[petsc-users] SNESGetJacobian Quasi-Newton

[Bikash Kanungo]

Hi,

I would like to access the approximate Jacobian in quasi-Newton solvers
(e.g., BFGS) to analyze its condition number. I guess for BFGS, where the
approximate Jacobian is built from outer products of several vectors coming
from current and previous gradient vectors, the approximate Jacobian might
not be stored explicitly as a matrix and instead the Jacobian times a
vector is performed in a matrix-free manner. My reason for believing so is
the fact that when I try to retrieve the Jacobian matrix using
SNESGetJacobian and feed it to SLEPc, I incur segmentation fault at
EPSSetOperators.

If that's the case, is there a way to still get access to the approximate
Jacobian and feed it to SLEPc for eigen analysis, like with the use of
MatShell operations?

Thanks,
Bikash

-- 
Bikash S. Kanungo
PhD Student
Computational Materials Physics Group
Mechanical Engineering
University of Michigan
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