MPI_Type_create_subarray和MPI_SEND [英] MPI_Type_create_subarray and MPI_Send

问题描述

这是我的第一个问题在这里计算器。我有两个过程，一个根0和从1。从机分配一个二维数组（CHUNK_ROWS + 2，CHUNK_COLUMNS + 2），要发送[CHUNK_ROWS] [CHUNK_COLUMNS]子阵。根分配一个二维数组（行，列）并接收希望从DDD存储[0] [0]和打印子阵。结果我得到它的wrong..Why？
我知道这是一个无感code，但它只是一个简单的程序，应该帮助我在更复杂的项目。
在这里，code：

this is my first question here in stackoverflow. I have two processes, a root 0 and a slave 1. Slave allocates a 2d array (CHUNK_ROWS+2,CHUNK_COLUMNS+2) and wants to send a [CHUNK_ROWS][CHUNK_COLUMNS] subarray. Root allocates a 2d array (ROWS,COLUMNS) and receives the subarray that wants to store from ddd[0][0] and print it. The result I get it's wrong..Why? I know this is a non sense code but it's only a simple program that should help me in more complex project. Here the code:

#include <mpi.h>
#include <iostream>
using namespace std;

#define ROWS 10
#define COLUMNS 10
#define CHUNK_ROWS 5
#define CHUNK_COLUMNS 5
#define TAG 0

int** alloca_matrice(int righe, int colonne)
{
int** matrice=NULL;
int i;

// per allocare la matrice devo fare in questo modo al fine di avere le righe contigue in memoria
// e poter così utilizzare il tipo 'colonna' che definisco con MPI_Type_Vector()
matrice = (int **)malloc(righe * sizeof(int*));

if(matrice != NULL){
    matrice[0] = (int *)malloc(righe*colonne*sizeof(int));
    if(matrice[0]!=NULL)
        for(i=1; i<righe; i++)
            matrice[i] = matrice[0]+i*colonne;
    else{
        free(matrice);
        matrice = NULL;
    }
}
else{
    matrice = NULL;
}
return matrice;
}


int main(int argc, char* argv[])
{

int my_id, numprocs,length,i,j;
int ndims, sizes[2],subsizes[2],starts[2];
int** DEBUG_CH;
int** ddd;
char name[BUFSIZ];
MPI_Datatype subarray;
MPI_Status status;
MPI_Init(&argc, &argv) ;                    // Chiamata obbligatoria di inizializzazione    
MPI_Comm_rank(MPI_COMM_WORLD, &my_id) ;     // Ottiene l'identificativo del processo
MPI_Comm_size(MPI_COMM_WORLD, &numprocs) ;  // Ottiene quanti processi sono attivi
MPI_Get_processor_name(name, &length);      // Il nome del nodo dove il processo ? in esecuzione



if(my_id==1){
    //creo una sottomatrice ripulita dalle ghost cells
    ndims=2;
    sizes[0] = CHUNK_ROWS+2;
    sizes[1] = CHUNK_COLUMNS+2;
    subsizes[0] = CHUNK_ROWS;
    subsizes[1] = CHUNK_COLUMNS;
    starts[0] = 1;
    starts[1] = 1;
    MPI_Type_create_subarray(ndims,sizes,subsizes,starts,MPI_ORDER_C,MPI_INT,&subarray);
    MPI_Type_commit(&subarray);

    DEBUG_CH = alloca_matrice(CHUNK_ROWS+2,CHUNK_COLUMNS+2);
    for(i=0; i<CHUNK_ROWS+2; i++){
        for(j=0; j<CHUNK_COLUMNS+2; j++){
            if(i==0 || i==CHUNK_ROWS+1 || j==0 || j==CHUNK_COLUMNS+1)
                DEBUG_CH[i][j] = 5;
            else
                DEBUG_CH[i][j] = 1;
        }
    }
    MPI_Send(DEBUG_CH,1,subarray,0,TAG,MPI_COMM_WORLD);
    MPI_Type_free(&subarray);
}
if(my_id==0){
    //creo una sottomatrice ripulita dalle ghost cells
    ndims=2;
    sizes[0] = ROWS;
    sizes[1] = COLUMNS;
    subsizes[0] = CHUNK_ROWS;
    subsizes[1] = CHUNK_COLUMNS;
    starts[0] = 0;
    starts[1] = 0;
    MPI_Type_create_subarray(ndims,sizes,subsizes,starts,MPI_ORDER_C,MPI_INT,&subarray);
    MPI_Type_commit(&subarray);

    ddd = alloca_matrice(ROWS,COLUMNS);
    MPI_Recv(ddd[0],1,subarray,1,TAG,MPI_COMM_WORLD,&status);
    MPI_Type_free(&subarray);
    for(i=0; i<CHUNK_ROWS; i++){
        for(j=0; j<CHUNK_COLUMNS; j++){
            printf("%d ",ddd[i][j]);
        }
        printf("\n");
    }
}
MPI_Finalize();                             // Chiusura di MPI.
return 0;
}

先谢谢了。

推荐答案

Congratulazioni，您的code几乎是完美的，有一个在你就在MPI_RECV得到了MPI_SEND只是一个愚蠢的错误。

Congratulazioni, your code is almost perfect, there's just one silly mistake in the MPI_Send which you got right in the MPI_Recv.

有关发送，你有

MPI_Send(DEBUG_CH,1,subarray,0,TAG,MPI_COMM_WORLD);

而对于recv的，你有

whereas for the Recv, you have

MPI_Recv(ddd[0],1,subarray,1,TAG,MPI_COMM_WORLD,&status);

第二个是正确的。您需要发送一个数据指针开始的地方;这不是DEBUG_CH，这是一个指针的指针整数，但与放大器;（DEBUG_CH [0] [0]），或等价地，DEBUG_CH [0]，当你与DDD确实

The second is right. You need to send a pointer to where the data starts; that's not DEBUG_CH, which is a pointer to a pointer to ints, but &(DEBUG_CH[0][0]), or equivalently, DEBUG_CH[0], as you did with ddd.

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