Question

当我尝试在程序中调用多个MPI_Send或MPI_Recv时，可执行文件在节点和根目录中被挂起。即，当它试图执行第二MPI_Send或MPI_Recv时，通信被阻止。同时，二进制文件在机器中以100％运行。

当我尝试在Windows 7 64位中使用OpenMPI 1.6.3 64位运行此代码时，它成功运行。但是相同的代码在Linux中不起作用，即具有OpenMPI 1.6.3 -64位的CentOS 6.3 x86_64。我做了什么问题。

发布以下代码

#include <mpi.h>

int main(int argc, char** argv) {
MPI::Init();
int rank = MPI::COMM_WORLD.Get_rank();
int size = MPI::COMM_WORLD.Get_size();
char name[256] = { };
int len = 0;
MPI::Get_processor_name(name, len);

printf("Hi I'm %s:%d\n", name, rank);

if (rank == 0) 
{
    while (size >= 1) 
    {
        int val, stat = 1;
        MPI::Status status;
        MPI::COMM_WORLD.Recv(&val, 1, MPI::INT, 1, 0, status);
        int source = status.Get_source();
        printf("%s:%d received %d from %d\n", name, rank, val, source);

        MPI::COMM_WORLD.Send(&stat, 1, MPI::INT, 1, 2);
        printf("%s:%d sent status %d\n", name, rank, stat);

        size--;
    }
} else 
{
    int val = rank + 10;
    int stat = 0;
    printf("%s:%d sending %d...\n", name, rank, val);
    MPI::COMM_WORLD.Send(&val, 1, MPI::INT, 0, 0);
    printf("%s:%d sent %d\n", name, rank, val);

    MPI::Status status;
    MPI::COMM_WORLD.Recv(&stat, 1, MPI::INT, 0, 2, status);
    int source = status.Get_source();
    printf("%s:%d received status %d from %d\n", name, rank, stat, source);
}

size = MPI::COMM_WORLD.Get_size();
if (rank == 0) 
{
    while (size >= 1) 
    {
        int val, stat = 1;
        MPI::Status status;

        MPI::COMM_WORLD.Recv(&val, 1, MPI::INT, 1, 1, status);
        int source = status.Get_source();
        printf("%s:0 received %d from %d\n", name, val, source);

        size--;
    }

    printf("all workers checked in!\n");
} 
else
{
    int val = rank + 10 + 5;
    printf("%s:%d sending %d...\n", name, rank, val);
    MPI::COMM_WORLD.Send(&val, 1, MPI::INT, 0, 1);
    printf("%s:%d sent %d\n", name, rank, val);
}
MPI::Finalize();

return 0;

}

嗨，Hristo，我已按照您的说法更改了源代码并且代码再次发布

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

int main(int argc, char** argv) 
{
    int iNumProcess = 0, iRank = 0, iNameLen = 0, n;
    char szNodeName[MPI_MAX_PROCESSOR_NAME] = {};
    MPI_Status stMPIStatus;

    MPI_Init(&argc, &argv);
    MPI_Comm_size(MPI_COMM_WORLD, &iNumProcess);
    MPI_Comm_rank(MPI_COMM_WORLD, &iRank);
    MPI_Get_processor_name(szNodeName, &iNameLen);

    printf("Hi I'm %s:%d\n", szNodeName, iRank);

    if (iRank == 0) 
    {
        int iNode = 1;
        while (iNumProcess > 1) 
        {
            int iVal = 0, iStat = 1;
            MPI_Recv(&iVal, 1, MPI_INT, MPI_ANY_SOURCE, 0, MPI_COMM_WORLD, &stMPIStatus);
            printf("%s:%d received %d\n", szNodeName, iRank, iVal);

            MPI_Send(&iStat, 1, MPI_INT, iNode, 1, MPI_COMM_WORLD);
            printf("%s:%d sent Status %d\n", szNodeName, iRank, iStat);

