#include <stdlib.h>
#include <string.h>

void matmul(double a[], double b[], double c[], size_t m, size_t n, size_t p)
{
  size_t i,j,k;
  double r;
  memset(c,0,n*p*sizeof(double));
  for (i=0; i<n; i++)
    for (k=0; k<m; k++)
      for (j=0; j<p; j++)
        c[i*p+j] += a[i*m+k]*b[k*p+j];
}