matrix norm

[nanguaxiaofendui]

Hello all，
I have two questions:

1. Can the user provide the preprocessor pmat?
2. How to output matrix norm?
   thanks

[lindsayad]

1. MOOSE almost always supplies the preconditioning matrix to PETSc. You control what goes into the preconditioning matrix via how computeQpJacobian and computeQpOffDiagJacobian methods are implemented and what you supply in the Preconditioning block of your input file
2. This is not possible to do from the command line or MOOSE input file currently. In your application though you could use the API: https://petsc.org/release/docs/manualpages/Mat/MatNorm/

[nanguaxiaofendui]

thank you