[petsc-users] MatSetValues and values cache

[Alexander Grayver]

On 06.06.2012 13:06, Jed Brown wrote:
> On Wed, Jun 6, 2012 at 5:22 AM, Alexander Grayver 
> <agrayver at gfz-potsdam.de <mailto:agrayver at gfz-potsdam.de>> wrote:
>
>     In my program I assemble huge matrix (~500 millions of double
>     complex nnz) and all MatSetValues calls are done before
>     MatAssemblyBegin(A, MAT_FINAL_ASSEMBLY).
>     I'm wondering if it makes sense to use MatAssemblyBegin(A,
>     MAT_FLUSH_ASSEMBLY) in between? In docs it is said:
>     >> MatSetValues
>     <http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/MatSetValues.html#MatSetValues>()
>     generally caches the values.
>
>     How does the caching work actually? Is this additionally allocated
>     memory (dynamic or not)?
>
>
> Only entries that are generated on a different process than they need 
> to be stored will be cached. If you generate most entries on the 
> correct process (the owned rows for MPI*AIJ matrices), there is no 
> need to flush.

Jed,

Makes sense. I should have thought about that. I have off process 
entries, although not many.
Thanks.

>
> You can also look at -log_summary to see if an inordinate amount of 
> time is spent in assembly.


-- 
Regards,
Alexander

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20120606/4f4ae627/attachment.html>