<div dir="ltr"><div dir="ltr">On Thu, Dec 3, 2020 at 11:16 AM 王一甲 <<a href="mailto:wangyijia@lsec.cc.ac.cn">wangyijia@lsec.cc.ac.cn</a>> wrote:<br></div><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><p>
        To any one who it may concern:
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        Hi, my name is Wang Yijia from Chinese Academy of Science. Recently I've been working on  some sparse linear system baseline tests using PETSc. When using gmres methods in KSP, I found that the option -ksp_gmres_cgs_refinement refine_always worked well on my sparse linear system, however I can not find more about how this process is done in the Hessenberg matrix generation(classical Gram-Schmidt process). I am curious about how the cgs iteration refinement process work in the whole KSP solve stage. I would appreciate it if you could offer some help.</p></blockquote><div>The code is fairly short:</div><div><br></div><div>  <a href="https://gitlab.com/petsc/petsc/-/blob/master/src/ksp/ksp/impls/gmres/borthog2.c">https://gitlab.com/petsc/petsc/-/blob/master/src/ksp/ksp/impls/gmres/borthog2.c</a></div><div><br></div><div>  Thanks,</div><div><br></div><div>     Matt</div><div> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><p>
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                                                                                                                                                                                     Yours sincerely
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                                                                                                                                                                                       Wang Yijia
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                                                                                                                                                                                       2020/12/3
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</p></blockquote></div><br clear="all"><div><br></div>-- <br><div dir="ltr" class="gmail_signature"><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div>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><div><br></div><div><a href="http://www.cse.buffalo.edu/~knepley/" target="_blank">https://www.cse.buffalo.edu/~knepley/</a><br></div></div></div></div></div></div></div></div>