[petsc-users] question about DA

[Jed Brown]

On Sat, Aug 27, 2011 at 17:09, Likun Tan <likunt at andrew.cmu.edu> wrote:

> Another question is, if the size is small in x and y directions, and large
> in z direction, i want more of processors, but the number is restricted to
> the size in x and y direction, since partition is not allowed in z
> direction, any way to improve efficiency?
>

This is a fundamental problem. If there is tight coupling in the z
direction, then it is algorithmically good to keep it on a single process,
but it is not good for parallel scalability because you are not allowed to
decompose in that direction. You can write a new integral function with the
z direction decomposed, but it's significantly more complicated.

The practical solution is usually to not decompose in z and pay the price of
somewhat reduced parallel scalability in exchange for simplicity,
algorithmic performance, and efficiency.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20110827/80fb3bbe/attachment.htm>