MPI学习四-集合通信

1.集合通信

 

 （1）广播：是一对多通信的典型例子，调用格式如下：

           MPI_Bcast（Address,Count,Datatype,Root,Comm）

          

#include <stdio.h>
#include <mpi.h>

int main(int argc,char **argv)
{
    int rank;
    int ibuf;
    
    MPI_Init(&argc,&argv);
    MPI_Comm_rank(MPI_COMM_WORLD,&rank);
    
    if(rank == 0)
      ibuf = 12345;
    else
      ibuf = 0;

    MPI_Bcast(&ibuf,1,MPI_INT,0,MPI_COMM_WORLD);

    if(rank != 0)
    {
      printf("my rank = %d ibuf = %d
",rank,ibuf);
    }
    MPI_Finalize();

    return 0;
}

运行结果：

 （2）广播

 

 

 实例：

#include <stdio.h>
#include <mpi.h>
int main(int argc,char **argv)
{
    int i;
    int rank,nproc;
    int isend,irecv[32];
    MPI_Comm comm = MPI_COMM_WORLD;
    MPI_Init(&argc,&argv);
    MPI_Comm_size(comm,&nproc);
    MPI_Comm_rank(comm,&rank);

    isend = rank + 1;
    MPI_Gather(&isend,1,MPI_INT,irecv,1,MPI_INT,0,comm);

    if(rank == 0)
    {
      for( i=0; i<nproc; i++)
      {
        printf("irecv = %d 
",irecv[i]);
      }
    }

    MPI_Finalize();


    return 0;
}

运行结果：

 （3）散播

 

 实例：

#include "stdio.h"  
#include "mpi.h"  
#include "stdlib.h"  
#define N 10
int main(int argc, char **argv)
{
    int size, rank;
    int* send;
    int *recv;
    int i = 0;

    MPI_Init(&argc, &argv);
    MPI_Comm_size(MPI_COMM_WORLD, &size);
    MPI_Comm_rank(MPI_COMM_WORLD, &rank);


    send = (int *)malloc(size*N*sizeof(int));
    recv = (int *)malloc(N*sizeof(int));

    if (rank == 0)
    {
        for (; i < size*N; i++) {
            send[i] = i;
        }
    }

    MPI_Scatter(send, N, MPI_INT,recv, N, MPI_INT, 0, MPI_COMM_WORLD);

    
    printf("------------------------------------------------
rank=%d
", rank);
    for (i = 0; i < N; i++)
    {
        printf("recv_buffer[%d] = %d
", i, recv[i]);
     }  
    printf("------------------------------------------------
");

    MPI_Finalize();  
    return 0;  
}  

运行结果：

实例：