SNESLINESEARCHBISECTION

Bisection line search. Similar to the critical point line search, SNESLINESEARCHCP, the bisection line search assumes that there exists some \(G(x)\) for which the SNESFunctionFn \(F(x) = grad G(x)\). This line search seeks to find the root of the directional derivative, that is \(F(x_k - \lambda Y_k) \cdot Y_k / ||Y_k|| = 0\), along the search direction \(Y_k\) through bisection.

Options Database Keys

• -snes_linesearch_max_it <50> - maximum number of bisection iterations for the line search

• -snes_linesearch_damping <1.0> - initial lambda on entry to the line search

• -snes_linesearch_rtol <1e-8> - relative tolerance for the directional derivative

• -snes_linesearch_atol <1e-6> - absolute tolerance for the directional derivative

• -snes_linesearch_ltol <1e-6> - minimum absolute change in lambda allowed

Notes

lambda is the scaling of the search direction (vector) that is computed by this algorithm. If there is no change of sign in the directional derivative from \(\lambda=0\) to the initial lambda (the damping), then the initial lambda will be used. Hence, this line search will always give a lambda in the interval \([0, damping]\). This method does NOT use the objective function if it is provided with SNESSetObjective().

See Also

SNES: Nonlinear Solvers, SNESLineSearch, SNESLineSearchType, SNESLineSearchCreate(), SNESLineSearchSetType(), SNESLINESEARCHCP

Level

intermediate

Location

src/snes/linesearch/impls/bisection/linesearchbisection.c

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