PetscObjectDereference

Indicates to any PetscObject that it is being referenced by one less PetscObject. This decreases the reference count for that object by one.

#include "petsc.h"    
int PetscObjectDereference(PetscObject obj)

Collective on PetscObject

obj -the PETSc object; this must be cast with (PetscObject), for example, PetscObjectDereference((PetscObject)mat);