[petsc-users] Computation to communication ratio for PETSc's routines

[Alexander Grayver]

On 13.06.2012 13:24, Matthew Knepley wrote:
> On Wed, Jun 13, 2012 at 6:45 PM, Alexander Grayver 
> <agrayver at gfz-potsdam.de <mailto:agrayver at gfz-potsdam.de>> wrote:
>
>     Hello,
>
>     As stated, I would like to estimate computation to communication
>     ratio for PETSc's linear algebra routines (e.g.
>     MatMult{Transpose}, MatPtAP, MatMatMult etc.)
>     As far as I understand the ratio depends on particular
>     implementation and number of processes one runs application on.
>     So I guess these formulas should be known?
>
>
> It depends on the input data. For example, block diagonal matrices do 
> not communicate in MatMult().
>
>     If not then I see one way to estimate it. Write app with those
>     operations, parse -log_summary and then divide flops/messages,
>     however the question is what information from -log_summary output
>     should be used for that?
>
>
> We give the number of messages and the average message length, so you 
> can get the total length across processes. Since
> each side records, we divide by 2 (I think, you should check 
> PetscLogView for specifics). You can also use PetscLogViewPython()
> to simplify parsing.

Is there total amount of flops given for different operations separately 
(I see max flops over all processes only)?

>
>    Matt
>
>     Thanks.
>
>     -- 
>     Regards,
>     Alexander
>
>
>
>
> -- 
> 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


-- 
Regards,
Alexander

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20120613/d92d8312/attachment.html>