Hi Jed,?
??Thank you for your reply. The Algorithm II is described in the paper?
@ARTICLE{yoginabben1,
??author = {Erlangga, Y.A. and R. Nabben},
??title = {On a multilevel {K}rylov Method for the {H}elmholtz Equation
preconditioned
by Shifted {L}aplacian},
??journal = {Electronic Transaction on Num. Analysis (ETNA)},
??year = {2008},
??volume = {31},
??pages = {403--424},
?}
??Kind wishes, Domenico.
________________________________
From: Jed Brown <jedbrown at mcs.anl.gov>
To: domenico lahaye <domenico_lahaye at yahoo.com>; PETSc users list
<petsc-users at mcs.anl.gov>
Cc: Abdul Hanan Sheikh <hanangul12 at yahoo.co.uk>
Sent: Thursday, July 5, 2012 7:47 PM
Subject: Re: [petsc-users] Adapting MatMult and PCMG functions in matrix-free
method.
Can you reference a paper or some notes on the algorithm?
On Thu, Jul 5, 2012 at 8:40 AM, domenico lahaye <domenico_lahaye at yahoo.com>
wrote:
Dear PETSc developers,
>
>? Thank you for your support to Abdul.
>
>
>
>?? We are in the process of developing a multilevel
>
>Krylov solver for the Helmholtz equation. Abdul
>
>has implemented Algorithm I for this purpose.
>
>We next would like to implement Algorithm II.
>
>Algorithm || amounts to replacing every occurrence
>
>of the system matrix $A$ in Algorithm I by
>
>$M^{-1} A$. This replacement should occur on all
>
>levels. We thought of two ways to realize this
>
>replacement.
>
>
>
>1) We thought of adopting a matrix-free approach,
>
>and to plug in the operation with? $M^{-1}$ there.
>
>This would require a ksp context inside MatMult.? ?
>
>We wonder whether this a approach is feasible to
>
>take.
>
>
>
>2) The other approach would by to implement a
>
>customized pcmg preconditioner that we can adapt
>
>to our needs. This could be a more elegant approach,
>
>at the cost of doing more work. Is the assumption
>
>that the second approach is more elegant correct
>
>and would you be able to give advice on how to tackle
>
>this approach?
>
>
>
>? Kind wishes, Domenico.
>
>
>
>
>
>
>________________________________
>
>
>
>
>
>----- Forwarded Message -----
>>From: Matthew Knepley <knepley at gmail.com>
>>To: Abdul Hanan Sheikh <hanangul12 at yahoo.co.uk>; PETSc users list
>><petsc-users at mcs.anl.gov>
>>Sent: Thursday, 5 July 2012, 15:45
>>Subject: Re: [petsc-users] Adapting MatMult and PCMG functions in matrix-free
>>method.
>>
>>
>>On Thu, Jul 5, 2012 at 7:34 AM, Abdul Hanan Sheikh <hanangul12 at
>>yahoo.co.uk> wrote:
>>
>>Dear developers and users,
>>>Summer greetings.
>>>We have few question listen below:?
>>>
>>>
>>>1.
>>>
>>>The first question is about adapting " MatMult " function in matrix-free
>>>method.
>>>We intend to incorporate a KSP context inside "MatMult" . The immediate
>>>question is how to
>>>provide more than one matrices as input.?
>>
>>
>>You provide extra data through the context for the MATSHELL
>>?
>>Is this idea of incorporating a KSP context inside "MatMult" function
>>workable ? Does it make any confrontation
>>>
>>>with philosophy of development of Petsc. ??
>>
>>
>>I am not sure you want this. Do you think PCKSP can do what you want? There
>>is not enough information here to help us answer.
>>?
>>2.
>>>
>>>An other advance level feedback is needed.
>>>
>>>?Re-implementing PCMG function {mg.c } will lead any violation of philosophy
>>>of Petsc-development ??
>>
>>
>>Again, there is not enough information. Can you do what you want by just
>>replacing the monitors?
>>
>>
>>? Thanks,
>>
>>
>>? ? ?Matt
>>?
>>3.
>>>
>>>Which one of the above both is more elegant and feasible to work on ?
>>>
>>>
>>>
>>>
>>>
>>>Thanking in anticipation,?Abdul
>>>
>>>
>>>
>>>
>>>
>>
>>
>>
>>--
>>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
>>
>>
>>
>
>
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