MATMFFD_WP#

Implements an approach for computing the differencing parameter h used with the finite difference based matrix-free Jacobian. From Walker-Pernice [PW98] $ $h = error_rel * sqrt(1 + ||u||) / ||a||$ $

Options Database Key#

-mat_mffd_compute_normu - Compute the norm of u every time see MatMFFDWPSetComputeNormU()

Notes#

$|| U ||$ does not change between linear iterations so is reused

In KSPGMRES $|| a || == 1$ and so does not need to ever be computed except at restart when it is recomputed. Thus requires no global collectives when used with KSPGMRES

References#

[PW98]

M. Pernice and H. F. Walker. NITSOL: a Newton iterative solver for nonlinear systems. SIAM J. Sci. Stat. Comput., 19:302–318, 1998.

Level#

intermediate

Location#

src/mat/impls/mffd/wp.c

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