C Algorithm

Open-source C projects categorized as Algorithm

Top 18 C Algorithm Projects

  • tbox

    🎁 A glib-like multi-platform c library

  • Klib

    A standalone and lightweight C library

    Project mention: Factor is faster than Zig | news.ycombinator.com | 2023-11-10

    In my example the table stores the hash codes themselves instead of the keys (because the hash function is invertible)

    Oh, I see, right. If determining the home bucket is trivial, then the back-shifting method is great. The issue is just that it’s not as much of a general-purpose solution as it may initially seem.

    “With a different algorithm (Robin Hood or bidirectional linear probing), the load factor can be kept well over 90% with good performance, as the benchmarks in the same repo demonstrate.”

    I’ve seen the 90% claim made several times in literature on Robin Hood hash tables. In my experience, the claim is a bit exaggerated, although I suppose it depends on what our idea of “good performance” is. See these benchmarks, which again go up to a maximum load factor of 0.95 (Although boost and Absl forcibly grow/rehash at 0.85-0.9):


    Tsl, Martinus, and CC are all Robin Hood tables (https://github.com/Tessil/robin-map, https://github.com/martinus/robin-hood-hashing, and https://github.com/JacksonAllan/CC, respectively). Absl and Boost are the well-known SIMD-based hash tables. Khash (https://github.com/attractivechaos/klib/blob/master/khash.h) is, I think, an ordinary open-addressing table using quadratic probing. Fastmap is a new, yet-to-be-published design that is fundamentally similar to bytell (https://www.youtube.com/watch?v=M2fKMP47slQ) but also incorporates some aspects of the aforementioned SIMD maps (it caches a 4-bit fragment of the hash code to avoid most key comparisons).

    As you can see, all the Robin Hood maps spike upwards dramatically as the load factor gets high, becoming as much as 5-6 times slower at 0.95 vs 0.5 in one of the benchmarks (uint64_t key, 256-bit struct value: Total time to erase 1000 existing elements with N elements in map). Only the SIMD maps (with Boost being the better performer) and Fastmap appear mostly immune to load factor in all benchmarks, although the SIMD maps do - I believe - use tombstones for deletion.

    I’ve only read briefly about bi-directional linear probing – never experimented with it.

  • Onboard AI

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  • sc

    Common libraries and data structures for C.

    Project mention: A simple hash table in C | news.ycombinator.com | 2023-06-13
  • quadsort

    Quadsort is a branchless stable adaptive mergesort faster than quicksort.

    Project mention: 10~17x faster than what? A performance analysis of Intel x86-SIMD-sort (AVX-512) | news.ycombinator.com | 2023-06-10


    As you can see, quadsort used 2 instead of 4 writes in the bi-directional parity merges. This was in June 2021, and would have compiled as branchless with clang, but as branched with gcc.

    When I added a compile time check to use ternary operations for clang I was not adapting your work. I was well aware that clang compiled ternary operations as branchless, but I wasn't aware that rust did as well. I added the compile time check to use ternary operations for a fair performance comparison against glidesort.


    As for ipnsort's small sort, it is very similar to quadsort's small sort, which uses stable sorting networks, instead of unstable sorting networks. From my perspective it's not exactly novel. I didn't go for unstable sorting networks in crumsort to increase code reuse, and to not reduce adaptivity.

  • earcut.hpp

    Fast, header-only polygon triangulation

  • blitsort

    Blitsort is an in-place stable adaptive rotate mergesort / quicksort.

    Project mention: Glidesort, a new stable sort in Rust up to ~4x faster for random data | /r/programming | 2023-02-03
  • fastrange

    A fast alternative to the modulo reduction

  • InfluxDB

    Collect and Analyze Billions of Data Points in Real Time. Manage all types of time series data in a single, purpose-built database. Run at any scale in any environment in the cloud, on-premises, or at the edge.

  • sha-2

    SHA-2 algorithm implementations (by amosnier)

    Project mention: COTP Generator | /r/C_Programming | 2023-06-23

    the lib i used as base its : https://github.com/amosnier/sha-2

  • fast_zlib

    Heavily optimized zlib compression algorithm

  • dslib

    :herb: A library of "connected" data structures

  • rhsort

    Robin Hood Sort, for uniform data

    Project mention: Need a Quick Favor: Help a Student with a Simple Click! | /r/github | 2023-11-19

    I’m in the midst of a class project that requires a GitHub repository with over 100 stars. It’s one of the key criteria I need to meet, and I’m almost there. The repo I’ve been contributing to is https://github.com/mlochbaum/rhsort , which aligns perfectly with my project's needs—except it’s a bit short on stars.

  • Miller_Shuffle_Algo

    New Shuffle algorithm with ultra low overhead and no annoying repetition.

    Project mention: New Shuffle algorithm with ultra low overhead and no annoying repetition | news.ycombinator.com | 2023-02-21
  • air-ctl

    C Language Template Library C语言 模板库

  • advanced-data-structures-and-algorithms-in-c

    Advanced Data Structures and Algorithms in C ( DSA )

  • libaca

    C Library of Aho-Corasick Algorithm based on Coordinate Hash Trie

    Project mention: A Trie Variant Balancing between Time, Space, and Simplicity; And a C Implementation of the Aho-Corasick Algorithm Based on It | /r/compsci | 2023-02-28

    Repo of the A.-C algorithm implementation: https://github.com/dongyx/libaca

  • PoxHash

    A block hashing algorithm with implementations in C, Rust, Go, Nim, Python and JS

    Project mention: How do crypto functions deal with the issue of character size? (e.g. Unicode) | /r/cryptography | 2023-06-18

    Hey guys. If you remember me from several months ago, with this object de art, I am here with a less cringy question than that of 'I made a hash function!!!111'. I apologize if this question is basic btw. My question is, how do crypto functions, of any kind, deal with character size? For example in C, wchar_t is either 2 or 4 bytes. So, if the implementation goes through the stream like stream++ it will be stepping word-wise not byte-wise. And then if another machine, using a different implementation, reads the stream byte-wise and not word-wise, then it won't get the same message right?

  • arduino-gas-index-algorithm

    Arduino Library for Sensirion's Gas Index Algorithm, providing a VOC and NOx Index output signal calculated from the SGP40/41 raw signals

    Project mention: Hey I’m using arduino to detect voc levels | /r/arduino | 2022-12-23

    Finally you can use Sensirons algorithm to calculate Sensirons VOC index.

  • HSL

    HSL to RGB and RGB to HSL

    Project mention: Can I keep the gradient when replace colors? (see comment) | /r/pygame | 2022-12-29
  • SaaSHub

    SaaSHub - Software Alternatives and Reviews. SaaSHub helps you find the best software and product alternatives

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 2023-11-19.

C Algorithm related posts


What are some of the best open-source Algorithm projects in C? This list will help you:

Project Stars
1 tbox 4,562
2 Klib 3,928
3 sc 2,118
4 quadsort 2,077
5 earcut.hpp 768
6 blitsort 698
7 fastrange 281
8 sha-2 166
9 fast_zlib 131
10 dslib 126
11 rhsort 68
12 Miller_Shuffle_Algo 41
13 air-ctl 31
14 advanced-data-structures-and-algorithms-in-c 9
15 libaca 7
16 PoxHash 7
17 arduino-gas-index-algorithm 6
18 HSL 2
SaaSHub - Software Alternatives and Reviews
SaaSHub helps you find the best software and product alternatives