Lisandro Dalcin <dalc...@gmail.com> writes: > On 21 March 2015 at 17:32, Emil Constantinescu <emcon...@mcs.anl.gov> wrote: >> When -ts_theta_adapt is used, then it detects the instability as an error >> and reduces the step by a lot! wlte=1.24e+03 which means that the reduction >> should be severe but the controller tries 0.1*dt and that seems to pass but >> it "jig-saws" (take a look at the next attempted step), which means that it >> is likely unstable. > > I think -ts_theta_adapt is seriously broken, I cannot make sense of > the way the error estimator is computed.
This was Shri's implementation. TSEvaluateStep_Theta looks wrong to me, both using U as an input and assuming that Xdot is set. I don't even know what the intended math is for a first-order embedded estimate in midpoint (theta=0.5).
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