slepc-3.21.1 2024-04-26
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Specifies which portion of the spectrum is to be sought.


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

Input Parameters

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

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


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()

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







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