#include "mat_mul.h"

#include <cstdlib>
#include <cstdio>
#include <pthread.h>

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

  //for (int i = row_start; i < row_end; ++i) {
  //for (int i = 0; i < M; ++i) {
  //    for (int j = 0; j < N; ++j) {
  //      for (int k = 0; k < K; ++k) {
  //        C[i * N + j] += A[i * K + k] * B[k * N + j];
  //      }
  //  }
  //}
  int x = * (int *) data;
  int start = x * (M / num_threads);
  int end = start + (M / num_threads);

  if (x == num_threads - 1)
  {
    end = M;
  }
  
  float Aik;
  int bs = 50;
  int k_max;
  
  for (int kk = 0; kk < K; kk += bs)
  {
    if ((kk + bs) < K)
    {
      k_max = kk + bs;
    }
    else
    {
      k_max = K;
    }

    for (int i = start; i < end; ++i)
    {
      for (int k = kk; k < k_max; ++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
  int i;
  int* p = (int*)malloc(sizeof(int) * num_threads);

  pthread_t thread[num_threads];

  for (i = 0; i < num_threads; i++)
  {
    p[i] = i;

    pthread_create(&thread[i], NULL, mat_mul_thread, &p[i]);
  }

  for (i = 0; i <num_threads; i++)
  {
    pthread_join(thread[i], NULL);
  }
  
  free(p);

}