[petsc-users] Fwd: ASM Index Sets Question

Justin Droba (JSC-EG3) [JETS] justin.c.droba at nasa.gov
Wed Mar 23 09:30:07 CDT 2016


Dear all,

SORRY ABOUT THE LAST MESSAGE! Hit send before I meant to!

Thank you for maintaining this wonderful software and this user mailing 
list!

I am attempting to use an additive Schwartz preconditioner with multiple 
blocks per processor.  I've been able to get it to work with one block 
per processor but not been successful with multiple. I believe I am not 
understanding correctly the construction of index sets for this case.

Let's consider a simple example: 16 nodes on a square with 4 blocks of 4x4:

Image


I want to put $\Omega_1$ and $\Omega_2$ on processor 1 and the other two 
on the second processor.  Do I make my index sets on processor 1

IS = {  {1,2,3,5,6,7,9,10,11}, {2,3,4,6,7,8,10,11,12} }
IS_LOCAL = { {1,2,5,6}, {3,4,7,8} }

and similarly for the other processor?  I tried this and it isn't quite 
working out.  Do I misunderstand something?

Thank you!

Best regards,
Justin

-- 
---------------------------------------------
Justin Droba, PhD
Applied Aeroscience and CFD Branch (EG3)
NASA Lyndon B. Johnson Space Center
JETS/Jacobs Technology, Inc. and HX5, LLC

*Office:* Building 16, Room 142
*Phone*: 281-483-1451
---------------------------------------------


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