Communications of the ACM
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How the “Frontier” Became the Slogan of Uncontrolled AI
Artificial intelligence (AI) has been billed as the next frontier of humanity: the newly available expanse whose exploration …
From Daniel Lemire's Blog
Science and Technology links (April 13 2024)
Our computer hardware exchange data using a standard called PCI Express. Your disk, your network and your GPU are limited by what PCI Express can do. Currently,...
From Daniel Lemire's Blog
Greatest common divisor, the extended Euclidean algorithm, and speed!
We sometimes need to find the greatest common divisor between two integers in software. The fastest way to compute the greatest common divisor might be the binary...
From Daniel Lemire's Blog
A simple algorithm to compute the square root of an integer, byte by byte
A reader asked me for some help in computing (1 – sqrt(0.5)) to an arbitrary precision, from scratch. A simpler but equivalent problem is to compute the squareContinue...
From Daniel Lemire's Blog
C++ web app with Crow: early scalability results
Last year, I looked at writing small “hello world” web applications in various programming languages (Go, JavaScript, Nim…). Go, using nothing but the standardContinue...
From Daniel Lemire's Blog
Science and Technology links (March 31 2024)
Large language models (e.g., ChatGPT) do better at legal questions that lawyers: Our empirical analysis benchmarks LLMs against a ground truth set by Senior Lawyers...
From Daniel Lemire's Blog
Fast and concise probabilistic filters in Python
Sometimes you need to filter out or filter in data quickly. Suppose that your employer maintains a list of forbidden passwords or URLs or words. You may store them...
From Daniel Lemire's Blog
Passing recursive C++ lambdas as function pointers
In modern C++, as in many popular languages, you can create ‘lambdas’. Effectively, they are potentially anonymous function instances that you can create on the...
From Daniel Lemire's Blog
How to read files quickly in JavaScript
Suppose you need to read several files on a server using JavaScript. There are many ways to read files in JavaScript with a runtime like Node.js. Which one is best...
From Daniel Lemire's Blog
How many political parties rule Canada? Fun with statistics
Canada has several political parties with elected member of parliament: the Liberals, the Conservatives, the Bloc Québecois, de NDP and the Green. But do the behave...
From Daniel Lemire's Blog
Book review: Theft of Fire by Devon Eriksen
When I was young, science fiction was the genre of choice for many engineers and scientists. But the genre declined significantly in recent years. Part of the problem...
From Daniel Lemire's Blog
Measuring energy usage: regular code vs. SIMD code
Modern processor have fancy instructions that can do many operations at one using wide registers: SIMD instructions. Intel and AMD have 512-bit registers and associated...
From Daniel Lemire's Blog
JSON Parsing: Intel Sapphire Rapids versus AMD Zen 4
Intel has release a new generation of server processors (Sapphire Rapids) while the latest AMD technology (Zen 4) is now broadly available. There are extensiveContinue...
From Daniel Lemire's Blog
How fast is rolling Karp-Rabin hashing?
A hash function maps values (e.g., strings) into a fixed number of strings, typically smaller than the original. It is useful to compare quickly two long strings...
From Daniel Lemire's Blog
C23: a slightly better C
One of the established and most popular programming languages is the C programming language. It is relatively easy to learn, and highly practical. Maybe surprisingly...
From Daniel Lemire's Blog
How much memory bandwidth do large Amazon instances offer?
In my previous post, I described how you can write a C++ program to estimate your read memory bandwidth. It is not very difficult: you allocate a large memory region...
From Daniel Lemire's Blog
Estimating your memory bandwidth
One of the limitations of a compute is the memory bandwidth. For the scope of this article, I define “memory bandwidth” as the maximal number of bytes you can bring...
From Daniel Lemire's Blog
Implementing the missing sign instruction in AVX-512
Intel and AMD have expanded the x64 instruction sets over time. In particular, the SIMD (Single instruction, multiple data) instructions have become progressively...
From Daniel Lemire's Blog
Science and Technology links (December 30th 2023)
Parenting does not appear to be able to determine the personality traits of a child. When the last ice age ended, 12,000 years ago, the Sahara was green and full...
From Daniel Lemire's Blog
Measuring the size of the cache line empirically
Our computers do not read or write memory in units of bits or even bytes. Rather memory is accessed in small blocks of memory called “cache line”. For a given system...
From Daniel Lemire's Blog