slepc-3.17.2 2022-08-09
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Specifies which portion of the spectrum is to be sought.


#include "slepceps.h" 
PetscErrorCode EPSSetWhichEigenpairs(EPS eps,EPSWhich which)
Logically Collective on eps

Input Parameters

eps  - eigensolver context obtained from EPSCreate()
which  - the portion of the spectrum to be sought

Possible values

The parameter 'which' can have one of these values

EPS_LARGEST_MAGNITUDE  - largest eigenvalues in magnitude (default)
EPS_SMALLEST_MAGNITUDE  - smallest eigenvalues in magnitude
EPS_LARGEST_REAL  - largest real parts
EPS_SMALLEST_REAL  - smallest real parts
EPS_LARGEST_IMAGINARY  - largest imaginary parts
EPS_SMALLEST_IMAGINARY  - smallest imaginary parts
EPS_TARGET_MAGNITUDE  - eigenvalues closest to the target (in magnitude)
EPS_TARGET_REAL  - eigenvalues with real part closest to target
EPS_TARGET_IMAGINARY  - eigenvalues with imaginary part closest to target
EPS_ALL  - all eigenvalues contained in a given interval or region
EPS_WHICH_USER  - user defined ordering set with EPSSetEigenvalueComparison()

Options Database Keys

-eps_largest_magnitude  - Sets largest eigenvalues in magnitude
-eps_smallest_magnitude  - Sets smallest eigenvalues in magnitude
-eps_largest_real  - Sets largest real parts
-eps_smallest_real  - Sets smallest real parts
-eps_largest_imaginary  - Sets largest imaginary parts
-eps_smallest_imaginary  - Sets smallest imaginary parts
-eps_target_magnitude  - Sets eigenvalues closest to target
-eps_target_real  - Sets real parts closest to target
-eps_target_imaginary  - Sets imaginary parts closest to target
-eps_all  - Sets all eigenvalues in an interval or region


Not all eigensolvers implemented in EPS account for all the possible values stated above. Also, some values make sense only for certain types of problems. If SLEPc is compiled for real numbers EPS_LARGEST_IMAGINARY and EPS_SMALLEST_IMAGINARY use the absolute value of the imaginary part for eigenvalue selection.

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

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

EPS_ALL is intended for use in combination with an interval (see EPSSetInterval()), when all eigenvalues within the interval are requested, or in the context of the CISS solver for computing all eigenvalues in a region. In those cases, the number of eigenvalues is unknown, so the nev parameter has a different sense, see EPSSetDimensions().

See Also

EPSGetWhichEigenpairs(), EPSSetTarget(), EPSSetInterval(),
EPSSetDimensions(), EPSSetEigenvalueComparison(), EPSWhich

Location: src/eps/interface/epsopts.c



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