Xiangdong <[email protected]> writes: > Hello everyone, > > As in the note of PCSOR, it corresponds to block Jacobi with SOR on each > block, not a true parallel SOR. > > 1) Is there a parallel sor implemented in PETSc, like the red-black Gauss > Seidel?
Coloring for all but the simplest operators produces a huge number of colors, especially in 3D. Colored operators use bandwidth less efficiently, thus tend to deliver poor performance. > 2) If it is not a true parallel SOR, then what is the difference between > options -pc_sor_forward and -pc_sor_local_forward? It seems that > pc_sor_forward does not work for mpiaij format. When is pc_sor_forward used? SOR_FORWARD_SWEEP is currently only used for serial SOR. MPI matrices use SOR_LOCAL_FORWARD_SWEEP to make it explicit that this is not "true" SOR. A future implementation (e.g., of Mark Adams' algorithm) would use SOR_FORWARD_SWEEP. If you think the local SOR is a problem, compare running the same problem in serial.
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