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

void matmul(float *A, float *B, float *C, int l, int m, int n)
{
  int i, j, k;

  for (i = 0; i < l; i++)
  {
    for (j = 0; j < n; j++)
    {
    float sum = 0.0;
    for (k = 0; k < m; k++)
      sum += A[i * m + k] * B[k * n + j];
    C[i*n+j] = sum;
    }
  }
}

void init_matrix(float *A, int h, int w)
{
  int i, j, k;
  for (i = 0; i < h; i++)
  {
    for (j = 0; j < w; j++)
    {
      A[i * w + j] = i + j;
    }
  }
}

void alloc_matrix(float **m_h, int h, int w)
{
  *m_h = (float *)malloc(sizeof(float) * h * w);
}

//
//   MAIN
//
int main(int argc, char *argv[])
{
  double time_spent = 0.0;
  float *Ah, *Bh, *Ch;
  int L, M, N;

  clock_t begin = clock();

  L = atoi(argv[1]);
  M = atoi(argv[2]);
  N = atoi(argv[3]);

  // prepare matrix A
  alloc_matrix(&Ah, L, M);
  init_matrix(Ah, L, M);

  // prepare matrix B
  alloc_matrix(&Bh, M, N);
  init_matrix(Bh, M, N);

  // allocate space for matrix C
  alloc_matrix(&Ch, L, N);

  // call matmul (Matrix Multiplication) function
  matmul(Ah, Bh, Ch, L, M, N);

  clock_t end = clock();
  time_spent += (double)(end - begin) / CLOCKS_PER_SEC;
  printf("The elapsed time to multiply a [%d x %d] matrix with a [%d x %d] matrix is %.2f seconds.\n\n",L,M,M,N,time_spent);

  return 0;
}