Current TS implementations never fited my needs. Why? My target application is solving incompressible NS equations with FEM and fully implicit schemes (trapezoidal rule with theta in [0.5, 1.0] ) and residual-based stabilization (SUPG/PSPG). Then I need to solve at each time step a nonlinear problem like F(t, u, t0, u0), where F is nonlinear in u. I'm surelly naive, and I could not accomodate my function and Jacobian code for the beuler/cn TS implementations.
Futhermore, I've recently convinced some coworkers to take advance of SNES/TS features and my Python wrappers (petsc4py) to manage the the time evolution of some problems related to fluid-structure interaction and mesh movement (formulated as an optimization problem, only nodal positions change, not remeshing needed for many timesteps). In order to support those applications setups, I've wrote a new TS implemetation, which enables users to (almost) completely define the temporal evolution of their problems, with pre/post solve/step methods and support for accept/reject steps and implementing timestep size control. Some of these features are available in some TS types, but not all-in-one. This code is available for review in petsc4py SVN repo (link below), an python example of this in action (very simple, just for testing all is working) is attached. Currently it only support implicit schemes and nonlinear problems, but I believe it can be extended to support explicit schemes and linear problems. http://petsc4py.googlecode.com/svn/trunk/petsc/lib/ext/src/ts/impls/implicit/user/ I want to know the opinion of PETSc core developers and potential users ot this, and I hope anyone can provide suggestions for improvements. After that, I can push this to petsc-dev for general availability (in fact, the code is almost ready to be integrated in petsc). Perhaps in the long term, all this can be integrated in the generic TS interface if that is appropriate. Of course, this would require some (I hope minor) changes in TS interface, some additions, and a reimplementation of some default TS types Regards, and I'm waiting for your comments. -- Lisandro Dalc?n --------------- Centro Internacional de M?todos Computacionales en Ingenier?a (CIMEC) Instituto de Desarrollo Tecnol?gico para la Industria Qu?mica (INTEC) Consejo Nacional de Investigaciones Cient?ficas y T?cnicas (CONICET) PTLC - G?emes 3450, (3000) Santa Fe, Argentina Tel/Fax: +54-(0)342-451.1594 -------------- next part -------------- A non-text attachment was scrubbed... Name: test_tsuser.py Type: text/x-python Size: 4014 bytes Desc: not available URL: <http://lists.mcs.anl.gov/pipermail/petsc-dev/attachments/20070917/05a7984e/attachment.py>
