I am trying to use PETSc to solve a non-linear problem. The problem I am facing is that I already have the Jacobian matrix formed in CSR format. Now I am trying to define a function FormJacobian which takes this preexisting matrix and writes it in PETSc format. For a small problem, I can use MatSetValue, looping over all non-zero elements one at a time. However, this turns out too slow for larger problems.
In my current implementation, I am using MatCreateSeqAIJ which works great. However, this approach does not seem to work to set the Jacobian. Any suggestions? Regards, Adolfo
