fmtlib vs. strstream: (1) constructing text message from numbers and strings - google bench

bench1_fmt

float dt1 = 13.35f;
volatile int dt2 = 100;
volatile bool repair = true;
#include <sstream>

static void CondStrstr(benchmark::State& state) {
  // Code before the loop is not measured
  std::string x = "hello";
  int c = 10;
  for (auto _ : state) {
    c *= -1;
    std::stringstream oss;
    oss << dt1 << " is " << x;
    if (c > 0) {
      oss << c << "errors";
    } else {
      oss << "ok";
    }

    if (repair) {
      oss << repair << " fixed";
    }

    if (dt2 > 1) {
      oss << dt2 << " dt2 ";
    }

  }
}
BENCHMARK(CondStrstr);


static void CondFmt(benchmark::State& state) {
  // Code before the loop is not measured
  std::string x = "hello";
  int c = 10;
  for (auto _ : state) {
    c *= -1;
    auto ret = fmt::format("{} is {}", dt1, x );

    if (c > 0) {
      ret += fmt::format(" {} errors", c);
    } else {
      ret += "ok";
    }

    if (repair) {
      ret += fmt::format("{} fixed ", repair);
    }

    if (dt2 > 1) {
      ret += fmt::format(" {} dt2", dt2);
    }

  }
}
BENCHMARK(CondFmt);

results:

Benchmark                  Time             CPU   Iterations
------------------------------------------------------------
CondStrstr              2636 ns         2622 ns       286515
CondStrstr              2614 ns         2598 ns       286515
CondStrstr              2607 ns         2595 ns       286515
CondStrstr              2649 ns         2627 ns       286515
CondStrstr              2709 ns         2689 ns       286515
CondStrstr              2680 ns         2668 ns       286515
CondStrstr              2655 ns         2630 ns       286515
CondStrstr              2709 ns         2686 ns       286515
CondStrstr              2655 ns         2642 ns       286515
CondStrstr              2616 ns         2579 ns       286515
CondStrstr_mean         2653 ns         2634 ns           10
CondStrstr_median       2652 ns         2629 ns           10
CondStrstr_stddev       37.0 ns         38.0 ns           10
CondFmt                  770 ns          767 ns       891145
CondFmt                  756 ns          753 ns       891145
CondFmt                  779 ns          769 ns       891145
CondFmt                  749 ns          746 ns       891145
CondFmt                  749 ns          742 ns       891145
CondFmt                  767 ns          763 ns       891145
CondFmt                  757 ns          754 ns       891145
CondFmt                  758 ns          755 ns       891145
CondFmt                  739 ns          736 ns       891145
CondFmt                  710 ns          703 ns       891145
CondFmt_mean             754 ns          749 ns           10
CondFmt_median           756 ns          753 ns           10
CondFmt_stddev          19.2 ns         19.2 ns           10