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bnd.hpp

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00001 /* -*- mode: C++; c-basic-offset: 2; indent-tabs-mode: nil -*- */
00002 /*
00003  *  Main authors:
00004  *     Christian Schulte <schulte@gecode.org>
00005  *
00006  *  Copyright:
00007  *     Christian Schulte, 2003
00008  *
00009  *  Last modified:
00010  *     $Date: 2011-10-09 15:06:06 +0200 (Sun, 09 Oct 2011) $ by $Author: schulte $
00011  *     $Revision: 12431 $
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 namespace Gecode { namespace Int { namespace Distinct {
00039 
00040   template<class View>
00041   forceinline
00042   Bnd<View>::Bnd(Home home, ViewArray<View>& x0)
00043     : Propagator(home), x(x0), y(home,x0) {
00044     // Both x and y initially contain the same variables
00045     //  - x is used for bounds propagation
00046     //  - y is used for performing singleton propagation
00047     // They can not be shared as singleton propagation removes
00048     // determined variables still required for bounds propagation.
00049     y.subscribe(home,*this,PC_INT_BND);
00050     int min = x[x.size()-1].min(), max = x[x.size()-1].max();
00051     for (int i=x.size()-1; i--; ) {
00052       min = std::min(min,x[i].min());
00053       max = std::max(max,x[i].max());
00054     }
00055     min_x = min; max_x = max;
00056   }
00057 
00058   template<class View>
00059   forceinline size_t
00060   Bnd<View>::dispose(Space& home) {
00061     y.cancel(home,*this,PC_INT_BND);
00062     (void) Propagator::dispose(home);
00063     return sizeof(*this);
00064   }
00065 
00066   template<class View>
00067   forceinline
00068   Bnd<View>::Bnd(Space& home, bool share, Bnd<View>& p)
00069     : Propagator(home,share,p), min_x(p.min_x), max_x(p.max_x) {
00070     x.update(home,share,p.x);
00071     y.update(home,share,p.y);
00072   }
00073 
00074   template<class View>
00075   Actor*
00076   Bnd<View>::copy(Space& home, bool share) {
00077     return new (home) Bnd<View>(home,share,*this);
00078   }
00079 
00080   template<class View>
00081   PropCost
00082   Bnd<View>::cost(const Space&, const ModEventDelta& med) const {
00083     if (View::me(med) == ME_INT_VAL)
00084       return PropCost::linear(PropCost::LO, y.size());
00085     else
00086       return PropCost::quadratic(PropCost::LO, x.size());
00087   }
00088 
00089 
00091   class Rank {
00092   public:
00093     int min, max;
00094   };
00095 
00097   template<class View>
00098   class MaxIncIdx {
00099   protected:
00100     ViewArray<View> x;
00101   public:
00102     forceinline
00103     MaxIncIdx(const ViewArray<View>& x0) : x(x0) {}
00104     forceinline bool
00105     operator ()(const int i, const int j) {
00106       return x[i].max() < x[j].max();
00107     }
00108   };
00109 
00111   template<class View>
00112   class MinIncIdx {
00113   protected:
00114     ViewArray<View> x;
00115   public:
00116     forceinline 
00117     MinIncIdx(const ViewArray<View>& x0) : x(x0) {}
00118     forceinline bool
00119     operator ()(const int i, const int j) {
00120       return x[i].min() < x[j].min();
00121     }
00122   };
00123 
00125   template<class View>
00126   class MinInc {
00127   public:
00128     forceinline bool
00129     operator ()(const View& x, const View& y) {
00130       return x.min() < y.min();
00131     }
00132   };
00133 
00135   class HallInfo {
00136   public:
00137     int bounds, t, d, h;
00138   };
00139 
00140   forceinline void
00141   pathset_t(HallInfo hall[], int start, int end, int to) {
00142     int k, l;
00143     for (l=start; (k=l) != end; hall[k].t=to) {
00144       l = hall[k].t;
00145     }
00146   }
00147 
00148   forceinline void
00149   pathset_h(HallInfo hall[], int start, int end, int to) {
00150     int k, l;
00151     for (l=start; (k=l) != end; hall[k].h=to) {
00152       l = hall[k].h;
