find_weights.c

error correction code

// ------------------------------------------------------------------------
// Name:    find_weights.c
// Author:  R.H. Morelos-Zaragoza
// Date:    February, 1996
//
// Description: Direct computation of the weight distribution of a linear 
// block code given its generator matrix
//
// ------------------------------------------------------------------------
// This program is complementary material for the book:
//
// R.H. Morelos-Zaragoza, The Art of Error Correcting Coding, Wiley, 2002.
//
// ISBN 0471 49581 6
//
// This and other programs are available at http://the-art-of-ecc.com
//
// You may use this program for academic and personal purposes only. 
// If this program is used to perform simulations whose results are 
// published in a journal or book, please refer to the book above.
//
// The use of this program in a commercial product requires explicit
// written permission from the author. The author is not responsible or 
// liable for damage or loss that may be caused by the use of this program. 
//
// Copyright (c) 2002. Robert H. Morelos-Zaragoza. All rights reserved.
// ------------------------------------------------------------------------
 
#include <stdio.h>
#include <math.h>

main(argc,argv)
int argc;
char **argv;
{
   int i1,i2,i3,i4,i5,i6,i7,i8;
   int i,j,tot,n,k,l,d_H,sum;
   double ii,jj,kk,nn;
   int g[1000][1000];
   int weight[1000];
   int c[1000];
   char fileG[100],fileH[100];
   FILE *fp1,*fp2,*fopen();
   void disp_matrix(),disp_array();
   void int_to_bin();

   if (argc != 4) 
     {
       printf("Usage: %s n k file\n", argv[0]);
       exit(1);
     }

   n = atoi(argv[1]);
   k = atoi(argv[2]);
   strcpy(fileG,argv[3]);

   nn = (double) n;
   kk = (double) k;

   fp1 = fopen(fileG,"r");

   for (i=0; i < n; i++) 
      weight[i] = 0;
      
   for (i=0; i < k; i++) 
   {   
      for (j=0; j < n; j++)
           fscanf(fp1,"%1d",&(g[i][j]));
      fscanf(fp1,"\n");
   }   
   fclose(fp1);
   
   for (ii=0.0;ii<pow(2.0,kk);ii=ii+1.0)
   {     
      int_to_bin(ii,c);  /* Taking ii in increasing order clears c[] automatically */
      sum = 0;
      for (j=0; j<n; j++)
      {
         tot = 0;
         for (l=0; l<k; l++)
         {
            tot = tot + c[l]*g[l][j];
         }
         tot = tot%2;
         sum = sum + tot;
      }
      weight[sum]++;
   }
   disp_array(weight,n);


}

void int_to_bin(ii,c)

     double ii;
     int c[];
{
     int i,j,q,r;

     q = (int) ii;
     j = 0;
     while (q>0)
     {
        r = q%2;
        q = q/2;
        c[j] = r;
        j++;
     }
}

void disp_array(array,n)
 
     int array[250];
     int n;
 
{
   int i;
 
   printf("i \tA[i]\n");
   for (i=0; i <= n; i++)
   {
       if (array[i] != 0)
       {
           printf("%d\t%d\n", i,array[i]);
       } 
   }    
}

void disp_matrix(matrix,n,k)

     int matrix[250][250];
     int n,k;

{
   int i,j;

   for (i=0; i < k; i++)
   {
       for (j=0; j < n; j++)
       { 
           printf("%d  ", matrix[i][j]);
       } 
       printf("\n");
   }
}