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
Unsigned comparisons using signed types
There are two main types of fixed-precision integers in modern software: unsigned and signed. In C++20 and above, the signed integers must use the two’s complement...
From Daniel Lemire's Blog
Speeding up C++ code with template lambdas
Let us consider a simple C++ function which divides all values in a range of integers: void divide(std::span<int> i, int d) { for (auto& value : i) { value /= d...
From Daniel Lemire's Blog
An overview of parallel programming (Go edition)
In practice, the software we write runs on several processors. Unfortunately, much of what we take for granted on a single processor becomes false when there are...
From Daniel Lemire's Blog
How fast can you open 1000 files?
Jarred Sumner, the main author of the Bun JavaScript engine, commented a few days ago on X that opening many files on macOS could be slow due to thread contention...
From Daniel Lemire's Blog
AVX-512 gotcha: avoid compressing words to memory with AMD Zen 4 processors
The recent AMD processors (Zen 4) provide extensive support for the powerful AVX-512 instructions. AVX-512 (Advanced Vector Extensions 512) is an extension to the...
From Daniel Lemire's Blog
Thread-safe memory copy
A common operation in software is the copy of a block of memory. In C/C++, we often call the function memcpy for this purpose. But what happens if, while you are...
From Daniel Lemire's Blog
Programmer time and the pitfalls of wasteful work
Programmer time is precious. This realization should shape our approach to software development, focusing our efforts on tasks that genuinely contribute to theContinue...
From Daniel Lemire's Blog
Regular expressions can blow up!
Regular expressions, often abbreviated as regex, are a powerful tool for pattern matching within text. For example, the expression \d*\.?\d+ would match a positive...
From Daniel Lemire's Blog
Checking whether an ARM NEON register is zero
Your phone probably runs on 64-bit ARM processors. These processors are ubiquitous: they power the Nintendo Switch, they power cloud servers at both Amazon AWSContinue...
From Daniel Lemire's Blog
JavaScript hashing speed comparison: MD5 versus SHA-256
Hashing algorithms convert input data into a fixed-size string of characters, known as a hash value or digest. These algorithms are one-way functions, meaning the...
From Daniel Lemire's Blog
Counting the digits of 64-bit integers
Given an integer in software, you may want to know how many decimal digits it needs. For example, the integer 100 requires 3 digits, the integer 9999 requires 4...
From Daniel Lemire's Blog
How does your URL parser handle Unicode?
Most strings today in software are Unicode strings. It means that you can include mathematical symbols, emojis and so forth. There are many different versions of...
From Daniel Lemire's Blog
Efficient In-Place UTF-16 Unicode Correction with ARM NEON
Modern-day text in software can be expected to be Unicode. Unicode is stored in two formats: UTF-8 and UTF-16. UTF-16 is an encoding system used by several platforms...
From Daniel Lemire's Blog
Simpler and faster parsing code with std::views::split
Parsing text files is often confusing irrespective of your programming language. It can also be surprising slow. As an example, let us consider the following problem...
From Daniel Lemire's Blog
Accessing the attributes of a struct in C++ as array elements?
In C++, it might be reasonable to represent a URL using a class or a struct made of several strings, like so: struct basic { std::string protocol; std::string username...
From Daniel Lemire's Blog
Data structures as jigs for programmers (Go edition)
A data structure in programming is a specific way of organizing and storing data in a computer so that it can be accessed and used efficiently. In woodworking or...
From Daniel Lemire's Blog
Parsing floats at over a gigabyte per second in C#
A few years ago, we wrote csFastFloat, a C# library to parse floating-point numbers faster. Given the string “3.1416”, it computes the binary value 3.1416. TheContinue...
From Daniel Lemire's Blog
Graduate degrees are overrated
Though I have many brilliant graduate students, I love working with undergraduate students. And I am not at all sure that you should favor people with graduateContinue...
From Daniel Lemire's Blog
Having fun with modern C++
Recent versions of the C++ language (C++20 and C++23) may allow you to change drastically how you program in C++. I want to provide some fun examples. Thanks to...
From Daniel Lemire's Blog