f12jef is a setup routine in a suite of routines consisting of
f12jaf,
f12jbf,
f12jef,
f12jjf and
f12jrf. It is used to find some of the eigenvalues, and the corresponding eigenvectors, of a standard or generalized eigenvalue problem defined by real symmetric or complex Hermitian matrices. The initialization routine
f12jaf must have been called prior to calling
f12jef. In addition calls to
f12jbf can be made to supply individual optional parameters to
f12jef.
The suite of routines is suitable for the solution of large sparse eigenproblems where only a few eigenvalues from a selected range of the spectrum are required.
f12jef is used to specify a search interval on the real line,
$[{E}_{\mathrm{min}},{E}_{\mathrm{max}}]$, within which eigenvalues will be sought (note that the eigenvalues of real symmetric and complex Hermitian eigenproblems are themselves real).
f12jef uses this interval to define nodes and weights for an elliptical contour to be used by the solvers
f12jjf or
f12jrf. Since this contour is symmetric when reflected in the real line, the routine needs only to define the nodes and weights for the upper half-contour.
Polizzi E (2009) Density-Matrix-Based Algorithms for Solving Eigenvalue Problems Phys. Rev. B. 79 115112
If on entry
${\mathbf{ifail}}=0$ or
$\mathrm{-1}$, explanatory error messages are output on the current error message unit (as defined by
x04aaf).
Not applicable.
Parts of the code for
f12jef are distributed under the BSD software License. Please refer to
Library Licensors for further details.