George Brown g0xA52A2A

UNIX famously uses fork+exec to create processes, a simple API that is nevertheless quite tricky to use correctly and that comes with a bunch of problems. The alternative, spawn, as used by VMS, Windows NT and recently POSIX, fixes many of these issues but it overly complex and makes it hard to add new features.

prepare() is a proposed API to simplify process creation. When calling prepare(), the current thread enters “preparation state.” That means, a nascent process is created and the current thread is moved to the context of this process, but without changing memory maps (this is similar to how vfork() works). Inside the nascent process, you can configure the environment as desired and then call prep_execve() to execute a new program. On success, prep_execve() leaves preparation state, moving the current thread back to the parent's process context and returns (!) the pid of the now grownup child. You can also use prep_exit() to abort the child without executing a new process, it similarly returns the pid

This document explains how I would implement an SSA-based compiler if I was writing one today.

This document is intentionally opinionated. It just tells you how I would do it. This document is intended for anyone who has read about SSA and understands the concept, but is confused about how exactly to put it into practice. If you're that person, then I'm here to show you a way to do it that works well for me. If you're looking for a review of other ways to do it, I recommend this post.

My approach works well when implementing the compiler in any language that easily permits cyclic mutable data structures. I know from experience that it'll work great in C++, C#, or Java. The memory management of this approach is simple (and I'll explain it), so you won't have to stress about use after frees.

I like my approach because it leads to an ergonomic API by minimizing the amount of special cases you have to worry about. Most of the compiler is analyses and transformations ov

Truly Optimal Evaluation with Unordered Superpositions

In this post, I'll address two subjects:

How to solve HVM's quadratic slowdown compared to GHC in some cases
Why that is relevant to logic programming, unification, and program search

Optimal Evaluators aren't Optimal

HVM3's Optimal Atomic Linker (with Polarization)

Atomic linking is at the heart of HVM's implementation: it is what allows threads to collaborate towards massive parallelism. All major HVM versions started with a better atomic linker. From slow, buggy locks (HVM1), to AtomicCAS (HVM1.5), to AtomicSwap (HVM2), the algorithm became simpler and faster over the years.

On the initial HVM3 implementation, I noticed that one of the cases on the atomic linker never happened. After some reasoning, I now understand why, and

Lightweight region memory management in a two-stage language

Intro
Basics
- Stage inference
Regions
- Bit-stealing
- Using regions
Eager regions

Higher-Order Company: Complete Historical Overview

This document is a complete historical overview of the Higher Order Company. If you want to learn anything about our background, a good way to do so is to feed this Gist into an AI (like Sonnet-3.5) and ask it any question!

My Search for a Perfect Language

It all started around 2015. I was an ambitious 21-year-old CS student who, somehow, had been programming for the last 10 years, and I had a clear goal:

I want to become the greatest programmer alive

A Short IPv6 Guide for Home IPv4 Admins

This guide is for homelab admins who understand IPv4s well but find setting up IPv6 hard or annoying because things work differently. In some ways, managing an IPv6 network can be simpler than IPv4, one just needs to learn some new concepts and discard some old ones.

Let’s begin.

First of all, there are some concepts that one must unlearn from ipv4:

Concept 1

Understanding the Phases Applicative

While I was researching how to do level-order traversals of a binary tree in Haskell, I came across a library called tree-traversals which introduced a fancy Applicative instance called Phases. It took me a lot of effort to understand how it works. Although I still have some unresolved issues, I want to share my journey.

Note: I was planning to post this article on Reddit. But I gave up because it was too long so here might be a better place.

See the discussion.

Note: This article is written in a beginner-friendly way. Experts may find it tedious.

	// compile with whatever then run PractRand:
	// ./test \| RNG_test stdin64 -tlmin 256KB -tf 2 -tlmax 512GB -seed 0

	//****************************************************************************
	// verbatim from: https://prng.di.unimi.it/xoroshiro128plus.c

	/* Written in 2016-2018 by David Blackman and Sebastiano Vigna (vigna@acm.org)

	To the extent possible under law, the author has dedicated all copyright
	and related and neighboring rights to this software to the public domain

	/* converter.c
	*
	* This code converts `.md` files into `.html` files.
	*
	* The main use is to write a static website in `.md` files, and then run this
	* program to convert it to `.html`
	*
	* The program relies on the following variables:
	*
	* - INPUT_FOLDER: full path of the website with `.md` files.