fmt_bnchmrk

benchmarks:

• CustomCode - simplified code from {fmt}, almost perfect in terms of performance
• FMTCompileMaster - header only, commit eef4ba9c02de46e5cce031db57268cc199c101fe to be precise
• FMTCompileMasterNOINLINERemovedFromFill - same as previous with FMT_NOINLINE removed from

  template <typename OutputIt, typename Char>
  FMT_NOINLINE FMT_CONSTEXPR OutputIt fill(OutputIt it, size_t n,
                                           const fill_t<Char>& fill) {
    auto fill_size = fill.size();
    if (fill_size == 1) return detail::fill_n(it, n, fill[0]);
    auto data = fill.data();
    for (size_t i = 0; i < n; ++i)
      it = copy_str<Char>(data, data + fill_size, it);
    return it;
  }

• FMTCompileSeparateFormatter - header only, a separate formatter class int_formatter, which takes basic_format_specs as template argument, thus it's able to prepare format() method at compile-time, requires C++20
• FMTCompileSeparateFormatterNOINLINERemovedFromFill - same as previous with FMT_NOINLINE removed from the same fill function as in FMTCompileMasterNOINLINERemovedFromFill
• ToChars - to_chars from C++17 <charconv> header used

here are results on my PC:

GCC 10 C++20

value == 0

Benchmark	Time
CustomCode	1.75 ns
FMTCompileMaster	11.5 ns
FMTCompileMasterNOINLINERemovedFromFill	11.3 ns
FMTCompileSeparateFormatter	10.8 ns
FMTCompileSeparateFormatterNOINLINERemovedFromFill	2.52 ns
ToChars	1.25 ns

value == 42

Benchmark	Time
CustomCode	2.79 ns
FMTCompileMaster	12.0 ns
FMTCompileMasterNOINLINERemovedFromFill	12.0 ns
FMTCompileSeparateFormatter	11.5 ns
FMTCompileSeparateFormatterNOINLINERemovedFromFill	3.53 ns
ToChars	2.49 ns

value == 273123

Benchmark	Time
CustomCode	6.15 ns
FMTCompileMaster	13.3 ns
FMTCompileMasterNOINLINERemovedFromFill	13.2 ns
FMTCompileSeparateFormatter	14.2 ns
FMTCompileSeparateFormatterNOINLINERemovedFromFill	7.49 ns
ToChars	3.76 ns

value == 9223372036854775807

Benchmark	Time
CustomCode	6.82 ns
FMTCompileMaster	14.5 ns
FMTCompileMasterNOINLINERemovedFromFill	14.4 ns
FMTCompileSeparateFormatter	16.6 ns
FMTCompileSeparateFormatterNOINLINERemovedFromFill	10.5 ns
ToChars	5.45 ns

Clang (main, 961e4384f4e938b901490912813ff0e8347cc3c0) C++20

value == 0

Benchmark	Time
CustomCode	1.55 ns
FMTCompileMaster	12.9 ns
FMTCompileMasterNOINLINERemovedFromFill	12.9 ns
FMTCompileSeparateFormatter	9.56 ns
FMTCompileSeparateFormatterNOINLINERemovedFromFill	1.56 ns
ToChars	1.89 ns

value == 42

Benchmark	Time
CustomCode	2.22 ns
FMTCompileMaster	13.3 ns
FMTCompileMasterNOINLINERemovedFromFill	13.4 ns
FMTCompileSeparateFormatter	10.6 ns
FMTCompileSeparateFormatterNOINLINERemovedFromFill	2.22 ns
ToChars	2.21 ns

value == 273123

Benchmark	Time
CustomCode	5.03 ns
FMTCompileMaster	14.7 ns
FMTCompileMasterNOINLINERemovedFromFill	14.8 ns
FMTCompileSeparateFormatter	13.4 ns
FMTCompileSeparateFormatterNOINLINERemovedFromFill	5.19 ns
ToChars	3.44 ns

value == 9223372036854775807

Benchmark	Time
CustomCode	6.47 ns
FMTCompileMaster	16.0 ns
FMTCompileMasterNOINLINERemovedFromFill	16.0 ns
FMTCompileSeparateFormatter	15.4 ns
FMTCompileSeparateFormatterNOINLINERemovedFromFill	6.49 ns
ToChars	4.92 ns