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<body class='hmmessage'><div dir='ltr'>Dear Matthew,<br><br>Thanks for the last Email. For the LSC preconditioner in Petsc, it allows to do inv(S)= inv(A10 A01) A10 A00 A01 inv(A10 A01). Is it also possible to do inv(S)= inv(Mp) Fp inv(Ap), where Mp and Ap are built by ourselves and not the same matrices. Thanks a lot.<br><br>Best,<br>Guoyi<br><br><div><hr id="stopSpelling">Date: Mon, 12 Oct 2015 08:46:35 -0500<br>Subject: Re: [petsc-users] How to implement pressure convection¨Cdiffusion preconditioner in petsz<br>From: knepley@gmail.com<br>To: coyigg@hotmail.com<br>CC: petsc-users@mcs.anl.gov<br><br><div dir="ltr"><div class="ecxgmail_extra"><div class="ecxgmail_quote">On Mon, Oct 12, 2015 at 1:49 AM, keguoyi <span dir="ltr"><<a href="mailto:coyigg@hotmail.com" target="_blank">coyigg@hotmail.com</a>></span> wrote:<br><blockquote class="ecxgmail_quote" style="border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex;">
<div><div dir="ltr">Dear Petsc developers and users, <br><br>This is Guoyi ke, a graduate student in Texas Tech University. I have a 2D Navier Stokes problem that has block matrices: J=[F B^T; B 0]. I want to build a pressure convection¨Cdiffusion preconditioner (PCD) P=[F B^T; 0 Sp]. Here, we let Sp=-Ap(Fp)^(-1)Mp approximate schur complement S=-BF^(-1)B^T, where Ap is pressure Laplacian matrix, Mp is pressure mass matrix, and Fp is convection-diffusion operators on pressure space.<br><br> We use right preconditioner J*P^(-1)=[F B^T; B 0] * [F B^T; 0 Sp]^(-1), and is it possible for Petsz to build and implement this precondioner P? Since (Sp)^(-1)=-(Mp)^(-1) Fp(Ap)^(-1), is it possible that we can solve (Mp)^(-1) and (Ap)^(-1) by CG method separately inside preconditioner P. <br></div></div></blockquote><div><br></div><div>Take a look at the PCFIELDSPLIT preconditioner. I think you want the LSC option for that (<a href="http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/PC/PCLSC.html" target="_blank">http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/PC/PCLSC.html</a>)</div><div>if I am reading your mail correctly.</div><div><br></div><div> Thanks,</div><div><br></div><div> Matt</div><div> </div><blockquote class="ecxgmail_quote" style="border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex;"><div><div dir="ltr">Any suggestion will be highly appreciated. Thank you so much!<br><br>Best,<br>Guoyi <br> </div></div>
</blockquote></div><br><br clear="all"><div><br></div>-- <br><div class="ecxgmail_signature">What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead.<br>-- Norbert Wiener</div>
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