digitalmars.D.bugs - [Issue 2352] New: unittest fails randomly
- d-bugmail puremagic.com (16/16) Sep 10 2008 http://d.puremagic.com/issues/show_bug.cgi?id=2352
- Jarrett Billingsley (3/19) Sep 10 2008 Looks like the unpredictable seed... isn't so unpredictable!
- d-bugmail puremagic.com (32/32) Sep 10 2008 http://d.puremagic.com/issues/show_bug.cgi?id=2352
- d-bugmail puremagic.com (16/46) Sep 10 2008 http://d.puremagic.com/issues/show_bug.cgi?id=2352
http://d.puremagic.com/issues/show_bug.cgi?id=2352 Summary: unittest fails randomly Product: D Version: 2.019 Platform: PC OS/Version: Windows Status: NEW Severity: normal Priority: P2 Component: Phobos AssignedTo: bugzilla digitalmars.com ReportedBy: bartosz relisoft.com I run unittest a lot and from time to time I see this error: Error: AssertError Failure std.random(476) It's hard to reproduce. --
Sep 10 2008
On Wed, Sep 10, 2008 at 7:17 PM, <d-bugmail puremagic.com> wrote:http://d.puremagic.com/issues/show_bug.cgi?id=2352 Summary: unittest fails randomly Product: D Version: 2.019 Platform: PC OS/Version: Windows Status: NEW Severity: normal Priority: P2 Component: Phobos AssignedTo: bugzilla digitalmars.com ReportedBy: bartosz relisoft.com I run unittest a lot and from time to time I see this error: Error: AssertError Failure std.random(476) It's hard to reproduce. --Looks like the unpredictable seed... isn't so unpredictable! Sorry.
Sep 10 2008
http://d.puremagic.com/issues/show_bug.cgi?id=2352 andrei metalanguage.com changed: What |Removed |Added ---------------------------------------------------------------------------- Status|NEW |RESOLVED Resolution| |FIXED The unpredictable seed is meant to vary from one run to the next, not necessarily from one call to the next, so the test is a bit incorrect. The function does this: uint unpredictableSeed() { static uint moseghint = 87324921; return cast(uint) (getpid ^ getUTCtime ^ ++moseghint); } (Bonus q: what does moseghint mean?) If it so happens that getUTCtime and moseghint e.g. change only LSB in lockstep from one call to the next, the returned values will be identical. I changed the function to this: uint unpredictableSeed() { static bool seeded; static MinstdRand0 rand; if (!seeded) { rand.seed(getpid ^ getUTCtime); } return cast(uint) (getUTCtime ^ rand.next); } It'll be a bit slower but also quite a bit less predictable. But I also removed the assert because even with the implementation above, it's not guaranteed that two successive returns can't be equal. --
Sep 10 2008
http://d.puremagic.com/issues/show_bug.cgi?id=2352The unpredictable seed is meant to vary from one run to the next, not necessarily from one call to the next, so the test is a bit incorrect. The function does this: uint unpredictableSeed() { static uint moseghint = 87324921; return cast(uint) (getpid ^ getUTCtime ^ ++moseghint); } (Bonus q: what does moseghint mean?) If it so happens that getUTCtime and moseghint e.g. change only LSB in lockstep from one call to the next, the returned values will be identical. I changed the function to this: uint unpredictableSeed() { static bool seeded; static MinstdRand0 rand; if (!seeded) { rand.seed(getpid ^ getUTCtime); } return cast(uint) (getUTCtime ^ rand.next); } It'll be a bit slower but also quite a bit less predictable. But I also removed the assert because even with the implementation above, it's not guaranteed that two successive returns can't be equal.I meant: uint unpredictableSeed() { static bool seeded; static MinstdRand0 rand; if (!seeded) { rand.seed(getpid ^ getUTCtime); seeded = true; } return cast(uint) (getUTCtime ^ rand.next); } It's in SVN. --
Sep 10 2008