Quick Bench String Compares

C/C++
Last updated on 2019-11-27
I’ve done this before, had to compare strings, I was curious what a Quick Bench graph might give me.
Full Code

#include <string.h>

static void IntCmpBaseline(benchmark::State& state) {
  uint32_t val1 = 123;
  uint32_t val2 = 1234;

  for (auto _ : state) {
    bool eq = val1 == val2;
    benchmark::DoNotOptimize(eq);
  }
}
BENCHMARK(IntCmpBaseline);

static void StdStrCmp(benchmark::State& state) {
  std::string str1("Some_quite_large_string1");
  std::string str2("Fome_quite_large_string2");

  for (auto _ : state) {
    bool eq = str1 == str2;
    benchmark::DoNotOptimize(eq);
  }
}
BENCHMARK(StdStrCmp);

static void CStrStrcmp(benchmark::State& state) {
  const char * str1 = "Some_quite_large_string1";
  const char * str2 = "Fome_quite_large_string2";

  for (auto _ : state) {
    bool eq = !!(strcmp(str1,str2) == 0);
    benchmark::DoNotOptimize(eq);
  }
}
BENCHMARK(CStrStrcmp);

static void CStrFirstCharThenStrcmp(benchmark::State& state) {
  const char * str1 = "Some_quite_large_string1";
  const char * str2 = "Fome_quite_large_string2";

  for (auto _ : state) {
    bool eq = false;

    uint32_t a = *(uint32_t*)str1;
    uint32_t b = *(uint32_t*)str2;

    if(a == b) {
      eq = !!(strcmp(str1,str2) == 0);
    }

    benchmark::DoNotOptimize(eq);
  }
}
BENCHMARK(CStrFirstCharThenStrcmp);

static void StdStrStrcmp(benchmark::State& state) {
  std::string str1 = "Some_quite_large_string1";
  std::string str2 = "Fome_quite_large_string2";

  for (auto _ : state) {
    bool eq = !!(strcmp(str1.c_str(),str2.c_str()) == 0);
    benchmark::DoNotOptimize(eq);
  }
}
BENCHMARK(StdStrStrcmp);

static void StdStrGetCStrEarlyStrcmp(benchmark::State& state) {
  std::string str1 = "Some_quite_large_string1";
  std::string str2 = "Fome_quite_large_string2";

  const char *cstr1 = str1.c_str();
  const char *cstr2 = str2.c_str();

  for (auto _ : state) {
    bool eq = !!(strcmp(cstr1, cstr2) == 0);
    benchmark::DoNotOptimize(eq);
  }
}
BENCHMARK(StdStrGetCStrEarlyStrcmp);

static void StdStrFirstCharThenStrcmp(benchmark::State& state) {
  std::string str1 = "Some_quite_large_string1";
  std::string str2 = "Fome_quite_large_string2";

  for (auto _ : state) {
    bool eq = false;

    uint32_t a = *(uint32_t*)str1.c_str();
    uint32_t b = *(uint32_t*)str2.c_str();

    if(a == b) {
      eq = !!(strcmp(str1.c_str(),str2.c_str()) == 0);
    }
    benchmark::DoNotOptimize(eq);
  }
}
BENCHMARK(StdStrFirstCharThenStrcmp);