[phobos] phobos commit, revision 2202

Dmitry Olshansky dmitry.olsh at gmail.com
Sun Nov 28 13:30:22 PST 2010


I can confirm, it still fails  on my AMD.
The problem maybe is that while fyl2x error is of the order of the last 
bit, the whole calculation got an error of some greater magnitude.

> This still doesn't pass on my AMD box.  I guess the error is being 
> caused indirectly somehow, allowing the magnitude of the error to 
> increase.  Anyhow, it fails on line 810 in 
> std.math.internal.gammafunction, which is:
>
> assert(feqrel(betaIncompleteInv(0x1.ff1275ae5b939bcap-41, 4.6713e18, 
> 0.0813601), 0x1.f97749d90c7adba8p-63L)>=real.mant_dig - 1);
>
> For me, on my AMD box,
>
> feqrel(betaIncompleteInv(0x1.ff1275ae5b939bcap-41, 4.6713e18, 
> 0.0813601), 0x1.f97749d90c7adba8p-63L) == 25
>
> If I change the assert to this level of leniency, then all unit tests 
> pass.  I don't understand the codebase and what that line is meant to 
> test well enough, though, to know whether it's reasonable to make the 
> unit test that lenient.
>
> On 11/28/2010 3:11 PM, dsource.org wrote:
>> phobos commit, revision 2202
>>
>>
>> user: Don Clugston
>>
>> msg:
>> Increase tolerance of this test, now that we know that failure is 
>> caused by a small imprecision in AMD's microcode.
>>
>> http://www.dsource.org/projects/phobos/changeset/2202
>>
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