source: CIVL/mods/dev.civl.abc/examples/c/matprod.c

#include <stdio.h>
#include <stdlib.h>

#define NRA 62                 /* number of rows in matrix A */
#define NCA 15                 /* number of columns in matrix A */
#define NCB 7                  /* number of columns in matrix B */

int main (int argc, char *argv[])
{
int     i, j, k, chunk;
double  a[NRA][NCA],           /* matrix A to be multiplied */
        b[NCA][NCB],           /* matrix B to be multiplied */
        c[NRA][NCB];           /* result matrix C */

chunk = 10;                    /* set loop iteration chunk size */

  {
    printf("Initializing matrices...\n");

  for (i=0; i<NRA; i++)
    for (j=0; j<NCA; j++)
      a[i][j]= i+j;

  for (i=0; i<NCA; i++)
    for (j=0; j<NCB; j++)
      b[i][j]= i*j;

  for (i=0; i<NRA; i++)
    for (j=0; j<NCB; j++)
      c[i][j]= 0;

  for (i=0; i<NRA; i++)
    {
    for(j=0; j<NCB; j++)
      for (k=0; k<NCA; k++)
        c[i][j] += a[i][k] * b[k][j];
    }
  }

printf("******************************************************\n");
printf("Result Matrix:\n");
for (i=0; i<NRA; i++)
  {
  for (j=0; j<NCB; j++)
    printf("%6.2f   ", c[i][j]);
  printf("\n");
  }
printf("******************************************************\n");
printf ("Done.\n");

}