[petsc-users] DMLocalToGlobal

[Dharmendar Reddy]

Thanks.  I assumed it to work. Can you add a note to man pages ? It
took me a lot of iterations to identify the incorrect usage as the
cause.

I will use CHKERRQ.


Thanks
Reddy

On Tue, Jan 21, 2014 at 10:04 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:
>
> On Jan 21, 2014, at 9:52 PM, Dharmendar Reddy <dharmareddy84 at gmail.com> wrote:
>
>> Hello,
>>         I am trying to understand the usage rule for DMLocalToGlobalBegin/End.
>>
>> I have a sequence of calls like this:
>>
>> call DMLocalToGlobalBegin(dm, localLB, INSERT_VALUES, LB, ierr)    ----- (1)
>>
>> call DMLocalToGlobalBegin(dm, localUB, INSERT_VALUES, UB, ierr)   ------ (2)
>>
>> call DMLocalToGlobalEnd(dm, localLB, INSERT_VALUES, LB, ierr)    ------- (3)
>>
>> call DMLocalToGlobalEnd(dm, localUB, INSERT_VALUES, UB, ierr)    --------(4)
>>
>>
>> call SNESVISetVariableBounds(snes,LB,UB, ierr)
>>
>>
>> SNES fails to run. I get function norm zero right in the first call
>> and simulation ends.
>>
>>
>> If i change the order of DM calls above to
>>
>> 1,3,2,4 then code works as expected
>>
>>
>> Does that mean the End call should occur immediately after Begin call ?
>
>   Currently they do need to be called in that order. Note that if you checked the ierr after (2) it would have indicated an error condition. I am surprised that PETSc didn’t print an error message “Scatter ctx already in use”. Note in FORTRAN you can do a lazy check of ierr with
>
>   call DMLocalToGlobalBegin(dm, localUB, INSERT_VALUES, UB, ierr) ; CHKERRQ(ierr)
>
>   so it does not make the Fortran code particularly ugly just put the CHKERRQ(ierr) on the same line as the code
>
>
>   Barry
>
>
>>
>>
>> Thanks
>> Reddy
>



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Dharmendar Reddy Palle
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