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How big are your SVE registers ? (AWS Graviton)
From Daniel Lemire's Blog

How big are your SVE registers ? (AWS Graviton)

Amazon has some neat ARM-based systems based on Amazon’s own chips (Graviton). You can access them through Amazon’s web services (AWS). These processors have advanced...

Generic number compression (zstd)
From Daniel Lemire's Blog

Generic number compression (zstd)

I have done a lot of work that involves compressing and uncompressing data. Most often, I work on data that has specific characteristics, e.g., sorted integers....

Science and Technology links (November 26 2022)
From Daniel Lemire's Blog

Science and Technology links (November 26 2022)

Molière’s famous play, Tartuffe, the main characters is outwardly pious but fundamentally deceitful. Are people who insist on broadcasting their high virtue better...

Making all your integers positive with zigzag encoding
From Daniel Lemire's Blog

Making all your integers positive with zigzag encoding

You sometimes feel the need to make all of your integers positive, without losing any information. That is, you want to map all of your integers from ‘signed’ integers...

What is the size of a byte[] array in Java?
From Daniel Lemire's Blog

What is the size of a byte[] array in Java?

Java allows you to create an array just big enough to contain 4 bytes, like so: byte[] array = new byte[4]; How much memory does this array take? If you have answered...

Rounding modes: std::from_chars versus strtod/strtof
From Daniel Lemire's Blog

Rounding modes: std::from_chars versus strtod/strtof

A recent C++ standard (C++17) introduced new functions to parse floating-point numbers std::from_chars, from strings (e.g., ASCII text) to binary numbers. How should...

A fast function to check your floating-point rounding mode
From Daniel Lemire's Blog

A fast function to check your floating-point rounding mode

For speed, we use finite-precision number types in software. When doing floating-point computations in software, the results are usually not exact. For example,...

Measuring the memory usage of your C++ program
From Daniel Lemire's Blog

Measuring the memory usage of your C++ program

In C++, we might implement dynamic lists using the vector template. The int-valued constructor of the vector template allocates at least enough memory to storeContinue...

Modern vector programming with masked loads and stores
From Daniel Lemire's Blog

Modern vector programming with masked loads and stores

When you start a program, it creates a ‘process’ which own its memory. Memory is allocated to a software process in blocks called ‘pages’. These pages might span...

Book Review : Template Metaprogramming with C++
From Daniel Lemire's Blog

Book Review : Template Metaprogramming with C++

I have spent the last few years programming often in C++. The C++ langage is probably one of the hardest to master. I still learn something new every week. Furthermore...

Science and Technology links (October 16 2022)
From Daniel Lemire's Blog

Science and Technology links (October 16 2022)

Doctors in Israel are toying with polygenic screening: it is a way to make it more likely that your baby will grow up to be healthy. In 2021, 337 million prescriptions...

The number of comparisons needed to sort a shuffled array: qsort  versus std::sort
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...

A review of elementary data types : numbers and strings
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...

Optimizing compilers deduplicate strings and arrays
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...

Science and Technology links (September 16 2022)
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...

Escaping strings faster with AVX-512
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...

Science and Technology links (September 12 2022)
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...

Catching sanitizer errors programmatically
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...

“Hello world” is slower in C++ than in C (Linux)
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...

Science and Technology links (August 7 2022)
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...
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