January 14, 2020
In one of the classes I teach, we end up writing assembly language programs. And while I explain the (sometimes very relative) benefits of writing assembly language, I use bubble sort as an example where even carefully crafted assembly language doesn’t mean much: it’s a bad algorithm to start with.

YoU CanT MaKE BuBBleSorT FaSTER With ASseMbLY

Except that it’s not quite true.

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4 Comments | algorithms, programming | Tagged: assembly language, AVX, bubble sort, Shell sort, sort, sorting, xmm, ymm, zmm | Permalink

Posted by Steven Pigeon

February 27, 2018
While searching for old notes—that I haven’t found anyway—I returned to an old blog entry and I thought I was kind of unsatisfactory, with be best part being swept under the carpet with a bit a faery dust, and very handwavingly.

So let’s work-out how to uniformly distribute points on a sphere in a more satisfactory fashion.

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Leave a Comment » | algorithms, Mathematics, programming | Tagged: Calculus, Curve Length, pseudo-random, random, Sphere, uniform random | Permalink

Posted by Steven Pigeon

January 9, 2018
Recently on Freenode channel ##cpp, I saw some code using an include-all-you-can header. The idea was to help beginners to the language, help them start programming without having to remember which header was which, and which headers are needed.

Is that really a good idea?

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Leave a Comment » | C-plus-plus, hacks, programming | Tagged: C, C Preprocessor, cmath, cpp, cstddef, cstdint, fstream, iomanip, iostream, list, Map, stl, Vector | Permalink

Posted by Steven Pigeon

April 4, 2017
Looking for something else in old notebooks, I found a diagram with no other indication, but clearly a low-cost random generator.

So, why not test it?

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Leave a Comment » | algorithms, Mathematics, programming | Tagged: notebook, PRNG, pseudorandom, simple | Permalink

Posted by Steven Pigeon

December 27, 2016
Sometime last week, a tweet from @nixCraft prompted the question, quite ironically, how do you get the maximum (largest positive) value for an integer?

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Leave a Comment » | C, C-plus-plus, C99, Portable Code, programming | Tagged: CHAR_BIT, intptr_t, INT_MAX, ptrdiff_t, size_t, stddef, stdint, uintptr_t | Permalink

Posted by Steven Pigeon

December 6, 2016
More often than I’d like, simple tasks turn out to be not that simple. For example, displaying (beautifully) a binary tree for debugging purpose in a terminal. Of course, one could still use lots of parentheses, but that does not lend itself to a very fast assessment of the tree. We could, however, use box drawing characters, as in DOS’s goode olde tymes, since they’re now part of the Unicode standard.

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3 Comments | algorithms, data structures, hacks, programming | Tagged: Box, Box-Drawing, Pretty-Printing, recursion, terminal, Tree, Unicode | Permalink

Posted by Steven Pigeon

September 20, 2016
Sometimes, you need to compute a function that’s complex, cumbersome, or which your favorite language doesn’t quite provide for. We may be interested in an exact implementation, or in a sufficiently good approximation. For the later, I often turn to Abramovitz and Stegun’s *Handbook of Mathematical Function*, a treasure trove of tables and approximations to hard functions. But *how* do they get all these approximations? The rational function approximations seemed the most mysterious of them all. Indeed, how can one come up with

for , for ?

Well, turns out, it’s hard work, but there’s a twist to it. Let’s see how it’s done!

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2 Comments | algorithms, bit twiddling, Mathematics, programming | Tagged: Equation System, MacLaurin Series, Padé Approximant, Padé Approximation, Taylor Series | Permalink

Posted by Steven Pigeon