"Christon, Mark A" <christon at lanl.gov> writes: > HI Mark, > > Thanks for the information. We thought something had changed and > could see it the effect, but couldn't quite pin it down.
So did you try running your old tests with -mg_levels_sub_pc_factor_zeropivot 1e-12 -mg_levels_sub_pc_factor_shift_amount 1e-12 I would expect this to only make a small difference. > To be clear our pressure-Poisson equation is a warm and fluffy > Laplacian, but typically quite stiff from a spectral point of view > when dealing with boundary-layer meshes and complex geometry ? our > norm. This is the first-order computational cost in our flow solver, > so hit's like the recent change are very problematic, and particularly > so when they break a number of regression tests that run nightly > across multiple platflorms. > > So, unfortunately, while I'd like to use something as Jacobi, it's > completely ineffective in for the operator (and RHS) in question. As Mark says, use -mg_levels_ksp_type chebyshev -mg_levels_pc_type jacobi (possibly with more explicit spectrum options). See Mark's paper http://www.columbia.edu/~ma2325/adams_poly.pdf
