<div class="gmail_extra">On Fri, Apr 27, 2012 at 9:53 AM, Wen Jiang <span dir="ltr"><<a href="mailto:jiangwen84@gmail.com" target="_blank">jiangwen84@gmail.com</a>></span> wrote:<br><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Hi,<br><br>I am using mumps in PETSc to solve a 0.2 million system on 128 cores. Within Newton-Raphson iteration, the system with same sparse structure but different values will be solved many times. And I specify the preconditioning matrix having same nonzero pattern. The first time solving costs around 900 seconds and later solving only takes around 200 seconds. So I am wondering why the time differs that much. By setting the same nonzero pattern of pc, which of the mumps control parameters does PETSc change? Thanks.<br>
</blockquote><div><br></div><div>The difference is that you do not have to perform the symbolic factorization again if the nonzero pattern does not change,</div><div>just the numeric factorization. The symbolic factorization is the costly step.</div>
<div><br></div><div> Matt</div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Regards,<br>Wen<br>
</blockquote></div><br><br clear="all"><div><br></div>-- <br>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<br>
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