Mat multiplication

mat_mul.c

// gcc -O3 one.c && ./a.out
#include <stdio.h>
#include <stdlib.h>
#include <time.h>

float rand_float() { return (float)rand() / (float)RAND_MAX; }

float *calcmatrix(float ***matrix, int **indices, int big_size) {

  float acc = 1;
  int i_loc, j_loc;
  float *res = (float *)malloc(big_size * sizeof(float));

  for (int i = 0; i < big_size; i++) {
    for (int j = 0; j < big_size; j++) {
      acc = 1;
      for (int z = 0; z < 32; z++) {
        i_loc = indices[z][i];
        j_loc = indices[z][j];
        // i_loc = 4;
        // j_loc = 5;
        acc *= matrix[z][i_loc][j_loc];
      }
      res[i] += acc;
    }
  }
  return res;
}

int main() {
  // create 3 dimension big matrix
  // 32, 16x16 matrices
  srand(time(0));

  int s, x, y;
  s = 32;
  x = y = 16;
  int ind_size = 10000;

  float ***mat = (float ***)malloc(s * sizeof(float **));
  for (int i = 0; i < s; i++) {
    mat[i] = (float **)malloc(x * sizeof(float *));
    for (int j = 0; j < x; j++) {
      mat[i][j] = (float *)malloc(y * sizeof(float));
    }
  }

  // Fill in matrix with random numbers
  for (int k = 0; k < s; k++) {
    for (int i = 0; i < x; i++) {
      for (int j = 0; j < y; j++) {
        mat[k][i][j] = rand_float();
      }
    }
  }

  int **indices = (int **)malloc(s * sizeof(int *));
  for (int k = 0; k < s; k++) {
    indices[k] = (int *)malloc(ind_size * sizeof(int));
  }

  // Fill in matrix with numbers from 0 to x
  for (int i = 0; i < s; i++) {
    for (int j = 0; j < ind_size; j++) {
      indices[i][j] = rand() % x;
    }
  }

  clock_t start_time = clock();
  float *val = calcmatrix(mat, indices, ind_size);
  clock_t end_time = clock();

  double time_taken = (double)(end_time - start_time) / CLOCKS_PER_SEC;
  //
  // Print the time taken to print the matrix
  printf("Time taken to calc the matrix: %f seconds\n", time_taken);
  // printf("val %s\n", val);
}