C++ benchmark for record padding.

padding_bench.cpp

#include <vector>

using namespace std;

struct Record1 {
    int a;
    char c;
    double d;
    bool e;
};

struct Record2 {
    double d;
    int a;
    char c;
    bool e;
};

const int N = 10000;

vector<Record1> recs1(N);
vector<Record2> recs2(N);

template <class T>
int count_as(const vector<T> recs) {
  int total = 0;
  for (const auto& rec : recs) {
    total += rec.a;
  }
  return total;
}

static void bench_1(benchmark::State& state) {
  int count = 0;
  for (auto _ : state) {
    benchmark::DoNotOptimize(count += count_as(recs1));
  }
}
BENCHMARK(bench_1);

static void bench_2(benchmark::State& state) {
  int count = 0;
  for (auto _ : state) {
    benchmark::DoNotOptimize(count += count_as(recs2));
  }
}
BENCHMARK(bench_2);