ryu
C++ Format
ryu | C++ Format | |
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12 | 161 | |
1,152 | 19,350 | |
- | 1.0% | |
5.9 | 9.7 | |
2 months ago | 5 days ago | |
C++ | C++ | |
Apache License 2.0 | GNU General Public License v3.0 or later |
Stars - the number of stars that a project has on GitHub. Growth - month over month growth in stars.
Activity is a relative number indicating how actively a project is being developed. Recent commits have higher weight than older ones.
For example, an activity of 9.0 indicates that a project is amongst the top 10% of the most actively developed projects that we are tracking.
ryu
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Printing double aka the most difficult problem in computer sciences
Nah. This is about ryu printf.
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Parquet: More than just “Turbo CSV”
> Google put in significant engineering effort into "Ryu", a parsing library for double-precision floating point numbers: https://github.com/ulfjack/ryu
It's not a parsing library, but a printing one, i.e., double -> string. https://github.com/fastfloat/fast_float is a parsing library, i.e., string -> double, not by Google though, but was indeed motivated by parsing JSON fast https://lemire.me/blog/2020/03/10/fast-float-parsing-in-prac...
- Faster way to convert double to string, not using "%f"?
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After obtaning a CS degree and 16 years of experience in industry, I feel somewhat confident that I can answer your programming questions correctly. Ask me anything
Me and Ryu agree that the answer should be 0.30000000000000004
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23 years into my career, I still love PHP and JavaScript
Apparently exact minimal float-to-string conversion is more recent than I thought, and many languages used to print more (Python?) or less (PHP) decimal digits than necessary to uniquely identify the bit pattern. Python correctly prints 46000.80 + 553.04 as 46553.840000000004, but I don't know if it ever prints more digits than needed. One recent algorithm for printing floats exactly is https://github.com/ulfjack/ryu, though I'm unaware what's the state-of-the-art (https://github.com/jk-jeon/dragonbox claims to be a benchmark and the best algorithm).
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What's the most elegant algo in your subjective view and why?
On the huge speedup side, you have the Ryū algorithm for decimal conversion (Video, Source), which is now finding its way in most standard libraries. But it isn't a hack, and a very dense, complex and precise algo, nothing like the fast-and-loose inverse square root.
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C++ devs at FAANG companies, what kind of work do you do?
Used a wizard's magic to print "3.14" faster
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how to make ftoa procedure from scratch
Here's a paper that details an optimized algorithm (reference implementation). It also contains a description of a correct, but slow algorithm as well as references to classic papers on the subject. Earlier the classic implementation was the dtoa one included in netlib by David Gay.
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Dragonbox 1.1.0 is released (a fast float-to-string conversion algorithm)
At the very core of all these theoretical stuffs, there is the theory of continued fractions. This is an immensely useful monster which I even dare call as the ultimate tool for floating-point formatting/parsing that everyone who wants to contribute in this field should learn. Before I learned continued fractions, my main tool for proving stuffs was the minmax Euclid algorithm (which is one of the greatest contributions of the wonderful Ryu paper), but it turns out that it is actually just a quite straightforward application of the theory of continued fractions. The main role minmax Euclid algorithm played was to estimate the maximum size of possible errors, but with continued fractions it is even possible to find the list of all examples that generate errors above a given threshold. This is something I desperately wanted but really couldn't do back in 2020.
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FastDoubleParser: Java port of Daniel Lemires fast_double_parser
Ryū algorithm, the converse (doubles to strings), is also much faster than using Java's number formatting classes.
https://github.com/ulfjack/ryu/blob/master/src/main/java/inf...
C++ Format
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C++ left arrow operator (2016)
Continuation passing monads form the basis of a perfectly valid and usable software architecture and programming pattern.
In the case of ostream and operator<<, this pattern reduces the number of intermediate objects that would otherwise be constructed.
