Matrix multiplication sequential code

mm.c

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <sys/time.h>
#include <assert.h>

#define RANDLIMIT	5	/* Magnitude limit of generated randno.*/
#define N		4  	/* Matrix Size */
#define NUMLIMIT 70.0

float a[N][N];
float b[N][N];
float c[N][N];

int main(int argc, char *argv[])
{
	struct timeval start, stop;
	int i, j, k;


	/* generate mxs  */
	for (i = 0; i < N; i++)
	for (j = 0; j < N; j++) {
		a[i][j] = 1 + (int)(NUMLIMIT*rand() / (RAND_MAX + 1.0));
		b[i][j] = (double)(rand() % RANDLIMIT);

	}

#ifdef PRINT
	/* print matrices */
	printf("Matrix A:\n");
	for (i = 0; i < N; i++){
		for (j = 0; j < N; j++)
			printf("%.3f\t", a[i][j]);
		printf("\n");
	}

	printf("Matrix B:\n");
	for (i = 0; i < N; i++){
		for (j = 0; j < N; j++)
			printf("%.3f\t", b[i][j]);
		printf("\n");
	}

	printf("Matrix C:\n");
	for (i = 0; i < N; i++){
		for (j = 0; j < N; j++)
			printf("%.3f\t", c[i][j]);
		printf("\n");
	}
#endif

	gettimeofday(&start, 0);

	for (i = 0; i < N; i++) {
		for (j = 0; j < N; j++) {
			c[i][j] = 0.0;
			for (k = 0; k < N; k++)
				c[i][j] = c[i][j] + a[i][k] * b[k][j];
		} /* end j loop */
	}

	gettimeofday(&stop, 0);

#ifdef PRINT
	/* print results*/
	printf("Answer c:\n");
	for (i = 0; i < N; i++){
		for (j = 0; j < N; j++)
			printf("%.3f\t", c[i][j]);
		printf("\n");
	}
#endif

	fprintf(stdout, "Time = %.6f\n\n",
		(stop.tv_sec + stop.tv_usec*1e-6) - (start.tv_sec + start.tv_usec*1e-6));
	return(0);
}