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Update readme
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Victor Zverovich
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README.rst
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README.rst
@ -57,21 +57,14 @@ See the `documentation <http://fmtlib.net/latest/>`_ for more details.
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Examples
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--------
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This prints ``Hello, world!`` to stdout:
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Print ``Hello, world!`` to ``stdout``:
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.. code:: c++
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fmt::print("Hello, {}!", "world"); // uses Python-like format string syntax
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fmt::printf("Hello, %s!", "world"); // uses printf format string syntax
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Arguments can be accessed by position and arguments' indices can be repeated:
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.. code:: c++
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std::string s = fmt::format("{0}{1}{0}", "abra", "cad");
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// s == "abracadabra"
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Format strings can be checked at compile time:
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Check a format string at compile time:
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.. code:: c++
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@ -94,7 +87,7 @@ Format strings can be checked at compile time:
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context_.on_error("argument index out of range");
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^
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{fmt} can be used as a safe portable replacement for ``itoa``
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Use {fmt} as a safe portable replacement for ``itoa``
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(`godbolt <https://godbolt.org/g/NXmpU4>`_):
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.. code:: c++
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@ -129,7 +122,7 @@ Formatting of user-defined types is supported via a simple
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std::string s = fmt::format("The date is {}", date{2012, 12, 9});
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// s == "The date is 2012-12-9"
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You can create your own functions similar to `format
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Create your own functions similar to `format
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<http://fmtlib.net/latest/api.html#format>`_ and
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`print <http://fmtlib.net/latest/api.html#print>`_
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which take arbitrary arguments (`godbolt <https://godbolt.org/g/MHjHVf>`_):
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@ -152,6 +145,108 @@ Note that ``vreport_error`` is not parameterized on argument types which can
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improve compile times and reduce code size compared to fully parameterized
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version.
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Benchmarks
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----------
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Speed tests
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~~~~~~~~~~~
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================= ============= ===========
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Library Method Run Time, s
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================= ============= ===========
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libc printf 1.01
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libc++ std::ostream 3.04
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{fmt} 1632f72 fmt::print 0.86
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tinyformat 2.0.1 tfm::printf 3.23
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Boost Format 1.67 boost::format 7.98
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Folly Format folly::format 2.23
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================= ============= ===========
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{fmt} is the fastest of the benchmarked methods, ~17% faster than ``printf``.
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The above results were generated by building ``tinyformat_test.cpp`` on macOS
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10.14.3 with ``clang++ -O3 -DSPEED_TEST -DHAVE_FORMAT``, and taking the best of
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three runs. In the test, the format string ``"%0.10f:%04d:%+g:%s:%p:%c:%%\n"``
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or equivalent is filled 2,000,000 times with output sent to ``/dev/null``; for
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further details refer to the `source
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<https://github.com/fmtlib/format-benchmark/blob/master/tinyformat_test.cpp>`_.
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Compile time and code bloat
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~~~~~~~~~~~~~~~~~~~~~~~~~~~
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The script `bloat-test.py
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<https://github.com/fmtlib/format-benchmark/blob/master/bloat-test.py>`_
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from `format-benchmark <https://github.com/fmtlib/format-benchmark>`_
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tests compile time and code bloat for nontrivial projects.
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It generates 100 translation units and uses ``printf()`` or its alternative
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five times in each to simulate a medium sized project. The resulting
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executable size and compile time (Apple LLVM version 8.1.0 (clang-802.0.42),
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macOS Sierra, best of three) is shown in the following tables.
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**Optimized build (-O3)**
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============= =============== ==================== ==================
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Method Compile Time, s Executable size, KiB Stripped size, KiB
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============= =============== ==================== ==================
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printf 2.6 29 26
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printf+string 16.4 29 26
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iostreams 31.1 59 55
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{fmt} 19.0 37 34
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tinyformat 44.0 103 97
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Boost Format 91.9 226 203
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Folly Format 115.7 101 88
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============= =============== ==================== ==================
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As you can see, {fmt} has 60% less overhead in terms of resulting binary code
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size compared to iostreams and comes pretty close to ``printf``. Boost Format
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and Folly Format have the largest overheads.
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``printf+string`` is the same as ``printf`` but with extra ``<string>``
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include to measure the overhead of the latter.
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**Non-optimized build**
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============= =============== ==================== ==================
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Method Compile Time, s Executable size, KiB Stripped size, KiB
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============= =============== ==================== ==================
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printf 2.2 33 30
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printf+string 16.0 33 30
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iostreams 28.3 56 52
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{fmt} 18.2 59 50
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tinyformat 32.6 88 82
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Boost Format 54.1 365 303
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Folly Format 79.9 445 430
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============= =============== ==================== ==================
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``libc``, ``lib(std)c++`` and ``libfmt`` are all linked as shared libraries to
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compare formatting function overhead only. Boost Format and tinyformat are
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header-only libraries so they don't provide any linkage options.
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Running the tests
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~~~~~~~~~~~~~~~~~
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Please refer to `Building the library`__ for the instructions on how to build
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the library and run the unit tests.
