slepc-3.7.3 2016-09-29
Report Typos and Errors

# PEPSetWhichEigenpairs

Specifies which portion of the spectrum is to be sought.

### Synopsis

    #include "slepcpep.h"
    PetscErrorCode PEPSetWhichEigenpairs(PEP pep,PEPWhich which)

Logically Collective on PEP

### Input Parameters

| pep | - eigensolver context obtained from PEPCreate()
| which | - the portion of the spectrum to be sought

### Possible values

The parameter 'which' can have one of these values

| PEP_LARGEST_MAGNITUDE | - largest eigenvalues in magnitude (default)
| PEP_SMALLEST_MAGNITUDE | - smallest eigenvalues in magnitude
| PEP_LARGEST_REAL | - largest real parts
| PEP_SMALLEST_REAL | - smallest real parts
| PEP_LARGEST_IMAGINARY | - largest imaginary parts
| PEP_SMALLEST_IMAGINARY | - smallest imaginary parts
| PEP_TARGET_MAGNITUDE | - eigenvalues closest to the target (in magnitude)
| PEP_TARGET_REAL | - eigenvalues with real part closest to target
| PEP_TARGET_IMAGINARY | - eigenvalues with imaginary part closest to target
| PEP_WHICH_USER | - user defined ordering set with PEPSetEigenvalueComparison()

### Options Database Keys

| -pep_largest_magnitude | - Sets largest eigenvalues in magnitude
| -pep_smallest_magnitude | - Sets smallest eigenvalues in magnitude
| -pep_largest_real | - Sets largest real parts
| -pep_smallest_real | - Sets smallest real parts
| -pep_largest_imaginary | - Sets largest imaginary parts
| -pep_smallest_imaginary | - Sets smallest imaginary parts
| -pep_target_magnitude | - Sets eigenvalues closest to target
| -pep_target_real | - Sets real parts closest to target
| -pep_target_imaginary | - Sets imaginary parts closest to target

### Notes

Not all eigensolvers implemented in PEP account for all the possible values stated above. If SLEPc is compiled for real numbers PEP_LARGEST_IMAGINARY and PEP_SMALLEST_IMAGINARY use the absolute value of the imaginary part for eigenvalue selection.

The target is a scalar value provided with PEPSetTarget().

The criterion PEP_TARGET_IMAGINARY is available only in case PETSc and SLEPc have been built with complex scalars.

### See Also

PEPGetWhichEigenpairs(), PEPSetTarget(), PEPSetEigenvalueComparison(), PEPWhich

Location: src/pep/interface/pepopts.c
Index of all PEP routines
Table of Contents for all manual pages
Index of all manual pages