[petsc-users] Dense Matrix setting local rows / local columns Question

[James A Charles]

Hello,

I'm trying to use a Dense Parallel matrix where there are no nonzeros that is rectangular of size Nxp where N >> p. P is anywhere from 2-6 typically and N can be of size 1E6 or more. 

For this I would like to only distribute the rows along the MPI processes and not have the columns distributed at all (local columns size = global column size). What is the best way to do this in Petsc? If it matters I am using Petsc3.4. 

The operations performed after the Matrix allocation are:

direct call to Lapack for QR factorization via pointer to array. 

Matrix multiply with an NxN matrix. 

I have this working in serial but when I try to distribute my matrices I get columns with size p*(number of processes). 

Thanks,
James