69 lines
1.9 KiB
C
69 lines
1.9 KiB
C
/*! @file ilu_relax_snode.c
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* \brief Identify initial relaxed supernodes
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*
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* <pre>
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* -- SuperLU routine (version 4.0) --
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* Lawrence Berkeley National Laboratory
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* June 1, 2009
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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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* ilu_relax_snode() - Identify the initial relaxed supernodes, assuming
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* that the matrix has been reordered according to the postorder of the
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* etree.
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* </pre>
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*/
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void
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ilu_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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* if j-th column starts a relaxed
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* supernode, relax_end[j] represents
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* the last column of this supernode */
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int *relax_fsupc /* first column in a supernode
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* relax_fsupc[j] represents the first
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* column of j-th supernode */
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)
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{
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register int j, f, parent;
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register int snode_start; /* beginning of a snode */
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ifill (relax_end, n, EMPTY);
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ifill (relax_fsupc, n, EMPTY);
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for (j = 0; j < n; j++) descendants[j] = 0;
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/* Compute the number of descendants of each node in the etree */
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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 = f = 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 with j being the last column. */
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relax_end[snode_start] = j; /* Last column is recorded */
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j++;
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relax_fsupc[f++] = snode_start;
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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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}
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