[mpich-discuss] Mpich2: problems with communications

[The Source]

I'm using mpich2 1.0.7. I installed and configured it on 2 machines, 
started daemons.
The problems begin when I launch my program: first MPI_Bcast succeeds, 
but the second one (or any other communication function) hangs. Source 
code is attached.

Also when I call MPI_Bcast, second machine deamon prints the following:
F9Virtual64_mpdman_1 (run282): invalid msg from lhs; expecting ringsize 
got: {}

Can anyone look at the code and tell me what's wrong?

#include <mpi.h>
#include <stdio.h>
#include <string.h>
#include <math.h>
#include <sys/time.h>

int main(int arg_c, char** arg_v)
{
    if(arg_c<2)
    {
        printf("Input file not specified\n");
        return 0;
    }
    if(MPI_Init(&arg_c, &arg_v)!=MPI_SUCCESS)
    {
        printf("MPI initialization failed\n");
        return 0;
    }
    int ProcNum, ProcRank;
    MPI_Comm_size(MPI_COMM_WORLD, &ProcNum);
    MPI_Comm_rank(MPI_COMM_WORLD, &ProcRank);
   
    int size;
    double e;
    double* A;
    double* b;
    double* x, *xprev;
   
    FILE* f=0;
    if(!ProcRank)
    {
        f=fopen(arg_v[1], "r");
        if(!f)
        {
            printf("Error opening input file\n");
            MPI_Finalize();
            return 0;
        }
        fscanf(f, "%d", &size);
        printf("Enter desired accuracy\n");
        scanf("%lf", &e);
    }
    if(!ProcRank)
        printf("Broadcasting matrix size\n");
    if(MPI_Bcast(&size, 1, MPI_INT, 0, MPI_COMM_WORLD)!=MPI_SUCCESS)
        if(!ProcRank)
            printf("Failed to broadcast matrix size\n");
    if(!ProcRank)
        printf("Broadcasting accuracy\n");
    if(MPI_Bcast(&e, 1, MPI_DOUBLE, 0, MPI_COMM_WORLD)!=MPI_SUCCESS)
        if(!ProcRank)
            printf("Failed to broadcast accuracy\n");
    A=new double[size*size];
    b=new double[size];
    x=new double[size];
    xprev=new double[size];
   
    memset(x, 0, size*sizeof(double));
    memset(xprev, 0, size*sizeof(double));
   
    if(!ProcRank)
    {
        for(int i=0; i<size; i++)
            for(int j=0; j<size; j++)
                fscanf(f, "%lf", &(A[i*size+j]));
        for(int i=0; i<size; i++)
            fscanf(f, "%lf", &(b[i]));
        fclose(f);
    }
   
    if(!ProcRank)
        printf("Waiting all processes to be initialized\n");
    MPI_Barrier(MPI_COMM_WORLD);
   
    if(!ProcRank)
        printf("Broadcasting matrix\n");
    MPI_Bcast(A, size*size, MPI_DOUBLE, 0, MPI_COMM_WORLD);
    if(!ProcRank)
        printf("Broadcasting b\n");
    MPI_Bcast(b, size, MPI_DOUBLE, 0, MPI_COMM_WORLD);
   
    double cursum, totalsum;
    int fin, itercount=0;
   
    if(!ProcRank)
        printf("Starting calculation\n");
    struct timeval tv1, tv2;
    gettimeofday(&tv1, 0);
    do
    {
        MPI_Bcast(xprev, size, MPI_DOUBLE, 0, MPI_COMM_WORLD);
        itercount++;
        for(int i=0; i<size; i++)
        {
            int snum=(size)/ProcNum;
            cursum=0.0;
            totalsum=0.0;
            for(int n=ProcRank*snum; 
n<((ProcRank==ProcNum-1)?(size):((ProcRank+1)*snum)); n++)
            {
                if(n<=i-1)
                    cursum+=A[i*size+n]*x[n];
                else
                    cursum+=A[i*size+n]*xprev[n];
            }
            MPI_Barrier(MPI_COMM_WORLD);
            MPI_Reduce(&cursum, &totalsum, 1, MPI_DOUBLE, MPI_SUM, 0, 
MPI_COMM_WORLD);
            if(!ProcRank)
            {
                x[i]=xprev[i]-1.0/A[i*size+i]*(totalsum-b[i]);
            }
        }
        if(!ProcRank)
        {
            fin=1;
            for(int i=0; i<size; i++)
                if(fabs(x[i]-xprev[i])>e)
                    fin=0;
            if(!fin)
                memcpy(xprev, x, size*sizeof(double));
        }
        MPI_Bcast(&fin, 1, MPI_INT, 0, MPI_COMM_WORLD);
    }
    while(!fin);
   
    gettimeofday(&tv2, 0);
   
    if(!ProcRank)
    {
        printf("Matrix A:\n");
        for(int i=0; i<size; i++)
        {
            for(int j=0; j<size; j++)
                printf("%lf ", A[i*size+j]);
            printf("\n");
        }
        printf("\n");
        printf("Line b:\n");
        for(int i=0; i<size; i++)
            printf("%lf ", b[i]);
        printf("\n");
       
        printf("Iteration number: %d\n", itercount);
        printf("Calculation time: %d microseconds\n", 
(tv2.tv_sec-tv1.tv_sec)*1000000+(tv2.tv_usec-tv1.tv_usec));
       
        printf("Results: \n");
        for(int i=0; i<size; i++)
            printf("x%d=%lf\n", i+1, x[i]);
    }
   
    MPI_Barrier(MPI_COMM_WORLD);
   
    delete [] A;
    delete [] b;
    delete [] x;
    delete [] xprev;
   
    MPI_Finalize();
   
    return 0;
}