[GiNaC-devel] Sqrfree_parfrac Issue GiNaC

Vladimir V. Kisil V.Kisil at leeds.ac.uk
Fri Jul 24 11:19:45 CEST 2020


Dear All,

I have attempted to add some more tests for sqrfree_parfrac() and it turned out that GiNaC crashes on x*(x^2-1)^(-1) with

terminate called after throwing an instance of 'std::runtime_error'
  what():  matrix::solve(): inconsistent linear system

Thus some further investigation is required in this routine.

Best wishes,
Vladimir

________________________________________
From: Vladimir V. Kisil <V.Kisil at leeds.ac.uk>
Sent: 23 July 2020 23:08
To: GiNaC-devel List
Cc: vittorio del duca; Claude Duhr; ginac-list at ginac.de; Konstantin Leyde; Vladimir V. Kisil
Subject: Re: Sqrfree_parfrac Issue GiNaC

Dear Konstantin,

Many thanks for reporting the bug with a detailed description. I am attaching a patch to fix it.

Best wishes,
Vladimir
--
Vladimir V. Kisil                 http://www.maths.leeds.ac.uk/~kisilv/
  Book:      Geometry of Mobius Maps       https://doi.org/10.1142/p835
  Soft:      Geometry of cycles         http://moebinv.sourceforge.net/
  Jupyter notebooks:       https://github.com/vvkisil/MoebInv-notebooks
________________________________________
From: GiNaC-list <ginac-list-bounces at ginac.de> on behalf of Konstantin Leyde <konstantin.leyde at live.com>
Sent: 22 July 2020 19:16
To: ginac-list at ginac.de
Cc: vittorio del duca; Claude Duhr
Subject: [GiNaC-list] Sqrfree_parfrac Issue GiNaC

Hello,

My name is Konstantin Leyde, and I am a master student in physics at the ETH Zurich.

For my thesis project, I have been working with the GiNaC library, and I have encountered an issue with the partial fractioning (sqrfree_parfrac) routine:
Unless I misunderstood the way the sqrfree_parfrac routine works, it appears that for special cases, the output of the sqrfree_parfrac routine misses a numerical prefactor for one term, and thus returns the wrong answer.

Please find attached a pdf, that explains the problem in more detail.
In this pdf (as well as separately) we have attached the code that shows the issue.


Many thanks in advance,

Best wishes,
Konstantin



More information about the GiNaC-devel mailing list