3 * This source code is part of
7 * GROningen MAchine for Chemical Simulations
10 * Written by David van der Spoel, Erik Lindahl, Berk Hess, and others.
11 * Copyright (c) 1991-2000, University of Groningen, The Netherlands.
12 * Copyright (c) 2001-2004, The GROMACS development team,
13 * check out http://www.gromacs.org for more information.
15 * This program is free software; you can redistribute it and/or
16 * modify it under the terms of the GNU General Public License
17 * as published by the Free Software Foundation; either version 2
18 * of the License, or (at your option) any later version.
20 * If you want to redistribute modifications, please consider that
21 * scientific software is very special. Version control is crucial -
22 * bugs must be traceable. We will be happy to consider code for
23 * inclusion in the official distribution, but derived work must not
24 * be called official GROMACS. Details are found in the README & COPYING
25 * files - if they are missing, get the official version at www.gromacs.org.
27 * To help us fund GROMACS development, we humbly ask that you cite
28 * the papers on the package - you can find them in the top README file.
30 * For more info, check our website at http://www.gromacs.org
33 * Green Red Orange Magenta Azure Cyan Skyblue
35 #ifndef GMX_LINEARALGEBRA_EIGENSOLVER_H
36 #define GMX_LINEARALGEBRA_EIGENSOLVER_H
38 #include "../legacyheaders/types/simple.h"
40 #include "sparsematrix.h"
46 /** Calculate eigenvalues/vectors a matrix stored in linear memory (not sparse).
48 * This routine uses lapack to diagonalize a matrix efficiently, and
49 * the eigenvalues/vectors will be sorted in ascending order on output.
50 * Gromacs comes with a built-in portable BLAS/LAPACK, but if performance
51 * matters it is advisable to link with an optimized vendor-provided library.
53 * \param a Pointer to matrix data, total size n*n
54 * The input data in the matrix will be destroyed/changed.
55 * \param n Side of the matrix to calculate eigenvalues for.
56 * \param index_lower Index of first eigenvector to determine.
57 * \param index_upper Last eigenvector determined is index_upper-1.
58 * \param eigenvalues Array of the eigenvalues on return. The length
59 * of this array _must_ be n, even if not all
60 * eigenvectors are calculated, since all eigenvalues
61 * might be needed as an intermediate step.
62 * \param eigenvectors If this pointer is non-NULL, the eigenvectors
63 * specified by the indices are returned as rows of
64 * a matrix, i.e. eigenvector j starts at offset j*n, and
77 /*! \brief Sparse matrix eigensolver.
79 * This routine is intended for large matrices that might not fit in memory.
81 * It will determine the neig lowest eigenvalues, and if the eigenvectors pointer
82 * is non-NULL also the corresponding eigenvectors.
84 * maxiter=100000 should suffice in most cases!
87 sparse_eigensolver(gmx_sparsematrix_t * A,