[petsc-users] [petsc-dev] Getting 2d array with updated ghost values from DM global vector

[Blaise Bourdin]

On Jul 3, 2012, at 4:10 AM, Barry Smith wrote:

> 
>   Blaise,
> 
>    I don't understand why the patch does anything:
> 
> -  *ierr = VecRestoreArray(*v,0);if (*ierr) return;
> +  PetscScalar *fa;
> +  *ierr = F90Array1dAccess(a,PETSC_SCALAR,(void**)&fa PETSC_F90_2PTR_PARAM(ptrd));
> +  *ierr = VecRestoreArray(*v,&fa);if (*ierr) return;
>   *ierr = F90Array1dDestroy(&a,PETSC_SCALAR PETSC_F90_2PTR_PARAM(ptrd));
> 
> All that passing &fa into VecRestoreArray() does is cause fa to be zeroed. Why would that have any affect on anything?


Not sure either, I quite don't understand this code, but I noticed that the logic of VecRestoreArrayF90 was different from that of DMDAVecRestoreArrayF90

src/vec/vec/interface/f90-custom/zvectorf90.c:33
  PetscScalar *fa;
  *__ierr = F90Array1dAccess(ptr,PETSC_SCALAR,(void**)&fa PETSC_F90_2PTR_PARAM(ptrd));if (*__ierr) return;
  *__ierr = F90Array1dDestroy(ptr,PETSC_SCALAR PETSC_F90_2PTR_PARAM(ptrd));if (*__ierr) return;
  *__ierr = VecRestoreArray(*x,&fa);

Why aren't the calls to F90Array1dAccess and F90Array1dDestroy necessary in the context of DMDAVecGetArrayF90?

Blaise



> 
>   Thanks
> 
>     Barry
> 
> On Jul 2, 2012, at 10:10 AM, Blaise Bourdin wrote:
> 
>> Hi,
>> 
>> There appears to be a bug in DMDAVecRestoreArrayF90. It is probably only triggered when the intel compilers. gfortran and intel seem to have very different internal implementations of fortran90 allocatable arrays. 
>> 
>> Developers, can you check if the attached patch makes sense? It will not fix the case of a 3d da with dof>1 since F90Array4dAccess is not implemented. Other than that, it seems to fix ex11f90 under linux and mac OS
>> 
>> <DMDAVecRestoreArrayF90.patch>
>> 
>> Blaise
>> 
>> 
>> 
>> On Jul 2, 2012, at 5:41 PM, TAY wee-beng wrote:
>> 
>>> On 2/7/2012 2:49 PM, Matthew Knepley wrote:
>>>> On Mon, Jul 2, 2012 at 3:58 AM, TAY wee-beng <zonexo at gmail.com> wrote:
>>>> Hi,
>>>> 
>>>> I have used DMDACreate2d for my code and then use:
>>>> 
>>>> call DMLocalToGlobalBegin(da,b_rhs_semi_local,INSERT_VALUES,b_rhs_semi_global,ierr)
>>>> 
>>>> call DMLocalToGlobalEnd(da,b_rhs_semi_local,INSERT_VALUES,b_rhs_semi_global,ierr)
>>>> 
>>>> to construct the global DM vector b_rhs_semi_global
>>>> 
>>>> Now I want to get the values with ghost values in a 2d array locally which is declared as:
>>>> 
>>>> real(8), allocatable :: array2d(:,:)
>>>> 
>>>> I guess I should use DMDAGetGhostCorners to get the corressponding indices and allocate it.  But what should I do next? How can I use something like VecGetArrayF90 to get to the pointer to access the local vector?
>>>> 
>>>> I can't use DMDAVecGetArrayF90/DMDAVecRestoreArrayF90 since I'm using intel fortran and they can't work. I can't use gfortran at the moment since I've problems with HYPRE with           gfortran in 3D.
>>>> 
>>>> Are you certain of this? That used to be true, but the current version should work for any F90.
>>>> 
>>>>   Matt
>>> 
>>> I just tested 3.3-p1 and it still doesn't work (example ex11f90 in dm). Is there a chance petsc-dev can work?
>>>> 
>>>> Thanks
>>>> 
>>>> -- 
>>>> Yours sincerely,
>>>> 
>>>> TAY wee-beng
>>>> 
>>>> 
>>>> 
>>>> 
>>>> -- 
>>>> 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
>>> 
>>> 
>> 
>> -- 
>> Department of Mathematics and Center for Computation & Technology
>> Louisiana State University, Baton Rouge, LA 70803, USA
>> Tel. +1 (225) 578 1612, Fax  +1 (225) 578 4276 http://www.math.lsu.edu/~bourdin
>> 
>> 
>> 
>> 
>> 
>> 
>> 
> 

-- 
Department of Mathematics and Center for Computation & Technology
Louisiana State University, Baton Rouge, LA 70803, USA
Tel. +1 (225) 578 1612, Fax  +1 (225) 578 4276 http://www.math.lsu.edu/~bourdin