[petsc-users] snessetjacobian question

[Milan Mitrovic]

> Don't destroy the matrix, just call the preallocation routines when the
> nonzero pattern changes.
> You can actually destroy the matrices from C, but I don't think there is a
> pure Fortran way to do it (it needs another pointer indirection) and you
> should never need to anyway.

How should I create a matrix without supplying the preallocation? just
set everything to zero and then call the prealloc routines later?

> What do you mean "complains"? You can certainly use a different
> preconditioning matrix.

I dont want to use a different matrix... I want to use the same... I
just dont want to get the error that I pasted in the first message...
and I have no idea why I get it in the first place...