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Victor Zverovich 2021-05-29 07:20:29 -07:00
parent 9d67988aed
commit 6fe04871f4
1 changed files with 42 additions and 4 deletions
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ChangeLog.rst
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@ -22,6 +22,48 @@
notable exception of floating-point numbers and pointers.
Thanks `@alexezeder (Alexey Ochapov) <https://github.com/alexezeder>`_.
* Optimized handling of format specifiers during format string compilation.
For example, hexadecimal formatting (``"{:x}"``) is 3-7x faster when using
``format_to`` with format string compilation and a stack-allocated buffer
(`#1944 <https://github.com/fmtlib/fmt/issues/1944>`_).
Before (7.1.3)::
----------------------------------------------------------------------------
Benchmark Time CPU Iterations
----------------------------------------------------------------------------
FMTCompileOld/0 15.5 ns 15.5 ns 43302898
FMTCompileOld/42 16.6 ns 16.6 ns 43278267
FMTCompileOld/273123 18.7 ns 18.6 ns 37035861
FMTCompileOld/9223372036854775807 19.4 ns 19.4 ns 35243000
----------------------------------------------------------------------------
After (8.x)::
----------------------------------------------------------------------------
Benchmark Time CPU Iterations
----------------------------------------------------------------------------
FMTCompileNew/0 1.99 ns 1.99 ns 360523686
FMTCompileNew/42 2.33 ns 2.33 ns 279865664
FMTCompileNew/273123 3.72 ns 3.71 ns 190230315
FMTCompileNew/9223372036854775807 5.28 ns 5.26 ns 130711631
----------------------------------------------------------------------------
And even faster than ``std::to_chars`` from libc++ compiled with clang on
macOS::
----------------------------------------------------------------------------
Benchmark Time CPU Iterations
----------------------------------------------------------------------------
ToChars/0 4.42 ns 4.41 ns 160196630
ToChars/42 5.00 ns 4.98 ns 140735201
ToChars/273123 7.26 ns 7.24 ns 95784130
ToChars/9223372036854775807 8.77 ns 8.75 ns 75872534
----------------------------------------------------------------------------
In other cases, especially involving ``std::string`` construction, the speed
up can be lower.
* Added the ``_cf`` user-defined literal to represent a compiled format string.
It can be used instead of the ``FMT_COMPILE`` macro
(`#2043 <https://github.com/fmtlib/fmt/pull/2043>`_,
@ -78,10 +120,6 @@
a ~15% reported reduction on one platform.
Thanks `@sergiud (Sergiu Deitsch) <https://github.com/sergiud>`_.
* Optimized handling of format specifiers during format string
compilation, including but not limited to hexadecimal formatting
(`#1944 <https://github.com/fmtlib/fmt/issues/1944>`_).
* Added support for ``std::byte`` and other formattable types to ``fmt::join``
(`#1981 <https://github.com/fmtlib/fmt/issues/1981>`_,
`#2040 <https://github.com/fmtlib/fmt/issues/2040>`_,