On Feb 19, 2011, at 10:17 PM, Matthew Knepley wrote: > On Sat, Feb 19, 2011 at 10:08 PM, Barry Smith <bsmith at mcs.anl.gov> 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
