[petsc-users] incomplete cholesky with a drop tolerance

Umut Tabak u.tabak at tudelft.nl
Sun Jul 22 13:26:17 CDT 2012

On 07/22/2012 08:22 PM, Jed Brown wrote:
> On Sun, Jul 22, 2012 at 1:16 PM, Umut Tabak <u.tabak at tudelft.nl 
> <mailto:u.tabak at tudelft.nl>> wrote:
>     I am not sure at the moment I should check it further but the mesh
>     is fine enough that this should not be a problem in the frequency
>     range of interest.
> If you are using the minimum to resolve the waves, then multigrid 
> won't buy you much (unless you use very technical coarse spaces for 
> which there is no particular software support). But if your waves are 
> lower frequency (e.g. due to geometric/coefficient structure), there 
> may be more benefit to using multigrid.
> Note that there is also a body of literature for solving Helmholtz 
> using multigrid preconditioners for Krylov methods by introducing a 
> complex shift.
I should check these, however the easiest(for the moment) using icc and 
cg is buying important cost savings at the moment, %20 percent is not 
that bad for a start even for that ill-conditioned system... I will try 
to read a bit more on these, thx.
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