Articles with tag algorithms

2023

[2021-03-11] How to check if any word is zero — I was curious what neat tricks compilers do use for condition like (a == 0 or b == 0 or c ==0). They do not offery anything fancy.

[2019-01-29] SIMDized counting byte in byte stream — SSE/AVX2/AVX512 can help a lot

[2018-11-18] SIMDized sum of all bytes in the array — part 2: signed bytes — std::accumulate(array, array + size, int32_t(0)) can be 2.5 times faster
[2018-11-14] Speeding up multiple vector operations using SIMD — rewriting a nested loop can boost k-means algorithm performance
[2018-10-24] SIMDized sum of all bytes in the array — std::accumulate(array, array + size, 0) can be six times faster
[2018-10-18] SIMDized check which bytes are in a set — functions like isspace with SSE/AVX2/AVX512 instructions
[2018-10-03] Finding index of the minimum value using SIMD instructions — compilers can't do this (yet)
[2018-05-13] AVX512 implementation of JPEG zigzag transformation — AVX512 code is 14 times faster than scalar transformation and almost 2 times faster than SSE
[2018-04-11] Is sorted using SIMD instructions — faster std::is_sorted
[2018-03-14] Intersection of ordered sets — a study of a special case (SIMD approach included)

[2016-12-22] AVX512 — first bit set in a large array
[2016-12-21] SWAR check if all chars are digits — we have a string and want to check if all its characters are ASCII digits
[2016-10-08] Sorting an AVX512 register — vectorized sorting of AVX512 register (or its portion, or more registers)
[2016-03-13] Implementing byte-wise lookup table with PSHUFB — a spin off from base64 decoding research, pretty straightforward use of pshufb

[2015-12-27] Base64 encoding — implementation study — this could be done slightly faster
[2015-10-25] Boolean function for the rescue — think out of the box and... use the most obvious solution
[2015-04-13] Speeding up bit-parallel population count — nearly 50% faster than naive version
[2015-04-08] SIMD-ized searching in unique constant dictionary — there is a ordered dictionary containing only unique keys, the dictionary is read only, and keys are 32-bit (SSE) or 64-bit (AVX2)
[2015-03-22] SIMD: detecting a bit pattern — trying to solve specific problem, different approaches are shown

[2014-10-15] Parsing decimal numbers — part 2: SSE — SSE procedure is able to convert two 8-digit numbers. The main instruction used in converting to numeric value is PMADDWD
[2014-10-12] Parsing decimal numbers — part 1: SWAR — SWAR techniques to multiply digits in parallel
[2014-09-25] Interpolation search revisited — interpolation search is quite interesting algorithm, however its properties make it unsuitable for most applications

[2013-12-29] Calculate floor value without FPU/SSE instruction
[2013-12-27] Convert float to int without FPU/SSE
[2013-11-23] Encoding array of unsigned integers — easily compress sequence of integers, how some special properties of sequence could be used to improve compression
[2013-09-30] SSE: trie lookup speedup — different methods of walking along paths in tries
[2013-09-15] Detecting intersection of convex polygons in 2D — another, slightly naive approach