"Jin, Shuangshuang" <[email protected]> writes: > Hello, PETSc developers, > I have a question regarding the performance of PETSc TS solver > expecially the TSTHETA. I used it to solve my DAE equations.
TSTHETA is not L-stable and not stiffly accurate, so it's not normally something that you'd want to use for a DAE. Make sure you're getting meaningful results and try switching to something like an ARKIMEX or ROSW since those are likely better for your problem. > I have recorded the solution times when different numbers of processors are > used: > > 2 processors: 1021 seconds, > 4 processors: 587.244 seconds, > 8 processors: 421.565 seconds, > 16 processors: 355.594 seconds, > 32 processors: 322.28 seconds, > 64 processors: 382.967 seconds. > > It seems like with 32 processors, it reaches the best > performance. However, 322.28 seconds to solve such DAE equations is > too slow than I expected. The number of equations (1152) is quite small, so I'm not surprised there is no further speedup. Can you explain more about your equations? > > I have the following questions based on the above results: > 1. Is this the usual DAE solving time in PETSc to for the problem with > this dimension? That depends what your function is. > 2. I was told that in TS, by default, ksp uses GMRES, and the > preconditioner is ILU(0), is there any other alterative ksp solver or > options I should use in the command line to solve the problem much > faster? I would use -ksp_type preonly -pc_type lu for such small problems. Is the system dense? > 3. Do you have any other suggestion for me to speed up the DAE > computation in PETSc? Can you describe what sort of problem you're dealing with, what causes the stiffness in your equations, what accuracy you want, etc.
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