gistfile1.txt

C:\Users\bion\Desktop>type bench.cpp
#include "benchmark/benchmark.h"
#pragma comment(lib, "benchmark")
#pragma comment(lib, "shlwapi")

#include <stddef.h>
#include <algorithm>
#include <random>
#include <string>
#include <string_view>
#include <vector>

template<class Parameter>
__declspec(noinline)
std::vector<size_t> even_char_indexes(Parameter target) {
    // get all the offsets to chars with even values in `target`
    std::vector<size_t> result;
    result.reserve(target.size());
    for (size_t idx = 0; idx < target.size(); ++idx) {
        if ((target[idx] & 1) == 0) {
            result.push_back(idx);
        }
    }

    return result;
}

template<class Parameter, size_t Count>
void benchmark_even_char_indexes(benchmark::State& state) {
    // fill a string of chars to test
    std::mt19937 gen(1729);
    char testData[Count];
    std::generate(testData, testData + Count, [&gen]() {
        return static_cast<char>(static_cast<unsigned char>(gen()));
        });

    for (auto _ : state) {
        even_char_indexes<Parameter>(testData);
    }
}

BENCHMARK_TEMPLATE2(benchmark_even_char_indexes, const std::string_view, 8);
BENCHMARK_TEMPLATE2(benchmark_even_char_indexes, const std::string_view, 16);
BENCHMARK_TEMPLATE2(benchmark_even_char_indexes, const std::string_view, 64);
BENCHMARK_TEMPLATE2(benchmark_even_char_indexes, const std::string_view, 256);
BENCHMARK_TEMPLATE2(benchmark_even_char_indexes, const std::string_view, 1024);
BENCHMARK_TEMPLATE2(benchmark_even_char_indexes, const std::string&, 8);
BENCHMARK_TEMPLATE2(benchmark_even_char_indexes, const std::string&, 16);
BENCHMARK_TEMPLATE2(benchmark_even_char_indexes, const std::string&, 64);
BENCHMARK_TEMPLATE2(benchmark_even_char_indexes, const std::string&, 256);
BENCHMARK_TEMPLATE2(benchmark_even_char_indexes, const std::string&, 1024);

BENCHMARK_MAIN();

C:\Users\bion\Desktop>cl /nologo /EHsc /wd4141 /W4 /WX /O2 /std:c++17 /MD /IC:\Dev\vcpkg\installed\x86-windows\include .\bench.cpp /link /LIBPATH:C:\Dev\vcpkg\installed\x86-windows\lib
bench.cpp

C:\Users\bion\Desktop>.\bench.exe
Run on (32 X 2592 MHz CPU s)
12/12/17 18:18:23
------------------------------------------------------------------------------------------------
Benchmark                                                         Time           CPU Iterations
------------------------------------------------------------------------------------------------
benchmark_even_char_indexes<const std::string_view,8>            67 ns         67 ns   11200000
benchmark_even_char_indexes<const std::string_view,16>           76 ns         78 ns   11200000
benchmark_even_char_indexes<const std::string_view,64>           90 ns         90 ns    7466667
benchmark_even_char_indexes<const std::string_view,256>          93 ns         94 ns    7466667
benchmark_even_char_indexes<const std::string_view,1024>         89 ns         89 ns    8960000
benchmark_even_char_indexes<const std::string&,8>                75 ns         75 ns    8960000
benchmark_even_char_indexes<const std::string&,16>              128 ns        128 ns    5600000
benchmark_even_char_indexes<const std::string&,64>              144 ns        144 ns    4977778
benchmark_even_char_indexes<const std::string&,256>             144 ns        143 ns    4480000
benchmark_even_char_indexes<const std::string&,1024>            144 ns        144 ns    4977778

C:\Users\bion\Desktop>