apply vs for-loop benchmark in R

apply_vs_for.R

#The task: sum 1000 different 10x10 matrices stored in a list

matrices <- vector(mode="list", length=1000)
for (i in seq_along(matrices)) {
  matrices[[i]] <- matrix(rnorm(1000), 10, 10)  
}

f1 <- function () {
  S <- matrix(0, 10, 10)
  for (M in matrices) {
    S <- S + M
  }
}

f2 <- function() {
  S <- apply(array(unlist(matrices),
                   dim = c(10, 10, 1000)),
             1:2, sum)
}

library(microbenchmark)
microbenchmark(for_loop = f1(), apply = f2())