What exactly changed between Feb 1 and the petsc-3.1 release with respect to shifting (including for (S)BAIJ). In Feb, I saw negative pivots and blamed certain performance characteristics on it. Now I don't see them, despite the fact that SBAIJ does not implement the same shifts that AIJ does. The performance now (or with 3.1) is significantly better, but I would like to be able to explain what's going on. Running with -pc_factor_shift_type none is still working much better than Feb 1 -dev and I would like to know why.
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