library(Rmpi)
library(snow)

# Initialize SNOW using MPI communication. The first line will get the
# number of MPI processes the scheduler assigned to us. Everything else 
# is standard SNOW

np <- mpi.universe.size()
cluster <- makeMPIcluster(np)

# Print the hostname for each cluster member
sayhello <- function()
{
	info <- Sys.info()[c("nodename", "machine")]
	paste("Hello from", info[1], "with CPU type", info[2])
}

names <- clusterCall(cluster, sayhello)
print(unlist(names))

# Compute row sums in parallel using all processes,
# then a grand sum at the end on the master process
parallelSum <- function(m, n)
{
	A <- matrix(rnorm(m*n), nrow = m, ncol = n)
	row.sums <- parApply(cluster, A, 1, sum)
	print(sum(row.sums))
}

parallelSum(500, 500)

stopCluster(cluster)
mpi.exit()