00153     }
00154   }
00155 
00156   forceinline int
00157   pathmin_h(const HallInfo hall[], int i) {
00158     while (hall[i].h < i)
00159       i = hall[i].h;
00160     return i;
00161   }
00162 
00163   forceinline int
00164   pathmin_t(const HallInfo hall[], int i) {
00165     while (hall[i].t < i)
00166       i = hall[i].t;
00167     return i;
00168   }
00169 
00170   forceinline int
00171   pathmax_h(const HallInfo hall[], int i) {
00172     while (hall[i].h > i)
00173       i = hall[i].h;
00174     return i;
00175   }
00176 
00177   forceinline int
00178   pathmax_t(const HallInfo hall[], int i) {
00179     while (hall[i].t > i)
00180       i = hall[i].t;
00181     return i;
00182   }
00183 
00184   template<class View>
00185   ExecStatus
00186   prop_bnd(Space& home, ViewArray<View>& x, int& min_x, int& max_x) {
00187     const int n = x.size();
00188 
00189     Region r(home);
00190 
00191     int* minsorted = r.alloc<int>(n);
00192     int* maxsorted = r.alloc<int>(n);
00193 
00194     unsigned int d = static_cast<unsigned int>(max_x - min_x) + 1;
00195 
00196     if (d < static_cast<unsigned int>(n))
00197       return ES_FAILED;
00198 
00199     if (d > 2*static_cast<unsigned int>(n)) {
00200       for (int i = n; i--; )
00201         minsorted[i]=maxsorted[i]=i;
00202 
00203       MinIncIdx<View> min_inc(x);
00204       Support::quicksort<int,MinIncIdx<View> >(minsorted, n, min_inc);
00205       MaxIncIdx<View> max_inc(x);
00206       Support::quicksort<int,MaxIncIdx<View> >(maxsorted, n, max_inc);
00207     } else {
00208 
00209       int* minbucket = r.alloc<int>(d);
00210       int* maxbucket = r.alloc<int>(d);
00211       for (unsigned int i=d; i--; )
00212         minbucket[i]=maxbucket[i]=0;
00213 
00214       for (int i=n; i--; ) {
00215         minbucket[x[i].min() - min_x]++;
00216         maxbucket[x[i].max() - min_x]++;
00217       }
00218 
00219       int c_min = 0, c_max = 0;
00220       for (unsigned int i=0; i<d; i++) {
00221         int t_min = minbucket[i];
00222         int t_max = maxbucket[i];
00223         minbucket[i] = c_min; c_min += t_min;
00224         maxbucket[i] = c_max; c_max += t_max;
00225       }
00226       assert((c_min == n) && (c_max == n));
00227 
00228       for (int i=n; i--; ) {
00229         minsorted[minbucket[x[i].min() - min_x]++] = i;
00230         maxsorted[maxbucket[x[i].max() - min_x]++] = i;
00231       }
00232     }
00233 
00234     // Update minimum and maximum information
00235     min_x = x[minsorted[0]].min();
00236     max_x = x[maxsorted[n-1]].max();
00237 
00238 
00239     // Setup rank and bounds info
00240     HallInfo* hall = r.alloc<HallInfo>(2*n+2);
00241     Rank* rank = r.alloc<Rank>(n);
00242 
00243     int nb = 0;
00244     {
00245       int min  = x[minsorted[0]].min();
00246       int max  = x[maxsorted[0]].max() + 1;
00247       int last = min - 2;
00248 
00249       hall[0].bounds = last;
00250 
00251       int i = 0;
00252       int j = 0;
00253       while (true) {
00254         if ((i < n) && (min < max)) {
00255           if (min != last)
00256             hall[++nb].bounds = last = min;
00257           rank[minsorted[i]].min = nb;
00258           if (++i < n)
00259             min = x[minsorted[i]].min();
00260         } else {
00261           if (max != last)
00262             hall[++nb].bounds = last = max;
00263           rank[maxsorted[j]].max = nb;
00264           if (++j == n)
00265             break;
00266           max = x[maxsorted[j]].max() + 1;
00267         }
00268       }
00269       hall[nb+1].bounds = hall[nb].bounds + 2;
00270     }
00271 
00272     // If tells cross holes, we do not compute a fixpoint
00273     ExecStatus es = ES_FIX;
00274 
00275     // Propagate lower bounds
00276     for (int i=nb+2; --i;) {
00277       hall[i].t = hall[i].h = i-1;
00278       hall[i].d = hall[i].bounds - hall[i-1].bounds;
