[mpich-discuss] Stuck in a MPI program

[Long Li]

 Hi,guys:

 I put 15 struct variables into a continuous memory at first by using memcpy(). And then I want to print out the element of first struct variable. The correct value is 1, but sometimes "0" is printed out. I do not know why. Can someone who is familar with C and MPI tell me the reason of that?

  Thanks,




#include <stdio.h>
#include <mpi.h>
#include <stdlib.h>
#include <string.h>
typedef struct message message;
struct message
{
  message*prev;
    message*next;
    int recv_pe;
};

//typedef struct message message;

int main (int argc, char **argv)
{
  int rank, size;
 
  int iter=10000;
  int number=15;
    
    int ierr,errclass;
  ierr=0; 
    MPI_Request request;
    MPI_Status status; 
    int send_buffer[5],recv_buffer[5];
  MPI_Init (&argc, &argv);    /* starts MPI */
  MPI_Comm_rank (MPI_COMM_WORLD, &rank);    /* get current process id */
  MPI_Comm_size (MPI_COMM_WORLD, &size);    /* get number of processes */
 
// MPI_Errhandler_set(MPI_COMM_WORLD,MPI_ERRORS_RETURN); /* return info about
//          errors */
//    printf( "Hello world from process %d of %d\n", rank, size );
    if(rank==0)
    {  
        int kk;
        for(kk=0;kk<iter;kk++)
                {
        int buffsize= number*sizeof(message);
            char*buffer=(char*)malloc(buffsize*sizeof(char));
       // void*buffer=(char*)malloc((unsigned)buffsize);
            int position=0;
            message* sendevent[number];
            int i;
            for(i=0,position=0;i<number;i++,position+=sizeof(message))
            {
                sendevent[i]=malloc(sizeof(message));
                sendevent[i]->recv_pe=i;
        memcpy(&buffer[position],sendevent[i],sizeof(message));
      }
            ierr= MPI_Isend(buffer,buffsize, MPI_BYTE,1, 1,MPI_COMM_WORLD,&request);         
            }

        }
    else
        {
          int kk;
            for(kk=0;kk<iter;kk++)
            {
        int buffsize=number*sizeof(message);
            char*buffer=(char*)malloc(sizeof(char)*buffsize);
            int position=0;
            message *tmp=NULL;
            int flag=0;
                int i;
                MPI_Request request;
                MPI_Status status2;
                while(flag==0)
                    {
                        MPI_Iprobe(MPI_ANY_SOURCE,
                        MPI_ANY_TAG,
                         MPI_COMM_WORLD,
                         &flag,
                         &status);
         }

         ierr=MPI_Irecv(buffer,buffsize,MPI_BYTE,0,1,MPI_COMM_WORLD,&request);                   
                
                for(i=0,position=0;i<number;i++,position+=sizeof(message))
                {
                 tmp=(message*)&buffer[position];
                 if(i==1&&tmp->recv_pe==0)
                 printf("error :recv data invalid\n");
                }
            }
        }
                
  MPI_Finalize();
  return 0;
}
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