#include "mat_mul.h"

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

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

static void* mat_mul_thread(void *data) {
  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 = 32;

  for (int kk=0; kk<K; kk+=bs) {
      for (int i=start; i<end; ++i) {
        for (int k=kk; k<std::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;

  pthread_t * thread;
  thread = (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(&thread[i], NULL, mat_mul_thread, pid);
  }

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