[petsc-users] Load balancing problem with DMDA

Xiao, Jianjun (IKET) jianjun.xiao at kit.edu
Thu Oct 15 08:55:24 CDT 2015


Yes. I would like to try. Where should I start?

From: Matthew Knepley <knepley at gmail.com>
Sent: Thursday, October 15, 2015 3:43 PM
To: Barry Smith
Cc: Xiao, Jianjun (IKET); petsc-users at mcs.anl.gov
Subject: Re: [petsc-users] Load balancing problem with DMDA

On Wed, Oct 14, 2015 at 3:32 PM, Barry Smith <bsmith at mcs.anl.gov<mailto:bsmith at mcs.anl.gov>> wrote:

> On Oct 14, 2015, at 3:11 PM, Xiao, Jianjun (IKET) <jianjun.xiao at kit.edu<mailto:jianjun.xiao at kit.edu>> wrote:
> Hello,
> We have a finite volume code with structured grid. We use the DMDA data structure.
> Now we have the load balancing problem as shown in the attached picture. The domain is decomposed into 4 partitions. The sub-domain in black (proc 2) is solid which is of no interest. We would like to calculate only the fluid part in proc 1, 3 and 4 which means the resource in proc 2 is wasted. Does DMDA now support multi-block with communication between blocks? I mean I build block 1 and assign to proc1, block 2 to proc 3 and block 3 to proc 4. So the solid sub-domain does not exist. Any suggestion?


> Or I have to do it using DMPLEX? Since data structure of the whole code  is based on  DMDA, is there any "simple way" to switch from DMDA to DMPLEX without changing the loop structure in the code?


  DMDA is for simple structured grids.

Using Plex would be some work since no one has ever used it to do FD. In fact, now I think the way to do this
is to only represent the vertices and edges. I would help you if you want to experiment with that.



> Thank you.
> Best regards
> Jianjun
> <pic.JPG>

What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead.
-- Norbert Wiener
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