MPI_Bcast hanging

我按照这里的示例添加了一些代码进行测试，但在添加新代码时出现了一些奇怪的结果。结果如下所示。它在这里挂断了，无法继续。

[0]: Before Bcast, buf is 777
[1]: Before Bcast, buf is 32767
[0]: After Bcast, buf is 777

从两个角度来看，这很奇怪：

1. 代码为if(rank==i) if(i==0) 时不会挂断

2. 乳清CCD_ 2在bcast前不为0。

这是代码：

#include <mpi.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
int main(int argc, char** argv) {
    int rank;
    int buf;
    const int root=0;
    MPI_Init(&argc, &argv);
    MPI_Comm_rank(MPI_COMM_WORLD, &rank);
    if(rank == root) {
       buf = 777;
    }
    printf("[%d]: Before Bcast, buf is %dn", rank, buf);
    // newly added
    for(int i=0; i<2; i++)
    {
        if(rank==i)
        {
            if(i==1)
            MPI_Bcast(&buf, 1, MPI_INT, rank, MPI_COMM_WORLD);
        }
    }
    // end newly added
    /* everyone calls bcast, data is taken from root and ends up in everyone's buf */
    MPI_Bcast(&buf, 1, MPI_INT, root, MPI_COMM_WORLD);
    printf("[%d]: After Bcast, buf is %dn", rank, buf);
    MPI_Finalize();
    return 0;
}

我真正想做的是实现以下功能：每个处理器运行部分处理，然后在获得结果后广播，其他处理器通过组合接收结果来更新自己的结果。

以下是代码的主要部分（原始代码来自libsvm）

struct decision_function
{
    double *alpha;
    double rho;
};
int gate_no = 2;
int p = 0;
int nr_class = 8;
for(int i=0;i<nr_class;i++)
{
    for(int j=i+1;j<nr_class;j++)
    {
        if(((world_rank==i-2*gate_no*(i/(2*gate_no))) && (i%(2*gate_no) < gate_no))||((world_rank==2*gate_no*(i/(2*gate_no)+1)-i-1)&&(i%(2*gate_no) >= gate_no)))
        {
            // some process for generating f[p] here
            ....
            MPI_Bcast(f[p].alpha, count[i]+count[j], MPI_DOUBLE, world_rank, MPI_COMM_WORLD);
        }
        ++p;
    }
}

但是这个代码不起作用，我也有一些错误。

Fatal error in PMPI_Bcast: Other MPI error, error stack:
PMPI_Bcast(1478)......................: MPI_Bcast(buf=0xcc7b40, count=2340, MPI_DOUBLE, root=1, MPI_COMM_WORLD) failed
MPIR_Bcast_impl(1321).................: 
MPIR_Bcast_intra(1119)................: 
MPIR_Bcast_scatter_ring_allgather(962): 
MPIR_Bcast_binomial(154)..............: message sizes do not match across processes in the collective