1 | // This file is part of Eigen, a lightweight C++ template library
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2 | // for linear algebra.
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3 | //
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4 | // Copyright (C) 2012 Désiré Nuentsa-Wakam <desire.nuentsa_wakam@inria.fr>
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5 | //
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6 | // This Source Code Form is subject to the terms of the Mozilla
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7 | // Public License v. 2.0. If a copy of the MPL was not distributed
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8 | // with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
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9 |
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10 | /* This file is a modified version of heap_relax_snode.c file in SuperLU
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11 | * -- SuperLU routine (version 3.0) --
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12 | * Univ. of California Berkeley, Xerox Palo Alto Research Center,
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13 | * and Lawrence Berkeley National Lab.
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14 | * October 15, 2003
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15 | *
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16 | * Copyright (c) 1994 by Xerox Corporation. All rights reserved.
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17 | *
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18 | * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY
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19 | * EXPRESSED OR IMPLIED. ANY USE IS AT YOUR OWN RISK.
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20 | *
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21 | * Permission is hereby granted to use or copy this program for any
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22 | * purpose, provided the above notices are retained on all copies.
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23 | * Permission to modify the code and to distribute modified code is
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24 | * granted, provided the above notices are retained, and a notice that
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25 | * the code was modified is included with the above copyright notice.
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26 | */
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27 |
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28 | #ifndef SPARSELU_RELAX_SNODE_H
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29 | #define SPARSELU_RELAX_SNODE_H
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30 |
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31 | namespace Eigen {
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32 |
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33 | namespace internal {
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34 |
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35 | /**
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36 | * \brief Identify the initial relaxed supernodes
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37 | *
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38 | * This routine is applied to a column elimination tree.
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39 | * It assumes that the matrix has been reordered according to the postorder of the etree
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40 | * \param n the number of columns
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41 | * \param et elimination tree
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42 | * \param relax_columns Maximum number of columns allowed in a relaxed snode
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43 | * \param descendants Number of descendants of each node in the etree
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44 | * \param relax_end last column in a supernode
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45 | */
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46 | template <typename Scalar, typename Index>
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47 | void SparseLUImpl<Scalar,Index>::relax_snode (const Index n, IndexVector& et, const Index relax_columns, IndexVector& descendants, IndexVector& relax_end)
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48 | {
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49 |
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50 | // compute the number of descendants of each node in the etree
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51 | Index j, parent;
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52 | relax_end.setConstant(emptyIdxLU);
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53 | descendants.setZero();
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54 | for (j = 0; j < n; j++)
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55 | {
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56 | parent = et(j);
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57 | if (parent != n) // not the dummy root
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58 | descendants(parent) += descendants(j) + 1;
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59 | }
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60 | // Identify the relaxed supernodes by postorder traversal of the etree
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61 | Index snode_start; // beginning of a snode
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62 | for (j = 0; j < n; )
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63 | {
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64 | parent = et(j);
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65 | snode_start = j;
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66 | while ( parent != n && descendants(parent) < relax_columns )
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67 | {
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68 | j = parent;
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69 | parent = et(j);
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70 | }
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71 | // Found a supernode in postordered etree, j is the last column
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72 | relax_end(snode_start) = j; // Record last column
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73 | j++;
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74 | // Search for a new leaf
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75 | while (descendants(j) != 0 && j < n) j++;
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76 | } // End postorder traversal of the etree
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77 |
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78 | }
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79 |
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80 | } // end namespace internal
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81 |
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82 | } // end namespace Eigen
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83 | #endif
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