[Bug math/13884] New: exp10 inaccurate

[Bug math/13884] New: exp10 inaccurate

[jsm28 at gcc dot gnu.org]

http://sourceware.org/bugzilla/show_bug.cgi?id=13884

             Bug #: 13884
           Summary: exp10 inaccurate
           Product: glibc
           Version: 2.15
            Status: NEW
          Severity: normal
          Priority: P2
         Component: math
        AssignedTo: unassigned@sourceware.org
        ReportedBy: jsm28@gcc.gnu.org
    Classification: Unclassified


The generic implementations of exp10, exp10f, exp10l (math/e_exp10*) use exp
(arg * log (10)) as their algorithm, which is inaccurate for large inputs (you
need some extra precision for calculating log (10) and doing the
multiplication).  For example, on x86_64, exp10f (36) has a 39ulp error, exp10
(305) has a 217ulp error and exp10l (4932) has a 5612ulp error.

It is likely that the x86 implementations of exp10f and exp10 are OK (because
of the extra x87 precision used for internal calculations), but that of exp10l
probably suffers the same issue as reported here (but I haven't tested the x86
functions).

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[Bug math/13884] exp10 inaccurate

[jsm28 at gcc dot gnu.org]

http://sourceware.org/bugzilla/show_bug.cgi?id=13884

--- Comment #1 from Joseph Myers <jsm28 at gcc dot gnu.org> 2012-04-30 09:41:34 UTC ---
Accuracy for float only fixed by:

commit 9568c0c2255045456a09b441f89c6641e27a4bec
Author: Joseph Myers <joseph@codesourcery.com>
Date:   Mon Apr 30 09:37:01 2012 +0000

    Fix exp10 spurious overflows (bug 13924).

double and long double still need to be fixed.

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[Bug math/13884] exp10 inaccurate

[jsm28 at gcc dot gnu.org]

http://sourceware.org/bugzilla/show_bug.cgi?id=13884

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

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

--- Comment #2 from Joseph Myers <jsm28 at gcc dot gnu.org> 2012-05-06 18:24:49 UTC ---
Fixed by:

commit d8b82cad1b525bdcbfff88d218c7c45032e4a3af
Author: Joseph Myers <joseph@codesourcery.com>
Date:   Sun May 6 18:23:44 2012 +0000

    Fix exp10 inaccuracy and exceptions (bugs 13884, 13914).

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[Bug math/13884] exp10 inaccurate

[fweimer at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=13884

Florian Weimer <fweimer at redhat dot com> changed:

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

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