This is the mail archive of the glibc-bugs@sourceware.org mailing list for the glibc project.


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

[Bug math/13884] New: exp10 inaccurate


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).

-- 
Configure bugmail: http://sourceware.org/bugzilla/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are on the CC list for the bug.


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]