naginterfaces.library.sparseig.feast_init¶
- naginterfaces.library.sparseig.feast_init()[source]¶
feast_init
initializes a data structure for the NAG FEAST suite of functions consisting offeast_init
,feast_option()
,feast_symm_contour()
,feast_gen_contour()
,feast_custom_contour()
,feast_real_symm_solve()
,feast_real_gen_solve()
,feast_complex_herm_solve()
,feast_complex_symm_solve()
,feast_complex_gen_solve()
,feast_poly_symm_solve()
,feast_poly_gen_solve()
andfeast_free()
. It is used to find some of the eigenvalues, and the corresponding eigenvectors, of a standard, generalized or polynomial eigenvalue problem.The suite of functions is suitable for the solution of large, sparse eigenproblems where only those eigenvalues within a selected region of the complex plane are required.
For full information please refer to the NAG Library document for f12ja
https://support.nag.com/numeric/nl/nagdoc_30.1/flhtml/f12/f12jaf.html
- Returns
- handleHandle
Holds a handle to the internal data structure used by the NAG FEAST suite.
- Notes
The NAG FEAST suite of functions is designed to calculate some of the eigenvalues, , and the corresponding eigenvectors, , of a standard eigenvalue problem , a generalized eigenvalue problem , where and are large and sparse, or a polynomial eigenvalue problem . It can also be used to find eigenvalues/eigenvectors of smaller scale dense problems. The NAG FEAST suite is based on the FEAST library, using contour integration to find the eigenvalues within a contour in the complex plane.
feast_init
is a setup function which must be called before the option setting functionfeast_option()
, before the contour definition functionsfeast_symm_contour()
,feast_gen_contour()
orfeast_custom_contour()
, and before the reverse communication solversfeast_real_symm_solve()
,feast_real_gen_solve()
,feast_complex_herm_solve()
,feast_complex_symm_solve()
,feast_complex_gen_solve()
,feast_poly_symm_solve()
orfeast_poly_gen_solve()
.This setup function initializes the handle to a data structure used internally by the NAG FEAST suite and sets (to their default values) all options that can be set by you via the option setting function
feast_option()
. For details of the options available and how to set them see Other Parameters for feast_option. When the handle is no longer needed,feast_free()
must be called to destroy it and deallocate all the allocated memory and data within.
- References
Polizzi, E, 2009, Density-Matrix-Based Algorithms for Solving Eigenvalue Problems, Phys. Rev. B. (79), 115112