Thread: MPI_Allreduce question

In the code below. I use MPI_Allreduce in order to sum the old_chrome[x].fitness.

Code:

#include <stdio.h>
#include <mpi.h>
#include <time.h>
#include <stdlib.h>


struct chromosome{
 int fitness;
 int glob_fit;
};
struct chromosome  old_chrome[10];




int main(int argc, char *argv[])
{int i,id,p,j;

  MPI_Init(&argc,&argv);
  MPI_Comm_rank(MPI_COMM_WORLD,&id);
  MPI_Comm_size(MPI_COMM_WORLD,&p);
  
  for(i=0;i<10;i++)
    {old_chrome[i].fitness=i;}

 for(i=0;i<10;i++)
   {   printf("rank=%d  i=%d  value= %d\n",id,i,old_chrome[i].fitness);}
 
 printf("\n");

 MPI_Allreduce(&old_chrome[0].fitness,&old_chrome[0].glob_fit,10,MPI_INT,MPI_SUM,MPI_COMM_WORLD);

 for(i=0;i<10;i++)
    {
      printf("rank %d i= %d  value %d\n",id,i,old_chrome[i].glob_fit);}
    


MPI_Finalize();
 return 0;
}

What happens is that for each old_chrome[i] i am taking the output only for the 5 first [0-4]. I guess that the number of elements in send buffer that I use (10) is half of the number needed (when I use 20 I am taking output from all) because I have two members in the structure (so need double memory) . Is there any way to have only the one member sended?

Can you post the code for these functions?

Also you should either move your functions above main and get rid of the declarations or move your declarations above the main procedure. As they are now, they're only valid inside main.

THanks for the reply codeplug.
Is there any other way to do this without changing these lines of code?

Many thanks on behalf

thank you. This is what I was thinking. No way to avoid loading network
many thanks