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spacenode.cpp

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00001 /* -*- mode: C++; c-basic-offset: 2; indent-tabs-mode: nil -*- */
00002 /*
00003  *  Main authors:
00004  *     Guido Tack <tack@gecode.org>
00005  *
00006  *  Copyright:
00007  *     Guido Tack, 2006
00008  *
00009  *  Last modified:
00010  *     $Date: 2009-09-29 12:49:42 +0200 (Tue, 29 Sep 2009) $ by $Author: tack $
00011  *     $Revision: 9766 $
00012  *
00013  *  This file is part of Gecode, the generic constraint
00014  *  development environment:
00015  *     http://www.gecode.org
00016  *
00017  * Permission is hereby granted, free of charge, to any person obtaining
00018  * a copy of this software and associated documentation files (the
00019  * "Software"), to deal in the Software without restriction, including
00020  * without limitation the rights to use, copy, modify, merge, publish,
00021  * distribute, sublicense, and/or sell copies of the Software, and to
00022  * permit persons to whom the Software is furnished to do so, subject to
00023  * the following conditions:
00024  *
00025  * The above copyright notice and this permission notice shall be
00026  * included in all copies or substantial portions of the Software.
00027  *
00028  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
00029  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
00030  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
00031  * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
00032  * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
00033  * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
00034  * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
00035  *
00036  */
00037 
00038 #include <gecode/gist/spacenode.hh>
00039 #include <gecode/gist/visualnode.hh>
00040 #include <gecode/search.hh>
00041 #include <stack>
00042 
00043 namespace Gecode { namespace Gist {
00044 
00045   // TODO nikopp: doxygen comments
00046   enum BranchKind {
00047     BK_NORMAL, BK_SPECIAL_IN, BK_SPECIAL_OUT, BK_STEP
00048   };
00049 
00051   class Branch {
00052   public:
00054     int alternative;
00056     SpaceNode* ownBest;
00057     const BranchKind branchKind;
00058     union {
00060       const SpecialDesc* special;
00062       const Choice* branch;
00064       const StepDesc* step;
00065     } desc;
00066 
00068     Branch(int a, const Choice* c, 
00069            SpaceNode* best = NULL, BranchKind bk = BK_NORMAL)
00070       : alternative(a), ownBest(best), branchKind(bk) {
00071         desc.branch = c;
00072       }
00073     Branch(int a, const SpecialDesc* d, BranchKind bk, SpaceNode* best = NULL)
00074       : alternative(a), ownBest(best), branchKind(bk) {
00075         desc.special = d;
00076       }
00077     Branch(int a, const StepDesc* d, BranchKind bk, SpaceNode* best = NULL)
00078       : alternative(a), ownBest(best), branchKind(bk) {
00079         desc.step = d;
00080       }
00081   };
00082 
00083   StepDesc::StepDesc(int steps) : noOfSteps(steps), debug(false) { }
00084 
00085   void
00086   StepDesc::toggleDebug(void) {
00087    debug = !debug;
00088   }
00089 
00090   SpecialDesc::SpecialDesc(std::string varName, int rel0, int v0)
00091   : vn(varName), v(v0), rel(rel0) { }
00092 
00093   BestNode::BestNode(SpaceNode* s0) : s(s0) {}
00094 
00095   int
00096   SpaceNode::recompute(BestNode* curBest, int c_d, int a_d) {
00097     int rdist = 0;
00098 
00099     if (workingSpace == NULL) {
00100       SpaceNode* curNode = this;
00101       SpaceNode* lastFixpoint = NULL;
00102 
00103       if(curNode->getStatus() != SPECIAL && curNode->getStatus() != STEP) {
00104         lastFixpoint = curNode;
00105       }
00106 
00107       std::stack<Branch> stck;
00108       bool specialNodeOnPath = false;
00109 
00110       while (curNode->copy == NULL) {
00111         SpaceNode* parent = curNode->getParent();
00112         int alternative = curNode->getAlternative();
