src/bdd/cudd/cuddInteract.c File Reference

#include "util_hack.h"
#include "cuddInt.h"

Include dependency graph for cuddInteract.c:

Go to the source code of this file.

Defines
#define	BPL   32
#define	LOGBPL   5
Functions
static void ddSuppInteract	ARGS ((DdNode *f, int *support))
static void ddClearLocal	ARGS ((DdNode *f))
static void ddUpdateInteract	ARGS ((DdManager *table, int *support))
static void ddClearGlobal	ARGS ((DdManager *table))
void	cuddSetInteract (DdManager *table, int x, int y)
int	cuddTestInteract (DdManager *table, int x, int y)
int	cuddInitInteract (DdManager *table)
static void	ddSuppInteract (DdNode *f, int *support)
static void	ddClearLocal (DdNode *f)
static void	ddUpdateInteract (DdManager *table, int *support)
static void	ddClearGlobal (DdManager *table)
Variables
static char rcsid[]	DD_UNUSED = "$Id: cuddInteract.c,v 1.1.1.1 2003/02/24 22:23:52 wjiang Exp $"

---

Define Documentation

#define BPL   32

CFile***********************************************************************

FileName [cuddInteract.c]

PackageName [cudd]

Synopsis [Functions to manipulate the variable interaction matrix.]

Description [Internal procedures included in this file:

• cuddSetInteract()
• cuddTestInteract()
• cuddInitInteract()

Static procedures included in this file:

• ddSuppInteract()
• ddClearLocal()
• ddUpdateInteract()
• ddClearGlobal()

The interaction matrix tells whether two variables are both in the support of some function of the DD. The main use of the interaction matrix is in the in-place swapping. Indeed, if two variables do not interact, there is no arc connecting the two layers; therefore, the swap can be performed in constant time, without scanning the subtables. Another use of the interaction matrix is in the computation of the lower bounds for sifting. Finally, the interaction matrix can be used to speed up aggregation checks in symmetric and group sifting.

The computation of the interaction matrix is done with a series of depth-first searches. The searches start from those nodes that have only external references. The matrix is stored as a packed array of bits; since it is symmetric, only the upper triangle is kept in memory. As a final remark, we note that there may be variables that do intercat, but that for a given variable order have no arc connecting their layers when they are adjacent.]

SeeAlso []

Author [Fabio Somenzi]

Copyright [ This file was created at the University of Colorado at Boulder. The University of Colorado at Boulder makes no warranty about the suitability of this software for any purpose. It is presented on an AS IS basis.]

Definition at line 61 of file cuddInteract.c.

#define LOGBPL   5

Definition at line 62 of file cuddInteract.c.

---

Function Documentation

static void ddClearGlobal ARGS

(

(DdManager *table)

)

[static]

static void ddUpdateInteract ARGS

(

(DdManager *table, int *support)

)

[static]

static void ddClearLocal ARGS

(

(DdNode *f)

)

[static]

static void ddSuppInteract ARGS

(

(DdNode *f, int *support)

)

[static]

AutomaticStart

int cuddInitInteract

(

DdManager *

table

)

Function********************************************************************

Synopsis [Initializes the interaction matrix.]

Description [Initializes the interaction matrix. The interaction matrix is implemented as a bit vector storing the upper triangle of the symmetric interaction matrix. The bit vector is kept in an array of long integers. The computation is based on a series of depth-first searches, one for each root of the DAG. Two flags are needed: The local visited flag uses the LSB of the then pointer. The global visited flag uses the LSB of the next pointer. Returns 1 if successful; 0 otherwise.]

SideEffects [None]

SeeAlso []

Definition at line 206 of file cuddInteract.c.

{
    int i,j,k;
    int words;
    long *interact;
    int *support;
    DdNode *f;
    DdNode *sentinel = &(table->sentinel);
    DdNodePtr *nodelist;
    int slots;
    int n = table->size;

    words = ((n * (n-1)) >> (1 + LOGBPL)) + 1;
    table->interact = interact = ALLOC(long,words);
    if (interact == NULL) {
        table->errorCode = CUDD_MEMORY_OUT;
        return(0);
    }
    for (i = 0; i < words; i++) {
        interact[i] = 0;
    }

    support = ALLOC(int,n);
    if (support == NULL) {
        table->errorCode = CUDD_MEMORY_OUT;
        FREE(interact);
        return(0);
    }

    for (i = 0; i < n; i++) {
        nodelist = table->subtables[i].nodelist;
        slots = table->subtables[i].slots;
        for (j = 0; j < slots; j++) {
            f = nodelist[j];
            while (f != sentinel) {
                /* A node is a root of the DAG if it cannot be
                ** reached by nodes above it. If a node was never
                ** reached during the previous depth-first searches,
                ** then it is a root, and we start a new depth-first
                ** search from it.
                */
                if (!Cudd_IsComplement(f->next)) {
                    for (k = 0; k < n; k++) {
                        support[k] = 0;
                    }
                    ddSuppInteract(f,support);
                    ddClearLocal(f);
                    ddUpdateInteract(table,support);
                }
                f = Cudd_Regular(f->next);
            }
        }
    }
    ddClearGlobal(table);

    FREE(support);
    return(1);

} /* end of cuddInitInteract */

void cuddSetInteract	(	DdManager *	table,
		int	x,
		int	y
	)

AutomaticEnd Function********************************************************************

Synopsis [Set interaction matrix entries.]

