:( Sorry, Another MPI Problem

[maverick_starst]

Hi, I can't seem to find a help forum dedicated to MPI, this was the closest I could find. Anyways, I am having problem with the following code:

#include <iostream>
#include <math.h>
#include <bitset>
#include <fstream>
#include <mpi.h>

using namespace std;

MPI_Request req;
MPI_Status stat;

MPI_Datatype type[2]={MPI_INT,MPI_DOUBLE};
MPI_Datatype MSG;
int blocklen[2]={1,1};
MPI_Aint disp[2]={0,sizeof(int)};

struct message{
    int position;
    double data;   // *** HERE ***
};
message snd,rcv;

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

    MPI_Init(&argc,&argv);
    MPI_Type_struct(2,blocklen,disp,type,&MSG);
    MPI_Type_commit(&MSG);
    double tt=0.0;
    int myRank,nProcs;
    MPI_Comm_rank(MPI_COMM_WORLD, &myRank);
    MPI_Comm_size(MPI_COMM_WORLD, &nProcs);
    if(myRank==0){
        tt=3.0;
        snd.data=tt;
        snd.position=1111;
        rcv.position=snd.position;
        for(int i=1;i<nProcs;i++){
            MPI_Isend(&snd,1,MSG,i,0,MPI_COMM_WORLD,&req);
            MPI_Wait(&req,&stat);
        }
    }
    else{
        MPI_Recv(&rcv,1,MSG,0,0,MPI_COMM_WORLD,&stat);
        tt=rcv.data;
    }
    cout << "Server " << myRank << " has " << tt << " and " << rcv.position << endl;

}

Basically all the code does is have the root process send the double 3.0 to the other process. When I run this code all servers but server 0 receive the message as 0 not 3. However, if I just change the line marks //*** HERE ** in struct to "float data" and use data as a float instead it works. Does anybody have any idea why this might be happening? I've tried fiddling with the MPI_Aint disp[2]={0,sizeof(int)}; line but that doesn't seem to do anything. Any help would be greatly appreciated.

P.S. please don't suggest I use bcast or some such , I need the code to have a coupled Isend and Rcv

[Salem]

Well most (if not all) of the MPI functions return a status result.
How about some RTM and adding some error checking.

Perhaps it will tell you why it isn't working, rather than you just "*shrug* it doesn't work"