BVSetDefiniteTolerance#

Set the tolerance to be used when checking a definite inner product.

Synopsis#

#include "slepcbv.h" 
PetscErrorCode BVSetDefiniteTolerance(BV bv,PetscReal deftol)

Logically Collective

Input Parameters#

bv - basis vectors
deftol - the tolerance

Options Database Key#

-bv_definite_tol - the tolerance

Notes#

When using a non-standard inner product, see BVSetMatrix(), the solver needs to compute \(\sqrt{z^*B z}\) for various vectors \(z\). If the inner product has not been declared indefinite, the value \(z^*B z\) must be positive, but due to rounding error a tiny value may become negative. A tolerance is used to detect this situation. Likewise, in complex arithmetic \(z^*B z\) should be real, and we use the same tolerance to check whether a nonzero imaginary part can be considered negligible.

This function sets this tolerance, which defaults to 10*PETSC_MACHINE_EPSILON. The default value should be good for most applications.

Level#

advanced

Location#

src/sys/classes/bv/interface/bvbasic.c

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