Procedure to subset the given BDD by choosing the heavier branches. More...

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

Include dependency graph for cuddSubsetHB.c:

Data Structures
struct	NodeData
	Data structure to store the information on each node. More...

struct	SubsetInfo
	Miscellaneous info. More...

Macros
#define	DBL_MAX_EXP 1024

#define	DEFAULT_PAGE_SIZE 2048

#define	DEFAULT_NODE_DATA_PAGE_SIZE 1024

#define	INITIAL_PAGES 128

Typedefs
typedef struct NodeData	NodeData_t

typedef struct SubsetInfo	SubsetInfo_t

Functions
DdNode *	Cudd_SubsetHeavyBranch (DdManager dd, DdNode f, int numVars, int threshold)
	Extracts a dense subset from a BDD with the heavy branch heuristic. More...

DdNode *	Cudd_SupersetHeavyBranch (DdManager dd, DdNode f, int numVars, int threshold)
	Extracts a dense superset from a BDD with the heavy branch heuristic. More...

DdNode *	cuddSubsetHeavyBranch (DdManager dd, DdNode f, int numVars, int threshold)
	The main procedure that returns a subset by choosing the heavier branch in the BDD. More...

static void	ResizeNodeDataPages (SubsetInfo_t *info)
	Resize the number of pages allocated to store the node data. More...

static void	ResizeCountMintermPages (SubsetInfo_t *info)
	Resize the number of pages allocated to store the minterm counts. More...

static void	ResizeCountNodePages (SubsetInfo_t *info)
	Resize the number of pages allocated to store the node counts. More...

static double	SubsetCountMintermAux (DdNode node, double max, st_table table, SubsetInfo_t *info)
	Recursively counts minterms of each node in the DAG. More...

static st_table *	SubsetCountMinterm (DdNode node, int nvars, SubsetInfo_t info)
	Counts minterms of each node in the DAG. More...

static int	SubsetCountNodesAux (DdNode node, st_table table, double max, SubsetInfo_t *info)
	Recursively counts the number of nodes under the dag. Also counts the number of nodes under the lighter child of this node. More...

static int	SubsetCountNodes (DdNode node, st_table table, int nvars, SubsetInfo_t *info)
	Counts the nodes under the current node and its lighter child. More...

static void	StoreNodes (st_table storeTable, DdManager dd, DdNode *node)
	Procedure to recursively store nodes that are retained in the subset. More...

static DdNode *	BuildSubsetBdd (DdManager dd, DdNode node, int size, st_table visitedTable, int threshold, st_table storeTable, st_table approxTable, SubsetInfo_t *info)
	Builds the subset BDD using the heavy branch method. More...

Detailed Description

Procedure to subset the given BDD by choosing the heavier branches.

See also: cuddSubsetSP.c

Author: Kavita Ravi

Copyright

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Function Documentation

◆ BuildSubsetBdd()

static DdNode* BuildSubsetBdd	(	DdManager *	dd,
		DdNode *	node,
		int *	size,
		st_table *	visitedTable,
		int	threshold,
		st_table *	storeTable,
		st_table *	approxTable,
		SubsetInfo_t *	info
	)

static

Builds the subset BDD using the heavy branch method.

The procedure carries out the building of the subset BDD starting at the root. Using the three different counts labelling each node, the procedure chooses the heavier branch starting from the root and keeps track of the number of nodes it discards at each step, thus keeping count of the size of the subset BDD dynamically. Once the threshold is satisfied, the procedure then calls ITE to build the BDD.

Side effects None

Parameters

dd	DD manager
node	current node
size	current size of the subset
visitedTable	visited table storing all node data
threshold	subsetting threshold
storeTable	store table
approxTable	approximation table
info	miscellaneous info

◆ Cudd_SubsetHeavyBranch()

DdNode* Cudd_SubsetHeavyBranch	(	DdManager *	dd,
		DdNode *	f,
		int	numVars,
		int	threshold
	)

Extracts a dense subset from a BDD with the heavy branch heuristic.

This procedure builds a subset by throwing away one of the children of each node, starting from the root, until the result is small enough. The child that is eliminated from the result is the one that contributes the fewer minterms. The parameter numVars is the maximum number of variables to be used in minterm calculation and node count calculation. The optimal number should be as close as possible to the size of the support of f. However, it is safe to pass the value returned by Cudd_ReadSize for numVars when the number of variables is under 1023. If numVars is larger than 1023, it will overflow. If a 0 parameter is passed then the procedure will compute a value which will avoid overflow but will cause underflow with 2046 variables or more.

Returns: a pointer to the BDD of the subset if successful. NULL if the procedure runs out of memory.

Side effects None

See also: Cudd_SubsetShortPaths Cudd_SupersetHeavyBranch Cudd_ReadSize

Parameters

dd	manager
f	function to be subset
numVars	number of variables in the support of f
threshold	maximum number of nodes in the subset

◆ Cudd_SupersetHeavyBranch()

DdNode* Cudd_SupersetHeavyBranch	(	DdManager *	dd,
		DdNode *	f,
		int	numVars,
		int	threshold
	)

Extracts a dense superset from a BDD with the heavy branch heuristic.

The procedure is identical to the subset procedure except for the fact that it receives the complement of the given function. Extracting the subset of the complement function is equivalent to extracting the superset of the function. This procedure builds a superset by throwing away one of the children of each node starting from the root of the complement function, until the result is small enough. The child that is eliminated from the result is the one that contributes the fewer minterms. The parameter numVars is the maximum number of variables to be used in minterm calculation and node count calculation. The optimal number should be as close as possible to the size of the support of f. However, it is safe to pass the value returned by Cudd_ReadSize for numVars when the number of variables is under 1023. If numVars is larger than 1023, it will overflow. If a 0 parameter is passed then the procedure will compute a value which will avoid overflow but will cause underflow with 2046 variables or more.

