[petsc-users] ghost values

[Gideon Simpson]

Other than zeroing things out, is there any substantive difference between DMCreateLocalVector and DMGetLocalVector?

-gideon

> On Apr 14, 2015, at 7:02 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:
> 
> 
>  When PETSc vectors are created initially they always have 0 everywhere. So if you use DMCreateLocalVector() it will have zero in all those ghost places (as well as everywhere else). 
> 
>   But if you use DMGetLocalVector() it returns vectors that maybe dirty so you need to fill in any locations you want to have a known value with that known value. Or call VecSet() to clear the entire vector.
> 
>  Barry
> 
>> On Apr 14, 2015, at 5:52 PM, Gideon Simpson <gideon.simpson at gmail.com> wrote:
>> 
>> If i use the DM_BOUNDARY_GHOSTED flag in the creation of a DMDA array, are the ghosted values automatically set to zero, or should they be manually set to zero if that’s the desired ghost value?
>> 
>> -gideon
>> 
>