[petsc-dev] XXXDestroy() mistaken design in PETSc

Matthew Knepley knepley at gmail.com
Tue Feb 15 17:26:40 CST 2011

On Tue, Feb 15, 2011 at 4:47 PM, Barry Smith <bsmith at mcs.anl.gov> 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

We catch this with other error detection. I do not think we would gain much

> 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);

True, but again I do not think the win is large.


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