/*************************************************************************

> File Name: mpi_parallelio.cpp

> Author:

> Mail:

> Created Time: 四 6/21 20:08:21 2018

************************************************************************/

#include <iostream>

#include <cstdio>

#include <cstdlib>

#include <string>

#include "mpi.h"

#include "util.h"

using namespace std;

int read_file(std::string, int* buf)

{

int tmp;

FILE* f = fopen("pio", "rb");

while(fread(&tmp, sizeof(int), 1, f) > 0)

cout << tmp << " ";

cout << endl;

fclose(f);

}

int main(int argc, char** argv)

{

int rank, size;

//array

const int N = 128;

int array[N] = {0};

int recv_array[N] = {0};

for(int i = 0; i < N; i++)

array[i] = i;

MPI_File fh;

MPI_Init(&argc, &argv);

MPI_Comm_size(MPI_COMM_WORLD, &size);

MPI_Comm_rank(MPI_COMM_WORLD, &rank);

const int BLOCK_SIZE = N / size;

MPI_Datatype etype, filetype;

MPI_Offset disp;

etype = MPI_INT;

MPI_Type_contiguous(BLOCK_SIZE, MPI_INT, &filetype);

MPI_Type_commit(&filetype);

MPI_File_open(MPI_COMM_WORLD, "pio", MPI_MODE_CREATE | MPI_MODE_WRONLY, MPI_INFO_NULL, &fh);

disp = rank * BLOCK_SIZE * sizeof(int);

MPI_File_set_view(fh, disp, etype, filetype, "native", MPI_INFO_NULL);

MPI_Status status;

MPI_File_write_all(fh, &array[rank * BLOCK_SIZE], BLOCK_SIZE, etype, &status);

MPI_File_close(&fh);

//MPI_Gather(&array[rank*2], 2, contig, &ret[rank], 2, contig, 0, MPI_COMM_WORLD);

MPI_Gather(&array[rank * BLOCK_SIZE], 1, filetype, recv_array, 1, filetype, 0, MPI_COMM_WORLD);

if(rank == 0)

{

for(int i = 0;i < N; i ++)

cout << recv_array[i] << " ";

cout << endl;

}

int *data = new int[N+1];

int cnt = 0;

if(rank == 0)

{

int tmp;

FILE* f = fopen("pio", "rb");

while(fread(&tmp, sizeof(int), 1, f) > 0)

{

cout << tmp << " ";

data[cnt++] = tmp;

}

cout << endl;

fclose(f);

bool isequal = true;

if(cnt != N)

isequal = false;

for(int i = 0;i < N; i ++)

if(recv_array[i] != data[i])

isequal = false;

if(isequal)

cout << "Right! : The gathered data is equal to data writed in file" << endl;

else

cout << "ERROR! : The gathered data is not equal to data writed in file" << endl;

}

MPI_Finalize();

return 0;

}