Another interesting observation: Solution leakage or inflation is most noticeable when the diffusion coefficient > convection coefficient whereas it's almost negligible when the inequality is flipped. One way to ameliorate the effect is to use linearGMRES as solver, however, in contrast to the constant memory use by the default solver, it accumulates machine memory over time steps at a radical rate (90MB vs. 2GB over 2000 time step). Pretty intriguing stuff.
Yun On Thu, Jul 12, 2012 at 4:57 PM, Yun Tao <[email protected]> wrote: > For those who're interested, a test using different solvers yield the > following results. > > First sign of leakage occurs at time step: > > 529 - default solver > 529 - linearPCG > 1597 - linearLU > >2000 - linearCGS > >2000 - linearGMRES > > Jonathan has also helpfully informed me of the difference between np.trapz > and direct cell volume calculation. The former indeed returns a reduced > value for the reason suggested. > > Thanks again for the kind assistance. > > Cheers, > > Yun > > > On Fri, Jul 6, 2012 at 7:31 AM, Daniel Wheeler > <[email protected]>wrote: > >> On Tue, Jul 3, 2012 at 1:34 AM, Yun Tao <[email protected]> wrote: >> >>> Hm. Reducing the mesh range (l=50. -> l=30.) does seem to introduce >>> leaking even when the initial cell volume = 1 (timestep 485). Why would the >>> domain matter when the BCs are zero-flux? >> >> >> The cell volumes averages do change, but very slowly. This could be due >> round off in the solver. The np.trapz seems to be very different from the >> cell average. Is that calculation taking into account that the values are >> cell centered so the end points may not be weighted correctly? >> >> -- >> Daniel Wheeler >> >> _______________________________________________ >> fipy mailing list >> [email protected] >> http://www.ctcms.nist.gov/fipy >> [ NIST internal ONLY: https://email.nist.gov/mailman/listinfo/fipy ] >> >> > > > -- > Graduate Group of Ecology Doctoral Candidate > Department of Environmental Science and Policy > Center for Population Biology > University of California, Davis > > > -- Graduate Group of Ecology Doctoral Candidate Department of Environmental Science and Policy Center for Population Biology University of California, Davis
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