slepc-3.22.2 2024-12-02
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# PEPCheckDefiniteQEP

Determines if a symmetric/Hermitian quadratic eigenvalue problem is definite or not.

### Synopsis

    #include "slepcpep.h"
    PetscErrorCode PEPCheckDefiniteQEP(PEP pep,PetscReal *xi,PetscReal *mu,PetscInt *definite,PetscInt *hyperbolic)

Collective

### Input Parameter

| pep | - eigensolver context

### Output Parameters

| xi | - first computed parameter
| mu | - second computed parameter
| definite | - flag indicating that the problem is definite
| hyperbolic | - flag indicating that the problem is hyperbolic

### Notes

This function is intended for quadratic eigenvalue problems, Q(lambda)=A*lambda^2+B*lambda+C, with symmetric (or Hermitian) coefficient matrices A,B,C.

On output, the flag 'definite' may have the values -1 (meaning that the QEP is not definite), 1 (if the problem is definite), or 0 if the algorithm was not able to determine whether the problem is definite or not.

If definite=1, the output flag 'hyperbolic' informs in a similar way about whether the problem is hyperbolic or not.

If definite=1, the computed values xi and mu satisfy Q(xi)<0 and Q(mu)>0, as obtained via the method proposed in [Niendorf and Voss, LAA 2010]. Furthermore, if hyperbolic=1 then only xi is computed.

### See Also

PEPSetProblemType()

### Level

advanced

### Location

src/pep/impls/krylov/stoar/qslice.c

### Examples

src/pep/tutorials/ex40.c
Index of all PEP routines
Table of Contents for all manual pages
Index of all manual pages