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Subject: [OMPI users] Basic Scatter Operation
From: Kevin Anthony Joy (kjoy96_at_[hidden])
Date: 2008-12-09 19:11:05


Good Evening All,
 
I'm very new to using MPI; I seem to be struggling to get a basic understanding of the MPI::Comm_World.Scatter Operation, It seem's as though a may be misunderstanding how the scatter operation works. Suppose i have an Array of x amount of doubles, let's say 3 doubles that i want to spread across three processes.
 
I have -
 
#include <iostream>#include <mpi.h>
int main(int argc, char* argv[]){ MPI_Init(&argc, &argv); int rank, procs; MPI_Comm_size(MPI_COMM_WORLD, &procs); MPI_Comm_rank(MPI_COMM_WORLD, &rank);
    double stat[3] ; stat[0] = 1.2; stat[1] = 65.3; stat[2] = 45.3;
    double test3[3];
    if (rank==0) {
    MPI::COMM_WORLD.Scatter( stat, 1, MPI::DOUBLE, &test3, 1, MPI::DOUBLE, 0); }
   std::cout << rank <<" rec'd " << test3[0] << std::endl;
   MPI_Finalize();}
 
Unfortunately, this doesn't output what i'd like. I'd like: Process 0 to output 1.2, process 1 to output 65.3 and process 2 to output 45.3 etc etc. I apologise if this question is very trivial.
 
Regards,
 
 
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