124 lines
3.6 KiB
C
124 lines
3.6 KiB
C
/*! @file heap_relax_snode.c
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* \brief Identify the initial relaxed supernodes
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*
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* <pre>
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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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* </pre>
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*/
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#include "slu_ddefs.h"
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/*! \brief
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*
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* <pre>
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* Purpose
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* =======
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* relax_snode() - Identify the initial relaxed supernodes, assuming that
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* the matrix has been reordered according to the postorder of the etree.
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* </pre>
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*/
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void
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heap_relax_snode (
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const int n,
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int *et, /* column elimination tree */
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const int relax_columns, /* max no of columns allowed in a
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relaxed snode */
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int *descendants, /* no of descendants of each node
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in the etree */
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int *relax_end /* last column in a supernode */
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)
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{
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register int i, j, k, l, parent;
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register int snode_start; /* beginning of a snode */
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int *et_save, *post, *inv_post, *iwork;
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int nsuper_et = 0, nsuper_et_post = 0;
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/* The etree may not be postordered, but is heap ordered. */
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iwork = (int*) intMalloc(3*n+2);
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if ( !iwork ) ABORT("SUPERLU_MALLOC fails for iwork[]");
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inv_post = iwork + n+1;
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et_save = inv_post + n+1;
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/* Post order etree */
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post = (int *) TreePostorder(n, et);
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for (i = 0; i < n+1; ++i) inv_post[post[i]] = i;
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/* Renumber etree in postorder */
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for (i = 0; i < n; ++i) {
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iwork[post[i]] = post[et[i]];
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et_save[i] = et[i]; /* Save the original etree */
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}
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for (i = 0; i < n; ++i) et[i] = iwork[i];
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/* Compute the number of descendants of each node in the etree */
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ifill (relax_end, n, EMPTY);
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for (j = 0; j < n; j++) descendants[j] = 0;
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for (j = 0; j < n; j++) {
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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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for (j = 0; j < n; ) {
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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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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 = SUPERLU_MIN(k, inv_post[i]);
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l = inv_post[j];
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if ( (l - k) == (j - snode_start) ) {
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/* It's also a supernode in the original etree */
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relax_end[k] = l; /* Last column is recorded */
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++nsuper_et;
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} else {
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for (i = snode_start; i <= j; ++i) {
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l = inv_post[i];
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if ( descendants[i] == 0 ) {
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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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}
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#if ( PRNTlevel>=1 )
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printf(".. heap_snode_relax:\n"
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"\tNo of relaxed snodes in postordered etree:\t%d\n"
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"\tNo of relaxed snodes in original etree:\t%d\n",
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nsuper_et_post, nsuper_et);
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#endif
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/* Recover the original etree */
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for (i = 0; i < n; ++i) et[i] = et_save[i];
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SUPERLU_FREE(post);
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SUPERLU_FREE(iwork);
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}
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