On Tue, 9 Nov 2010, Jed Brown wrote: > On Tue, Nov 9, 2010 at 12:11, Tim Kroeger <tim.kroeger at > cevis.uni-bremen.de> wrote: > Is it allowed to work with an index set (IS) with size 0? > > > Yes.
Good to hear, thank you. > In particular, using such an index set in VecScatter and > MatGetSubMatrix, I am creating the following > objects: > > v : a vector of size n>0, > w : a vector of size 0, > A : a matrix of size n\times0. > > Then I do > > MatMultAdd (A, w, v, v); > > This actually seems to change the value of v, although I supposed it > not to do so. > > > It sounds like you have a simple test case for this, could you send it? Well, as you know, I'm using PETSc only via libMesh. Creating a standalone PETSc test case is non-trivial for me. But I'll keep to this and will either find out that I did something wrong or produce a test case for you. It might be imporant to know that the original matrix is a ShellMatrix. Best Regards, Tim -- Dr. Tim Kroeger CeVis -- Center of Complex Systems and Visualization University of Bremen tim.kroeger at cevis.uni-bremen.de Universitaetsallee 29 tim.kroeger at mevis.fraunhofer.de D-28359 Bremen Phone +49-421-218-7710 Germany Fax +49-421-218-4236
