<div style="line-height:1.7;color:#000000;font-size:14px;font-family:arial"><DIV>Is there something that need attention when setting up PETSc? The -log_summary<BR>is no use in my system.<BR><BR><BR></DIV>>At 2012-11-03 23:31:52,"Jed Brown" <jedbrown@mcs.anl.gov> wrote:<BR>
<BLOCKQUOTE style="BORDER-LEFT: #ccc 1px solid; MARGIN: 0px 0px 0px 0.8ex; PADDING-LEFT: 1ex" id="isReplyContent">>1. <B>Always</B> send -log_summary when asking about performance.
<DIV>>2. AMG setup costs more, the solve should be faster, especially for large problems.</DIV>
<DIV>>3. 30k degrees of freedom is not large.</DIV>
<DIV class="gmail_extra"><BR><BR>
<DIV class="gmail_quote">>>On Sat, Nov 3, 2012 at 10:27 AM, 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>
<BLOCKQUOTE style="BORDER-LEFT: #ccc 1px solid; MARGIN: 0px 0px 0px 0.8ex; PADDING-LEFT: 1ex" class="gmail_quote">
<DIV style="LINE-HEIGHT: 1.7; FONT-FAMILY: arial; FONT-SIZE: 14px">
<DIV>>>Hello,</DIV>
<DIV>>> I have tried AMG, but there are some problems. I use the command:<BR>>> mpiexec -n 4 ./ex4f -ksp_type gmres -pc_type gamg -pc_gamg_agg_nsmooths 1 -ksp_gmres_restart 170 -ksp_rtol 1.0e-15 ->>ksp_converged_reason.<BR>>> The matrix has a size of 30000. However, compared with -pc_type asm,<BR>>>the amg need more time:asm needs 4.9s, amg needs 13.7s. I did several tests<BR>>>and got the same conclusion. When it begins, the screen shows the information: <BR>>>[0]PCSetData_AGG bs=1 MM=7601. I do not know the meaning. And if there is some<BR>>>parameters that affect the performance of AMG?<BR>>> Besides, I want to confirm a conception. In my view, AMG itself can be a solver<BR>>>like gmres. It can also be used as a preconditioner like jacobi and is used by combining<BR>>>with other solver. Is it right? If it is right, how use AMG solver?<BR
>>> My codes are attached.<BR>>> Thanks.<BR>>> Jim</DIV>
<DIV><BR><BR> </DIV>>At 2012-11-01 22:00:28,"Jed Brown" <<A href="mailto:jedbrown@mcs.anl.gov" target="_blank">jedbrown@mcs.anl.gov</A>> wrote:<BR>
<BLOCKQUOTE style="BORDER-LEFT: #ccc 1px solid; MARGIN: 0px 0px 0px 0.8ex; PADDING-LEFT: 1ex">
<DIV class="gmail_extra">>Yes, it's faster to understand this error message than to have "mysteriously slow performance".</DIV>
<DIV class="gmail_extra"><BR></DIV>
<DIV class="gmail_extra">><EM>* Preallocation routines now automatically set MAT_NEW_NONZERO_ALLOCATION_ERR, if you intentionally preallocate less than necessary then </EM>><EM>use MatSetOption(mat,MAT_NEW_NONZERO_ALLOCATION_ERR,PETSC_FALSE) to disable the error generation.<BR></EM><BR>><A href="http://www.mcs.anl.gov/petsc/documentation/changes/33.html" target="_blank">http://www.mcs.anl.gov/petsc/documentation/changes/33.html</A><BR><BR>
<DIV class="gmail_quote">>On Thu, Nov 1, 2012 at 8:57 AM, 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>
<BLOCKQUOTE style="BORDER-LEFT: rgb(204,204,204) 1px solid; MARGIN: 0px 0px 0px 0.8ex; PADDING-LEFT: 1ex" class="gmail_quote">
<DIV>>Do you mean that the two versions have a different in this point? If I use the new version, I have to</DIV>
<DIV>>make some modifications on my codes?</DIV></BLOCKQUOTE></DIV><BR></DIV></BLOCKQUOTE></DIV><BR><BR><SPAN title="neteasefooter"><SPAN></SPAN></SPAN></BLOCKQUOTE></DIV><BR></DIV></BLOCKQUOTE></div><br><br><span title="neteasefooter"><span id="netease_mail_footer"></span></span>