On Wed, Apr 25, 2012 at 1:42 PM, Dominik Szczerba <dominik at itis.ethz.ch>wrote:
> > Start by comparing residuals, with an without. Is SNES 0 the same? Is > KSP 0 > > the same? KSP 1? > > BCGS, with the option: > > 0 SNES Function norm 1.747536282885e+01 > 0 KSP unpreconditioned resid norm 1.747536282885e+01 true resid norm > 1.747536282885e+01 ||r(i)||/||b|| 1.000000000000e+00 > 1 KSP unpreconditioned resid norm 6.112827145626e-01 true resid norm > 1.751036369876e+01 ||r(i)||/||b|| 1.002002869425e+00 > > BCGS, without: > > 0 SNES Function norm 1.747536282885e+01 > 0 KSP unpreconditioned resid norm 1.747536282885e+01 true resid norm > 1.747536282885e+01 ||r(i)||/||b|| 1.000000000000e+00 > 1 KSP unpreconditioned resid norm 2.930616102426e-01 true resid norm > 2.930616102426e-01 ||r(i)||/||b|| 1.676998715922e-02 > > GMRES, with the option: > > 0 SNES Function norm 1.747536282885e+01 > 0 KSP unpreconditioned resid norm 1.747536282885e+01 true resid norm > 1.747536282885e+01 ||r(i)||/||b|| 1.000000000000e+00 > 1 KSP unpreconditioned resid norm 6.122286256494e-01 true resid norm > 1.747536251439e+01 ||r(i)||/||b|| 9.999999820055e-01 > Notice that there is no increase in the residual as is required. Notice also that there is no decrease. This must mean that the preconditioner is rank deficient, and I think it probably means that it is 0 since I find it hard to believe that P x produces no component in the b direction. Matt > GMRES, without: > > 0 SNES Function norm 1.747536282885e+01 > 0 KSP unpreconditioned resid norm 1.747536282885e+01 true resid norm > 1.747536282885e+01 ||r(i)||/||b|| 1.000000000000e+00 > 1 KSP unpreconditioned resid norm 6.122286294217e-01 true resid norm > 6.122286294218e-01 ||r(i)||/||b|| 3.503381505824e-02 > > Dominik > -- What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead. -- Norbert Wiener -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20120425/3e1361f4/attachment.htm>
