https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110801
--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> --- Created attachment 55739 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=55739&action=edit Add special case for format("{}", integer) With this patch std::format is much closer to fmt::format: Benchmark Time CPU Iterations -------------------------------------------------------- sprintf 554621 ns 553889 ns 1241 ostringstream 932465 ns 931258 ns 746 to_string 122602 ns 122425 ns 5424 format 241978 ns 241656 ns 2939 format_to 109541 ns 109391 ns 6282 std_format 282151 ns 281787 ns 2490 std_format_to 225596 ns 225301 ns 3080 std::format_to could still be faster. It should be potentially as fast as to_string. The patch is just a prototype that only optimizes for integers, but the idea could be extended to other types too. For integers, floats, strings, and pointers we can skip the formatter::parse and formatter::format calls for a "{}" format string and just do the basic output form, with none of the additional code for alternative presentation forms, alignment, width, precision etc. As well as short-circuiting most of the formatting logic, the other part of the optimization is writing directly to the output buffer if it is a contiguous iterator (or a sink iterator that writes to a contiguous container). This is more efficient than writing to a buffer and then copying to the output. This could be extended to work with a back_insert_iterator<string> or back_insert_iterator<vector>, as we could extract the container, resize it, and then write directly into it.
