[petsc-users] floating region help

[Gong Ding]

2011/9/20 Gong Ding<gdiso at ustc.edu>
Since the conductance of left part and right part is low, the middle region is floating.
Not really floating, just sensitive to parameters. It has a unique value, of physical interest, but if you change the conductivity or thickness of the thin region on either side, then it's value changes significantly. This is an ill-conditioned problem, but it's ill-conditioned for physically meaningful reasons. It's not singular and the smallest singular value has great significance, so a null space method is not appropriate. You could reformulate for a slightly different problem which would have a constant null space, but not for this problem.
Thanks. Any recommends for solving this type of problems?
It's our bottleneck now.
Direct solver works, but not efficient for large 3D problem.
Krylov space based solver seems not rubost enough.
A more exact ILU preconditioner may help?
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