c++ - 我的收集缓冲区是空的？

Question

我在从所有进程收集数据到进程主“root”时遇到问题，我可以发送数据 MPI_Bcast 但在 MPI_Gather 上，我的 countBuff 中存在所有问题我调试我的输出，这就是我所拥有的

output 

    brodcast data of 0
    brodcast data of 1
    MPI_Gather data rank 0 1
    from 0 to 1.00 KM:-842150451,from 1.00 to 2.00 KM:-842150451,from 2.00 to 5.00 KM:-842150451,grater than 5.00 KM:-842150451
    MPI_Type_free1
    delete countBuff
    MPI_Finalize
    brodcast data of 2
    MPI_Gather data rank 0 0
    MPI_Gather data rank 0 2
    from 0 to 1.00 KM:-842150451,from 1.00 to 2.00 KM:-842150451,from 2.00 to 5.00 KM:-842150451,grater than 5.00 KM:-842150451
    MPI_Type_free2
    delete countBuff
    MPI_Finalize

    job aborted:
    rank: node: exit code[: error message]
    0:: -1073741819: process 0 exited without calling finalize
    1:: 123
    2:: 123


the code 


void ProcesData(int rank,int numProcs)
{

    static countType count;
    MPI_Datatype recType = createRecType();
    //read file and populate the vectors
    ifstream foodbankFile("foodbanks.dat");
    ifstream residenceFile("residences.dat");

    // populate datavector
    std::vector<Foodbank> foodbankData((std::istream_iterator<Foodbank>(foodbankFile)),
        std::istream_iterator<Foodbank>());

    Residence res;
    int numLines = 0;


    while(!residenceFile.eof())
    {
        residenceFile >> res.x >>res.y;


        if ( numLines % numProcs == rank)
        {
            //call the  process
            //populate_distancesVector(res,foodbankData);
            analysis_range(populate_distancesVector(res,foodbankData),count);

        }
        ++numLines;

    }


    cout<<"brodcast data of "<<rank<<endl;
    MPI_Bcast(&count, 1, recType, rank, MPI_COMM_WORLD);
    MPI_Type_free(&recType);
    //std::cout<< "for Rank"<<rank<< ",from 0 to 1.00 KM:"<<count.range1<<",%"<<count.preset1
    //<<",from 1.00 to 2.00 KM:"<<count.range2<<",%"<<count.preset2<<",from 2.00 to 5.00 KM:"
    //<<count.range3<<",%"<<count.preset3<<",grater than 5.00 KM:"<<count.range4<<",%"<<count.preset3<<std::endl;
}


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

        if( MPI_Init(&argc, &argv) == MPI_SUCCESS )
        {
            // Get the number of processes and the rank of this process
            int procRank,numProcs;
            MPI_Comm_size(MPI_COMM_WORLD, &numProcs);
            MPI_Comm_rank(MPI_COMM_WORLD, &procRank);


            ProcesData(procRank,numProcs);


            // Create a derived type for passing the rec array
            MPI_Datatype recType = createRecType();
            static countType count;
            countType* countBuff  = new countType[numProcs];

            MPI_Gather(&count, 1, recType, &countBuff, 1, recType,0, MPI_COMM_WORLD);
            cout<<"MPI_Gather data rank 0 "<<procRank<<endl;
            //MPI_Allgather(&count, 1, recType, &countBuff, 1, recType,MPI_COMM_WORLD);

            std::cout<<"from 0 to 1.00 KM:"<<countBuff[0].range1<<",from 1.00 to 2.00 KM:"
                <<countBuff[0].range2<<",from 2.00 to 5.00 KM:"<<countBuff[0].range3
                <<",grater than 5.00 KM:"<<countBuff[0].range4<<std::endl;


            cout<<"MPI_Type_free"<<procRank<<endl;
            MPI_Type_free(&recType);
            cout<<"delete countBuff"<<endl;

            cout<<"MPI_Finalize"<<endl;
            MPI_Finalize();


        }
        return 0;
    }

Answer 1

一开始我误读了你的帖子。抱歉。

看看这段代码:

        ProcesData(procRank,numProcs);


        // Create a derived type for passing the rec array
        MPI_Datatype recType = createRecType();
        static countType count;
        countType* countBuff  = new countType[numProcs];

        MPI_Gather(&count, 1, recType, &countBuff, 1, recType,0, MPI_COMM_WORLD);
        cout<<"MPI_Gather data rank 0 "<<procRank<<endl;

问题在于 MPI_Gather 发送 &count。但请仔细阅读代码。将发送的count值是多少？

要么你误解了 Bcast 和 Gather - 它们没有关系。一点也不! - 或者，您错误地认为来自 ProcessData 的“计数”将神奇地流入来自 main 的“计数”。他们不会。这些是不同的变量。在这种情况下，只需从 ProcessData 中返回计数即可。

查看 http://mpitutorial.com/mpi-scatter-gather-and-allgather/ 中的示例它们与您正在尝试做的事情非常相似。

编辑:

嗯..实际上，在第四次阅读你的代码后，我不明白你想发送什么以及发送到哪里。做出决定:您想将“计数”发送给所有工作人员，还是想读取所有工作人员的计数？如果您想要一个典型的情况，当一些工作人员读取输入文件的某些部分时，每个工作人员都会计算一些内容，然后“收集”结果 - 请参阅上面的链接。否则，你将不得不详细说明，因为我的想象力已经结束了。