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<random>: Fix mersenne_twister_engine special case behavior #1631

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merged 8 commits into from
Jun 29, 2021
Merged

<random>: Fix mersenne_twister_engine special case behavior #1631

merged 8 commits into from
Jun 29, 2021

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@statementreply statementreply commented Feb 8, 2021 •
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  • Fixes mersenne_twister_engine random number generation when m = n or n = 1. [rand.eng.mers]/1:

    [...] all subscripts applied to X are to be taken modulo n.

  • Fixes mersenne_twister_engine seeding when input is degenerate.
  • Also removes the trailing space of text output.

@statementreply statementreply requested a review from a team as a code owner February 8, 2021 06:13
miscco
miscco reviewed Feb 8, 2021
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I am not really that deep into mersenne twister so some superficial comments that made me scratch my head

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@StephanTLavavej StephanTLavavej added the bug Something isn't working label Feb 8, 2021
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Code cleanup
92b2a46 
Revert some const-folded values to their original expressions, so they
look similar to other code paths.

Reduce scope of `_Ix`.

Mark `_Tmp` as const.
@statementreply
Swap _M_mod_n if branches
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StephanTLavavej approved these changes Jun 17, 2021
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@StephanTLavavej StephanTLavavej removed their assignment Jun 17, 2021
@CaseyCarter CaseyCarter removed their assignment Jun 23, 2021
@StephanTLavavej StephanTLavavej self-assigned this Jun 24, 2021
@StephanTLavavej StephanTLavavej merged commit 6780481 into microsoft:main Jun 29, 2021
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Thanks for fixing these 3 bugs - clearly chosen because 3 is both a Mersenne prime exponent and a Mersenne prime itself! 😹

@statementreply statementreply deleted the fix-mersenne-twister branch August 28, 2021 06:00
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@miscco miscco miscco left review comments

@StephanTLavavej StephanTLavavej StephanTLavavej approved these changes

@CaseyCarter CaseyCarter CaseyCarter approved these changes

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