Functions for ZDD group sifting. More...

#include "util.h"
#include "mtrInt.h"
#include "cuddInt.h"

Include dependency graph for cuddZddGroup.c:

Functions
MtrNode *	Cudd_MakeZddTreeNode (DdManager *dd, unsigned int low, unsigned int size, unsigned int type)
	Creates a new ZDD variable group. More...

int	cuddZddTreeSifting (DdManager *table, Cudd_ReorderingType method)
	Tree sifting algorithm for ZDDs. More...

static int	zddTreeSiftingAux (DdManager table, MtrNode treenode, Cudd_ReorderingType method)
	Visits the group tree and reorders each group. More...

static int	zddReorderChildren (DdManager table, MtrNode treenode, Cudd_ReorderingType method)
	Reorders the children of a group tree node according to the options. More...

static void	zddFindNodeHiLo (DdManager table, MtrNode treenode, int lower, int upper)
	Finds the lower and upper bounds of the group represented by treenode. More...

static int	zddUniqueCompareGroup (void const ptrX, void const ptrY)
	Comparison function used by qsort. More...

static int	zddGroupSifting (DdManager *table, int lower, int upper)
	Sifts from treenode->low to treenode->high. More...

static int	zddGroupSiftingAux (DdManager *table, int x, int xLow, int xHigh)
	Sifts one variable up and down until it has taken all positions. Checks for aggregation. More...

static int	zddGroupSiftingUp (DdManager table, int y, int xLow, Move *moves)
	Sifts up a variable until either it reaches position xLow or the size of the DD heap increases too much. More...

static int	zddGroupSiftingDown (DdManager table, int x, int xHigh, Move *moves)
	Sifts down a variable until it reaches position xHigh. More...

static int	zddGroupMove (DdManager table, int x, int y, Move *moves)
	Swaps two groups and records the move. More...

static int	zddGroupMoveBackward (DdManager *table, int x, int y)
	Undoes the swap two groups. More...

static int	zddGroupSiftingBackward (DdManager table, Move moves, int size)
	Determines the best position for a variables and returns it there. More...

static void	zddMergeGroups (DdManager table, MtrNode treenode, int low, int high)
	Merges groups in the DD table. More...

Detailed Description

Functions for ZDD group sifting.

Author: Fabio Somenzi

Copyright

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.

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Function Documentation

◆ Cudd_MakeZddTreeNode()

MtrNode* Cudd_MakeZddTreeNode	(	DdManager *	dd,
		unsigned int	low,
		unsigned int	size,
		unsigned int	type
	)

Creates a new ZDD variable group.

The group starts at variable and contains size variables. The parameter low is the index of the first variable. If the variable already exists, its current position in the order is known to the manager. If the variable does not exist yet, the position is assumed to be the same as the index. The group tree is created if it does not exist yet.

Returns: a pointer to the group if successful; NULL otherwise.

Side effects The ZDD variable tree is changed.

See also: Cudd_MakeTreeNode

Parameters

dd	manager
low	index of the first group variable
size	number of variables in the group
type	MTR_DEFAULT or MTR_FIXED

◆ cuddZddTreeSifting()

int cuddZddTreeSifting	(	DdManager *	table,
		Cudd_ReorderingType	method
	)

Tree sifting algorithm for ZDDs.

Assumes that a tree representing a group hierarchy is passed as a parameter. It then reorders each group in postorder fashion by calling zddTreeSiftingAux. Assumes that no dead nodes are present.

Returns: 1 if successful; 0 otherwise.

Side effects None

Parameters

table	DD table
method	reordering method for the groups of leaves

◆ zddFindNodeHiLo()

static void zddFindNodeHiLo	(	DdManager *	table,
		MtrNode *	treenode,
		int *	lower,
		int *	upper
	)

static

Finds the lower and upper bounds of the group represented by treenode.

The high and low fields of treenode are indices. From those we need to derive the current positions, and find maximum and minimum.

Side effects The bounds are returned as side effects.

