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[Octave-bug-tracker] [bug #54550] inaccurate result of gammainc
From: |
anonymous |
Subject: |
[Octave-bug-tracker] [bug #54550] inaccurate result of gammainc |
Date: |
Wed, 22 Aug 2018 03:50:41 -0400 (EDT) |
User-agent: |
Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/68.0.3440.84 Safari/537.36 |
URL:
<http://savannah.gnu.org/bugs/?54550>
Summary: inaccurate result of gammainc
Project: GNU Octave
Submitted by: None
Submitted on: Wed 22 Aug 2018 07:50:39 AM UTC
Category: Octave Function
Severity: 3 - Normal
Priority: 5 - Normal
Item Group: Inaccurate Result
Status: None
Assigned to: None
Originator Name: Michael Schmidt
Originator Email: address@hidden
Open/Closed: Open
Discussion Lock: Any
Release: 4.4.0
Operating System: GNU/Linux
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Details:
With octave 4.4.0, calling
c = (gammainc(77,2)-1)/eps;
delivers c = 31
wheras octave 4.2.1 (presumably correctly) delivers c = 0. For those arguments
(x=77) and (a=2), a subfunction gammainc_s is called (case 8). If this call is
suppressed (setting flag_s to 0 at line 205), the correct value is computed
and the issue disappears.
This is not a fix but it indicates that the subfunction gammainc_s may have an
issue or it is applied within a wrong region of arguments.
_______________________________________________________
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<http://savannah.gnu.org/bugs/?54550>
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