[petsc-dev] MatISGetLocalMat: need to MatDestroy the returned local matrice ?

[Barry Smith]

   Jed,

     Should this utilize the Get/Restore paradigm? 

     If not should the name be different to prevent confusion? Currently we have 

  XXXCreate -->  user needs to call a destroy

   XXXXGetYYY  --> user needs to call a restore (but not always?)

   Could we introduce say

    XXXAccessYYY   --> user does not call destroy or restore ?

  Barry

> On May 19, 2017, at 9:20 AM, Jed Brown <jed at jedbrown.org> wrote:
> 
> Thanks.  I just pushed this.
> 
> commit 96a6f12955a790d77f6eb7eb6b1dcf9dd5e1cf30
> Author: Jed Brown <jed at jedbrown.org>
> Date:   Fri May 19 08:17:45 2017 -0600
> 
>    MatISGetLocalMat: add note on reference counting
> 
>    Reported-by: Franck Houssen <franck.houssen at inria.fr>
> 
> diff --git a/src/mat/impls/is/matis.c b/src/mat/impls/is/matis.c
> index dc4a894aae..287c0aa554 100644
> --- a/src/mat/impls/is/matis.c
> +++ b/src/mat/impls/is/matis.c
> @@ -837,6 +837,9 @@ PetscErrorCode MatISGetLocalMat_IS(Mat mat,Mat *local)
>   matrix and want to provide it to the inner matrix object to improve the performance
>   of the MatSetValues() operation.
> 
> +  This function does not increase the reference count for the local Mat.  Do not destroy it and do not attempt to use
> +  your reference after destroying the parent mat.
> +
> .seealso: MATIS
> @*/
> PetscErrorCode MatISGetLocalMat(Mat mat,Mat *local)
> 
> Franck Houssen <franck.houssen at inria.fr> writes:
> 
>> Hello, 
>> 
>> Do I need to MatDestroy the local matrix returned by MatISGetLocalMat ? (the global matrix has been created with MatCreateIS) 
>> 
>> Tried to look in the source tree... But I'am not sure to get the answer: in petsc-3.7.6/src/mat/impls/is/matis.c, MatISGetLocalMat seems to call MatISGetLocalMat_C, but, I can't find MatISGetLocalMat_C in the source tree !?... 
>> 
>> Franck