<- [[:bugs]] ====== nan ====== //hansjoerg seybold, 2009-07-22 04:05 // ~~DISCUSSION~~ hello, I was playing a bit around with the couette.cpp example using adaptive timestepping in a domain 15x2x15 with the following parameters const Real dtmin = 0.001; const Real dtmax = 0.02; const Real CFLmin = 0.40; const Real CFLmax = 0.55; I tried several resolutions for the spectral calculations and when i increase the number of modes for Ny to values >=50 (49 works 50 not any more) i get a nan in the further calculations. The bug seems to be independant from the X-Z resolution. I also tried fixed timestepping with very small dt (CLF<0.3) but the error appeared nevertheless As integrators i tried SBDF3+SMRK2 and CNAB2 running with plain channelflow-1.4.1, g++ (GCC) 4.2.3 20071030 (prerelease) (SUSE Linux) After the adaption step / first printout step for fixed dt i get the following output TimeStep::adjust(CFL) { n : 95 -> 50 dt : 0.0105263 -> 0.02 CFL : nan -> nan } adjusting timestep t == 1 CFL == nan L2Norm(u) == nan divNorm(u) == nan dPdx == 0 Ubulk == nan I compiled channelflow in optimized mode as i do not have the debug fftw3 libraries on my system. Any hints where i could look for the bug? hj