[petsc-dev] be careful comparing two PETSc objects by pointer

[Barry Smith]

  PETSc developers,

   Never "save" a vector (without increasing its reference count) (or any object) and later check if another vector is the same object by comparing the pointers. It could be the original vector was destroy and later a new one was created that uses the same memory so the comparison says equal when they were not. 

   Instead save the PetscObjectGetId() and compare the Ids; the Ids for objects are always unique (even if the object was destroyed).

   I found a nasty use of this in TS (which I may have written) which took Satish and I a while to debug.


   Barry