<div style="line-height:1.7;color:#000000;font-size:14px;font-family:arial"><DIV>Hello, Matt</DIV>
<DIV> The results of the parallel and the serial are <SPAN id="src_1_3" jQuery17103119459660716153="97" data-aligning="#src_1_3,#tran_1_4">identical by the "-ksp_rtol 1.0e-15 -ksp_converged_reason -ksp_monitor_true_residual".</SPAN></DIV>
<DIV><SPAN jQuery17103119459660716153="97" data-aligning="#src_1_3,#tran_1_4"> I will make a <SPAN id="tran_2_8" data-aligning="#src_2_8,#tran_2_8" jQuery17107117125654621121="29">careful</SPAN> <SPAN id="tran_2_9" data-aligning="#src_2_9,#tran_2_9" jQuery17107117125654621121="30">analysis</SPAN> of these <SPAN id="tran_1_6" data-aligning="#src_1_6,#tran_1_6" jQuery17107117125654621121="64">parameters next day because it is late night here now.</SPAN></SPAN></DIV>
<DIV><SPAN jQuery17103119459660716153="97" data-aligning="#src_1_3,#tran_1_4"><SPAN data-aligning="#src_1_6,#tran_1_6" jQuery17107117125654621121="64"> Thanks again. Jim</SPAN></SPAN><BR></DIV>>ÔÚ 2012-05-26 22:26:20£¬"Matthew Knepley" <knepley@gmail.com> дµÀ£º<BR>
<BLOCKQUOTE style="BORDER-LEFT: #ccc 1px solid; MARGIN: 0px 0px 0px 0.8ex; PADDING-LEFT: 1ex" id="isReplyContent">>On Sat, May 26, 2012 at 2:22 PM, w_ang_temp <SPAN dir="ltr"><<A href="mailto:w_ang_temp@163.com" target="_blank">w_ang_temp@163.com</A>></SPAN> wrote:<BR>
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<DIV>>Hello,Matt<BR>> Thanks again.<BR>> What you said("Use -ksp_type preonly -pc_type lu") means that I should use a direct solver.And I am puzzled.<BR></DIV></DIV></BLOCKQUOTE>
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<DIV>>Okay, you want to remove variables from the investigation. You say there is a difference between</DIV>
<DIV>>the parallel and serial solve. We do this all the time, so it is not a bug. It is an issue of understanding.</DIV>
<DIV>>First, take away the tolerance issues:</DIV>
<DIV><BR></DIV>> -ksp_rtol 1.0e-15 -ksp_converged_reason -ksp_monitor_true_residual</DIV>
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<DIV>>and send output of the serial and parallel run.</DIV>
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<DIV>> Matt</DIV>
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<DIV>> (1)I think this problem (single processor is ok and more than one are problematic)is typical,but I cannot <BR>>find useful infomation both in the manual and the petsc-users.So can you give me some explanation for this <BR>>phenomenon.<BR>> (2)When I use -pc_type lu,the error message is "Matrix format mpiaij does not have a built-in PETSc LU!".<BR>> (3)The manual says that "This approach prevents the user from the unexpected surprise of having a <BR>>corrupted matrix after a linear solve"(P72).So do you mean the problem of mine is here?<BR>> (4)Generally I want to use the iterative approach other than the direct method.<BR>> As a beginne r,I have to learn more about the manual.And also I think an experienced senior will be a more<BR>> useful help for me because I have gotten stuck on this problem for more than a week.<BR>> Thanks. Jim<BR><BR></DIV>
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<DIV><BR></DIV>>At 2012-05-26 20:17:42,"Matthew Knepley" <<A href="mailto:knepley@gmail.com" target="_blank">knepley@gmail.com</A>> wrote:<BR>
<BLOCKQUOTE style="BORDER-LEFT: #ccc 1px solid; MARGIN: 0px 0px 0px 0.8ex; PADDING-LEFT: 1ex">>Use -ksp_type preonly -pc_type lu.
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<DIV> > Matt</DIV></BLOCKQUOTE></DIV><BR><BR><SPAN title="neteasefooter"><SPAN></SPAN></SPAN></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></BLOCKQUOTE></div><br><br><span title="neteasefooter"><span id="netease_mail_footer"></span></span>