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@yamnikov-oleg
yamnikov-oleg / LICENSE
Last active January 14, 2025 10:58
Shared (interprocess) mutexes on Linux
MIT License
Copyright (c) 2018 Oleg Yamnikov
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
@davedice
davedice / InflatableSeqLock.cpp
Last active January 17, 2021 00:53
Inflatable SeqLock
// InflatableSeqLock
// Copyright(C) 2016 Oracle and/or its affiliates
// Dave Dice : https://blogs.oracle.com/dave
//
// Remarks:
// * Implements composite writer mutex and seqlock in a single word-sized lock.
// Allows optimistic reading and pessimistic writing.
// Readers don't write to shared synchronization metadata, which helps avoid
// coherence traffic. Readers must tolerate observing inconsistent state, however.
// * Writer mutex is based on LIFO-CR lock from http://arxiv.org/abs/1511.06035.
@causal-agent
causal-agent / babyjit.c
Created October 13, 2016 03:09
Baby's First JIT
#include <stdlib.h>
#include <stdio.h>
#include <stdint.h>
#include <sys/mman.h>
#include <unistd.h>
#include <err.h>
#include <sysexits.h>
typedef int32_t (*fptr)(int32_t);
@kentonv
kentonv / SCM_RIGHTS.md
Last active April 7, 2025 11:56
SCM_RIGHTS API quirks

As tested on Linux:

  • An SCM_RIGHTS ancillary message is "attached" to the range of data bytes sent in the same sendmsg() call.
  • However, as always, recvmsg() calls on the receiving end don't necessarily map 1:1 to sendmsg() calls. Messages can be coalesced or split.
  • The recvmsg() call that receives the first byte of the ancillary message's byte range also receives the ancillary message itself.
  • To prevent multiple ancillary messages being delivered
@pkhuong
pkhuong / dynamic-variance.py
Last active January 9, 2023 21:03
Fully dynamic variance for a bag of observations
import math
import struct
import unittest
import hypothesis.strategies as st
from hypothesis.stateful import Bundle, RuleBasedStateMachine, consumes, invariant, multiple, precondition, rule
class VarianceStack:
def __init__(self):
self.n = 0
@keichan34
keichan34 / config.fish
Created April 17, 2020 01:24
My Fish-shell config
function fish_greeting
echo "! COMPUTER_NAME"
end
set -x EDITOR vim
set -x LESS -asrRix8
set -x LANG en_US.UTF-8
set -x LC_ALL en_US.UTF-8
set -x LANGUAGE en_US.UTF-8
@creativcoder
creativcoder / main.rs
Last active November 5, 2023 13:23
Merge k sorted arrays in Rust
// Blog post: https://creativcoder.dev/merge-k-sorted-arrays-rust
// Merge 2 sorted arrays
fn merge_2(a: &[i32], b: &[i32]) -> Vec<i32> {
let (mut i, mut j) = (0, 0);
let mut sorted = vec![];
let remaining;
let remaining_idx;
loop {
if a[i] < b[j] {
// This can grow a Robin Hood linear probing hash table near word-at-a-time memcpy speeds. If you're confused why I use 'keys'
// to describe the hash values, it's because my favorite perspective on Robin Hood (which I learned from Paul Khuong)
// is that it's just a sorted gap array which is MSB bucketed and insertion sorted per chain:
// https://pvk.ca/Blog/2019/09/29/a-couple-of-probabilistic-worst-case-bounds-for-robin-hood-linear-probing/
// The more widely known "max displacement" picture of Robin Hood hashing also has strengths since the max displacement
// can be stored very compactly. You can see a micro-optimized example of that here for small tables where the max displacement
// can fit in 4 bits: Sub-nanosecond Searches Using Vector Instructions, https://www.youtube.com/watch?v=paxIkKBzqBU
void grow(Table *table) {
u64 exp = 64 - table->shift;
// We grow the table downward in place by a factor of 2 (not counting the overflow area at table->end).
# I happened to be looking at some of Cranelift's code, and I noticed that their constant-time dominates()
# check was using a somewhat more ad-hoc version of a hidden gem from the data structures literature called the
# parenthesis representation for trees. As far as I know, this was invented by Jacobson in his 1989 paper
# Space-Efficient Static Trees and Graphs. I first learned about it from the slightly later paper by Munro and Raman
# called Succinct Representations of Balanced Parentheses and Static Trees. I figured I'd give it an extremely
# quick intro and then show how it leads to a (slightly better) version of Cranelift's algorithm.
#
# This parenthesis representation of trees is surprisingly versatile, but its most striking feature is that
# it lets us query the ancestor relationship between two nodes in a tree in constant time, with a few instructions.
# And the idea is extremely simple and intuitive if you just draw the right kind of picture.
@pkhuong
pkhuong / yannakakis.md
Last active November 8, 2024 15:56
A minimal version of Yannakakis's algorithm for mostly plain Python
#!/usr/bin/env sed -re s|^|\x20\x20\x20\x20| -e s|^\x20{4}\x23\x23{(.*)$|<details><summary>\1</summary>\n| -e s|^\x20{4}\x23\x23}$|\n</details>| -e s|^\x20{4}\x23\x23\x20?|| -e s|\x0c|\x20|
license, imports
# Yannakakis.py by Paul Khuong
#
# To the extent possible under law, the person who associated CC0 with
# Yannakakis.py has waived all copyright and related or neighboring rights
# to Yannakakis.py.