mdw@git.distorted.org.uk Git - storin/blob - matrix.c

   1 /* -*-c-*-
   2  *
   3  * $Id: matrix.c,v 1.2 2000/07/02 15:22:07 mdw Exp $
   4  *
   5  * Matrix arithmetic mod %$2^{24}$%
   6  *
   7  * (c) 2000 Mark Wooding
   8  */
   9
  10 /*----- Licensing notice --------------------------------------------------*
  11  *
  12  * Copyright (c) 2000 Mark Wooding
  13  * All rights reserved.
  14  *
  15  * Redistribution and use in source and binary forms, with or without
  16  * modification, are permitted provided that the following conditions are
  17  * met:
  18  *
  19  * 1. Redistributions of source code must retain the above copyright
  20  *    notice, this list of conditions and the following disclaimer.
  21  *
  22  * 2, Redistributions in binary form must reproduce the above copyright
  23  *    notice, this list of conditions and the following disclaimer in the
  24  *    documentation and/or other materials provided with the distribution.
  25  *
  26  * 3. The name of the authors may not be used to endorse or promote
  27  *    products derived from this software without specific prior written
  28  *    permission.
  29  *
  30  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
  31  * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
  32  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN
  33  * NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
  34  * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  35  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
  36  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  37  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
  38  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
  39  * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  40  * POSSIBILITY OF SUCH DAMAGE.
  41  *
  42  * Instead of accepting the above terms, you may redistribute and/or modify
  43  * this software under the terms of either the GNU General Public License,
  44  * or the GNU Library General Public License, published by the Free
  45  * Software Foundation; either version 2 of the License, or (at your
  46  * option) any later version.
  47  */
  48
  49 /*----- Revision history --------------------------------------------------*
  50  *
  51  * $Log: matrix.c,v $
  52  * Revision 1.2  2000/07/02 15:22:07  mdw
  53  * Fix licence text.  Change to matinv to mark inputs as constants.
  54  *
  55  * Revision 1.1  2000/05/21 11:28:30  mdw
  56  * Initial check-in.
  57  *
  58  */
  59
  60 /*----- Header files ------------------------------------------------------*/
  61
  62 #include <assert.h>
  63 #include <stdio.h>
  64 #include <stdlib.h>
  65
  66 #include "arith24.h"
  67 #include "bits.h"
  68 #include "matrix.h"
  69
  70 /*----- Main code ---------------------------------------------------------*/
  71
  72 /* --- @matmul@ --- *
  73  *
  74  * Arguments:   @uint24 *d@ = pointer to destination matrix
  75  *              @uint24 *a, *b@ = pointer to operand matrices
  76  *              @unsigned x, y, z@ = dimensions of the operand matrices
  77  *
  78  * Returns:     ---
  79  *
  80  * Use:         Performs matrix multiplication mod %$2^{24}$%.  The matrix
  81  *              @d@ may not overlap either operand matrix.
  82  */
  83
  84 void matmul(uint24 *d, const uint24 *a, const uint24 *b,
  85             unsigned x, unsigned y, unsigned z)
  86 {
  87   unsigned i, j, k;
  88
  89   for (i = 0; i < x; i++) {
  90     const uint24 *bb = b;
  91     for (j = 0; j < z; j++) {
  92       uint24 n = 0;
  93       for (k = 0; k < y; k++)
  94         n += a[k] * bb[k * z];
  95       *d++ = U24(n);
  96       bb++;
  97     }
  98     a += y;
  99   }
 100 }
 101
 102 /* --- @matinv@ --- *
 103  *
 104  * Arguments:   @uint24 *d@ = pointer to destination matrix
 105  *              @const uint24 *a@ = pointer to operand matrix
 106  *              @unsigned x, y@ = dimensions of operand matrix
 107  *
 108  * Returns:     Zero if the matrix was successfully inverted, %$-1$% if the
 109  *              matrix is singular.
 110  *
 111  * Use:         Computes the mod %$2^{24}$% inverse of a square matrix.
 112  */
 113
 114 int matinv(uint24 *d, const uint24 *a, unsigned x, unsigned y)
 115 {
 116   unsigned i, j, k;
 117   uint24 *aa;
 118   uint32 *p, *q, *r, *s;
 119
 120   assert(x == y);
 121
 122   aa = malloc(sizeof(uint24) * x * y);
 123   if (!aa) {
 124     fprintf(stderr, "unable to allocate memory\n");
 125     exit(EXIT_FAILURE);
 126   }
 127   memcpy(aa, a, sizeof(uint24) * x * y);
 128
 129   p = d;
 130   for (i = 0; i < x; i++) {
 131     for (j = 0; j < y; j++)
 132       *p++ = i == j;
 133   }
 134
 135   for (i = 0; i < x; i++) {
 136     uint24 c = inv24(aa[(x + 1) * i]);
 137     if (!c)
 138       goto fail;
 139     r = aa + y * i;
 140     s = d + y * i;
 141     for (j = 0; j < y; j++) {
 142       r[j] = U24(r[j] * c);
 143       s[j] = U24(s[j] * c);
 144     }
 145     for (j = 0; j < x; j++) {
 146       if (j == i)
 147         continue;
 148       p = aa + y * j;
 149       q = d + y * j;
 150       c = p[i];
 151       for (k = 0; k < y; k++) {
 152         p[k] = U24(p[k] - c * r[k]);
 153         q[k] = U24(q[k] - c * s[k]);
 154       }
 155     }
 156   }
 157
 158   free(aa);
 159   return (0);
 160
 161 fail:
 162   free(aa);
 163   return (-1);
 164 }
 165
 166 /*----- That's all, folks -------------------------------------------------*/