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Re: [Bug-gsl] gsl 2.3.0 bug?

From: Patrick Alken
Subject: Re: [Bug-gsl] gsl 2.3.0 bug?
Date: Tue, 20 Nov 2018 17:29:13 +0000
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.3.0


   I converted your main.cpp to C (I couldn't make it compile with my 
g++). Also I linked it against GSL v2.5, but the CQUAD code hasn't 
changed since 2.3 as far as I know. The program works as expected (C 
code attached).

$ ./main
result = 4.390157623791e-164
abserr = 0.000000000000e+00
nevals = 33

Mathematica agrees with the result to about 11 significant digits.

I am unable to diagnose problems with fgsl since I have never used it.


On 11/20/18 9:36 AM, Rico Buchholz wrote:
> Hello!
> I am working with a fortran project which uses fgsl (v1.2.0, together 
> with gsl v2.3.0).
> The code reports an arithmetic exception in an integration routine, 
> when trying to integrate exp(-x^2) from x=19.3 to 20.0.
> I would expect the code to work without problems (maybe underflow or 
> denormal).
> Trying to create a minimal working example i came up with the attached 
> file (the cmake input i used for compilation is also attached, sorry I 
> could not boil this further down).
> As a corresponding version for c++ works (also attached), this might 
> relate to a bug in fgsl, but for me (a person without knowledge of the 
> internals), that seems questionable according to what causes the 
> problem and what not.
> The output is as follows:
> Program received signal SIGFPE: Floating-point exception - erroneous 
> arithmetic operation.
> Backtrace for this error:
> #0  0x7fa39acc5d1d in ???
> #1  0x7fa39acc4f7d in ???
> #2  0x7fa39a1e405f in ???
> #3  0x560ac54c9eff in ???
> #4  0x560ac54860cf in neo2
>     at 
> /afs/itp.tugraz.at/user/buchholz/Programs/neo2-minimal/NEO-2-QL/neo2.f90:31
> #5  0x560ac54861d8 in main
>     at 
> /afs/itp.tugraz.at/user/buchholz/Programs/neo2-minimal/NEO-2-QL/neo2.f90:4
> It does not occur with the alternative integration routine commented 
> in the code.
> This does not occur, if one reduces the lower bound to 19.2 or smaller 
> (which is a reason why I suspect that this might be a gsl bug - a bug 
> in the interface should have no influence on this).
> With kind regards
> Rico Buchholz
> PS: I did also send the bug report to fgsl.

Attachment: main.c
Description: main.c

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