--- a/ChangeLog	Sat Mar 27 10:07:10 2010 +0100
+++ b/ChangeLog	Sat Mar 27 18:23:54 2010 +0100
@@ -1,3 +1,8 @@
+2010-03-27  David Bateman  <dbateman@free.fr>
+
+	* acinclude.m4 (OCTAVE_CHECK_OPENMP): Macro to check for OpenMP support
+	* configure.ac: Use it here. Disable OpenMP support by default
+
 2010-03-25  John W. Eaton  <jwe@octave.org>
 
 	* bootstrap.conf (gnulib_modules): Sort the list.

--- a/acinclude.m4	Sat Mar 27 10:07:10 2010 +0100
+++ b/acinclude.m4	Sat Mar 27 18:23:54 2010 +0100
@@ -1065,6 +1065,35 @@
 fi
 ])
 dnl
+dnl Check for support of OpenMP with a given compiler flag. If
+dnl found define HAVE_OPENMP and add the compile flag to CFLAGS
+dnl and CXXFLAGS.
+dnl
+AC_DEFUN([OCTAVE_CHECK_OPENMP],
+[AC_MSG_CHECKING([for support of OpenMP])
+XCFLAGS="$CFLAGS"
+CFLAGS="$CFLAGS $1"
+AC_CACHE_VAL(octave_cv_check_openmp,[
+AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
+#include <omp.h>
+#include <stdio.h>
+]], [[
+int main(int argc, char* argv[])
+{
+  _Pragma("omp parallel")  
+  printf("Hello, world.\n");
+  return 0;
+}
+]])],octave_cv_openmp=yes, octave_cv_openmmp=no, octave_cv_openmp=no)])
+AC_MSG_RESULT($octave_cv_openmp)
+if test "$octave_cv_openmp" = yes; then
+  AC_DEFINE(HAVE_OPENMP,1,[Define if compiler supports OpenMP])
+  CXXFLAGS="$CXXFLAGS $1"
+else
+  CFLAGS="$XCFLAGS"
+fi
+])
+dnl
 dnl Configure paths for FreeType2
 dnl Marcelo Magallon 2001-10-26, based on gtk.m4 by Owen Taylor
 dnl

--- a/configure.ac	Sat Mar 27 10:07:10 2010 +0100
+++ b/configure.ac	Sat Mar 27 18:23:54 2010 +0100
@@ -427,6 +427,26 @@
   ;;
 esac
 
+## Test whether the compiler supports OpenMP. Experimental so disable by 
+## default. Enable it with the flag --enable-openmp
+USE_OPENMP=false
+AC_ARG_ENABLE(openmp,
+  [AS_HELP_STRING([--enable-openmp],
+     [(EXPERIMENTAL) use OpenMP SMP multi-threading])],
+  [if test "$enableval" = yes; then USE_OPENMP=true; fi], [])
+if $USE_OPENMP; then
+  case "$canonical_host_type" in
+    *-*-mingw* | *-*-cygwin* | *-*-gnu*)
+    OCTAVE_CHECK_OPENMP(-fopenmp)
+    ;;
+    *-*-msdosmsvc)
+    ## FIXME is this the right flag for MSVC?
+    OCTAVE_CHECK_OPENMP(-openmp)
+    ;;
+    ## Add other compilers supporting OpenMP here
+  esac
+fi
+
 AC_SUBST(XTRA_CFLAGS)
 AC_SUBST(XTRA_CXXFLAGS)
 
@@ -2314,6 +2334,19 @@
   warn_msg_printed=true
 fi
 
+if $USE_OPENMP; then
+  AC_MSG_WARN([])
+  AC_MSG_WARN([You used the EXPERIMENTAL --enable-openmp option.])
+  AC_MSG_WARN([Are you sure that is what you want to do?])
+  AC_MSG_WARN([])
+  AC_MSG_WARN([This option enables experimental SMP multithreding])
+  AC_MSG_WARN([code that has had very little testing. There is no])
+  AC_MSG_WARN([certainity that the results returned by Octave with])
+  AC_MSG_WARN([this option enabled will be correct.])
+  AC_MSG_WARN([])
+  warn_msg_printed=true
+fi
+
 native_graphics=true
 if test -n "$warn_freetype"; then
   AC_MSG_WARN([$warn_freetype])

--- a/liboctave/ChangeLog	Sat Mar 27 10:07:10 2010 +0100
+++ b/liboctave/ChangeLog	Sat Mar 27 18:23:54 2010 +0100
@@ -1,3 +1,8 @@
+2010-03-27  David Bateman  <dbateman@free.fr>
+
+	* oct-openmp.h: New file.
+	* Makefile.am (INCS): Add it here.
+
 2010-03-26  Jaroslav Hajek  <highegg@gmail.com>
 
 	* Sparse.cc (Sparse<T>::index (const idx_vector&, const idx_vector&, bool)):

--- a/liboctave/Makefile.am	Sat Mar 27 10:07:10 2010 +0100
+++ b/liboctave/Makefile.am	Sat Mar 27 18:23:54 2010 +0100
@@ -223,6 +223,7 @@
   oct-mem.h \
   oct-mutex.h \
   oct-norm.h \
+  oct-openmp.h \
   oct-passwd.h \
   oct-rand.h \
   oct-rl-edit.h \

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/liboctave/oct-openmp.h	Sat Mar 27 18:23:54 2010 +0100
@@ -0,0 +1,34 @@
+/*
+
+Copyright (C) 2010 David Bateman
+
+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/>.
+
+*/
+
+#if !defined (octave_openmp_h)
+#define octave_openmp_h 1
+
+/* A macro to make using OpenMP easier, and easier to disable */
+#ifdef HAVE_OPENMP
+#include <omp.h>
+#define OCTAVE_OMP_PRAGMA(x) _Pragma (#x)
+#else
+#define OCTAVE_OMP_PRAGMA(x)
+#endif
+
+#endif