/* 
 * To compile: gcc -O3 naive_mm.c 
 *
 * To run: ./a.out matrix_size iterations 
 * for example: './a.out 2048 2' would report to time
 * to perform the multiplication of 2048x2048 matrices 2 times
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/time.h>

struct timeval t1, t2;

void  naive_mm(int size, double *a, double *b, double *c) 
{
	int i, j, k;
	for (i=0; i<size; i++)
		for (j=0; j < size; j++)
			for (k=0; k<size; k++) {
				*(c+i*size + j) = *(c+i*size + j) + *(a+i*size + k) *  *(b +k*size + j);
			}
}


int main( int argc, char *argv[])
{
	double *A, *B, *C, *W, *Z, *WORK;
	int  N, M, i;

	if (argc != 3) {
		printf("Usage: ./a.out matrix_size iter\n");
		exit(0);
	}

	N= atoi(argv[1]);
	M = atoi(argv[2]);

	srand48(100);

	A = (double *)malloc(N*N*sizeof(double));
	B = (double *)malloc(N*N*sizeof(double));
	C = (double *)malloc(N*N*sizeof(double));
	for (i=0; i<N*N; ++i) {
		A[i] = drand48();
		B[i] = drand48();
	}

  
	gettimeofday(&t1, NULL);
	for (i=0; i<M; i++) {
		naive_mm(N, B, A, C);
	}
	gettimeofday(&t2, NULL);
	
	printf("Time for the matrix multiplication is %d milliseconds\n",
	       (t2.tv_sec - t1.tv_sec)*1000 + 
	       (t2.tv_usec - t1.tv_usec) / 1000);

#ifdef CHECK
	{
		FILE *fd;
		if ((fd = fopen("tmp333", "w")) == NULL) {
			printf("Cannot open tmp333\n"); exit(0);
		}
		
		for (i=0; i<N*N; i++)
			fprintf(fd, "%6.2lf\n", C[i]);
		fclose(fd);
	}
#endif
  
	return 0;
}