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num::chebyshev_preconditioner_from_below

Defined in header <linear/solvers/chebyshev.hpp>

template <class Op>
chebyshev_preconditioner<Op>
chebyshev_preconditioner_from_below(const Op &A, real lambda_min, idx degree = 4);

Build a Chebyshev preconditioner from a known \(\lambda_{\min}\), estimating \(\lambda_{\max}\) by power iteration.

lambda_min must be a true lower bound on the spectrum; it is not inferred from a condition number, since too large a value makes the polynomial indefinite.

Parameters

  • A: SPD operator.
  • lambda_min: Lower bound on the spectrum.
  • degree: Polynomial degree, and operator applications per solve.