[libcxx-commits] [PATCH] D65041: Change requirements on linear_congruential_engine

[Zoe Carver via Phabricator via libcxx-commits]

zoecarver created this revision.
zoecarver added reviewers: mclow.lists, ldionne, EricWF.
Herald added subscribers: libcxx-commits, dexonsmith, christof.

This patch changes how linear_congruential_engine picks its randomization algorithm. It adds two restrictions, `_OverflowOK` and `_SchrageOK`. `_OverflowOK` means that `m` is a power of two so using the classic `(a * x + c) % m` will create a meaningless overflow. The second checks that Schrage's algorithm will produce results that are in bounds of `min` and `max`. This patch fixes 27839 <https://bugs.llvm.org/show_bug.cgi?id=27839>.


Repository:
  rCXX libc++

https://reviews.llvm.org/D65041

Files:
  libcxx/include/random
  libcxx/test/std/numerics/rand/rand.eng/rand.eng.lcong/alg.pass.cpp
  libcxx/test/std/numerics/rand/rand.eng/rand.eng.lcong/params.fail.cpp

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