Benchmark results

D:\build>type ..\vclib-benchmarks\benchmarks\make_pair_str.cpp
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <string>
#include <algorithm>
#include <random>
#include <benchmark/benchmark.h>

using namespace std;

__declspec(noinline) char *make_pair_c_opt(char const *s1, char const *s2)
{
    const size_t s1Len = strlen(s1);
    const size_t s2Len = strlen(s2);
    size_t len = s1Len + s2Len + 4;
    char *str = (char *)malloc(len + 1);
    if (str) {
        char *next = str;
        *next++ = '(';
        memcpy(next, s1, s1Len);
        next += s1Len;
        *next++ = ',';
        *next++ = ' ';
        memcpy(next, s2, s2Len);
        next += s2Len;
        *next++ = ')';
        *next++ = '\0';
    }

    return str;
}

__declspec(noinline) char *make_pair_c(char const *s1, char const *s2)
{
    int len = snprintf(nullptr, 0, "(%s, %s)", s1, s2);
    char *str = (char *)malloc(len + 1);
    if (str) {
        snprintf(str, len, "(%s, %s)", s1, s2);
        str[len] = 0;
    }
    return str;
}

__declspec(noinline) string make_pair_cpp(char const *s1, char const *s2)
{
    string result("(");
    result += s1;
    result += ", ";
    result += s2;
    result += ')';
    return result;
}

__declspec(noinline) string make_pair_cpp_reserve(char const *s1, char const *s2)
{
    const size_t s1Len = strlen(s1);
    const size_t s2Len = strlen(s2);
    size_t len = s1Len + s2Len + 4;
    string result;
    result.reserve(len);
    result += '(';
    result.append(s1, s1Len);
    result += ", ";
    result.append(s2, s2Len);
    result += ')';
    return result;
}

__declspec(noinline) string make_pair_cpp_opt(char const *s1, char const *s2)
{
    const size_t s1Len = strlen(s1);
    const size_t s2Len = strlen(s2);
    size_t len = s1Len + s2Len + 4;
    string result(len, '\0');
    auto next = result.begin();
    *next++ = '(';
    next = copy_n(s1, s1Len, next);
    *next++ = ',';
    *next++ = ' ';
    next = copy_n(s2, s2Len, next);
    *next++ = ')';
    return result;
}

string gen_random_string() {
    random_device rd;
    string result(100, '\0');
    for (char& c : result) {
        c = static_cast<char>(rd());
    }

    return result;
}

const string g_in1Str = gen_random_string();
const char * g_in1 = g_in1Str.c_str();
const string g_in2Str = gen_random_string();
const char * g_in2 = g_in2Str.c_str();

static void make_pair_c_opt_bench(benchmark::State& state) {
    for (auto _ : state) {
        free(make_pair_c_opt(g_in1, g_in2));
    }
}

BENCHMARK(make_pair_c_opt_bench);

static void make_pair_c_bench(benchmark::State& state) {
    for (auto _ : state) {
        free(make_pair_c(g_in1, g_in2));
    }
}

BENCHMARK(make_pair_c_bench);

static void make_pair_cpp_bench(benchmark::State& state) {
    for (auto _ : state) {
        (void)make_pair_cpp(g_in1, g_in2);
    }
}

BENCHMARK(make_pair_cpp_bench);

static void make_pair_cpp_reserve_bench(benchmark::State& state) {
    for (auto _ : state) {
        (void)make_pair_cpp_reserve(g_in1, g_in2);
    }
}

BENCHMARK(make_pair_cpp_reserve_bench);

static void make_pair_cpp_opt_bench(benchmark::State& state) {
    for (auto _ : state) {
        (void)make_pair_cpp(g_in1, g_in2);
    }
}

BENCHMARK(make_pair_cpp_opt_bench);

BENCHMARK_MAIN();

D:\build>.\make_pair_str.exe
07/19/18 13:52:34
Running .\make_pair_str.exe
Run on (32 X 2592 MHz CPU s)
CPU Caches:
  L1 Data 32K (x16)
  L1 Instruction 32K (x16)
  L2 Unified 1048K (x16)
  L1 Data 32K (x16)
  L1 Instruction 32K (x16)
  L2 Unified 1048K (x16)
  L3 Unified 25952K (x1)
-------------------------------------------------------------------
Benchmark                            Time           CPU Iterations
-------------------------------------------------------------------
make_pair_c_opt_bench              116 ns        117 ns    6400000
make_pair_c_bench                  364 ns        361 ns    1947826
make_pair_cpp_bench                217 ns        218 ns    3446154
make_pair_cpp_reserve_bench        139 ns        138 ns    4977778
make_pair_cpp_opt_bench            218 ns        220 ns    3200000

D:\build>