Daniel Lemire

youtube.com

JavaScript

benchmarks

Redis is an in-memory database. Salvatore Sanfilippo started it in 2009, and it is now one of the most widely deployed pieces of server software. It is often used as a cache in front of a slower database. You talk to it…

Anthropic

Anthropicstartups

Python

Python used to have limited parallelism, due to its global interpreter lock (GIL). Only one thread could run Python code at a time. Python 3.14 comes in a free-threaded version (python3.14t), without the global interpre…

Python

JavaScriptbenchmarks

WebSocket is a standard protocol to hook up a client and a server in a persistent manner. It is commonly used for live chat, notifications, multiplayer games, collaborative editing, and streaming dashboards. Many server…

JavaScriptdiscipline

OpenAI

Python

data centers

Anthropic

compilers

I write a lot about data parallelism. About how our processors have special instructions that can do several operations at once. They are often critical to get the best performance out of a CPU. Compilers are sometimes…

compilers

LinuxJavaScript

When you build a program, the compiler turns each source file into an object file. Then a linker stitches all the object files and libraries into one executable. On Linux, the default linker is usually GNU ld (also call…

Linuxcompilers

We have many ways to ensure software quality. Unit testing. Fuzz testing. Integration testing. And so forth. I’d like to propose a method that was unthinkable before: ephemeral testing. (Ephemeral is a fancy word for ‘t…

software quality

Much of my research is on arXiv. I was one of the early adopters. It is simply a repository of research papers with PDF and metadata. It makes it convenient to find research without any paywall. Physicists started it in…

(October 1st). They say it is about the size of a fridge. It has one kilowatt of solar power. It is about the power of a household. It was launched on a Falcon 9 rocket (SpaceX). It should run for about a year. Google p…

solardata centers

A common way to store JSON data is to write one document per line. We call it NDJSON or JSON Lines. Log files, database exports and machine-learning datasets often come in this format. The files can be large, so we may…

Our software represents strings using the UTF-16 or the UTF-8 formats. Most text on the web is UTF-8, but Java, C# or JavaScript represents the strings as UTF-16 to the programmer. Sometimes we need to transcode (conver…

JavaScript

1. Begin by genuinely listening to them. Make sure that you understand them. It is often useful to ask for confirmation: restate what you think they are saying and make sure that you understand. Physically, it helps to…

The simdjson library is a C++ library to parse and generate JSON. It is used in Node.js, ClickHouse, Meta Velox, StarRocks, Apache Doris, the Ladybird browser and many other systems. We released version 4.0 a year ago,…

JavaScript

C# strings are UTF-16. Most characters are one 16-bit code unit. Characters outside the basic multilingual plane, emoji included, take two: a high surrogate (U+D800 to U+DBFF) followed by a low surrogate (U+DC00 to U+DF…

To get a PhD, you typically have to enroll in a graduate program. Then you complete a few relatively easy courses. You might need to pass a comprehensive examination that checks whether you have a basic understanding of…

We create new strings all the time. How quickly can you produce short strings in your programming languge? To create a meaningful string, we convert an integer to a string. In Python, that is str(i). The loop stores eac…

Python

Mainstream economists have been advocating for the marvellous effects of global trade for decades. Who needs these factory jobs anyway? We’ll be designing the robots and the nuclear rockets. Except that, no. It does not…

economistsrobotics

I maintain and comaintain several open-source libraries. Some of them are widely used: ada parses URLs in Node.js, fast_float parses numbers in GCC’s standard library and in Chromium, simdjson parses JSON in Node.js, si…

JavaScript

If AI is causing mass unemployment among software developers, it is not showing up in the data yet. The USA had more software developers as a percentage of the population in 2025 than in 2021. On average salaries are sl…

AI and jobs

Python