[dune-functions] Bug in DiscreteGlobalBasisFunction

[Carsten Gräser]

Dear all,
yesterday I fixed a bug that I introduced in the master branch of
DiscreteGlobalBasisFunction some time ago. I'd like to point this out,
because as a nasty consequence the function silently computed wrong numbers
in a special case. To be precise this happened if all of the following apply:

* You're using either the master or the releases/2.8 branch.
* You use DiscreteGlobalBasis with a SubspaceBasis.
* The tree path associated to the SubspaceBasis contains non-zero entries.

E.g. this is the case when writing the pressure component to vtk in the
Stokes example coming with dune-functions. Unfortunately this case was not
covered by our tests so far. The bug is now fixed in both branches. For
details see:

   https://gitlab.dune-project.org/staging/dune-functions/-/merge_requests/310

I really hope that this did not effect anyone else despite me.

Best regards,
Carsten

-- 
Prof. Dr. Carsten Gräser
Freie Universität Berlin
Institut für Mathematik
Arnimallee 6
14195 Berlin, Germany
phone: +49 30 838 72637
fax  : +49 30 838 472637
email: graeser at mi.fu-berlin.de
URL  : http://page.mi.fu-berlin.de/graeser