Reproducing performance results for vector insertion with google benchmark

Question

Recently I saw the following result regarding the insertion of elements into the front of std::list and std::vector:

• for std::list the time is linear
• for std::vectorthe time polynomial
• but for a small number of elements (<800) std::vector beats list

src: https://github.com/CppCon/CppCon2022/blob/main/Presentations/Refresher-on-Containers-Algorithms-and-Performance.pdf

I tried to reproduce these results with google benchmark.

#include <benchmark/benchmark.h>

static void bm_vec(benchmark::State &state) {
    for (auto _ : state)
    {
        state.PauseTiming();
        std::vector<int> v ;
        benchmark::DoNotOptimize(v.data());
        state.ResumeTiming();
        for (int i = 0; i < state.range(0); i++)
        {
           v.insert(v.begin(), 1);
        }
        benchmark::ClobberMemory();
    }
}

BENCHMARK(bm_vec)->DenseRange(10,2000,10);

static void bm_list(benchmark::State &state) {
    
    for (auto _ : state)
    {
        state.PauseTiming();
        std::list<int> v ;
        benchmark::DoNotOptimize(v.front());
        state.ResumeTiming();
        for (int i = 0; i < state.range(0); i++)
        {
            v.insert(v.begin(), 1);
        }
        
    }
}
BENCHMARK(bm_list)->DenseRange(10,2000,10);

BENCHMARK_MAIN();

But my results did not reproduce the desired effect:

Does anyone know what I need to improve to get the desired result?

Answer 1

Setting O3( add_compile_options(-O3) ) solved the problem.