Also always send the output from running with -log_summary whenever you ask performance questions so we know what kind of performance it is getting.
Barry On Aug 12, 2013, at 8:14 PM, Jed Brown <[email protected]> wrote: > "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.