◆ zddGroupMove()

static int zddGroupMove	(	DdManager *	table,
		int	x,
		int	y,
		Move **	moves
	)

static

Swaps two groups and records the move.

Returns: the number of keys in the DD table in case of success; 0 otherwise.

Side effects None

◆ zddGroupMoveBackward()

static int zddGroupMoveBackward	(	DdManager *	table,
		int	x,
		int	y
	)

static

Undoes the swap two groups.

Returns: 1 in case of success; 0 otherwise.

Side effects None

◆ zddGroupSifting()

static int zddGroupSifting	(	DdManager *	table,
		int	lower,
		int	upper
	)

static

Sifts from treenode->low to treenode->high.

If croupcheck == CUDD_GROUP_CHECK7, it checks for group creation at the end of the initial sifting. If a group is created, it is then sifted again. After sifting one variable, the group that contains it is dissolved.

Returns: 1 in case of success; 0 otherwise.

Side effects None

◆ zddGroupSiftingAux()

static int zddGroupSiftingAux	(	DdManager *	table,
		int	x,
		int	xLow,
		int	xHigh
	)

static

Sifts one variable up and down until it has taken all positions. Checks for aggregation.

There may be at most two sweeps, even if the group grows. Assumes that x is either an isolated variable, or it is the bottom of a group. All groups may not have been found. The variable being moved is returned to the best position seen during sifting.

Returns: 1 in case of success; 0 otherwise.

Side effects None

◆ zddGroupSiftingBackward()

static int zddGroupSiftingBackward	(	DdManager *	table,
		Move *	moves,
		int	size
	)

static

Determines the best position for a variables and returns it there.

Returns: 1 in case of success; 0 otherwise.

Side effects None

◆ zddGroupSiftingDown()

static int zddGroupSiftingDown	(	DdManager *	table,
		int	x,
		int	xHigh,
		Move **	moves
	)

static

Sifts down a variable until it reaches position xHigh.

Assumes that x is the bottom of a group (or a singleton). Records all the moves.

Returns: 1 in case of success; 0 otherwise.

Side effects None

◆ zddGroupSiftingUp()

static int zddGroupSiftingUp	(	DdManager *	table,
		int	y,
		int	xLow,
		Move **	moves
	)

static

Sifts up a variable until either it reaches position xLow or the size of the DD heap increases too much.

Assumes that y is the top of a group (or a singleton). Checks y for aggregation to the adjacent variables. Records all the moves that are appended to the list of moves received as input and returned as a side effect.

Returns: 1 in case of success; 0 otherwise.

Side effects None

◆ zddMergeGroups()

static void zddMergeGroups	(	DdManager *	table,
		MtrNode *	treenode,
		int	low,
		int	high
	)

static

Merges groups in the DD table.

Creates a single group from low to high and adjusts the idex field of the tree node.

Side effects None

◆ zddReorderChildren()

static int zddReorderChildren	(	DdManager *	table,
		MtrNode *	treenode,
		Cudd_ReorderingType	method
	)

static

Reorders the children of a group tree node according to the options.

After reordering puts all the variables in the group and/or its descendents in a single group. This allows hierarchical reordering. If the variables in the group do not exist yet, simply does nothing.

Returns: 1 if successful; 0 otherwise.

Side effects None

◆ zddTreeSiftingAux()

static int zddTreeSiftingAux	(	DdManager *	table,
		MtrNode *	treenode,
		Cudd_ReorderingType	method
	)

static

Visits the group tree and reorders each group.

Recursively visits the group tree and reorders each group in postorder fashion.

Returns: 1 if successful; 0 otherwise.

Side effects None

◆ zddUniqueCompareGroup()

static int zddUniqueCompareGroup	(	void const *	ptrX,
		void const *	ptrY
	)

static

Comparison function used by qsort.

Comparison function used by qsort to order the variables according to the number of keys in the subtables.

Returns: the difference in number of keys between the two variables being compared.

Side effects None