slepc-3.16.1 2021-11-17
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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_ALL  - all eigenvalues contained in a given interval or region
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
-pep_all  - Sets all eigenvalues in an interval or region

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.

PEP_ALL is intended for use in combination with an interval (see PEPSetInterval()), when all eigenvalues within the interval are requested, and also for computing all eigenvalues in a region with the CISS solver. In both cases, the number of eigenvalues is unknown, so the nev parameter has a different sense, see PEPSetDimensions().

See Also

PEPGetWhichEigenpairs(), PEPSetTarget(), PEPSetInterval(),
PEPSetDimensions(), PEPSetEigenvalueComparison(), PEPWhich

Location: src/pep/interface/pepopts.c

Examples

src/pep/tutorials/ex38.c.html

Index of all PEP routines
Table of Contents for all manual pages
Index of all manual pages