[petsc-users] ghost values

[Barry Smith]

  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
>