[Bug math/14064] New: libm-test.inc ulps calculation incorrect for subnormals

[Bug math/14064] New: libm-test.inc ulps calculation incorrect for subnormals

[jsm28 at gcc dot gnu.org]

http://sourceware.org/bugzilla/show_bug.cgi?id=14064

             Bug #: 14064
           Summary: libm-test.inc ulps calculation incorrect for
                    subnormals
           Product: glibc
           Version: 2.15
            Status: NEW
          Severity: normal
          Priority: P2
         Component: math
        AssignedTo: unassigned@sourceware.org
        ReportedBy: jsm28@gcc.gnu.org
    Classification: Unclassified


libm-test.inc:check_float_internal calculates ulps errors thus:

        case FP_NORMAL:
          ulp = diff / FUNC(ldexp) (1.0, FUNC(ilogb) (expected) - MANT_DIG);
          break;
        case FP_SUBNORMAL:
          ulp = (FUNC(ldexp) (diff, MANT_DIG)
                 / FUNC(ldexp) (1.0, FUNC(ilogb) (expected)));

(MANT_DIG is one less than the appropriate one of FLT_MANT_DIG, DBL_MANT_DIG,
LDBL_MANT_DIG.)  The calculation for subnormals has the effect of assuming they
have as many significant mantissa bits as normal values; it may have been
written on the incorrect understanding that ilogb for a subnormal returns the
smallest normal exponent rather than the mathematical exponent of the input.

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[Bug math/14064] libm-test.inc ulps calculation incorrect for subnormals

[jsm28 at gcc dot gnu.org]

http://sourceware.org/bugzilla/show_bug.cgi?id=14064

Joseph Myers <jsm28 at gcc dot gnu.org> changed:

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

--- Comment #1 from Joseph Myers <jsm28 at gcc dot gnu.org> 2012-05-06 18:21:12 UTC ---
Fixed by:

commit 6c23e11c4dd036e65073d4e4d6bc971a445deaea
Author: Joseph Myers <joseph@codesourcery.com>
Date:   Sun May 6 18:20:21 2012 +0000

    Fix libm-test.inc ulps calculation for subnormals (bug 14064).

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[Bug math/14064] libm-test.inc ulps calculation incorrect for subnormals

[fweimer at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=14064

Florian Weimer <fweimer at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
              Flags|                            |security-

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