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fix accuracy of IteratorRandom::choose() #1059

Merged
merged 3 commits into from Oct 17, 2020
Merged

fix accuracy of IteratorRandom::choose() #1059

merged 3 commits into from Oct 17, 2020

Commits on Oct 11, 2020

  1. remove unneccessary admonition from choose docs 

    IteratorRandom::choose also guarantees O(1) performance for slices, so
there is no need to recommend an alternative
    @kazcw
    kazcw committed Oct 11, 2020
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Commits on Oct 13, 2020

  1. document the ExactSizeIterator optimization in choose()

    @kazcw
    kazcw committed Oct 13, 2020
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Commits on Oct 16, 2020

  1. accurate IteratorRandom::choose() 

    f64 reciprocal is inexact, with residuals on the order of 1 / 2^54.

For example: the probability gen_bool(1.0 / 3) == true is:
6004799503160661/18014398509481984
Using gen_range is exact for all values of `consumed`.

NOTE: this is a value stability-breaking change

fixes rust-random#1058
    @kazcw
    kazcw committed Oct 16, 2020
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