R help - Feb 2011 - Rmpi; sample code not running, the slaves won't execute commands

Hi All,

I'm trying to parallelize some code using Rmpi and I've started with a
sample 'hello world' program that's available at
http://math.acadiau.ca/ACMMaC/Rmpi/sample.html. The code is as
follows;

# Load the R MPI package if it is not already loaded.
if (!is.loaded("mpi_initialize")) {
	library("Rmpi")
}
# Spawn as many slaves as possible
mpi.spawn.Rslaves(nslaves=3)
# In case R exits unexpectedly, have it automatically clean up
# resources taken up by Rmpi (slaves, memory, etc...)
.Last <- function(){
	if (is.loaded("mpi_initialize")){
		if (mpi.comm.size(1) > 0){
			print("Please use mpi.close.Rslaves() to close slaves.")
			mpi.close.Rslaves()
		}
		print("Please use mpi.quit() to quit R")
		.Call("mpi_finalize")
	}
}
# Tell all slaves to return a message identifying themselves
mpi.remote.exec(paste("I
am",mpi.comm.rank(),"of",mpi.comm.size()))
# Tell all slaves to close down, and exit the program
mpi.close.Rslaves()
mpi.quit()

My output is as follows;
> source("./test_Rmpi.R")
	3 slaves are spawned successfully. 0 failed.
master (rank 0, comm 1) of size 4 is running on: minanha
slave1 (rank 1, comm 1) of size 4 is running on: minanha
slave2 (rank 2, comm 1) of size 4 is running on: minanha
slave3 (rank 3, comm 1) of size 4 is running on: minanha

While trying to parallelize one of my other functions, I found that
the master seems to be sending the messages and executing its portion
of the program, but the slaves are not responding. However, the slaves
do seem to send the initial message to the master that they are ready
to receive a job, which prompts the master to send the job. So,
noticing that problem, I tried to execute the 'hello world' program
above and, as you can see, the slaves are spawned, but they won't
print the text in the mpi.remote.exec() function. Any ideas?

Chris

On Tue, 01-Feb-2011 at 11:01AM -0500, Chris Carleton wrote:

[...]

|> 
|> My output is as follows;
|> 

|> > source("./test_Rmpi.R")

How was test_Rmpi.R created?  Was it using sink()?

|> 	3 slaves are spawned successfully. 0 failed.
|> master (rank 0, comm 1) of size 4 is running on: minanha
|> slave1 (rank 1, comm 1) of size 4 is running on: minanha
|> slave2 (rank 2, comm 1) of size 4 is running on: minanha
|> slave3 (rank 3, comm 1) of size 4 is running on: minanha
|> 

[...]

|> noticing that problem, I tried to execute the 'hello world'
program
|> above and, as you can see, the slaves are spawned, but they won't
|> print the text in the mpi.remote.exec() function. Any ideas?

Are you saying that there was no response at all from the other three
lines?  They work fine for me.  I suspect that you have something not
quite finished with your MPI setup.  I doubt the problem is with Rmpi
itself, but then of course, there's not much to work on.

HTH



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