Thanks for all the suggestions! Increasing the value of icntl_14 in MUMPS helps a lot for my case.
Do you have any suggestions for higher-order methods in saddle-point problems? Mike Dave May <[email protected]> 于2018年10月11日周四 上午1:50写道： > > > On Sat, 6 Oct 2018 at 12:42, Matthew Knepley <[email protected]> wrote: > >> On Fri, Oct 5, 2018 at 9:08 PM Mike Wick <[email protected]> >> wrote: >> >>> Hello PETSc team: >>> >>> I am trying to solve a PDE problem with high-order finite elements. The >>> matrix is getting denser and my experience is that MUMPS just outperforms >>> iterative solvers. >>> >> >> If the problem is elliptic, there is a lot of evidence that the P1 >> preconditioner is descent for the system. Some people >> just project the system to P1, invert that with multigrid, and use that >> as the PC for Krylov. It should be worth trying. >> > > Matt means project to P1 directly from your high order function space in > one step. It is definitely worth trying. > For those interested, this approach is first described and discussed (to > my knowledge) in this paper: > > Persson, Per-Olof, and Jaime Peraire. "An efficient low memory implicit DG > algorithm for time dependent problems." *44th AIAA Aerospace Sciences > Meeting and Exhibit*. 2006. > > >> Moreover, as Jed will tell you, forming matrices for higher order is >> counterproductive. You should apply those matrix-free. >> > > I definitely agree with that. > > Cheers, > Dave > > > >> >> Thanks, >> >> Matt >> >> >>> For certain problems, MUMPS just fail in the middle for no clear reason. >>> I just wander if there is any suggestion to improve the robustness of >>> MUMPS? Or in general, any suggestion for interative solver with very >>> high-order finite elements? >>> >>> Thanks! >>> >>> Mike >>> >> >> >> -- >> What most experimenters take for granted before they begin their >> experiments is infinitely more interesting than any results to which their >> experiments lead. >> -- Norbert Wiener >> >> https://www.cse.buffalo.edu/~knepley/ >> <http://www.cse.buffalo.edu/~knepley/> >> >
