Thanks, Hong and Matt, I think the matrix is singular. I will be checking the implementation.
Fande, On Tue, Oct 10, 2017 at 8:57 AM, Hong <[email protected]> wrote: > Fande, > '-pc_factor_shift_amount 1' is huge. > Try use petsc default shift amount '1.e-14' by > '-pc_factor_shift_type nonzero' only. > > Hong > > On Tue, Oct 10, 2017 at 9:40 AM, Matthew Knepley <[email protected]> > wrote: > >> On Tue, Oct 10, 2017 at 10:36 AM, Kong, Fande <[email protected]> wrote: >> >>> Hi Developers, >>> >>> I am trying to use the native LU in PETSc to compute a matrix (arising >>> from a fluid-structure interaction problem). I encounter a zero pivot. The >>> matrix gives the wrong Newton direction when using "-pc_factor_shift_type >>> nonzero -pc_factor_shift_amount 1". I hence guess the matrix is >>> singular. >>> >>> Any easy way to detect if or not the matrix is singular?? >>> >> >> That is the easiest way, namely having LU fail. You can catch the failure >> and do something useful. >> >> Matt >> >> >>> Fande, >>> >> >> >> >> -- >> 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 >> >> https://www.cse.buffalo.edu/~knepley/ >> <https://urldefense.proofpoint.com/v2/url?u=http-3A__www.caam.rice.edu_-7Emk51_&d=DwMFaQ&c=54IZrppPQZKX9mLzcGdPfFD1hxrcB__aEkJFOKJFd00&r=DUUt3SRGI0_JgtNaS3udV68GRkgV4ts7XKfj2opmiCY&m=OzufXo0CFDWCGheboXxUMvKt3soawuoLxqtBqJtH4tc&s=50QybFKpScUhuVT0fSUA4vPnZJrmTUdY0BKJlNOBCS4&e=> >> > >
