#include "mat_mul.h"

#include <cstdlib>
#include <cstdio>
#include <pthread.h>
#include <algorithm>
using namespace std;

static float *A, *B, *C;
static int M, N, K;
static int num_threads;

static void* mat_mul_thread(void *data) {
  // TODO: parallelize & optimize matrix multiplication
  // A[M*K] * B[K*N] = C[M*N];  
  int pid = * (int *) data;
  
  int slice = M / num_threads;
  int start = pid * slice;
  int end = pid == num_threads - 1 ? M : (pid + 1) * slice;
	
  float Aik;
  int bs = 64; // Block size
  for (int kk = 0; kk < K; kk += bs) {
      for (int i = start; i < end; ++i) {
        for (int k = kk; k < min(kk + bs, K); ++k) {
	  Aik = A[i * K + k];
  	  for (int j = 0; j < N; ++j) {
	    C[i * N + j] += Aik * B[k * N + j];		
	  }
	}
      }	      
  }

  return NULL; 
}

void mat_mul(float *_A, float *_B, float *_C, int _M, int _N, int _K, int _num_threads) {
  A = _A, B = _B, C = _C;
  M = _M, N = _N, K = _K;
  num_threads = _num_threads;

  // TODO: create '_num_threads' pthreads
  pthread_t *threads;
  threads = (pthread_t *) malloc(sizeof(pthread_t) * num_threads);

  for(int i = 0; i < num_threads; i++) {
    int * pid = (int *) malloc(sizeof(int));
    *pid = i;
    pthread_create(&threads[i], NULL, mat_mul_thread, pid);
  }

  for(int i =0; i < num_threads; i++) {
    pthread_join(threads[i], NULL);
  }
}