, opts)", "invalid TYPE specified");
+%! opts.type = [];
+%! fail ("ilu (A_tiny, opts)", "invalid TYPE specified");
+%!test
+%! opts.droptol = -1;
+%! fail ("ilu (A_tiny, opts)", "DROPTOL must be a non-negative real scalar");
+%! opts.droptol = 0.5i;
+%! fail ("ilu (A_tiny, opts)", "DROPTOL must be a non-negative real scalar");
+%! opts.droptol = [];
+%! fail ("ilu (A_tiny, opts)", "DROPTOL must be a non-negative real scalar");
+%!test
+%! opts.milu = "foo";
+%! fail ("ilu (A_tiny, opts)", 'MILU must be one of "off"');
+%! opts.milu = 1;
+%! fail ("ilu (A_tiny, opts)", 'MILU must be one of "off"');
+%! opts.milu = [];
+%! fail ("ilu (A_tiny, opts)", 'MILU must be one of "off"');
+%!test
+%! opts.udiag = -1;
+%! fail ("ilu (A_tiny, opts)", "UDIAG must be 0 or 1");
+%! opts.udiag = 0.5i;
+%! fail ("ilu (A_tiny, opts)", "UDIAG must be 0 or 1");
+%! opts.udiag = [];
+%! fail ("ilu (A_tiny, opts)", "UDIAG must be 0 or 1");
+%!test
+%! opts.thresh = -1;
+%! fail ("ilu (A_tiny, opts)", "THRESH must be a scalar");
+%! opts.thresh = 0.5i;
+%! fail ("ilu (A_tiny, opts)", "THRESH must be a scalar");
+%! opts.thresh = [];
+%! fail ("ilu (A_tiny, opts)", "THRESH must be a scalar");
+