Transforming a matrix into a Petsc Matrix

Question

Hi!
Is there a easy way to obtain a Petsc matrix from a "normal" one?

This is what I have: I assemble a mass matrix and I lump it, but I need to change some of its values. Then I need to convert it back to a PETSc matrix in order to use the solve function and apply the bc.

Thanks,
Cristina

Answer 1

       # convert matrix to petsc
    from petsc4py import PETSc
    fullA = self.fullA.tocsr()
    fullE = self.fullE.tocsc()
    fullAT = self.fullA.T.tocsr()
    fullET = self.fullE.T.tocsc()

    fullApetsc = PETSc.Mat().createAIJ(size=fullA.shape, csr=(fullA.indptr, fullA.indices, fullA.data))
    fullEpetsc = PETSc.Mat().createAIJ(size=fullE.shape, csr=(fullE.indptr, fullE.indices, fullE.data))
    fullATpetsc = PETSc.Mat().createAIJ(size=fullAT.shape, csr=(fullAT.indptr, fullAT.indices, fullAT.data))
    fullETpetsc = PETSc.Mat().createAIJ(size=fullET.shape, csr=(fullET.indptr, fullET.indices, fullET.data))
    fullApetsc.assemble()
    fullEpetsc.assemble()
    fullATpetsc.assemble()
    fullETpetsc.assemble()

the way from scipy to petsc

Comments

Thanks for the answer and sorry for the delay.. I was thinking about a different way to solve may problem but I didn't find anything..
I tried with your suggestion but I got
from petsc4py import PETSc
ImportError: No module named petsc4py

Why?
and my second question is: How do the commands work? Why four commands?
Thanks