Description [Given a pair of variables 0 <= x < y < table->size, sets the corresponding bit of the interaction matrix to 1.]

SideEffects [None]

SeeAlso []

Definition at line 125 of file cuddInteract.c.

{
    int posn, word, bit;

#ifdef DD_DEBUG
    assert(x < y);
    assert(y < table->size);
    assert(x >= 0);
#endif

    posn = ((((table->size << 1) - x - 3) * x) >> 1) + y - 1;
    word = posn >> LOGBPL;
    bit = posn & (BPL-1);
    table->interact[word] |= 1L << bit;

} /* end of cuddSetInteract */

int cuddTestInteract	(	DdManager *	table,
		int	x,
		int	y
	)

Function********************************************************************

Synopsis [Test interaction matrix entries.]

Description [Given a pair of variables 0 <= x < y < table->size, tests whether the corresponding bit of the interaction matrix is 1. Returns the value of the bit.]

SideEffects [None]

SeeAlso []

Definition at line 160 of file cuddInteract.c.

{
    int posn, word, bit, result;

    if (x > y) {
        int tmp = x;
        x = y;
        y = tmp;
    }
#ifdef DD_DEBUG
    assert(x < y);
    assert(y < table->size);
    assert(x >= 0);
#endif

    posn = ((((table->size << 1) - x - 3) * x) >> 1) + y - 1;
    word = posn >> LOGBPL;
    bit = posn & (BPL-1);
    result = (table->interact[word] >> bit) & 1L;
    return(result);

} /* end of cuddTestInteract */

static void ddClearGlobal

(

DdManager *

table

)

[static]

Function********************************************************************

Synopsis [Scans the DD and clears the LSB of the next pointers.]

Description [The LSB of the next pointers are used as markers to tell whether a node was reached by at least one DFS. Once the interaction matrix is built, these flags are reset.]

SideEffects [None]

SeeAlso []

Definition at line 380 of file cuddInteract.c.

{
    int i,j;
    DdNode *f;
    DdNode *sentinel = &(table->sentinel);
    DdNodePtr *nodelist;
    int slots;

    for (i = 0; i < table->size; i++) {
        nodelist = table->subtables[i].nodelist;
        slots = table->subtables[i].slots;
        for (j = 0; j < slots; j++) {
            f = nodelist[j];
            while (f != sentinel) {
                f->next = Cudd_Regular(f->next);
                f = f->next;
            }
        }
    }

} /* end of ddClearGlobal */

static void ddClearLocal

(

DdNode *

f

)

[static]

Function********************************************************************

Synopsis [Performs a DFS from f, clearing the LSB of the then pointers.]

Description []

SideEffects [None]

SeeAlso []

Definition at line 317 of file cuddInteract.c.

{
    if (cuddIsConstant(f) || !Cudd_IsComplement(cuddT(f))) {
        return;
    }
    /* clear visited flag */
    cuddT(f) = Cudd_Regular(cuddT(f));
    ddClearLocal(cuddT(f));
    ddClearLocal(Cudd_Regular(cuddE(f)));
    return;

} /* end of ddClearLocal */

static void ddSuppInteract	(	DdNode *	f,
		int *	support
	)			[static]

Function********************************************************************

Synopsis [Find the support of f.]

Description [Performs a DFS from f. Uses the LSB of the then pointer as visited flag.]

SideEffects [Accumulates in support the variables on which f depends.]

SeeAlso []

Definition at line 286 of file cuddInteract.c.

{
    if (cuddIsConstant(f) || Cudd_IsComplement(cuddT(f))) {
        return;
    }

    support[f->index] = 1;
    ddSuppInteract(cuddT(f),support);
    ddSuppInteract(Cudd_Regular(cuddE(f)),support);
    /* mark as visited */
    cuddT(f) = Cudd_Complement(cuddT(f));
    f->next = Cudd_Complement(f->next);
    return;

} /* end of ddSuppInteract */

static void ddUpdateInteract	(	DdManager *	table,
		int *	support
	)			[static]

Function********************************************************************

Synopsis [Marks as interacting all pairs of variables that appear in support.]

Description [If support[i] == support[j] == 1, sets the (i,j) entry of the interaction matrix to 1.]

SideEffects [None]

SeeAlso []

Definition at line 346 of file cuddInteract.c.

{
    int i,j;
    int n = table->size;

    for (i = 0; i < n-1; i++) {
        if (support[i] == 1) {
            for (j = i+1; j < n; j++) {
                if (support[j] == 1) {
                    cuddSetInteract(table,i,j);
                }
            }
        }
    }

} /* end of ddUpdateInteract */

---

Variable Documentation

char rcsid [] DD_UNUSED = "$Id: cuddInteract.c,v 1.1.1.1 2003/02/24 22:23:52 wjiang Exp $" [static]

Definition at line 80 of file cuddInteract.c.