[petsc-users] EXTERNAL: Re: petsc 3.4.3

[Barry Smith]

> On Mar 17, 2015, at 11:38 AM, <Carol.Brickley at awe.co.uk> <Carol.Brickley at awe.co.uk> wrote:
> 
> Barry,
> 
> Thanks - I have used the preallocation routines to allocate the non zero row length and am also looking at other ideas as discussed in these web pages. We are expecting a petsc structured matrix to solve more quickly than the corresponding CSR matrix but it is still slower!!

  In order to know why it is slower we need to understand what part is slower: assembling the matrix, building the preconditioner, solving the system etc. Also the time depends a great deal on problem size, for smaller problems one method may be much faster, while for a much larger problem a different method will be much better.
> 
> Would it be correct to also use the PetscWrapper::SparseMatrix::SparseMatrix
> method to speed things up further?

   I don't know what that is.

   If you can run the problem with -log_summary and send us the output it would give a starting point for understanding where the time is being spent.

  Barry

> 
> Thanks,
> 
> Carol
> 
> 
> 
> Dr Carol Brickley 
> BSc,PhD,ARCS,DIC,MBCS
> 
> Senior Software Engineer
> Applied Computer Science
> DS+T,
> AWE
> Aldermaston
> Reading
> Berkshire
> RG7 4PR
> 
> Direct: 0118 9855035
> 
> 
> -----Original Message-----
> From: Barry Smith [mailto:bsmith at mcs.anl.gov] 
> Sent: 16 March 2015 21:35
> To: Brickley Carol AWE
> Cc: petsc-users at mcs.anl.gov
> Subject: EXTERNAL: Re: [petsc-users] petsc 3.4.3
> 
> 
>  We'd need more specific details on why it is slower than you think it should be. Is the it built with optimization (i.e. ./configure --with-debugging=0) ? Are the solvers converging with more iterations than expected http://www.mcs.anl.gov/petsc/documentation/faq.html#newton http://www.mcs.anl.gov/petsc/documentation/faq.html#kspdiverged ? Is the machine perhaps not suitable to for the simulations http://www.mcs.anl.gov/petsc/documentation/faq.html#computers? 
> 
>  Barry
> 
> 
>> On Mar 16, 2015, at 2:18 PM, <Carol.Brickley at awe.co.uk> <Carol.Brickley at awe.co.uk> wrote:
>> 
>> All
>> 
>> I am using petsc 3.4.3 but finding it not working as quickly as it should. Any ideas?
>> 
>> Carol  
>> 
>> Dr Carol Brickley 
>> BSc,PhD,ARCS,DIC,MBCS
>> 
>> Senior Software Engineer
>> Applied Computer Science
>> DS+T,
>> AWE
>> Aldermaston
>> Reading
>> Berkshire
>> RG7 4PR
>> 
>> Direct: 0118 9855035
>> 
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> 
> 
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