Hi, 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?
If anyone knows the answer I'd appreciate it. Thanks Dan _______________________________________________
