I have been working with CT_MultiLevel in an attempt to solve the non-conformally-flat constraint equations and I'm wondering if there is an error in the thorn. Where I'm potentially seeing an issue is in CT_SolvePsiEquation.cc and CT_SolveErrorEquation.cc in the definitions of dtime (for both files this is line 33 in the Brahe release).
First of all, having 0.5 in this definition means that the coefficient for the central point in the finite difference is hard-coded to a second order stencil. When using fourth order, this coefficient should be 0.4, I believe. This effectively changes the SOR omega.
More importantly, I don't think it accounts for ct_cxx, ct_cyy, or ct_czz. So the central point in the finite difference is not getting multiplied by whatever coefficient the user is setting.
Am I misunderstanding how the thorn works or are these really problems? I've attached what I believe is a way to fix them. Thanks for your help.
Kyle Slinker