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__ http://fmtlib.net/latest/usage.html#building-the-library
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Benchmarks reside in a separate repository,
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`format-benchmarks <https://github.com/fmtlib/format-benchmark>`_,
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so to run the benchmarks you first need to clone this repository and
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generate Makefiles with CMake::
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$ git clone --recursive https://github.com/fmtlib/format-benchmark.git
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$ cd format-benchmark
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$ cmake .
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Then you can run the speed test::
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$ make speed-test
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or the bloat test::
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$ make bloat-test
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Projects using this library
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---------------------------
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@ -331,108 +426,6 @@ than ``fmt::format_int`` on Karma's own benchmark,
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see `Fast integer to string conversion in C++
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<http://zverovich.net/2013/09/07/integer-to-string-conversion-in-cplusplus.html>`_.
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Benchmarks
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----------
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Speed tests
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~~~~~~~~~~~
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================= ============= ===========
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Library Method Run Time, s
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================= ============= ===========
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libc printf 1.01
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libc++ std::ostream 3.04
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fmt 1632f72 fmt::print 0.86
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tinyformat 2.0.1 tfm::printf 3.23
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Boost Format 1.67 boost::format 7.98
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Folly Format folly::format 2.23
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================= ============= ===========
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{fmt} is the fastest of the benchmarked methods, ~17% faster than ``printf``.
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The above results were generated by building ``tinyformat_test.cpp`` on macOS
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10.14.3 with ``clang++ -O3 -DSPEED_TEST -DHAVE_FORMAT``, and taking the best of
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three runs. In the test, the format string ``"%0.10f:%04d:%+g:%s:%p:%c:%%\n"``
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or equivalent is filled 2,000,000 times with output sent to ``/dev/null``; for
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further details refer to the `source
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<https://github.com/fmtlib/format-benchmark/blob/master/tinyformat_test.cpp>`_.
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Compile time and code bloat
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~~~~~~~~~~~~~~~~~~~~~~~~~~~
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The script `bloat-test.py
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<https://github.com/fmtlib/format-benchmark/blob/master/bloat-test.py>`_
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from `format-benchmark <https://github.com/fmtlib/format-benchmark>`_
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tests compile time and code bloat for nontrivial projects.
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It generates 100 translation units and uses ``printf()`` or its alternative
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five times in each to simulate a medium sized project. The resulting
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executable size and compile time (Apple LLVM version 8.1.0 (clang-802.0.42),
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macOS Sierra, best of three) is shown in the following tables.
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**Optimized build (-O3)**
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============= =============== ==================== ==================
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Method Compile Time, s Executable size, KiB Stripped size, KiB
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============= =============== ==================== ==================
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printf 2.6 29 26
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printf+string 16.4 29 26
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iostreams 31.1 59 55
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{fmt} 19.0 37 34
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tinyformat 44.0 103 97
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Boost Format 91.9 226 203
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Folly Format 115.7 101 88
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============= =============== ==================== ==================
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As you can see, {fmt} has 60% less overhead in terms of resulting binary code
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size compared to iostreams and comes pretty close to ``printf``. Boost Format
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and Folly Format have the largest overheads.
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``printf+string`` is the same as ``printf`` but with extra ``<string>``
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include to measure the overhead of the latter.
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**Non-optimized build**
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============= =============== ==================== ==================
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Method Compile Time, s Executable size, KiB Stripped size, KiB
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============= =============== ==================== ==================
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printf 2.2 33 30
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printf+string 16.0 33 30
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iostreams 28.3 56 52
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{fmt} 18.2 59 50
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tinyformat 32.6 88 82
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Boost Format 54.1 365 303
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Folly Format 79.9 445 430
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============= =============== ==================== ==================
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``libc``, ``lib(std)c++`` and ``libfmt`` are all linked as shared libraries to
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compare formatting function overhead only. Boost Format and tinyformat are
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header-only libraries so they don't provide any linkage options.
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Running the tests
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~~~~~~~~~~~~~~~~~
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Please refer to `Building the library`__ for the instructions on how to build
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the library and run the unit tests.
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__ http://fmtlib.net/latest/usage.html#building-the-library
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Benchmarks reside in a separate repository,
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`format-benchmarks <https://github.com/fmtlib/format-benchmark>`_,
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so to run the benchmarks you first need to clone this repository and
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generate Makefiles with CMake::
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$ git clone --recursive https://github.com/fmtlib/format-benchmark.git
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$ cd format-benchmark
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$ cmake .
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Then you can run the speed test::
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$ make speed-test
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or the bloat test::
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$ make bloat-test
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FAQ
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---
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@ -459,7 +452,7 @@ A: use ``std::tuple``:
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License
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-------
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fmt is distributed under the BSD `license
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{fmt} is distributed under the BSD `license
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<https://github.com/fmtlib/fmt/blob/master/LICENSE.rst>`_.
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The `Format String Syntax
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@ -475,7 +468,7 @@ It only applies if you distribute the documentation of fmt.
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Acknowledgments
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---------------
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The fmt library is maintained by Victor Zverovich (`vitaut
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The {fmt} library is maintained by Victor Zverovich (`vitaut
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<https://github.com/vitaut>`_) and Jonathan Müller (`foonathan
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<https://github.com/foonathan>`_) with contributions from many other people.
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See `Contributors <https://github.com/fmtlib/fmt/graphs/contributors>`_ and
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