On Wed 2008-09-17 10:00, Derek Gaston wrote: > On Sep 17, 2008, at 9:42 AM, Roy Stogner wrote: > The step_tolerance is meant to correspond to something close to your > relative step tolerance... and I would have named it that except I'm > not entirely sure that Petsc does use a scaled relative step tolerance > (as I suspect you are doing). I believe that they use the absolute > step size instead (which is really a bummer). I don't think Petsc has > any kind of decreasing tolerance with successive steps. Petsc's > convergence tests are really pretty poor. > > Trilinos (specifically NOX) has a sophisticated system for convergence > criteria... you can actually specify any boolean combination (not just > OR's like Petsc) of many different things and present that as a > convergence test. For now though, I figured I would just make the > default behavior be something like Petsc... where you just OR together > all 5 tolerances.
As you may know, you can set any test you like using SNESSetConvergenceTest(). Also, the Eisenstat-Walker `trick' is implemented (see -snes_ksp_ew) to control the tolerance for the linear solve. S. C. Eisenstat and H. F. Walker, "Choosing the forcing terms in an inexact Newton method", SISC 17 (1), pp.16-32, 1996. You can adjust linear solve parameters inside the nonlinear solve by manipulating the KSP in your convergence test. Jed
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