Mercurial > octave
view libinterp/corefcn/__expint__.cc @ 24986:0b9e7fcaab91 stable
doc: grammarcheck docstrings in C++ files ahead of 4.4 release.
* defaults.cc, dirfns.cc, load-save.cc, pr-flt-fmt.cc, quadcc.cc, regexp.cc,
qr.cc: Use Octave conventions in documentation strings.
author | Rik <rik@octave.org> |
---|---|
date | Fri, 23 Mar 2018 10:29:45 -0700 |
parents | c280560d9c96 |
children | 576ff914979c |
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/* Copyright (C) 2018 Michele Ginesi 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 (HAVE_CONFIG_H) # include "config.h" #endif #include "CNDArray.h" #include "defun.h" #include "fCNDArray.h" DEFUN (__expint__, args, , doc: /* -*- texinfo -*- @deftypefn {} {@var{y} =} __expint__ (@var{x}) Continued fraction expansion for the exponential integral. @end deftypefn */) { int nargin = args.length (); if (nargin != 1) print_usage (); octave_value_list retval; bool is_single = args(0).is_single_type (); int numel_x = args(0).numel (); // Initialize output dimension vector dim_vector output_dv (numel_x, 1); // Lentz's algorithm in two cases: single and double precision if (is_single) { // Initialize output and inputs FloatComplexColumnVector output (output_dv); FloatComplexNDArray x; if (numel_x == 1) x = FloatComplexNDArray (output_dv, args(0).float_complex_value ()); else x = args(0).float_complex_array_value (); // Initialize variables used in algorithm static const FloatComplex tiny = pow (2, -50); static const float eps = std::numeric_limits<float>::epsilon (); FloatComplex cone (1.0, 0.0); FloatComplex czero (0.0, 0.0); FloatComplex xj = x(0); FloatComplex y = tiny; FloatComplex Cj = y; FloatComplex Dj = czero; FloatComplex alpha_j = cone; FloatComplex beta_j = czero; FloatComplex Deltaj = czero; int j = 1; int maxit = 100; // Loop over all elements for (octave_idx_type i = 0; i < numel_x; ++i) { // Catch Ctrl+C OCTAVE_QUIT; // Variable initialization for the current element xj = x(i); y = tiny; Cj = y; Dj = czero; alpha_j = cone; beta_j = xj; Deltaj = czero; j = 1; // Lentz's algorithm while ((std::abs (Deltaj - cone) > eps) && (j < maxit)) { Dj = beta_j + alpha_j * Dj; if (Dj == czero) Dj = tiny; Cj = beta_j + alpha_j / Cj; if (Cj == czero) Cj = tiny; Dj = cone / Dj; Deltaj = Cj * Dj; y *= Deltaj; alpha_j = floor ((j + 1) / 2); if ((j % 2) == 0) beta_j = xj; else beta_j = cone; j++; } output(i) = y; } retval(0) = output; } else { // Initialize output and inputs ComplexColumnVector output (output_dv); ComplexNDArray x; if (numel_x == 1) x = ComplexNDArray (output_dv, args(0).complex_value ()); else x = args(0).complex_array_value (); // Initialize variables used in algorithm static const Complex tiny = pow (2, -100); static const double eps = std::numeric_limits<double>::epsilon (); Complex cone (1.0, 0.0); Complex czero (0.0, 0.0); Complex xj = x(0); Complex y = tiny; Complex Cj = y; Complex Dj = czero; Complex alpha_j = cone; Complex beta_j = xj; Complex Deltaj = czero; int j = 1; int maxit = 200; // Loop over all scenarios for (octave_idx_type i = 0; i < numel_x; ++i) { // Catch Ctrl+C OCTAVE_QUIT; // Variable initialization for the current element xj = x(i); y = tiny; Cj = y; Dj = czero; alpha_j = cone; beta_j = xj; Deltaj = czero; j = 1; // Lentz's algorithm while ((std::abs (Deltaj - cone) > eps) && (j < maxit)) { Dj = beta_j + alpha_j * Dj; if (Dj == czero) Dj = tiny; Cj = beta_j + alpha_j / Cj; if (Cj == czero) Cj = tiny; Dj = cone / Dj; Deltaj = Cj * Dj; y *= Deltaj; alpha_j = floor ((j + 1) / 2); if ((j % 2) == 0) beta_j = xj; else beta_j = cone; j++; } output(i) = y; } retval(0) = output; } return retval; }