foreach_bench.R

library(compiler)
library(foreach)

f.original <- function() {
  x <- 0
  for (p in 1:2) {
    for (i in 1:500) {
      for (j in 1:5000) {
        x <- x + i * j
      }
    }
  }
  x
}

f.foreach <- function() {
  x <- 0
  foreach(p = 1:2, .combine = rbind) %do% 
    for (i in 1:500) {
      for (j in 1:5000) {
        x <- x + i * j
      }
    }
  x
}

f.cmpfun <- function(x) {
  f <- cmpfun(function(x) {
    for (i in 1:500) {
      for (j in 1:5000) {
        x <- x + i * j
      }
    }
    x
  })
  f(f(0))
}

library(microbenchmark)
microbenchmark(f.original(),f.foreach(),f.cmpfun(), times=100)