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        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.
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                                                                                                                                                                                     Yours sincerely
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                                                                                                                                                                                       Wang Yijia
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                                                                                                                                                                                       2020/12/3
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