If you object to iostream on religious or stylistic grounds, there's always fmt which is more like Go or Python string interpolation.[0]
0. https://fmt.dev
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C++ Game Utility Libraries: for Game Dev Rustaceans
GitHub repo: fmtlib/fmt
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Creating k-NN with C++ (from Scratch)
cmake_minimum_required(VERSION 3.5) project(knn_cpp CXX) # Set up C++ version and properties include(CheckIncludeFileCXX) check_include_file_cxx(any HAS_ANY) check_include_file_cxx(string_view HAS_STRING_VIEW) check_include_file_cxx(coroutine HAS_COROUTINE) set(CMAKE_CXX_STANDARD 20) set(CMAKE_BUILD_TYPE Debug) set(CMAKE_CXX_STANDARD_REQUIRED ON) set(CMAKE_CXX_EXTENSIONS OFF) # Copy data file to build directory file(COPY ${CMAKE_CURRENT_SOURCE_DIR}/iris.data DESTINATION ${CMAKE_CURRENT_BINARY_DIR}) # Download library usinng FetchContent include(FetchContent) FetchContent_Declare(matplotplusplus GIT_REPOSITORY https://github.com/alandefreitas/matplotplusplus GIT_TAG origin/master) FetchContent_GetProperties(matplotplusplus) if(NOT matplotplusplus_POPULATED) FetchContent_Populate(matplotplusplus) add_subdirectory(${matplotplusplus_SOURCE_DIR} ${matplotplusplus_BINARY_DIR} EXCLUDE_FROM_ALL) endif() FetchContent_Declare( fmt GIT_REPOSITORY https://github.com/fmtlib/fmt.git GIT_TAG 7.1.3 # Adjust the version as needed ) FetchContent_MakeAvailable(fmt) # Add executable and link project libraries and folders add_executable(${PROJECT_NAME} main.cc) target_link_libraries(${PROJECT_NAME} PUBLIC matplot fmt::fmt) aux_source_directory(lib LIB_SRC) target_include_directories(${PROJECT_NAME} PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}) target_sources(${PROJECT_NAME} PRIVATE ${LIB_SRC}) add_subdirectory(tests)
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Optimizing the unoptimizable: a journey to faster C++ compile times
Good catch, thanks! Fixed now. This explains why the difference was kinda low compared to another benchmark: https://github.com/fmtlib/fmt?tab=readme-ov-file#compile-tim....
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Learn Modern C++
> This is from C++23, right?
std::println is, yes.
> I wonder how available this is within compilers
https://en.cppreference.com/w/cpp/compiler_support says clang, gcc, and msvc all support it, though I don't know how recent those versions are off the top of my head.
In my understanding, with this specific feature, if you want a polyfill for older compilers, or to use some more cutting-edge features that haven't been standardized yet, https://github.com/fmtlib/fmt is available to you.
- The C++20 Naughty and Nice List for Game Devs
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For processing strings, streams in C++ can be slow
{fmt} has internal buffering but it's not yet exposed to users. There is a feature request for it: https://github.com/fmtlib/fmt/issues/2354. FILE buffering is not too bad but it can be easily optimized: https://www.zverovich.net/2020/08/04/optimal-file-buffer-siz....
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adoption of fmt based logging
Automatic use of operator<< when that exists was present in fmt until version 9.0.0. In version 9 you could use FMT_DEPRECATED_OSTREAM to opt in the old behaviour, but this too was removed in version 10.0.0. Now there is no way to automatically use operator<<.
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What's your favorite c++20 feature that should've been there 10 years ago?
You can install it https://github.com/fmtlib/fmt
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Codebases to read
Additionally, if you like low level stuff, check out libfmt (https://github.com/fmtlib/fmt) - not a big project, not difficult to understand. Or something like simdjson (https://github.com/simdjson/simdjson).
What are some alternatives?
dragonbox - Reference implementation of Dragonbox in C++
spdlog - Fast C++ logging library.
concise-encoding - The secure data format for a modern world
Better Enums - C++ compile-time enum to string, iteration, in a single header file
proust - Compiling implementation of mustache
ZXing - ZXing ("Zebra Crossing") barcode scanning library for Java, Android
rapidgzip - Gzip Decompression and Random Access for Modern Multi-Core Machines
FastFormat - The fastest, most robust C++ formatting library
itoa - Fast integer to ascii / integer to string conversion
ZBar - Clone of the mercurial repository http://zbar.hg.sourceforge.net:8000/hgroot/zbar/zbar
oss-fuzz - OSS-Fuzz - continuous fuzzing for open source software.
Scintilla