zsnode_dfs.c

SuperLU is a general purpose library for the direct solution of large, sparse, nonsymmetric systems

/*! @file zsnode_dfs.c
 * \brief Determines the union of row structures of columns within the relaxed node
 *
 * <pre>
 * -- SuperLU routine (version 2.0) --
 * Univ. of California Berkeley, Xerox Palo Alto Research Center,
 * and Lawrence Berkeley National Lab.
 * November 15, 1997
 *
 * 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.
 * </pre>
 */


#include "slu_zdefs.h"

/*! \brief
 *
 * <pre>
 * Purpose
 * =======
 *    zsnode_dfs() - Determine the union of the row structures of those 
 *    columns within the relaxed snode.
 *    Note: The relaxed snodes are leaves of the supernodal etree, therefore, 
 *    the portion outside the rectangular supernode must be zero.
 *
 * Return value
 * ============
 *     0   success;
 *    >0   number of bytes allocated when run out of memory.
 * </pre>
 */

int
zsnode_dfs (
	   const int  jcol,	    /* in - start of the supernode */
	   const int  kcol, 	    /* in - end of the supernode */
	   const int  *asub,        /* in */
	   const int  *xa_begin,    /* in */
	   const int  *xa_end,      /* in */
	   int        *xprune,      /* out */
	   int        *marker,      /* modified */
	   GlobalLU_t *Glu          /* modified */
	   )
{

    register int i, k, ifrom, ito, nextl, new_next;
    int          nsuper, krow, kmark, mem_error;
    int          *xsup, *supno;
    int          *lsub, *xlsub;
    int          nzlmax;
    
    xsup    = Glu->xsup;
    supno   = Glu->supno;
    lsub    = Glu->lsub;
    xlsub   = Glu->xlsub;
    nzlmax  = Glu->nzlmax;

    nsuper = ++supno[jcol];	/* Next available supernode number */
    nextl = xlsub[jcol];

    for (i = jcol; i <= kcol; i++) {
	/* For each nonzero in A[*,i] */
	for (k = xa_begin[i]; k < xa_end[i]; k++) {	
	    krow = asub[k];
	    kmark = marker[krow];
	    if ( kmark != kcol ) { /* First time visit krow */
		marker[krow] = kcol;
		lsub[nextl++] = krow;
		if ( nextl >= nzlmax ) {
		    if ( mem_error = zLUMemXpand(jcol, nextl, LSUB, &nzlmax, Glu) )
			return (mem_error);
		    lsub = Glu->lsub;
		}
	    }
    	}
	supno[i] = nsuper;
    }

    /* Supernode > 1, then make a copy of the subscripts for pruning */
    if ( jcol < kcol ) {
	new_next = nextl + (nextl - xlsub[jcol]);
	while ( new_next > nzlmax ) {
	    if ( mem_error = zLUMemXpand(jcol, nextl, LSUB, &nzlmax, Glu) )
		return (mem_error);
	    lsub = Glu->lsub;
	}
	ito = nextl;
	for (ifrom = xlsub[jcol]; ifrom < nextl; )
	    lsub[ito++] = lsub[ifrom++];	
        for (i = jcol+1; i <= kcol; i++) xlsub[i] = nextl;
	nextl = ito;
    }

    xsup[nsuper+1] = kcol + 1;
    supno[kcol+1]  = nsuper;
    xprune[kcol]   = nextl;
    xlsub[kcol+1]  = nextl;

    return 0;
}