[petsc-users] Index set with zero size

[Tim Kroeger]

Dear all,

Is it allowed to work with an index set (IS) with size 0?

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.

Are such index sets allowed or not?  If not, what about index sets 
having local size 0 on some processors?

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