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[Bug math/10357] New: casinh(x) loses precision near x=0
- From: "pav at iki dot fi" <sourceware-bugzilla at sourceware dot org>
- To: glibc-bugs at sources dot redhat dot com
- Date: 1 Jul 2009 21:07:18 -0000
- Subject: [Bug math/10357] New: casinh(x) loses precision near x=0
- Reply-to: sourceware-bugzilla at sourceware dot org
The `casinh(x)` implementation in glibc-2_10-branch loses precision for small x.
The following assertion should pass:
assert(casinh(1e-20) == 9.9999999999999995e-21);
However, with Glibc 2.9 it does not: `casinh(1e-20) == 0` with it. In Glibc
sources (math/s_asinh.c), casinh is computed from y=log(x + sqrt(1 + x*x)). In
finite precision, this yields y=0 for |x| < floating-point epsilon.
--
Summary: casinh(x) loses precision near x=0
Product: glibc
Version: 2.10
Status: NEW
Severity: minor
Priority: P2
Component: math
AssignedTo: aj at suse dot de
ReportedBy: pav at iki dot fi
CC: glibc-bugs at sources dot redhat dot com
http://sourceware.org/bugzilla/show_bug.cgi?id=10357
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