[petsc-users] Tuning the parallel performance of a 3D FEM CFD code

[Barry Smith]

On May 18, 2011, at 10:08 AM, Henning Sauerland wrote:

> 
> On 15.05.2011, at 15:59, Jed Brown wrote:
> 
>> This is a problem, but you can still order unknowns in the vector so that velocity and pressure all come together, then AIJ/Inode will treat the components together which will tend to make ILU stronger.
> 
> The results using the interlaced ordering are more pronounced than expected. The number of iterations did increase significantly using ILU(0) (~430 vs. ~170 per Picard iteration on 4 PEs) which makes it 4-5 times slower.

   So interlacing the variables makes ILU() much worse in both iteration count and time?


   Barry

> However, the iteration count almost stays constant when moving to more processors! ILU(2) again reduces the iteration count (~100) while being slower compared to ILU(0).
> 
> 
> I really appreciate your suggestions so far!
> 
> Henning