Matt,
You use http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/MatGetLocalSubMatrix.html http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Vec/VecGetSubVector.html to put values directly into the subvectors and submatrices. This interacts well with MatNest, so it can be optimized after you get it working. Thanks, MatNest and VecNest is what I was looking for. I have a one more question: if I generate a vector with VecCreateNest, will it be allocated separately, or does it somehow reuse the space from the original subvectors? Artur
