naginterfaces.library.sparseig.feast_​init

naginterfaces.library.sparseig.feast_init()

feast_init initializes a data structure for the NAG FEAST suite of functions consisting of feast_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() and feast_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_30.3/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, $\lambda$, and the corresponding eigenvectors, $x$, of a standard eigenvalue problem $Ax=\lambda x$, a generalized eigenvalue problem $Ax=\lambda Bx$, where $A$ and $B$ are large and sparse, or a polynomial eigenvalue problem ${\sum }_i{\lambda }^i{A}_{i}x=0$. 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 function feast_option(), before the contour definition functions feast_symm_contour(), feast_gen_contour() or feast_custom_contour(), and before the reverse communication solvers feast_real_symm_solve(), feast_real_gen_solve(), feast_complex_herm_solve(), feast_complex_symm_solve(), feast_complex_gen_solve(), feast_poly_symm_solve() or feast_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

See also

naginterfaces.library.examples.sparseig.feast_poly_gen_solve_ex.main()