Micro benchmark for arma::shuffle

shuffle_bench.cpp

#include <benchmark/benchmark.h>
#include <algorithm>
#include <armadillo>

static void baseline(benchmark::State& state) {
  while (state.KeepRunning()) {
    arma::vec test(100, arma::fill::randn);
    benchmark::DoNotOptimize(test);
  }
}


static void arma_shuffle(benchmark::State& state) {
  while (state.KeepRunning()) {
    arma::vec test(100, arma::fill::randn);
    test = std::move(arma::shuffle(test));
  }
}

static void std_shuffle(benchmark::State& state) {
  while (state.KeepRunning()) {
    arma::vec test(100, arma::fill::randn);
    std::random_shuffle(test.begin(), test.end());
  }
}

BENCHMARK(baseline);
BENCHMARK(arma_shuffle);
BENCHMARK(std_shuffle);

BENCHMARK_MAIN();

stdout

λ mlpack_spike/random ∴ g++ shuffle_bench.cpp -O2 -Wall -std=c++11 -lbenchmark -larmadillo -pthread
λ mlpack_spike/random ∴ ./a.out
Run on (4 X 3660.03 MHz CPU s)
2017-07-23 23:20:32
Benchmark             Time           CPU Iterations
---------------------------------------------------
baseline           3472 ns       3472 ns     199661
arma_shuffle       8323 ns       8323 ns      83864
std_shuffle        5346 ns       5346 ns     126702