Exemplo n.º 1
0
/*
 * Nonsymmetric elimination tree
 */
int
sp_coletree(
	    int *acolst, int *acolend, /* column start and end past 1 */
	    int *arow,                 /* row indices of A */
	    int nr, int nc,            /* dimension of A */
	    int *parent	               /* parent in elim tree */
	    )
{
	int	*root;			/* root of subtee of etree 	*/
	int     *firstcol;		/* first nonzero col in each row*/
	int	rset, cset;             
	int	row, col;
	int	rroot;
	int	p;
	int     *pp;

	root = mxCallocInt (nc);
	initialize_disjoint_sets (nc, &pp);

	/* Compute firstcol[row] = first nonzero column in row */

	firstcol = mxCallocInt (nr);
	for (row = 0; row < nr; firstcol[row++] = nc);
	for (col = 0; col < nc; col++) 
		for (p = acolst[col]; p < acolend[col]; p++) {
			row = arow[p];
			firstcol[row] = SUPERLU_MIN(firstcol[row], col);
		}

	/* Compute etree by Liu's algorithm for symmetric matrices,
           except use (firstcol[r],c) in place of an edge (r,c) of A.
	   Thus each row clique in A'*A is replaced by a star
	   centered at its first vertex, which has the same fill. */

	for (col = 0; col < nc; col++) {
		cset = make_set (col, pp);
		root[cset] = col;
		parent[col] = nc; /* Matlab */
		for (p = acolst[col]; p < acolend[col]; p++) {
			row = firstcol[arow[p]];
			if (row >= col) continue;
			rset = find (row, pp);
			rroot = root[rset];
			if (rroot != col) {
				parent[rroot] = col;
				cset = link (cset, rset, pp);
				root[cset] = col;
			}
		}
	}

	SUPERLU_FREE (root);
	SUPERLU_FREE (firstcol);
	finalize_disjoint_sets (pp);
	return 0;
}
Exemplo n.º 2
0
/*! \brief Symmetric elimination tree
 *
 * <pre>
 *      p = spsymetree (A);
 *
 *      Find the elimination tree for symmetric matrix A.
 *      This uses Liu's algorithm, and runs in time O(nz*log n).
 *
 *      Input:
 *        Square sparse matrix A.  No check is made for symmetry;
 *        elements below and on the diagonal are ignored.
 *        Numeric values are ignored, so any explicit zeros are 
 *        treated as nonzero.
 *      Output:
 *        Integer array of parents representing the etree, with n
 *        meaning a root of the elimination forest.
 *      Note:  
 *        This routine uses only the upper triangle, while sparse
 *        Cholesky (as in spchol.c) uses only the lower.  Matlab's
 *        dense Cholesky uses only the upper.  This routine could
 *        be modified to use the lower triangle either by transposing
 *        the matrix or by traversing it by rows with auxiliary
 *        pointer and link arrays.
 *
 *      John R. Gilbert, Xerox, 10 Dec 1990
 *      Based on code by JRG dated 1987, 1988, and 1990.
 *      Modified by X.S. Li, November 1999.
 * </pre>
 */
int
sp_symetree_dist(
	    int_t *acolst, int_t *acolend, /* column starts and ends past 1 */
	    int_t *arow,            /* row indices of A */
	    int_t n,                /* dimension of A */
	    int_t *parent	    /* parent in elim tree */
	    )
{
	int_t	*root;		    /* root of subtee of etree 	*/
	int_t	rset, cset;             
	int_t	row, col;
	int_t	rroot;
	int_t	p;
	int_t   *pp;

#if ( DEBUGlevel>=1 )
	CHECK_MALLOC(0, "Enter sp_symetree()");
#endif

	root = mxCallocInt (n);
	initialize_disjoint_sets (n, &pp);

	for (col = 0; col < n; col++) {
		cset = make_set (col, pp);
		root[cset] = col;
		parent[col] = n; /* Matlab */
		for (p = acolst[col]; p < acolend[col]; p++) {
			row = arow[p];
			if (row >= col) continue;
			rset = find (row, pp);
			rroot = root[rset];
			if (rroot != col) {
				parent[rroot] = col;
				cset = link (cset, rset, pp);
				root[cset] = col;
			}
		}
	}
	SUPERLU_FREE (root);
	finalize_disjoint_sets (pp);

#if ( DEBUGlevel>=1 )
	CHECK_MALLOC(0, "Exit sp_symetree()");
#endif
	return 0;
} /* SP_SYMETREE_DIST */
Exemplo n.º 3
0
/*
 * Symmetric elimination tree
 */
int
sp_symetree(
	    int *acolst, int *acolend, /* column starts and ends past 1 */
	    int *arow,            /* row indices of A */
	    int n,                /* dimension of A */
	    int *parent	    /* parent in elim tree */
	    )
{
	int	*root;		    /* root of subtree of etree 	*/
	int	rset, cset;             
	int	row, col;
	int	rroot;
	int	p;

	root = mxCallocInt (n);
	initialize_disjoint_sets (n);

	for (col = 0; col < n; col++) {
		cset = make_set (col);
		root[cset] = col;
		parent[col] = n; /* Matlab */
		for (p = acolst[col]; p < acolend[col]; p++) {
			row = arow[p];
			if (row >= col) continue;
			rset = find (row);
			rroot = root[rset];
			if (rroot != col) {
				parent[rroot] = col;
				cset = link (cset, rset);
				root[cset] = col;
			}
		}
	}
	SUPERLU_FREE (root);
	finalize_disjoint_sets ();
	return 0;
} /* SP_SYMETREE */