> Does anyone know, loosely, what PETSc's Block Jacobi preconditioner > implemented in the deal.ii petsc wrappers does? I can't figure it out > from the PETSc documentation. I know (or am pretty sure) that the > matrix, B, to be inverted is the matrix A (where Ax=b is what we are > solving) with the entries not in one of the diagonal blocks removed (as > in http://www.netlib.org/linalg/html_templates/node56.html), so to > invert B is to invert all of the diagonal blocks independently. But how > are THOSE blocks inverted? Direct solver? Conjugate gradients? > Incomplete LU?
This page gives a clue: http://www-unix.mcs.anl.gov/petsc/petsc-2/snapshots/petsc-current/docs/manualpages/PC/PCBJACOBI.html So each block is inverted using its own solver. Here, section 4.4.4, page 71, is the full answer: http://www.maths.bath.ac.uk/~masrs/ma50177/petsc-2.1.6/manual.pdf The default solver for each block is to apply the preconditioner (I assume a single step), which is ILU(0). W. ------------------------------------------------------------------------- Wolfgang Bangerth email: [EMAIL PROTECTED] www: http://www.math.tamu.edu/~bangerth/ _______________________________________________
