/* Multiply two matrices.
 *
 * Copyright: 1990, K. Martinez and J. Cupitt
 *
 * 23/10/10
 * 	- gtk-doc
 */

/*

	This file is part of VIPS.

	VIPS is free software; you can redistribute it and/or modify
	it under the terms of the GNU Lesser General Public License as published by
	the Free Software Foundation; either version 2 of the License, or
	(at your option) any later version.

	This program 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 Lesser General Public License for more details.

	You should have received a copy of the GNU Lesser General Public License
	along with this program; if not, write to the Free Software
	Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
	02110-1301  USA

 */

/*

	These files are distributed with VIPS - http://www.vips.ecs.soton.ac.uk

 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif /*HAVE_CONFIG_H*/
#include <glib/gi18n-lib.h>

#include <stdio.h>

#include <vips/vips.h>
#include <vips/vips7compat.h>

/**
 * im_matmul:
 * @in1: input matrix
 * @in2: input matrix
 * @filename: name for output matrix
 *
 * Multiplies two DOUBLEMASKs. Result matrix is made and returned.
 * Pass the filename to set for the output.
 *
 * The scale and offset members of @in1 and @in2 are ignored.
 *
 * See also: im_mattrn(), im_matinv().
 *
 * Returns: the result matrix on success, or %NULL on error.
 */
DOUBLEMASK *
im_matmul(DOUBLEMASK *in1, DOUBLEMASK *in2, const char *name)
{
	int xc, yc, col;
	double sum;
	DOUBLEMASK *mat;
	double *out, *a, *b;
	double *s1, *s2;

	/* Check matrix sizes.
	 */
	if (in1->xsize != in2->ysize) {
		im_error("im_matmul", "%s", _("bad sizes"));
		return NULL;
	}

	/* Allocate output matrix.
	 */
	if (!(mat = im_create_dmask(name, in2->xsize, in1->ysize)))
		return NULL;

	/* Multiply.
	 */
	out = mat->coeff;
	s1 = in1->coeff;

	for (yc = 0; yc < in1->ysize; yc++) {
		s2 = in2->coeff;

		for (col = 0; col < in2->xsize; col++) {
			/* Get ready to sweep a row.
			 */
			sum = 0.0;
			a = s1;
			b = s2;

			for (sum = 0.0, xc = 0; xc < in1->xsize; xc++) {
				sum += *a++ * *b;
				b += in2->xsize;
			}

			*out++ = sum;
			s2++;
		}

		s1 += in1->xsize;
	}

	return mat;
}
