[petsc-users] about DA

[Ethan Coon]

On Wed, 2011-08-31 at 16:23 -0400, Likun Tan wrote:
> Hello,
> 
> I have a quick question about DA. When use DAVecGetArray() to set values
> to the array and run the program with mpiexec, does DAVecGetArray()
> compute in parallel?
> 

DAVecGetArray() only gives you access to the local portion (plus any
ghost nodes) of the global vec.  The portion of the data you get is
indexed by global numbering, so the indices into the pointer should
range from 

xs --> xs+m

where these values are given by

DAGetGhostCorners() or DAGetCorners()

http://www.mcs.anl.gov/petsc/petsc-as/snapshots/petsc-current/docs/manualpages/DA/DAGetGhostCorners.html#DAGetGhostCorners

So yes, you should only do the local portion of the calculation to set
set the values.

Ethan

> Thanks in advance,
> Likun
> 
> 
> 
> 

-- 
------------------------------------
Ethan Coon
Post-Doctoral Researcher
Applied Mathematics - T-5
Los Alamos National Laboratory
505-665-8289

http://www.ldeo.columbia.edu/~ecoon/
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