[Help-gsl] gsl-1.16 integration/qpsrt2.c: Function large_interval is doing what it is supposed to?

[seneika00]

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.