distr/cudd/cuddLiteral.c

   1 /**CFile***********************************************************************
   2
   3   FileName    [cuddLiteral.c]
   4
   5   PackageName [cudd]
   6
   7   Synopsis    [Functions for manipulation of literal sets represented by
   8   BDDs.]
   9
  10   Description [External procedures included in this file:
  11                 <ul>
  12                 <li> Cudd_bddLiteralSetIntersection()
  13                 </ul>
  14             Internal procedures included in this file:
  15                 <ul>
  16                 <li> cuddBddLiteralSetIntersectionRecur()
  17                 </ul>]
  18
  19   Author      [Fabio Somenzi]
  20
  21   Copyright   [Copyright (c) 1995-2004, Regents of the University of Colorado
  22
  23   All rights reserved.
  24
  25   Redistribution and use in source and binary forms, with or without
  26   modification, are permitted provided that the following conditions
  27   are met:
  28
  29   Redistributions of source code must retain the above copyright
  30   notice, this list of conditions and the following disclaimer.
  31
  32   Redistributions in binary form must reproduce the above copyright
  33   notice, this list of conditions and the following disclaimer in the
  34   documentation and/or other materials provided with the distribution.
  35
  36   Neither the name of the University of Colorado nor the names of its
  37   contributors may be used to endorse or promote products derived from
  38   this software without specific prior written permission.
  39
  40   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  41   "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  42   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  43   FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
  44   COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  45   INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
  46   BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  47   LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  48   CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  49   LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
  50   ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  51   POSSIBILITY OF SUCH DAMAGE.]
  52
  53 ******************************************************************************/
  54
  55 #include "util.h"
  56 #include "cuddInt.h"
  57
  58
  59 /*---------------------------------------------------------------------------*/
  60 /* Constant declarations                                                     */
  61 /*---------------------------------------------------------------------------*/
  62
  63 /*---------------------------------------------------------------------------*/
  64 /* Stucture declarations                                                     */
  65 /*---------------------------------------------------------------------------*/
  66
  67 /*---------------------------------------------------------------------------*/
  68 /* Type declarations                                                         */
  69 /*---------------------------------------------------------------------------*/
  70
  71 /*---------------------------------------------------------------------------*/
  72 /* Variable declarations                                                     */
  73 /*---------------------------------------------------------------------------*/
  74
  75 #ifndef lint
  76 static char rcsid[] DD_UNUSED = "$Id: cuddLiteral.c,v 1.8 2004/08/13 18:04:50 fabio Exp $";
  77 #endif
  78
  79 /*---------------------------------------------------------------------------*/
  80 /* Macro declarations                                                        */
  81 /*---------------------------------------------------------------------------*/
  82
  83 /**AutomaticStart*************************************************************/
  84
  85 /*---------------------------------------------------------------------------*/
  86 /* Static function prototypes                                                */
  87 /*---------------------------------------------------------------------------*/
  88
  89
  90 /**AutomaticEnd***************************************************************/
  91
  92
  93 /*---------------------------------------------------------------------------*/
  94 /* Definition of exported functions                                          */
  95 /*---------------------------------------------------------------------------*/
  96
  97
  98 /**Function********************************************************************
  99
 100   Synopsis    [Computes the intesection of two sets of literals
 101   represented as BDDs.]
 102
 103   Description [Computes the intesection of two sets of literals
 104   represented as BDDs. Each set is represented as a cube of the
 105   literals in the set. The empty set is represented by the constant 1.
 106   No variable can be simultaneously present in both phases in a set.
 107   Returns a pointer to the BDD representing the intersected sets, if
 108   successful; NULL otherwise.]
 109
 110   SideEffects [None]
 111
 112 ******************************************************************************/
 113 DdNode *
 114 Cudd_bddLiteralSetIntersection(
 115   DdManager * dd,
 116   DdNode * f,
 117   DdNode * g)
 118 {
 119     DdNode *res;
 120
 121     do {
 122         dd->reordered = 0;
 123         res = cuddBddLiteralSetIntersectionRecur(dd,f,g);
 124     } while (dd->reordered == 1);
 125     return(res);
 126
 127 } /* end of Cudd_bddLiteralSetIntersection */
 128
 129
 130 /*---------------------------------------------------------------------------*/
 131 /* Definition of internal functions                                          */
 132 /*---------------------------------------------------------------------------*/
 133
 134
 135 /**Function********************************************************************
 136
 137   Synopsis    [Performs the recursive step of
 138   Cudd_bddLiteralSetIntersection.]
 139
 140   Description [Performs the recursive step of
 141   Cudd_bddLiteralSetIntersection. Scans the cubes for common variables,
 142   and checks whether they agree in phase.  Returns a pointer to the
 143   resulting cube if successful; NULL otherwise.]
