# EPSCompareEigenvalues

Compares two (possibly complex) eigenvalues according to a certain criterion.

### Synopsis

    #include "slepceps.h"
    PetscErrorCode EPSCompareEigenvalues(EPS eps,PetscScalar ar,PetscScalar ai,PetscScalar br,PetscScalar bi,PetscInt *result)

Not Collective

### Input Parameters

| eps | - the eigensolver context
| ar | - real part of the 1st eigenvalue
| ai | - imaginary part of the 1st eigenvalue
| br | - real part of the 2nd eigenvalue
| bi | - imaginary part of the 2nd eigenvalue

### Output Parameter

res - result of comparison

### Notes

### The returning parameter 'res' can be

| negative | - if the 1st eigenvalue is preferred to the 2st one
| zero | - if both eigenvalues are equally preferred
| positive | - if the 2st eigenvalue is preferred to the 1st one

The criterion of comparison is related to the 'which' parameter set with EPSSetWhichEigenpairs().

### See Also

EPSSortEigenvalues(), EPSSetWhichEigenpairs()

Location: src/eps/interface/solve.c
Index of all EPS routines
Table of Contents for all manual pages
Index of all manual pages