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
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
Data structure size and cache-line accesses
On many systems, memory is accessed in fixed blocks called “cache lines”. On Intel systems, the cache line spans 64 bytes. That is, if you access memory at byte...
From Daniel Lemire's Blog
Parsing JSON faster with Intel AVX-512
Many recent Intel processors benefit from a new family of instructions called AVX-512. These instructions operate over wide registers (up to 512 bits) and follow...
From Daniel Lemire's Blog
Avoid exception throwing in performance-sensitive code
There are various ways in software to handle error conditions. In C or Go, one returns error code. Other programming languages like C++ or Java prefer to throwContinue...
From Daniel Lemire's Blog
Faster bitset decoding using Intel AVX-512
I refer to “bitset decoding” as the action of finding the positions of the 1s in a stream of bits. For example, given the integer value 0b11011 (or 27 in decimal)...
From Daniel Lemire's Blog
Fast bitset decoding using Intel AVX-512
In software, we often use ‘bitsets’: you work with arrays of bits to represent sets of small integers. It is a concise and fast data structure. Sometimes you want...
From Daniel Lemire's Blog
Removing characters from strings faster with AVX-512
In software, it is a common problem to want to remove specific characters from a string. To make the problem precise, let us consider the removal of all ASCII control...
From Daniel Lemire's Blog
An overview of version control in programming
In practice, computer code is constantly being transformed. At the beginning of a project, the computer code often takes the form of sketches that are gradually...
From Daniel Lemire's Blog
Floats have 15-digit accuracy in their normal range
In programming languages like JavaScript or Python, numbers are typically represented using 64-bit IEEE number types (binary64). For these numbers, we have 15 digits...
From Daniel Lemire's Blog
String representations are not unique: learn to normalize!
Most strings in software today are represented using the unicode standard. The unicode standard can represent most human readable strings. Unicode works by representing...
From Daniel Lemire's Blog
Converting integers to decimal strings faster with AVX-512
In most systems, integers are stored using a fixed binary representation. It is common to store integers using 32-bit or 64-bit words. You sometimes need to convert...
From Daniel Lemire's Blog
Writing out large arrays in Go: binary.Write is inefficient for large arrays
Programmers often need to write data structures to disk or to networks. The data structure then needs to be interpreted as a sequence of bytes. Regarding integer...
From Daniel Lemire's Blog
Enforcement by software
At my university, one of our internal software systems allows a professor to submit a revision to a course. The professor might change the content or the objectives...
From Daniel Lemire's Blog