On Feb 19, 2011, at 10:17 PM, Matthew Knepley wrote:

On Sat, Feb 19, 2011 at 10:08 PM, Barry Smith <[email protected]> wrote:

What about

extern PetscErrorCode VecDestroy_(Vec); #define VecDestroy(a) (VecDestroy_(a) || (((a) = 0),0))

Not exactly PETSc style, but allows the switch without changing the API.

Why not let VecDestroy_() take the pointer?

Could do that. I think it is equivalent.

Also, what about having a configure mode that goes back to the old interface (on by default), but allow the new one to be configured. Might involve putting in #define stuff, or changing files a little, but it seems cleaner.

Won't that configure code also have to change all the calls to Destroy() to pass in the &? My goal was to not change the API (since you feared the universal breakage) hence not add the * to the API. And I hate to have two valid ways of doing the same thing VecFree(Vec*) (for new users) and VecDestroy(Vec) for old users. Barry

Matt

Barry

On Feb 15, 2011, at 4:47 PM, Barry Smith wrote:

...

In MPI one calls MPI_Comm_free(&comm) to allow the MPI implementation to set the pointer explicitly to 0 after the object is destroyed.

In Petsc XXXDestroy() does not pass the pointer (because it seemed too unnatural to me in 1994) thus not allowing 0ing the pointer.

Was this a bad design decision? Should it be revisited?

Barry

Two use cases

1) error detection when someone tries to reuse a freed object

2) when removing some objects from a data structure that will be used data one currently needs to do

XXXXDestroy(mystruct->something);CHKERRQ(ierr); mystruct->something = 0;

instead of the cleaner XXXDestroy(&mystruct->something);CHKERRQ(ierr);

-- What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead. -- Norbert Wiener