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<body class='hmmessage'><div dir='ltr'>Hi,<br><br>I have a linear system with about 161^3=4,173,281 unknowns. I used the default KSP solver(to my understand it is GMRES) to solve it. The relative tolerance is set as 1.266e-9. The number of iterations is 5373 and the computing time problem is about 23.65 mins with 128 processes. With the same problem, but I selected a pre-conditioner such as hypre, the number of iterations can be reduced dramatically, however, the computing time increases somewhat.<br><br>May someone give me some suggestions on selection of KSP solver to solve a large scale linear system faster? Thanks a lot.<br> </div></body>
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