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
The number of comparisons needed to sort a shuffled array: qsort versus std::sort
Given an array of N numbers of type double, the standard way to sort it in C is to invoke the qsort function qsort(array, N, sizeof(double), compare); where compare...
From Daniel Lemire's Blog
A review of elementary data types : numbers and strings
Computer programming starts with the organization of the data into data structures. In almost all cases, we work with strings or numbers. It is critical to understand...
From Daniel Lemire's Blog
Optimizing compilers deduplicate strings and arrays
When programming, it can be wasteful to store the same constant data again and again. You use more memory, you access more data. Thankfully, your optimizing compiler...
From Daniel Lemire's Blog
Science and Technology links (September 16 2022)
Attractive female students get better grades. They lose this benefit when courses move online. A research paper is much more likely to be highly ranked if the author...
From Daniel Lemire's Blog
Escaping strings faster with AVX-512
When programming, we often have to ‘escape’ strings. A standard way to do it is to insert the backslash character (\) before some characters such as the doubleContinue...
From Daniel Lemire's Blog
Science and Technology links (September 12 2022)
A standard dataset in artificial-intelligence research has ten percent of its images mislabeled. Yet state-of-the-art algorithms achieve better-than-90% classification...
From Daniel Lemire's Blog
Catching sanitizer errors programmatically
The C and C++ languages offer little protection against programmer errors. Errors do not always show up where you expect. You can silently corrupt the content of...
From Daniel Lemire's Blog
“Hello world” is slower in C++ than in C (Linux)
A simple C program might print ‘hello world’ on screen: #include <stdio.h> #include <stdlib.h> int main() { printf("hello world\n"); return EXIT_SUCCESS; } YouContinue...
From Daniel Lemire's Blog
Science and Technology links (August 7 2022)
Increase in computing performance explain up to 94% of the performance improvements in field such as weather prediction, protein folding, and oil exploration: information...
From Daniel Lemire's Blog
Comparing strtod with from_chars (GCC 12)
A reader (Richard Ebeling) invited me to revisit an older blog post: Parsing floats in C++: benchmarking strtod vs. from_chars. Back then I reported that switching...
From Daniel Lemire's Blog
Round a Direction Vector to an 8-Way Compass
Modern game controllers can point in a wide range of directions. Game designers sometimes want to convert the joystick direction to get 8-directional movement.Continue...
From Daniel Lemire's Blog
Science and Technology links (July 23rd 2022)
Compared to 1800, we eat less saturated fat and much more processed food and vegetable oils and it does not seem to be good for us: Saturated fats from animal sources...
From Daniel Lemire's Blog
Negative incentives in academic research
In the first half of the XXth century, there were relatively few scientists, and these scientists were generally not lavishly funded. Yet it has been convincingly...
From Daniel Lemire's Blog
How quickly can you convert floats to doubles (and back)?
Many programming languages have two binary floating-point types: float (32-bit) and double (64-bit). It reflects the fact that most general-purpose processors supports...
From Daniel Lemire's Blog
Filtering numbers faster with SVE on Graviton 3 processors
Processors come, roughly, in two large families x64 processors from Intel and AMD, and ARM processors from Apple, Samsung, and many other vendors. For a long time...
From Daniel Lemire's Blog
Go generics are not bad
When programming, we often need to write ‘generic’ functions where the exact data type is not important. For example, you might want to write a simple functionContinue...
From Daniel Lemire's Blog
Looking at assembly code with gdb
Most of us write code using higher level languages (Go, C++), but if you want to understand the code that matters to your processor, you need to look at the ‘assembly...
From Daniel Lemire's Blog
Filtering numbers quickly with SVE on Amazon Graviton 3 processors
I have had access to Amazon’s latest ARM processors (graviton 3) for a few weeks. To my knowledge, these are the first widely available processors supporting Scalable...
From Daniel Lemire's Blog
Memory-level parallelism : Intel Ice Lake versus Amazon Graviton 3
One of the most expensive operation in a processor and memory system is a random memory access. If you try to read a value in memory, it can take tens of nanosecond...
From Daniel Lemire's Blog