bugGNU Scientific Library - Bugs: bug #40116, possible error in integration...

 
 

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bug #40116: possible error in integration routines

Submitted by:  Patrick Alken <psa>
Submitted on:  Thu 26 Sep 2013 09:34:45 PM UTC  
 
Category: Runtime errorSeverity: 3 - Normal
Operating System: Status: None
Assigned to: NoneOpen/Closed: Open
Release: 

Thu 26 Sep 2013 09:34:45 PM UTC, original submission:

(from seneika00@aol.com)

Hello,

I apologize if this is the wrong place. I’m currently working with the integration utilities
of GSL and I’d like some help about this particular point.

I’m not sure the function defined in the file integration/qpsrt2.c and invoked, for example,
at line 418 of integration/qags.c is doing what it should, according to the original
algorithm, nor according to the comment

/* test whether the interval to be bisected next is the
smallest interval. */

at line 415 of qags.c.

In the QUADPACK version (http://www.netlib.org/quadpack/dqagse.f), at line 360 we can
see the actual test being performed

if(dabs(blist(maxerr)-alist(maxerr)).gt.small) go to 90

I think the refining loop may fail at some point, since the loop won’t cycle when the test
evaluates to true.

I don’t have a buggy case to report but it seems to me that it isn’t right.

Thank you for any help,
Seneika.

Patrick Alken <psa>
Project Administrator

 

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