belm0

Structured concurrency and Lua (part 1)

John Belmonte, 2022-Sep

I've started writing a toy structured concurrency implementation for the Lua programming language. Some motivations:

• use it as a simple introduction to structured concurrency from the perspective of Lua (this article)
• learn the fundamental properties of structured concurrency and how to implement them
• share code that could become the starting point for a real Lua library and framework

So what is structured concurrency? For now, I'll just say that it's a programming paradigm that makes managing concurrency (arguably the hardest problem of computer science) an order of magnitude easier in many contexts. It achieves this in ways that seem subtle to us—clearly so, since its utility didn't reach critical mass until around 2018[^sc_birth] (just as control structures like functions, if, and while weren't introduced to languages until long after the first compu

alf-p-steinbach

Why COW was deemed ungood for std::string.

COW, short for copy on write, is a way to implement mutable strings so that creating strings and logically copying strings, is reduced to almost nothing; conceptually they become free operations like no-ops.

Basic idea: to share a data buffer among string instances, and only make a copy for a specific instance (the copy on write) when that instance's data is modified. The general cost of this is only an extra indirection for accessing the value of a string, so a COW implementation is highly desirable. And so the original C++ standard, C++98, and its correction C++03, had special support for COW implementations, and e.g. the g++ compiler's std::string implementations used COW.

So why was that support dropped in C++11?

In particular, would the same reason or reasons apply to a reference counted immutable string value class?

imneme

#ifndef LEHMER_HPP_INCLUDED
#define LEHMER_HPP_INCLUDED 1

/*
 * A C++ implementation of fast, 128-bit, Lehmer-style PRNGs
 *
 * The MIT License (MIT)
 *
 * Copyright (c) 2018 Melissa E. O'Neill
 *

imneme

#ifndef SFC_HPP_INCLUDED
#define SFC_HPP_INCLUDED 1

/*
 * A C++ implementation of Chris Doty-Humphrey's SFC PRNG(s)
 *
 * The MIT License (MIT)
 *
 * Copyright (c) 2018 Melissa E. O'Neill
 *

imneme

#ifndef GJRAND_HPP_INCLUDED
#define GJRAND_HPP_INCLUDED 1

/*
 * A C++ implementation of David Blackman's GJrand PRNG(s)
 *
 * The MIT License (MIT)
 *
 * Copyright (c) 2018 Melissa E. O'Neill
 *

imneme

#ifndef JSF_HPP_INCLUDED
#define JSF_HPP_INCLUDED 1

/*
 * A C++ implementation of a Bob Jenkins Small Fast (Noncryptographic) PRNGs
 *
 * The MIT License (MIT)
 *
 * Copyright (c) 2018 Melissa E. O'Neill
 *

asukakenji

Go (Golang) GOOS and GOARCH

All of the following information is based on go version go1.17.1 darwin/amd64.

GOOS Values

GOOS	Out of the Box
aix	✅
android	✅

lattner

Swift Concurrency Manifesto

Author: Chris Lattner

Chinese Translation by Jason Yu

Contents

• Introduction
• Overall Vision

ageis

security and hardening options for systemd service units

A common and reliable pattern in service unit files is thus:

NoNewPrivileges=yes
PrivateTmp=yes
PrivateDevices=yes
DevicePolicy=closed
ProtectSystem=strict

vasanthk

System Design Cheatsheet

Picking the right architecture = Picking the right battles + Managing trade-offs

Basic Steps

1. Clarify and agree on the scope of the system

• User cases (description of sequences of events that, taken together, lead to a system doing something useful)
  • Who is going to use it?
  • How are they going to use it?