122 lines
3.7 KiB
C
122 lines
3.7 KiB
C
/* ========================================================================= */
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/* === AMD_post_tree ======================================================= */
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/* ========================================================================= */
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/* ------------------------------------------------------------------------- */
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/* AMD, Copyright (c) Timothy A. Davis, */
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/* Patrick R. Amestoy, and Iain S. Duff. See ../README.txt for License. */
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/* email: davis at cise.ufl.edu CISE Department, Univ. of Florida. */
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/* web: http://www.cise.ufl.edu/research/sparse/amd */
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/* ------------------------------------------------------------------------- */
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/* Post-ordering of a supernodal elimination tree. */
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#include "amd_internal.h"
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GLOBAL Int AMD_post_tree
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(
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Int root, /* root of the tree */
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Int k, /* start numbering at k */
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Int Child [ ], /* input argument of size nn, undefined on
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* output. Child [i] is the head of a link
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* list of all nodes that are children of node
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* i in the tree. */
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const Int Sibling [ ], /* input argument of size nn, not modified.
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* If f is a node in the link list of the
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* children of node i, then Sibling [f] is the
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* next child of node i.
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*/
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Int Order [ ], /* output order, of size nn. Order [i] = k
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* if node i is the kth node of the reordered
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* tree. */
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Int Stack [ ] /* workspace of size nn */
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#ifndef NDEBUG
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, Int nn /* nodes are in the range 0..nn-1. */
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#endif
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)
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{
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Int f, head, h, i ;
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#if 0
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/* --------------------------------------------------------------------- */
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/* recursive version (Stack [ ] is not used): */
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/* --------------------------------------------------------------------- */
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/* this is simple, but can caouse stack overflow if nn is large */
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i = root ;
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for (f = Child [i] ; f != EMPTY ; f = Sibling [f])
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{
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k = AMD_post_tree (f, k, Child, Sibling, Order, Stack, nn) ;
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}
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Order [i] = k++ ;
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return (k) ;
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#endif
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/* --------------------------------------------------------------------- */
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/* non-recursive version, using an explicit stack */
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/* --------------------------------------------------------------------- */
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/* push root on the stack */
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head = 0 ;
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Stack [0] = root ;
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while (head >= 0)
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{
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/* get head of stack */
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ASSERT (head < nn) ;
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i = Stack [head] ;
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AMD_DEBUG1 (("head of stack "ID" \n", i)) ;
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ASSERT (i >= 0 && i < nn) ;
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if (Child [i] != EMPTY)
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{
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/* the children of i are not yet ordered */
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/* push each child onto the stack in reverse order */
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/* so that small ones at the head of the list get popped first */
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/* and the biggest one at the end of the list gets popped last */
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for (f = Child [i] ; f != EMPTY ; f = Sibling [f])
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{
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head++ ;
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ASSERT (head < nn) ;
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ASSERT (f >= 0 && f < nn) ;
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}
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h = head ;
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ASSERT (head < nn) ;
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for (f = Child [i] ; f != EMPTY ; f = Sibling [f])
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{
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ASSERT (h > 0) ;
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Stack [h--] = f ;
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AMD_DEBUG1 (("push "ID" on stack\n", f)) ;
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ASSERT (f >= 0 && f < nn) ;
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}
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ASSERT (Stack [h] == i) ;
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/* delete child list so that i gets ordered next time we see it */
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Child [i] = EMPTY ;
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}
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else
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{
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/* the children of i (if there were any) are already ordered */
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/* remove i from the stack and order it. Front i is kth front */
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head-- ;
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AMD_DEBUG1 (("pop "ID" order "ID"\n", i, k)) ;
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Order [i] = k++ ;
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ASSERT (k <= nn) ;
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}
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#ifndef NDEBUG
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AMD_DEBUG1 (("\nStack:")) ;
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for (h = head ; h >= 0 ; h--)
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{
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Int j = Stack [h] ;
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AMD_DEBUG1 ((" "ID, j)) ;
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ASSERT (j >= 0 && j < nn) ;
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}
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AMD_DEBUG1 (("\n\n")) ;
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ASSERT (head < nn) ;
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#endif
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}
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return (k) ;
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}
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