Multi Thread Benchmark in D

bench.d

import std.parallelism,
       std.algorithm,
       std.datetime,
       std.stdio,
       std.range,
       std.conv,
       std.math;

enum times = 100;
bool sideEffectTask;

void singleThread() {
  real[] cache;

  writeln("BEGIN singleThread");

  foreach(i; times.iota) {
    foreach(j; times.iota) {
      foreach(k; times.iota) {
        if (sideEffectTask) {
          cache ~= log(i + j + k + 1);
        } else {
          cast(void)(log(i + j + k + 1));
        }
      }
    }
  }

  writeln("END singleThread");
}

void multiThread() {
  real[] cache;

  writeln("BEGIN multiThread");

  foreach(i; times.iota.parallel) {
    foreach(j; times.iota.parallel) {
      foreach(k; times.iota.parallel) {
        if (sideEffectTask) {
          cache ~= log(i + j + k + 1);
        } else {
          cast(void)(log(i + j + k + 1));
        }
      }
    }
  }

  writeln("END multiThread");
}

void main() {
  writeln("---- NON SIDE EFFECT ----");
  auto result1 = benchmark!(singleThread, multiThread)(1);
  writeln("non-parallel: ", result1[0].length);
  writeln("parallel:    ", result1[1].length);

  sideEffectTask = true;
  writeln("---- SIDE EFFECT ----");
  auto result2 = benchmark!(singleThread, multiThread)(1);
  writeln("non-parallel: ", result2[0].length);
  writeln("parallel:    ", result2[1].length);

  writeln("NON SIDE EFFECT / SIDE EFFECT");
  writeln(" -> non-parallel / non-pararell :=> ", [result1[0], result2[0]].map!(x => x.length).reduce!"a/b");
  writeln(" ->     parallel /     pararell :=> ", [result1[1], result2[1]].map!(x => x.length).reduce!"a/b");
  writeln(" ->     parallel / non-pararell :=> ", [result1[1], result2[0]].map!(x => x.length).reduce!"a/b");
  writeln(" -> non-parallel /     pararell :=> ", [result1[0], result2[1]].map!(x => x.length).reduce!"a/b");
}
/*
Example(My Environment is MacBook Pro Retina Mid 2014(i5 2.6GHz)):

---- NON SIDE EFFECT ----
BEGIN singleThread
END singleThread
BEGIN multiThread
END multiThread
non-parallel: 279135744
parallel:    149555610
---- SIDE EFFECT ----
BEGIN singleThread
END singleThread
BEGIN multiThread
END multiThread
non-parallel: 133004875
parallel:    116941918
NON SIDE EFFECT / SIDE EFFECT
 -> non-parallel / non-pararell :=> 2
 ->     parallel /     pararell :=> 1
 ->     parallel / non-pararell :=> 1
 -> non-parallel /     pararell :=> 2
rdmd bench  1.44s user 0.15s system 112% cpu 1.404 total
*/