Detect Cores from Multiple Nodes

Question

I have a script in R that takes advantage of the doParallel package and the parallelized foreach function. I am currently registering my cluster by using a variation of the detectCores() command, which works quite well as the machine I am using has 32 cores.

My question is, if I have access to HPC resources with multiple Linux machines, is it possible to detectCores() from multiple machines and implement them in a single foreach call?

For example, if I submit my HPC job so that it uses two nodes, is it possible to get the detectCores() function to produce a value of 64 rather than 32?

Answer 1

Example summarizing solution in the comments of the top post:

library("parallel")

find_workers <- function(nodes) {
  nodes <- unique(nodes)
  cl <- makeCluster(nodes)
  on.exit(stopCluster(cl))

  ns <- clusterCall(cl, fun = detectCores)
  rep(nodes, times = ns)
}

workers <- find_workers(c("n1", "n2", "n3"))
cl <- makeCluster(workers)