[petsc-dev] Get/Create fixes and questions

[Matthew Knepley]

On Wed, Sep 25, 2013 at 11:40 AM, Barry Smith <bsmith at mcs.anl.gov> wrote:

>
> 1)
>    The following five routines create objects that the user needs to call
> destroy on, the called object does not keep a reference
>
>    MatGetFactor()
>    MatGetVecs()
>    KSPGetVecs()
>    PetscOptionsGetViewer()
>    DMDAGetRay()
>
>    These should be changed to use Create
>
> 2)
>    The routine
>
>    DMDASetGetMatrix()
>
>     affects is DMCreateMatrix() so this should be    DMSetCreateMatrix()
>
> 3)
>     The following routines
>
>     MatGetSubMatrix()
>     MatGetRedundantMatrix()
>     MatGetMultiProcBlock()
>     MatGetSubMatrices()
>     MatGetSubMatricesParallel()
>
>
>      create a matrix and do not keep a reference to it so likely should be
> changed to Create() BUT they all take
> a MatReuse option so after the initial call do not create (yet another
> matrix).
>
>     Should these be changed to Create?
>
>     If no one objects I will change 1-3 (and Jed will demand a deprecation
> warning that I might do if I can figure out how)
>
> 4)
>      a)  Many XXXXGetYYY() routines have a XXXXRestoreYYY()
>
>      b)  The rest of the XXXGetYYY() routines without XXXRestoreYYY() you
> are NOT suppose to call destroy on the objects (except for ones like in 1-3
> that are miss-named)?
>
>      If we were starting PETSc today would we use a different word for the
> two cases, for example,
>
>            XXXXObtainYYY() and XXXXRestoreYYY() and
>           XXXXGetYYY()?
>
>      I think Matt suggested somehow distinguishing the two types of Get in
> the manual pages somehow? Usually they say something somewhere on the page
> about calling the restore already, is that enough?


I did, somewhat like Collective. The worst situation we have is when you
call a Get(), but the Restore() is not
technically necessary, which happens sometimes at least in DMPlex.

   Matt


>
>    Barry

-- 
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
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