blob: 6f75d500e5f831f414175ce46dbceffa0acd5539 [file] [log] [blame]
 // This file is part of Eigen, a lightweight C++ template library // for linear algebra. // // Copyright (C) 2012 Désiré Nuentsa-Wakam // // This Source Code Form is subject to the terms of the Mozilla // Public License v. 2.0. If a copy of the MPL was not distributed // with this file, You can obtain one at http://mozilla.org/MPL/2.0/. /* This file is a modified version of heap_relax_snode.c file in SuperLU * -- SuperLU routine (version 3.0) -- * Univ. of California Berkeley, Xerox Palo Alto Research Center, * and Lawrence Berkeley National Lab. * October 15, 2003 * * Copyright (c) 1994 by Xerox Corporation. All rights reserved. * * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY * EXPRESSED OR IMPLIED. ANY USE IS AT YOUR OWN RISK. * * Permission is hereby granted to use or copy this program for any * purpose, provided the above notices are retained on all copies. * Permission to modify the code and to distribute modified code is * granted, provided the above notices are retained, and a notice that * the code was modified is included with the above copyright notice. */ #ifndef SPARSELU_HEAP_RELAX_SNODE_H #define SPARSELU_HEAP_RELAX_SNODE_H namespace Eigen { namespace internal { /** * \brief Identify the initial relaxed supernodes * * This routine applied to a symmetric elimination tree. * It assumes that the matrix has been reordered according to the postorder of the etree * \param n The number of columns * \param et elimination tree * \param relax_columns Maximum number of columns allowed in a relaxed snode * \param descendants Number of descendants of each node in the etree * \param relax_end last column in a supernode */ template void SparseLUImpl::heap_relax_snode (const Index n, IndexVector& et, const Index relax_columns, IndexVector& descendants, IndexVector& relax_end) { // The etree may not be postordered, but its heap ordered IndexVector post; internal::treePostorder(StorageIndex(n), et, post); // Post order etree IndexVector inv_post(n+1); for (StorageIndex i = 0; i < n+1; ++i) inv_post(post(i)) = i; // inv_post = post.inverse()??? // Renumber etree in postorder IndexVector iwork(n); IndexVector et_save(n+1); for (Index i = 0; i < n; ++i) { iwork(post(i)) = post(et(i)); } et_save = et; // Save the original etree et = iwork; // compute the number of descendants of each node in the etree relax_end.setConstant(emptyIdxLU); Index j, parent; descendants.setZero(); for (j = 0; j < n; j++) { parent = et(j); if (parent != n) // not the dummy root descendants(parent) += descendants(j) + 1; } // Identify the relaxed supernodes by postorder traversal of the etree Index snode_start; // beginning of a snode StorageIndex k; Index nsuper_et_post = 0; // Number of relaxed snodes in postordered etree Index nsuper_et = 0; // Number of relaxed snodes in the original etree StorageIndex l; for (j = 0; j < n; ) { parent = et(j); snode_start = j; while ( parent != n && descendants(parent) < relax_columns ) { j = parent; parent = et(j); } // Found a supernode in postordered etree, j is the last column ++nsuper_et_post; k = StorageIndex(n); for (Index i = snode_start; i <= j; ++i) k = (std::min)(k, inv_post(i)); l = inv_post(j); if ( (l - k) == (j - snode_start) ) // Same number of columns in the snode { // This is also a supernode in the original etree relax_end(k) = l; // Record last column ++nsuper_et; } else { for (Index i = snode_start; i <= j; ++i) { l = inv_post(i); if (descendants(i) == 0) { relax_end(l) = l; ++nsuper_et; } } } j++; // Search for a new leaf while (descendants(j) != 0 && j < n) j++; } // End postorder traversal of the etree // Recover the original etree et = et_save; } } // end namespace internal } // end namespace Eigen #endif // SPARSELU_HEAP_RELAX_SNODE_H