#include "mat_mul.h"

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

#include <omp.h>
#include <algorithm>
#include "util.h"

#define NODE0 0

using namespace std;

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

#define ITILE 32
#define JTILE 1024
#define KTILE 1024

static void mat_mul_omp() {
	// TODO: parallelize & optimize matrix multiplication
	// Use num_threads per node
	// A[M*K] * B[K*N] = C[M*N];

	int node_rows = M / mpi_world_size;

	int start, end, rows;
	start = mpi_rank * node_rows;
	end = (mpi_rank == mpi_world_size - 1) ? M : (mpi_rank+1)*node_rows;
	rows = end - start;

	int tid = omp_get_thread_num();

	int slice = rows / num_threads;
	start = tid * slice + min(tid, rows % num_threads);
	end = (tid + 1) * slice + min(tid + 1, rows % num_threads);

	#pragma omp parallel for
	for (int ii = start; ii < end; ii += ITILE) {
		for( int jj = 0; jj < N; jj += JTILE) {
			for (int kk = 0; kk < K; kk += KTILE) {

				for (int k = kk; k < min(K, kk + KTILE); ++k) {
					for (int i = ii; i < min(end, ii + ITILE); ++i) {
						float Aik = A[i * K + k];
						for (int j = jj; j < min(N, jj + JTILE); ++j) {
							C[i * N + j] += Aik * B[k * N + j];
						}
					}
				}
			}
		}
	}
}

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

	// TODO: parallelize & optimize matrix multiplication on multi-node
	// You must allocate & initialize A, B, C for non-root processes	
	MPI_Request request;
	MPI_Status status;

	// FIXME: for now, only root process runs the matrix multiplication.	
	if (mpi_rank == 0){
		int node_rows = M / mpi_world_size;
		int start, end, rows;

		for(int node = 1; node < mpi_world_size; node++) {
			start = node * node_rows;
			end = (node == mpi_world_size - 1) ? M : (node + 1) * node_rows;
			rows = end - start;

			MPI_Isend(&A[start*K], rows*K, MPI_FLOAT, node, 0, MPI_COMM_WORLD, &request);
			MPI_Isend(B, K*N, MPI_FLOAT, node, 0, MPI_COMM_WORLD, &request);
		}

		#pragma omp parallel num_threads(num_threads)
		mat_mul_omp();

		for(int node = 1; node < mpi_world_size; node++) {
			start = node * node_rows;
			end = (node == mpi_world_size - 1) ? M : (node + 1) * node_rows;
			rows = end - start;

			MPI_Recv(&C[start*N], rows*N, MPI_FLOAT, node, 0, MPI_COMM_WORLD, &status);
		}
	}
	else {
		int node_rows = M / mpi_world_size;
		int start, end, rows;
		start = mpi_rank * node_rows;
		end = (mpi_rank == mpi_world_size - 1) ? M : (mpi_rank + 1) * node_rows;
		rows = end - start;

		alloc_mat(&A, M, K);
		alloc_mat(&B, K, N);
		alloc_mat(&C, M, N);
		zero_mat(C, M, N);

		MPI_Recv(A, rows*K, MPI_FLOAT, NODE0, 0, MPI_COMM_WORLD,&status);
		MPI_Recv(B, K*N, MPI_FLOAT, NODE0, 0, MPI_COMM_WORLD,&status);

		#pragma omp parallel num_threads(num_threads)
		mat_mul_omp();

		MPI_Isend(C, rows*N, MPI_FLOAT, NODE0, 0, MPI_COMM_WORLD,&request);
	}
}