 144
 145   SideEffects [None]
 146
 147 ******************************************************************************/
 148 DdNode *
 149 cuddBddLiteralSetIntersectionRecur(
 150   DdManager * dd,
 151   DdNode * f,
 152   DdNode * g)
 153 {
 154     DdNode *res, *tmp;
 155     DdNode *F, *G;
 156     DdNode *fc, *gc;
 157     DdNode *one;
 158     DdNode *zero;
 159     unsigned int topf, topg, comple;
 160     int phasef, phaseg;
 161
 162     statLine(dd);
 163     if (f == g) return(f);
 164
 165     F = Cudd_Regular(f);
 166     G = Cudd_Regular(g);
 167     one = DD_ONE(dd);
 168
 169     /* Here f != g. If F == G, then f and g are complementary.
 170     ** Since they are two cubes, this case only occurs when f == v,
 171     ** g == v', and v is a variable or its complement.
 172     */
 173     if (F == G) return(one);
 174
 175     zero = Cudd_Not(one);
 176     topf = cuddI(dd,F->index);
 177     topg = cuddI(dd,G->index);
 178     /* Look for a variable common to both cubes. If there are none, this
 179     ** loop will stop when the constant node is reached in both cubes.
 180     */
 181     while (topf != topg) {
 182         if (topf < topg) {      /* move down on f */
 183             comple = f != F;
 184             f = cuddT(F);
 185             if (comple) f = Cudd_Not(f);
 186             if (f == zero) {
 187                 f = cuddE(F);
 188                 if (comple) f = Cudd_Not(f);
 189             }
 190             F = Cudd_Regular(f);
 191             topf = cuddI(dd,F->index);
 192         } else if (topg < topf) {
 193             comple = g != G;
 194             g = cuddT(G);
 195             if (comple) g = Cudd_Not(g);
 196             if (g == zero) {
 197                 g = cuddE(G);
 198                 if (comple) g = Cudd_Not(g);
 199             }
 200             G = Cudd_Regular(g);
 201             topg = cuddI(dd,G->index);
 202         }
 203     }
 204
 205     /* At this point, f == one <=> g == 1. It suffices to test one of them. */
 206     if (f == one) return(one);
 207
 208     res = cuddCacheLookup2(dd,Cudd_bddLiteralSetIntersection,f,g);
 209     if (res != NULL) {
 210         return(res);
 211     }
 212
 213     /* Here f and g are both non constant and have the same top variable. */
 214     comple = f != F;
 215     fc = cuddT(F);
 216     phasef = 1;
 217     if (comple) fc = Cudd_Not(fc);
 218     if (fc == zero) {
 219         fc = cuddE(F);
 220         phasef = 0;
 221         if (comple) fc = Cudd_Not(fc);
 222     }
 223     comple = g != G;
 224     gc = cuddT(G);
 225     phaseg = 1;
 226     if (comple) gc = Cudd_Not(gc);
 227     if (gc == zero) {
 228         gc = cuddE(G);
 229         phaseg = 0;
 230         if (comple) gc = Cudd_Not(gc);
 231     }
 232
 233     tmp = cuddBddLiteralSetIntersectionRecur(dd,fc,gc);
 234     if (tmp == NULL) {
 235         return(NULL);
 236     }
 237
 238     if (phasef != phaseg) {
 239         res = tmp;
 240     } else {
 241         cuddRef(tmp);
 242         if (phasef == 0) {
 243             res = cuddBddAndRecur(dd,Cudd_Not(dd->vars[F->index]),tmp);
 244         } else {
 245             res = cuddBddAndRecur(dd,dd->vars[F->index],tmp);
 246         }
 247         if (res == NULL) {
 248             Cudd_RecursiveDeref(dd,tmp);
 249             return(NULL);
 250         }
 251         cuddDeref(tmp); /* Just cuddDeref, because it is included in result */
 252     }
 253
 254     cuddCacheInsert2(dd,Cudd_bddLiteralSetIntersection,f,g,res);
 255
 256     return(res);
 257
 258 } /* end of cuddBddLiteralSetIntersectionRecur */
 259
 260
 261 /*---------------------------------------------------------------------------*/
 262 /* Definition of static functions                                            */
 263 /*---------------------------------------------------------------------------*/
 264