#include "mat_mul.h"

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

#ifndef BLK_SIZE
#define BLK_SIZE  48
#endif

#define MIN(x, y) (((x) < (y)) ? (x) : (y))

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

static void* mat_mul_thread(void *data) {
  long id = *((long *)data);
  long chunk = M / num_threads;
  long start = chunk * id;
  long end = start + chunk;

  if (id == num_threads - 1)
    end = M;

  for (int kk = 0; kk < K; kk += BLK_SIZE) {
    for (int i = start; i < end; i++) {
      for (int k = kk; k < MIN(kk + BLK_SIZE, K); k++) {
        register float 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 *threads = (pthread_t *)malloc(_num_threads * sizeof(pthread_t));
  long *ids = (long *)malloc(_num_threads * sizeof(long));

  for (int i = 0; i < _num_threads; i++) {
    ids[i] = i;
    pthread_create(&threads[i], NULL, mat_mul_thread, (void *)&ids[i]);
  }

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

  free(ids);
  free(threads);
}