Initialize "parallel" cluster on R startup

.Rprofile.R

require("utils")
require("parallel")

# do not start in RStudio
if (Sys.getenv("RSTUDIO_USER_IDENTITY") == "" && !file.exists(".cluster")) {
	cat(Sys.getpid(), file=".cluster")
	Cluster <- makeCluster(detectCores())
}

.First <- function() source("src/main.r")   # should load all other sources
.Last <- function() {
	if (exists("Cluster")) {
		stopCluster(Cluster)
		file.remove(".cluster")
	}
}