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From: "redi at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug target/94087] std::random_device often fails when used from multiple threads Date: Thu, 14 May 2020 11:46:59 +0000 [thread overview] Message-ID: <bug-94087-4-7OzAEMsIUT@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-94087-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94087 --- Comment #19 from Jonathan Wakely <redi at gcc dot gnu.org> --- If you mean the mersenne twister in the std::random_device object, that's a union member and doesn't exist when a proper source (/dev/random, rdrand, rdseed etc) is available. So we'd need to add *another* mersenne twister object (which would double the size of std::random_device, changing ABI, or have to be global and protected by a mutex, or thread-local) and we'd have to seed it so it's not 100% deterministic, and MT has a state size of 19968 bits which needs a lot of seeding. It's not a good choice for many reasons.
next prev parent reply other threads:[~2020-05-14 11:46 UTC|newest] Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-03-08 2:51 [Bug libstdc++/94087] New: " coryan+gccbugzilla at google dot com 2020-03-08 7:51 ` [Bug target/94087] " pinskia at gcc dot gnu.org 2020-03-08 7:51 ` pinskia at gcc dot gnu.org 2020-03-08 8:08 ` pinskia at gcc dot gnu.org 2020-03-08 12:04 ` coryan+gccbugzilla at google dot com 2020-03-08 12:09 ` coryan+gccbugzilla at google dot com 2020-03-09 9:44 ` redi at gcc dot gnu.org 2020-03-09 12:10 ` coryan+gccbugzilla at google dot com 2020-03-09 12:24 ` redi at gcc dot gnu.org 2020-04-23 3:30 ` wnereiz at kawashiro dot org 2020-05-14 10:27 ` rguenth at gcc dot gnu.org 2020-05-14 10:30 ` rguenth at gcc dot gnu.org 2020-05-14 10:44 ` redi at gcc dot gnu.org 2020-05-14 10:51 ` redi at gcc dot gnu.org 2020-05-14 11:35 ` redi at gcc dot gnu.org 2020-05-14 11:35 ` hjl.tools at gmail dot com 2020-05-14 11:37 ` rguenther at suse dot de 2020-05-14 11:38 ` rguenther at suse dot de 2020-05-14 11:41 ` rguenther at suse dot de 2020-05-14 11:46 ` redi at gcc dot gnu.org [this message] 2020-05-14 11:51 ` rguenther at suse dot de 2020-05-14 12:01 ` redi at gcc dot gnu.org 2020-05-14 12:02 ` redi at gcc dot gnu.org 2020-05-14 12:05 ` redi at gcc dot gnu.org 2020-05-19 22:23 ` cvs-commit at gcc dot gnu.org 2020-05-23 8:18 ` redi at gcc dot gnu.org 2020-07-09 8:49 ` avi@cloudius-systems.com 2020-07-09 9:14 ` cvs-commit at gcc dot gnu.org 2020-07-09 9:14 ` redi at gcc dot gnu.org
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