Top 3 C math-library Projects

sleef

17 583 8.1 C

SIMD Library for Evaluating Elementary Functions, vectorized libm and DFT

Project mention: The Case of the Missing SIMD Code | news.ycombinator.com | 2023-06-08

I'm the main author of Highway, so I have some opinions :D Number of operations/platforms supported are important criteria.
A hopefully unbiased commentary:
Simde allows you to take existing nonportable intrinsics and get them to run on another platform. This is useful when you have a bunch of existing code and tight deadlines. The downside is less than optimal performance - a portable abstraction can be more efficient than forcing one platform to exactly match the semantics of another. Although a ton of effort has gone into Simde, sometimes it also resorts to autovectorization which may or may not work.
Eigen and SLEEF are mostly math-focused projects that also have a portability layer. SLEEF is designed for C and thus has type suffixes which are rather verbose, see https://github.com/shibatch/sleef/blob/master/src/libm/sleef... But it offers a complete (more so than Highway's) libm.
openlibm

3 486 6.4 C

High quality system independent, portable, open source libm implementation

Project mention: Openlibm and Julia | /r/Julia | 2023-05-21

Note that openlibm is not all new code. Rather it’s based on the libm from a couple of the BSDs. See LICENSE.md
InfluxDB

www.influxdata.com
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libdfp

1 92 6.9 C

Decimal Floating Point C Library

NOTE: The open source projects on this list are ordered by number of github stars. The number of mentions indicates repo mentiontions in the last 12 Months or since we started tracking (Dec 2020). The latest post mention was on 2023-06-08.