            MPI_Recv(&iVal, 1, MPI_INT, MPI_ANY_SOURCE, 2, MPI_COMM_WORLD, &stMPIStatus);
            printf("%s:%d received %d\n", szNodeName, iRank, iVal);

            iNumProcess--;
            iNode++;
        }

        printf("all workers checked in!\n");
    }
    else 
    {
        int iVal = iRank + 10;
        int iStat = 0;
        printf("%s:%d sending %d...\n", szNodeName, iRank, iVal);
        MPI_Send(&iVal, 1, MPI_INT, 0, 0, MPI_COMM_WORLD);
        printf("%s:%d sent %d\n", szNodeName, iRank, iVal);

        MPI_Recv(&iStat, 1, MPI_INT, 0, 1, MPI_COMM_WORLD, &stMPIStatus);
        printf("%s:%d received status %d\n", szNodeName, iRank, iVal);

        iVal = 20;
        printf("%s:%d sending %d...\n", szNodeName, iRank, iVal);
        MPI_Send(&iVal, 1, MPI_INT, 0, 2, MPI_COMM_WORLD);
        printf("%s:%d sent %d\n", szNodeName, iRank, iVal);

    }

    MPI_Finalize();

    return 0;
}

我得到的输出如下。即，在发送发送/接收之后，root无限等待，并且节点以100％的CPU利用率进行破坏。它的输出低于

Hi I'm N1433:1
N1433:1 sending 11...
Hi I'm N1425:0
N1425:0 received 11
N1425:0 sent Status 1
N1433:1 sent 11
N1433:1 received status 11
N1433:1 sending 20...

这里N1433和N1425是机器名称。请帮忙

Answer 1

主人的代码是错误的。它总是发送和等待来自相同等级的消息 - 等级1。因此，如果以mpiexec -np 2 ...运行，程序将只能正常运行。您可能想要做的是使用MPI_ANY_SOURCE作为源排名，然后使用该源排名作为发送操作中的目标。您也不应该使用while (size >= 1)，因为排名0没有与自己交谈，预计通信次数会少于size。

if (rank == 0) 
{
    while (size > 1)
    //     ^^^^^^^^
    {
        int val, stat = 1;
        MPI::Status status;
        MPI::COMM_WORLD.Recv(&val, 1, MPI::INT, MPI_ANY_SOURCE, 0, status);
        // Use wildcard source here ------------^^^^^^^^^^^^^^
        int source = status.Get_source();
        printf("%s:%d received %d from %d\n", name, rank, val, source);

        MPI::COMM_WORLD.Send(&stat, 1, MPI::INT, source, 2);
        // Send back to the same process --------^^^^^^
        printf("%s:%d sent status %d\n", name, rank, stat);

        size--;
    }
} else

在工人身上做这样的事情毫无意义：

MPI::Status status;
MPI::COMM_WORLD.Recv(&stat, 1, MPI::INT, 0, 2, status);
// Source rank is fixed here ------------^
int source = status.Get_source();
printf("%s:%d received status %d from %d\n", name, rank, stat, source);

您已在接收操作中指定等级0作为来源，因此它只能接收来自等级0的消息。除status.Get_source()之外，0无法返回除MPI::COMM_WORLD.Recv()之外的任何值，除非发生了一些通信错误，在这种情况下，Boost.MPI会抛出异常。

代码中的第二个循环也是如此。

顺便说一句，您使用的是以前的官方标准C ++绑定。它们在MPI-2.2中被弃用，最新版本的标准（MPI-3.0）完全删除了它们，因为MPI论坛不再支持它们。您应该使用C绑定，或者依赖于{{1}}等第三方C ++接口。

Answer 2

安装和MPICH2而不是OpenMPI后，它成功运行。我认为在我的集群机器中使用OpenMPI 1.6.3存在一些问题。

OpenMPI多个MPI_Send和MPI_recv无法正常工作

2 个答案: