http://gdcproject.org/bugzilla/show_bug.cgi?id=14

--- Comment #1 from Johannes Pfau <johannespfau@gmail.com> 2012-09-25 12:13:08 UTC ---
What is this test supposed to do?

----
    int exp;
    real mantissa = frexp(123.456, exp);
    assert(equals(mantissa * pow(2.0L, cast(real)exp), 123.456, 19));
----
equals: x = 67.456
equals: y = 123.456
equals: ndigits = 19
bufx = '67.45600000000000307'
bufy = '123.4560000000000031'
core.exception.AssertError@testmath.d(170): Assertion failure

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http://gdcproject.org/bugzilla/show_bug.cgi?id=14

--- Comment #2 from Iain Buclaw <ibuclaw@gdcproject.org> 2012-09-25 16:53:49 UTC ---
An alternate option could be to rethink the codegen for floating comparisons in GDC overall, as certain floating point comparisons fail in GDC x86/x86_64 too.


Problem:
Simply doing (A == B) is not correct.


Possible solution:
The comparison with an epsilon value is what most tends to be done in game
programming.

However the following:
(diff = A - B, (diff < EPSILON) && (-diff > EPSILON)))

Is a bit of wasted processing for something that should be fast, yet effective.


Here's an interesting read-up: http://realtimecollisiondetection.net/blog/?p=89


Regards
Iain

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Johannes Pfau <johannespfau@gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
         AssignedTo|ibuclaw@gdcproject.org      |johannespfau@gmail.com

--- Comment #3 from Johannes Pfau <johannespfau@gmail.com> 2012-09-27 17:35:31 UTC ---
Not sure if we should do anything about this in the compiler. I wonder what dmd does?

Anyway: https://github.com/D-Programming-Language/dmd/pull/1146 http://forum.dlang.org/thread/k3v614$2882$1@digitalmars.com

hopefully fixed soon in upstream

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Iain Buclaw <ibuclaw@gdcproject.org> changed:

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                 CC|                            |ibuclaw@gdcproject.org

--- Comment #4 from Iain Buclaw <ibuclaw@gdcproject.org> 2012-09-27 17:38:07 UTC ---
Cool beans.

By the way, if there's anything you need downstreaming to gdc, just send it my way.

Thanks.

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Johannes Pfau <johannespfau@gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |FIXED

--- Comment #5 from Johannes Pfau <johannespfau@gmail.com> 2012-10-01 15:12:20 UTC ---
@Iain sure, I'll do that. But most of those fixes are just errors in the test suite, not really errors in the library/compiler, so that stuff can wait till the 2.061 merge.

testmath.d has been removed from the test suite in upstream dmd (2.061), so I'm
closing this. I hope Don won't forget the fix for frexp though.
https://github.com/D-Programming-Language/dmd/commit/77ad29c6b38897881e849d6f80165921febe1293

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