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From: "jsm28 at gcc dot gnu.org" <sourceware-bugzilla@sourceware.org> To: glibc-bugs@sourceware.org Subject: [Bug math/17061] New: [ldbl-128/ldbl-128ibm] coshl inaccurate near 0 Date: Mon, 16 Jun 2014 21:22:00 -0000 [thread overview] Message-ID: <bug-17061-131@http.sourceware.org/bugzilla/> (raw) https://sourceware.org/bugzilla/show_bug.cgi?id=17061 Bug ID: 17061 Summary: [ldbl-128/ldbl-128ibm] coshl inaccurate near 0 Product: glibc Version: 2.19 Status: NEW Severity: normal Priority: P2 Component: math Assignee: unassigned at sourceware dot org Reporter: jsm28 at gcc dot gnu.org The ldbl-128 and ldbl-128ibm implementations of coshl have a threshold for small arguments for which the result (to nearest) is 1. However, in those cases they return 1 + expm1(abs(x)) rather than 1, and while the threshold is small enough for cosh(x) (1 + x^2/2 + ...) to be 1, it's not small enough for 1 + abs(x) to be 1, resulting in large errors. E.g., for ldbl-128: Failure: Test: cosh (0x1p-72) Result: is: 1.00000000000000000000e+00 0x1.00000000000000000100p+0 should be: 1.00000000000000000000e+00 0x1.00000000000000000000p+0 difference: 2.11758236813575084767e-22 0x1.00000000000000000000p-72 ulp : 1099511627776.0000 max.ulp : 1.0000 and for ldbl-128ibm: Failure: Test: cosh (0x1p-56) Result: is: 1.00000000000000001388e+00 0x1.00000000000001000000p+0 should be: 1.00000000000000000000e+00 0x1.00000000000000000000p+0 difference: 1.38777878078144567553e-17 0x1.00000000000000000000p-56 ulp : 562949953421312.0000 max.ulp : 3.0000 -- You are receiving this mail because: You are on the CC list for the bug.
next reply other threads:[~2014-06-16 21:22 UTC|newest] Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top 2014-06-16 21:22 jsm28 at gcc dot gnu.org [this message] 2014-06-17 6:56 ` [Bug math/17061] " fweimer at redhat dot com 2014-06-23 20:21 ` cvs-commit at gcc dot gnu.org 2014-06-23 20:22 ` jsm28 at gcc dot gnu.org
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