Zitat von Jed Brown <jedbrown at mcs.anl.gov>: > On Fri, Nov 18, 2011 at 07:53, Thomas Witkowski < > Thomas.Witkowski at tu-dresden.de> wrote: > >> Defining the sparsity pattern is no problem. But is there any >> documentation on MatFDColoringApply? The online function reference is quite >> short and is not mentioned in the manuel. So, I have no real idea how this >> is related to my question. > > > You can find an example in snes/examples/tutorials/ex15.c > > The point is that it can compute the Schur complement by coloring. In your > case, you can do subdomain solves independently, so you can compute > > S = K_PiPi - K_PiB inv(K_BB) K_BPi > > on each subdomain using > > Tmp = inv(K_BB) K_BPi (via MatMatSolve)
Some technical question on this point: How can I explicitly factorize a sequential matrix? Is MatLUFactor the correct function to do it? If so, how can I provide the package (i.e. umfpack) that should be used for factorization? Thomas > > Tmp2 = K_PiB * Tmp (via MatMatMult) > > S = K_PiPi - Tmp2 (via MatAXPY) > > > You would then assemble the resulting independent matrices into the global > matrix. >
