[petsc-users] Recommended unknowns per processor

[TAY wee-beng]

On 3/8/2012 11:10 AM, thomas wrote:
> Hi,
> look at the FAQ
>
> http://www.mcs.anl.gov/petsc/documentation/faq.html#slowerparallel
>
> "There must be enough work for each process to overweigh the 
> communication time. We recommend an absolute minimum of about 10,000 
> unknowns per process, better is 20,000 or more."

Hi Thomas,

Thanks for the info.

Btw, is there an upper limit? When the unknowns are 100,000 or more per 
process, is it better (as in faster) to use more processes instead (e.g. 
20,000 per process)?
>
> Regards
> Thomas Huxhorn
>
> On 08/03/2012 09:03 AM, TAY wee-beng wrote:
>> Hi,
>>
>> I remembered that in one of the mails, someone mentions the recommended
>> unknowns on each processor when doing parallel solving.
>>
>> However, I can't find that mail. Can someone enlighten me? Also, is this
>> number problem dependent?
>>
>> Btw, I'm using PETSc to solve linear equations using BCGS.
>>
>> Thanks!
>>
>