Dear All,
I have been trying to figure out how to appropriately index a matrix
that was created from a DMPlex with a section defined for it.
I created the matrix with DMCreateMatrix() and I tried to index the
entries by using the ISLocalToGlobalMapping obtained from
DMGetLocalToGlobalMapping, with the local indices being those obtained from
PetscSectionGetOffset() with the appropriate points from the D.A.G. However
this does not seem to work.
In particular, with the ISLocalToGlobalMapping, what I understand is
that it gives the relationship of the local indexing to the global indexing,
however there are negative numbers in this mapping which I fail to find an
explanation of in the documentation. In addition, there do not appear to be
redundant indexes to the global matrix as one would expect in a distributed
DMPlex because there can be some of the same points on different processors.
Any help is greatly appreciated.
Thank you for your time,
Matthew W. Kury
Ph.D. Candidate
CMRL UC Berkeley
M.S. Mechanical Engineering UC Berkeley, 2014
