microsoft / microsoft/STL

`<algorithm>`: Investigate further optimizations for `shuffle()` and `sample()`

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performance
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Description

After seeing #5735, @lemire pointed me to Batched Ranged Random Integer Generation published in Aug 2024 by Nevin Brackett-Rozinsky and himself, which sounds very promising for the STL:

Pseudorandom values are often generated as 64-bit binary words. These random words need to be converted into ranged values without statistical bias. We present an efficient algorithm to generate multiple independent uniformly-random bounded integers from a single uniformly-random binary word, without any bias. In the common case, our method uses one multiplication and no division operations per value produced. In practice, our algorithm can more than double the speed of unbiased random shuffling for small to moderately large arrays.

He expects that it would probably take just a few lines of code.

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Research direction

Start by reading the linked paper on Batched Ranged Random Integer Generation and inspect the STL implementations of shuffle() and sample(). Determine whether the proposed approach applies to these algorithms and establish a way to compare the resulting performance and statistical behavior; done means a concrete optimization direction supported by those investigations.

Written by the indexing model from the issue text.

Assessment

Tech stack
cpp
Domain
performance
Issue type
Feature
Difficulty
5/5
Estimated time
Over a week
Activity status
Quiet
Clarity
Needs clarification
Newbie friendliness
35/100

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