00113 
00114         if (curNode->getStatus() == STEP) {
00115           Branch b(alternative, curNode->desc.step, BK_STEP);
00116           stck.push(b);
00117           if (lastFixpoint == NULL && parent->getStatus() == BRANCH) {
00118              lastFixpoint = parent;
00119           }
00120       } else if (curNode->getStatus() == SPECIAL) {
00121           Branch b(alternative, curNode->desc.special, BK_SPECIAL_IN);
00122           stck.push(b);
00123           if(lastFixpoint == NULL && parent->getStatus() == BRANCH) {
00124             lastFixpoint = parent;
00125           }
00126           specialNodeOnPath = true;
00127           // TODO nikopp: if the root node is failed, it neither has a copy nor a parent and we are not allowed to do the following
00128         } else if (parent->getStatus() == SPECIAL || parent->getStatus() == STEP) {
00129            Branch b(alternative, curNode->desc.special, BK_SPECIAL_OUT);
00130           stck.push(b);
00131         } else {
00132           Branch b(alternative, parent->desc.branch,
00133                    curBest == NULL ? NULL : curNode->ownBest);
00134           stck.push(b);
00135         }
00136 
00137         curNode = parent;
00138         rdist++;
00139       }
00140       Space* curSpace = curNode->copy->clone();
00141       curNode->setDistance(0);
00142 
00143       SpaceNode* lastBest = NULL;
00144       SpaceNode* middleNode = curNode;
00145       int curDist = 0;
00146 
00147       while (!stck.empty()) {
00148         if (a_d >= 0 &&
00149             curDist > a_d &&
00150             middleNode->getStatus() != SPECIAL &&
00151             middleNode->getStatus() != STEP &&
00152             curDist == rdist / 2) {
00153             if (curSpace->status() == SS_FAILED) {
00154               workingSpace = curSpace;
00155               return rdist;
00156             } else {
00157               middleNode->copy = curSpace->clone();
00158             }
00159         }
00160         Branch b = stck.top(); stck.pop();
00161 
00162         if(middleNode == lastFixpoint) {
00163           curSpace->status();
00164         }
00165 
00166         switch (b.branchKind) {
00167         case BK_NORMAL:
00168             {
00169               curSpace->commit(*b.desc.branch, b.alternative);
00170             }
00171             break;
00172         case BK_STEP:
00173             {
00174             }
00175             break;
00176         case BK_SPECIAL_IN:
00177             {
00178             }
00179             break;
00180         case BK_SPECIAL_OUT:
00181          // really do nothing
00182           break;
00183         }
00184 
00185         if (b.ownBest != NULL && b.ownBest != lastBest) {
00186           b.ownBest->acquireSpace(curBest, c_d, a_d);
00187           if (b.ownBest->workingSpace->status() != SS_SOLVED) {
00188             // in the presence of weakly monotonic propagators, we may have to
00189             // use search to find the solution here
00190             Space* dfsSpace = Gecode::dfs(b.ownBest->workingSpace);
00191             delete b.ownBest->workingSpace;
00192             b.ownBest->workingSpace = dfsSpace;
00193           }
00194           curSpace->constrain(*b.ownBest->workingSpace);
00195           lastBest = b.ownBest;
00196         }
00197         curDist++;
00198         middleNode = middleNode->getChild(b.alternative);
00199         middleNode->setDistance(curDist);
00200       }
00201       workingSpace = curSpace;
00202 
00203     }
00204     return rdist;
00205   }
00206 
00207   void
00208   SpaceNode::acquireSpace(BestNode* curBest, int c_d, int a_d) {
00209     SpaceNode* p = getParent();
00210 
00211     if (getStatus() == UNDETERMINED && curBest != NULL && ownBest == NULL &&
00212         p != NULL && curBest->s != p->ownBest) {
00213           ownBest = curBest->s;
00214     }
00215 
00216     if (getStatus() != SPECIAL && getStatus() != STEP) {
00217       if (workingSpace == NULL && p != NULL && p->workingSpace != NULL) {
