Dear People,
This may not be the right place to ask a question about Rmpi, but I don't
know of a better one.
I am trying to get a simple program working using Rmpi with the model of 1
R master and n C slaves. What I am trying to do is have each of the C
slaves generate a random number from U[0,1], and then have the master
collect all n numbers as a vector and output it. However even doing this
is rather over my head. I'm trying to use rsprng and sprng, but I am sure
what I am currently doing is wrong.
I enclose a first attempt. Any suggestions would be appreciated. Thanks in
advance.
Faheem.
*************************************************************************
rand.R
*************************************************************************
library(Rmpi)
rand <- function ()
{
if (mpi.comm.size(1) > 1)
stop ("It seems some slaves running on comm 1.")
mpi.comm.spawn("./rand")
mpi.intercomm.merge(2,0,1)
mpi.init.sprng()
free.sprng() #does this function exist here?
rdata <- double(sum(mpi.comm.size(1)))
out <- mpi.gather(0, 2, rdata) ##this isn't right
mpi.comm.free()
out
}
*************************************************************************
rand.c
*************************************************************************
#include <mpi.h>
#include <sprng.h>
int main(int argc, char **argv)
{
double rand;
double* randarray;
MPI_Comm slavecomm, all_processes;
/*Initialize MPI*/
MPI_Init(&argc, &argv);
MPI_Comm_get_parent(&slavecomm);
MPI_Intercomm_merge(slavecomm, 1, &all_processes);
/*How many processes are there?*/
MPI_Comm_size(all_processes, &size);
/*Which one am I?*/
MPI_Comm_rank(all_processes, &rank);
init_sprng()
rand = sprng();
free.sprng()
randarray = (double *)malloc(sizeof(double)*size);
/*Gather random numbers from all C slave processes*/
/* Using randarray doesn't make sense since this should correspond
to the rdata vector in the R master process */
MPI_GAther(&rand, 1, 1, MPI_DOUBLE, randarray, 1, MPI_DOUBLE, 0, all_processes);
/*All done*/
MPI_Comm_free(&all_processes);
MPI_Finalize();
exit(0);
}
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