128 lines
4.0 KiB
C
128 lines
4.0 KiB
C
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// This file is part of Eigen, a lightweight C++ template library
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// for linear algebra.
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//
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// Copyright (C) 2012 Désiré Nuentsa-Wakam <desire.nuentsa_wakam@inria.fr>
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//
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// This Source Code Form is subject to the terms of the Mozilla
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// Public License v. 2.0. If a copy of the MPL was not distributed
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// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
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/* This file is a modified version of heap_relax_snode.c file in SuperLU
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* -- SuperLU routine (version 3.0) --
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* Univ. of California Berkeley, Xerox Palo Alto Research Center,
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* and Lawrence Berkeley National Lab.
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* October 15, 2003
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*
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* Copyright (c) 1994 by Xerox Corporation. All rights reserved.
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*
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* THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY
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* EXPRESSED OR IMPLIED. ANY USE IS AT YOUR OWN RISK.
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*
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* Permission is hereby granted to use or copy this program for any
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* purpose, provided the above notices are retained on all copies.
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* Permission to modify the code and to distribute modified code is
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* granted, provided the above notices are retained, and a notice that
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* the code was modified is included with the above copyright notice.
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*/
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#ifndef SPARSELU_HEAP_RELAX_SNODE_H
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#define SPARSELU_HEAP_RELAX_SNODE_H
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namespace Eigen {
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namespace internal {
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/**
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* \brief Identify the initial relaxed supernodes
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*
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* This routine applied to a symmetric elimination tree.
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* It assumes that the matrix has been reordered according to the postorder of the etree
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* \param n The number of columns
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* \param et elimination tree
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* \param relax_columns Maximum number of columns allowed in a relaxed snode
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* \param descendants Number of descendants of each node in the etree
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* \param relax_end last column in a supernode
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*/
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template <typename Scalar, typename Index>
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void SparseLUImpl<Scalar,Index>::heap_relax_snode (const Index n, IndexVector& et, const Index relax_columns, IndexVector& descendants, IndexVector& relax_end)
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{
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// The etree may not be postordered, but its heap ordered
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IndexVector post;
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internal::treePostorder(n, et, post); // Post order etree
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IndexVector inv_post(n+1);
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Index i;
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for (i = 0; i < n+1; ++i) inv_post(post(i)) = i; // inv_post = post.inverse()???
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// Renumber etree in postorder
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IndexVector iwork(n);
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IndexVector et_save(n+1);
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for (i = 0; i < n; ++i)
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{
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iwork(post(i)) = post(et(i));
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}
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et_save = et; // Save the original etree
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et = iwork;
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// compute the number of descendants of each node in the etree
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relax_end.setConstant(emptyIdxLU);
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Index j, parent;
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descendants.setZero();
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for (j = 0; j < n; j++)
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{
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parent = et(j);
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if (parent != n) // not the dummy root
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descendants(parent) += descendants(j) + 1;
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}
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// Identify the relaxed supernodes by postorder traversal of the etree
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Index snode_start; // beginning of a snode
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Index k;
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Index nsuper_et_post = 0; // Number of relaxed snodes in postordered etree
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Index nsuper_et = 0; // Number of relaxed snodes in the original etree
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Index l;
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for (j = 0; j < n; )
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{
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parent = et(j);
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snode_start = j;
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while ( parent != n && descendants(parent) < relax_columns )
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{
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j = parent;
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parent = et(j);
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}
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// Found a supernode in postordered etree, j is the last column
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++nsuper_et_post;
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k = n;
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for (i = snode_start; i <= j; ++i)
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k = (std::min)(k, inv_post(i));
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l = inv_post(j);
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if ( (l - k) == (j - snode_start) ) // Same number of columns in the snode
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{
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// This is also a supernode in the original etree
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relax_end(k) = l; // Record last column
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++nsuper_et;
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}
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else
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{
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for (i = snode_start; i <= j; ++i)
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{
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l = inv_post(i);
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if (descendants(i) == 0)
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{
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relax_end(l) = l;
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++nsuper_et;
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}
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}
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}
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j++;
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// Search for a new leaf
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while (descendants(j) != 0 && j < n) j++;
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} // End postorder traversal of the etree
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// Recover the original etree
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et = et_save;
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}
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} // end namespace internal
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} // end namespace Eigen
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#endif // SPARSELU_HEAP_RELAX_SNODE_H
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