Returns: a pointer to the BDD of the superset if successful. NULL if intermediate result causes the procedure to run out of memory.

Side effects None

See also: Cudd_SubsetHeavyBranch Cudd_SupersetShortPaths Cudd_ReadSize

Parameters

dd	manager
f	function to be superset
numVars	number of variables in the support of f
threshold	maximum number of nodes in the superset

◆ cuddSubsetHeavyBranch()

DdNode* cuddSubsetHeavyBranch	(	DdManager *	dd,
		DdNode *	f,
		int	numVars,
		int	threshold
	)

The main procedure that returns a subset by choosing the heavier branch in the BDD.

Here a subset BDD is built by throwing away one of the children. Starting at root, annotate each node with the number of minterms (in terms of the total number of variables specified - numVars), number of nodes taken by the DAG rooted at this node and number of additional nodes taken by the child that has the lesser minterms. The child with the lower number of minterms is thrown away and a dyanmic count of the nodes of the subset is kept. Once the threshold is reached the subset is returned to the calling procedure.

Side effects None

See also: Cudd_SubsetHeavyBranch

Parameters

dd	DD manager
f	current DD
numVars	maximum number of variables
threshold	threshold size for the subset

◆ ResizeCountMintermPages()

static void ResizeCountMintermPages ( SubsetInfo_t * info )

static

Resize the number of pages allocated to store the minterm counts.

The procedure moves the counter to the next page when the end of the page is reached and allocates new pages when necessary.

Side effects Changes the size of minterm pages, page, page index, maximum: number of pages freeing stuff in case of memory out.

◆ ResizeCountNodePages()

static void ResizeCountNodePages ( SubsetInfo_t * info )

static

Resize the number of pages allocated to store the node counts.

The procedure moves the counter to the next page when the end of the page is reached and allocates new pages when necessary.

Side effects Changes the size of pages, page, page index, maximum: number of pages freeing stuff in case of memory out.

◆ ResizeNodeDataPages()

static void ResizeNodeDataPages ( SubsetInfo_t * info )

static

Resize the number of pages allocated to store the node data.

The procedure moves the counter to the next page when the end of the page is reached and allocates new pages when necessary.

Side effects Changes the size of pages, page, page index, maximum: number of pages freeing stuff in case of memory out.

◆ StoreNodes()

static void StoreNodes	(	st_table *	storeTable,
		DdManager *	dd,
		DdNode *	node
	)

static

Procedure to recursively store nodes that are retained in the subset.

Side effects None

See also: StoreNodes

◆ SubsetCountMinterm()

static st_table* SubsetCountMinterm	(	DdNode *	node,
		int	nvars,
		SubsetInfo_t *	info
	)

static

Counts minterms of each node in the DAG.

Similar to the Cudd_CountMinterm procedure except this returns the minterm count for all the nodes in the bdd in an st_table.

Side effects none

See also: SubsetCountMintermAux

Parameters

node	function to be analyzed
nvars	number of variables node depends on
info	miscellaneous info

◆ SubsetCountMintermAux()

static double SubsetCountMintermAux	(	DdNode *	node,
		double	max,
		st_table *	table,
		SubsetInfo_t *	info
	)

static

Recursively counts minterms of each node in the DAG.

Similar to the cuddCountMintermAux which recursively counts the number of minterms for the dag rooted at each node in terms of the total number of variables (max). This procedure creates the node data structure and stores the minterm count as part of the node data structure.

Side effects Creates structures of type node quality and fills the st_table

See also: SubsetCountMinterm

Parameters

node	function to analyze
max	number of minterms of constant 1
table	visitedTable table
info	miscellaneous info

◆ SubsetCountNodes()

static int SubsetCountNodes	(	DdNode *	node,
		st_table *	table,
		int	nvars,
		SubsetInfo_t *	info
	)

static

Counts the nodes under the current node and its lighter child.

Calls a recursive procedure to count the number of nodes of a DAG rooted at a particular node and the number of nodes taken by its lighter child.

Side effects None

See also: SubsetCountNodesAux

Parameters

node	function to be analyzed
table	node quality table
nvars	number of variables node depends on
info	miscellaneous info

◆ SubsetCountNodesAux()

static int SubsetCountNodesAux	(	DdNode *	node,
		st_table *	table,
		double	max,
		SubsetInfo_t *	info
	)

static

Recursively counts the number of nodes under the dag. Also counts the number of nodes under the lighter child of this node.

Note that the same dag may be the lighter child of two different nodes and have different counts. As with the minterm counts, the node counts are stored in pages to be space efficient and the address for these node counts are stored in an st_table associated to each node.

Side effects Updates the node data table with node counts

See also: SubsetCountNodes

Parameters

node	current node
table	table to update node count, also serves as visited table.
max	maximum number of variables

Data Structures

Macros

Typedefs

Functions

Detailed Description

Function Documentation

◆ BuildSubsetBdd()

◆ Cudd_SubsetHeavyBranch()

◆ Cudd_SupersetHeavyBranch()

◆ cuddSubsetHeavyBranch()

◆ ResizeCountMintermPages()

◆ ResizeCountNodePages()

◆ ResizeNodeDataPages()

◆ StoreNodes()

◆ SubsetCountMinterm()

◆ SubsetCountMintermAux()

◆ SubsetCountNodes()

◆ SubsetCountNodesAux()