cluster_spec.R

#generates a cluster specification for the "spec" argument of the parallel::makeCluster() function
#ips: vector of computer ips within the local network: c('10.42.0.1', '10.42.0.34', '10.42.0.104')
#cores: vector of integers with the number of cores available on each computer, in the same order as ips: cores = c(7, 4, 4)
#user: character, name of the user in the different computers. Only one user name allowed.
#returns a list that can be used directly as input for the "spec" argument of makeCluster().
cluster_spec <- function(
  ips,
  cores,
  user
){
  
  #creating initial list
  spec <- list()
  
  for(i in 1:length(ips)){
    spec[[i]] <- list()
    spec[[i]]$host <- ips[i]
    spec[[i]]$user <- user
    spec[[i]]$ncore <- cores[i]
  }

  #generating nodes from the list of machines
  spec <- lapply(
    spec, 
    function(spec.i) rep(
      list(
        list(
          host = spec.i$host, 
          user = spec.i$user)
        ), 
      spec.i$ncore
      )
  )

  #formating into a list of lists
  spec <- unlist(
    spec, 
    recursive = FALSE
  )
  
  return(spec)
  
}