00218         // If parent has a working space, steal it
00219         workingSpace = p->workingSpace;
00220         p->workingSpace = NULL;
00221         if (p->desc.branch != NULL)
00222           workingSpace->commit(*p->desc.branch, getAlternative());
00223 
00224         if (ownBest != NULL) {
00225           ownBest->acquireSpace(curBest, c_d, a_d);
00226           if (ownBest->workingSpace->status() != SS_SOLVED) {
00227             // in the presence of weakly monotonic propagators, we may have to
00228             // use search to find the solution here
00229             Space* dfsSpace = Gecode::dfs(ownBest->workingSpace);
00230             delete ownBest->workingSpace;
00231             ownBest->workingSpace = dfsSpace;
00232           }
00233           workingSpace->constrain(*ownBest->workingSpace);
00234         }
00235         int d = p->getDistance()+1;
00236         if (d > c_d && c_d >= 0 &&
00237             getStatus() != SPECIAL && getStatus() != STEP &&
00238             workingSpace->status() == SS_BRANCH) {
00239           copy = workingSpace->clone();
00240           d = 0;
00241         }
00242         setDistance(d);
00243       }
00244     }
00245 
00246     if (workingSpace == NULL) {
00247       if (recompute(curBest, c_d, a_d) > c_d && c_d >= 0 &&
00248           getStatus() != SPECIAL && getStatus() != STEP &&
00249           workingSpace->status() == SS_BRANCH) {
00250             copy = workingSpace->clone();
00251             setDistance(0);
00252       }
00253     }
00254 
00255     if (getStatus() != SPECIAL && getStatus() != STEP) {
00256       // always return a fixpoint
00257       workingSpace->status();
00258       if (copy == NULL && p != NULL && isOpen() &&
00259           p->copy != NULL && p->getNoOfOpenChildren() == 1 &&
00260           p->getParent() != NULL) {
00261         // last alternative optimization
00262         copy = p->copy;
00263         p->copy = NULL;
00264         setDistance(0);
00265         p->setDistance(p->getParent()->getDistance()+1);
00266         
00267         if(p->desc.branch != NULL)
00268           copy->commit(*p->desc.branch, getAlternative());
00269 
00270         if (ownBest != NULL) {
00271           ownBest->acquireSpace(curBest, c_d, a_d);
00272           if (ownBest->workingSpace->status() != SS_SOLVED) {
00273             // in the presence of weakly monotonic propagators, we may have to
00274             // use search to find the solution here
00275             Space* dfsSpace = Gecode::dfs(ownBest->workingSpace);
00276             delete ownBest->workingSpace;
00277             ownBest->workingSpace = dfsSpace;
00278           }
00279           copy->constrain(*ownBest->workingSpace);
00280         }
00281         if (copy->status() == SS_FAILED) {
00282           delete copy;
00283           copy = NULL;
00284         }
00285       }
00286     }
00287   }
00288 
00289   void
00290   SpaceNode::closeChild(bool hadFailures, bool hadSolutions) {
00291     setHasFailedChildren(hasFailedChildren() || hadFailures);
00292     setHasSolvedChildren(hasSolvedChildren() || hadSolutions);
00293 
00294     bool allClosed = true;
00295     for (int i=getNumberOfChildren(); i--;) {
00296       if (static_cast<SpaceNode*>(getChild(i))->isOpen()) {
00297         allClosed = false;
00298         break;
00299       }
00300     }
00301 
00302     if (allClosed) {
00303       setHasOpenChildren(false);
00304       for (unsigned int i=0; i<getNumberOfChildren(); i++)
00305         setHasSolvedChildren(hasSolvedChildren() ||
00306           static_cast<SpaceNode*>(getChild(i))->hasSolvedChildren());
00307       SpaceNode* p = static_cast<SpaceNode*>(getParent());
00308       if (p != NULL) {
00309         delete copy;
00310         copy = NULL;
00311         p->closeChild(hasFailedChildren(), hasSolvedChildren());
00312       }
00313     } else {
00314       
00315       if (hadSolutions) {
