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digitalmars.D.bugs - [Issue 5566] New: [64-bit] More erratic FP results with size_t

reply d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=5566

           Summary: [64-bit] More erratic FP results with size_t
           Product: D
           Version: D2
          Platform: x86_64
        OS/Version: Windows
            Status: NEW
          Keywords: wrong-code
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: nobody puremagic.com
        ReportedBy: dsimcha yahoo.com


--- Comment #0 from David Simcha <dsimcha yahoo.com> 2011-02-12 08:37:43 PST ---
I think this bug might have the same root cause as bug 5565.  It was reduced
from completely different code and I don't really understand the root cause of
either very well, though, so I'm filing a separate bug report in case I'm
wrong.  Even if it is related to 5565, this test case is simpler.

import std.math, std.stdio;

double fun(ulong k, ulong n, double p) {
    return pow(1.0 - p,  cast(double) n);
}

void main() {
    // Should print 0.8 ^ 10 = 0.1073741824.  Prints 0.956352.
    writeln(fun(0, 10, 0.2));
}

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next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=5566



--- Comment #1 from David Simcha <dsimcha yahoo.com> 2011-02-12 08:38:43 PST ---
Argh, again I forgot to mention, this test case does not reproduce the bug if
inlining is enabled, probably because fun() gets inlined.  In the larger case I
reduced it from, inlining could be enabled and the bug would still be
reproduced.

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prev sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=5566


Walter Bright <bugzilla digitalmars.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |bugzilla digitalmars.com
         Resolution|                            |FIXED


--- Comment #2 from Walter Bright <bugzilla digitalmars.com> 2011-02-12
21:54:05 PST ---
https://github.com/D-Programming-Language/dmd/commit/4a61292e28a47bd7808eb4b1ff459537599beec6

https://github.com/D-Programming-Language/dmd/commit/b496185f71837483bf478315a8a62c53d6eae174

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