<html><head></head><body><div style="color:#000; background-color:#fff; font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, Sans-Serif;font-size:13px"><div id="yui_3_16_0_ym19_1_1487214835214_4454"><span>Thank you all for your help !</span></div><div></div><div id="yui_3_16_0_ym19_1_1487214835214_4455"> </div><div class="signature" id="yui_3_16_0_ym19_1_1487214835214_4456">rgds<br>LX</div> <div class="qtdSeparateBR"><br><br></div><div class="yahoo_quoted" style="display: block;"> <div style="font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, Sans-Serif; font-size: 13px;"> <div style="font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, Sans-Serif; font-size: 16px;"> <div dir="ltr"><font size="2" face="Arial"> On Thursday, 16 February 2017, 3:29, Patrick Sanan <patrick.sanan@gmail.com> wrote:<br></font></div> <br><br> <div class="y_msg_container">On Wed, Feb 15, 2017 at 8:26 PM, Barry Smith <<a shape="rect" ymailto="mailto:bsmith@mcs.anl.gov" href="mailto:bsmith@mcs.anl.gov">bsmith@mcs.anl.gov</a>> wrote:<br clear="none">><br clear="none">>> On Feb 15, 2017, at 7:03 AM, lixin chu <<a shape="rect" ymailto="mailto:lixin_chu@yahoo.com" href="mailto:lixin_chu@yahoo.com">lixin_chu@yahoo.com</a>> wrote:<br clear="none">>><br clear="none">>> I think the chapter 4 of the user manual more or less answers my first question already ...<br clear="none">>><br clear="none">>> rgds<br clear="none">>> lixin<br clear="none">>><br clear="none">>><br clear="none">>> On Wednesday, 15 February 2017, 14:40, lixin chu <<a shape="rect" ymailto="mailto:lixin_chu@yahoo.com" href="mailto:lixin_chu@yahoo.com">lixin_chu@yahoo.com</a>> wrote:<br clear="none">>><br clear="none">>><br clear="none">>> Hello,<br clear="none">>> New to PETSc, appreciate any help -<br clear="none">>><br clear="none">>> I have done some experiment with MUMPS (the direct solver for sparse matrix), and very interested to try out PETSc now. I have a large sparse symmetric matrix (3 millions x 3 millions, complex data type).<br clear="none">>><br clear="none">>> Some questions I have:<br clear="none">>> - I am assuming that I should select one algorithm of "Krylov methods", which algorithm is a good option, GMRES, CG, or others ? (I am not a domain expert, but helping developing a program to test the matrix).<br clear="none">><br clear="none">> GMRES is a "safe" choice. You can try -ksp_type cg -ksp_cg_type symmetric (or if the matrix is hermitian; i.e. transpose A = complex conjugate of A then type hermitian instead of symmetric).<br clear="none">><br clear="none">><br clear="none">>> - do all the algorithms support distributed architecture (multiple machines, multiple cores)<br clear="none">><br clear="none">> Yes<br clear="none">><br clear="none">>> - are there any performance test data ? (total run time for example)<br clear="none">><br clear="none">> Run your code with -view_summary and it will print information at the end about where it has spent the time doing the computation.<br clear="none">Barry probably meant -log_view here.<div class="yqt8530980777" id="yqtfd66156"><br clear="none">><br clear="none">><br clear="none">>><br clear="none">>><br clear="none">>> thank you very much,<br clear="none">>> LX<br clear="none">>><br clear="none">>><br clear="none">><br clear="none"></div><br><br></div> </div> </div> </div></div></body></html>