00316         setHasSolvedChildren(true);
00317         SpaceNode* p = getParent();
00318         while (p != NULL && !p->hasSolvedChildren()) {
00319           p->setHasSolvedChildren(true);
00320           p = p->getParent();
00321         }
00322       }
00323       if (hadFailures) {
00324         SpaceNode* p = getParent();
00325         while (p != NULL && !p->hasFailedChildren()) {
00326           p->setHasFailedChildren(true);
00327           p = p->getParent();
00328         }        
00329       }
00330     }
00331 
00332   }
00333 
00334   SpaceNode::SpaceNode(Space* root)
00335   : workingSpace(root), ownBest(NULL), nstatus(0) {
00336     desc.branch = NULL;
00337     if (root == NULL) {
00338       setStatus(FAILED);
00339       setHasSolvedChildren(false);
00340       setHasFailedChildren(true);
00341       setNumberOfChildren(0);
00342       copy = root;
00343       return;
00344     }
00345     if (!root->failed())
00346       copy = root->clone();
00347     else
00348       copy = root;
00349     setStatus(UNDETERMINED);
00350     setHasSolvedChildren(false);
00351     setHasFailedChildren(false);
00352   }
00353 
00354   SpaceNode::~SpaceNode(void) {
00355     if(getStatus() == SPECIAL)
00356       delete desc.special;
00357     else if (getStatus() == STEP)
00358       delete desc.step;
00359     else
00360       delete desc.branch;
00361     delete copy;
00362     delete workingSpace;
00363   }
00364 
00365 
00366   int
00367   SpaceNode::getNumberOfChildNodes(NodeAllocator& na,
00368                                    BestNode* curBest, Statistics& stats,
00369                                    int c_d, int a_d) {
00370     int kids = 0;
00371     if (isUndetermined()) {
00372       stats.undetermined--;
00373       acquireSpace(curBest, c_d, a_d);
00374       switch (workingSpace->status(stats)) {
00375       case SS_FAILED:
00376         {
00377           purge();
00378           kids = 0;
00379           setHasOpenChildren(false);
00380           setHasSolvedChildren(false);
00381           setHasFailedChildren(true);
00382           setStatus(FAILED);
00383           stats.failures++;
00384           // stats.newDepth(getDepth());
00385           SpaceNode* p = getParent();
00386           if (p != NULL)
00387             p->closeChild(true, false);
00388         }
00389         break;
00390       case SS_SOLVED:
00391         {
00392           // Deletes all pending branchers
00393           (void) workingSpace->choice();
00394           kids = 0;
00395           setStatus(SOLVED);
00396           setHasOpenChildren(false);
00397           setHasSolvedChildren(true);
00398           setHasFailedChildren(false);
00399           stats.solutions++;
00400           if (curBest != NULL) {
00401             curBest->s = this;
00402           }
00403           SpaceNode* p = getParent();
00404           if (p != NULL)
00405             p->closeChild(false, true);
00406         }
00407         break;
00408       case SS_BRANCH:
00409         desc.branch = workingSpace->choice();
00410         kids = desc.branch->alternatives();
00411         setHasOpenChildren(true);
00412         setStatus(BRANCH);
00413         stats.choices++;
00414         stats.undetermined += kids;
00415         break;
00416       }
00417       static_cast<VisualNode*>(this)->changedStatus();
00418       setNumberOfChildren(kids);
00419       for (int i=kids; i--;) {
00420         setChild(i, new (na) VisualNode());
00421       }
00422     } else {
00423       kids = getNumberOfChildren();
00424     }
00425     return kids;
00426   }
00427 
00428   int
00429   SpaceNode::getNoOfOpenChildren(void) {
00430     if (!hasOpenChildren())
00431       return 0;
00432     int noOfOpenChildren = 0;
00433     for (int i=getNumberOfChildren(); i--;)
00434       noOfOpenChildren += (static_cast<SpaceNode*>(getChild(i))->isOpen());
00435     return noOfOpenChildren;
00436   }
00437 
00438 }}
00439 
00440 // STATISTICS: gist-any