00279     }
00280     for (int i=0; i<n; i++) { // visit intervals in increasing max order
00281       int x0 = rank[maxsorted[i]].min;
00282       int z = pathmax_t(hall, x0+1);
00283       int j = hall[z].t;
00284       if (--hall[z].d == 0)
00285         hall[z = pathmax_t(hall, hall[z].t=z+1)].t = j;
00286       pathset_t(hall, x0+1, z, z); // path compression
00287       int y = rank[maxsorted[i]].max;
00288       if (hall[z].d < hall[z].bounds-hall[y].bounds)
00289         return ES_FAILED;
00290       if (hall[x0].h > x0) {
00291         int w = pathmax_h(hall, hall[x0].h);
00292         int m = hall[w].bounds;
00293         ModEvent me = x[maxsorted[i]].gq(home,m);
00294         if (me_failed(me))
00295           return ES_FAILED;
00296         if ((me == ME_INT_VAL) ||
00297             ((me == ME_INT_BND) && (m != x[maxsorted[i]].min())))
00298           es = ES_NOFIX;
00299         pathset_h(hall, x0, w, w); // path compression
00300       }
00301       if (hall[z].d == hall[z].bounds-hall[y].bounds) {
00302         pathset_h(hall, hall[y].h, j-1, y); // mark hall interval
00303         hall[y].h = j-1;
00304       }
00305     }
00306 
00307     // Propagate upper bounds
00308     for (int i=nb+1; i--;) {
00309       hall[i].t = hall[i].h = i+1;
00310       hall[i].d = hall[i+1].bounds - hall[i].bounds;
00311     }
00312     for (int i=n; --i>=0; ) { // visit intervals in decreasing min order
00313       int x0 = rank[minsorted[i]].max;
00314       int z = pathmin_t(hall, x0-1);
00315       int j = hall[z].t;
00316       if (--hall[z].d == 0)
00317         hall[z = pathmin_t(hall, hall[z].t=z-1)].t = j;
00318       pathset_t(hall, x0-1, z, z);
00319       int y = rank[minsorted[i]].min;
00320       if (hall[z].d < hall[y].bounds-hall[z].bounds)
00321         return ES_FAILED;
00322       if (hall[x0].h < x0) {
00323         int w = pathmin_h(hall, hall[x0].h);
00324         int m = hall[w].bounds - 1;
00325         ModEvent me = x[minsorted[i]].lq(home,m);
00326         if (me_failed(me))
00327           return ES_FAILED;
00328         if ((me == ME_INT_VAL) ||
00329             ((me == ME_INT_BND) && (m != x[maxsorted[i]].min())))
00330           es = ES_NOFIX;
00331         pathset_h(hall, x0, w, w);
00332       }
00333       if (hall[z].d == hall[y].bounds-hall[z].bounds) {
00334         pathset_h(hall, hall[y].h, j+1, y);
00335         hall[y].h = j+1;
00336       }
00337     }
00338 
00339     return es;
00340   }
00341 
00342   template<class View>
00343   ExecStatus
00344   prop_bnd(Space& home, ViewArray<View>& x) {
00345     int min = x[x.size()-1].min(), max = x[x.size()-1].max();
00346     for (int i=x.size()-1; i--; ) {
00347       min = std::min(min,x[i].min());
00348       max = std::max(max,x[i].max());
00349     }
00350     return prop_bnd(home, x, min, max);
00351   }
00352 
00353   template<class View>
00354   ExecStatus
00355   Bnd<View>::propagate(Space& home, const ModEventDelta& med) {
00356     assert(x.size() > 1);
00357 
00358     if (View::me(med) == ME_INT_VAL) {
00359       ExecStatus es = prop_val<View,false>(home,y);
00360       GECODE_ES_CHECK(es);
00361       if (y.size() < 2)
00362         return home.ES_SUBSUMED(*this);
00363       if (es == ES_FIX)
00364         return home.ES_FIX_PARTIAL(*this,View::med(ME_INT_BND));
00365     }
00366 
00367     if (y.size() == 2)
00368       GECODE_REWRITE(*this,Rel::Nq<View>::post(home(*this),y[0],y[1]));
00369 
00370     ExecStatus es = prop_bnd<View>(home,x,min_x,max_x);
00371 
00372     GECODE_ES_CHECK(es);
00373 
00374     const int n = x.size();
00375 
00376     if ((n > 2*y.size()) && (n > 6)) {
00377       // If there are many assigned views, try to eliminate them
00378       unsigned int d = static_cast<unsigned int>(max_x - min_x) + 1;
00379       if (d > 2*static_cast<unsigned int>(n)) {
00380         MinInc<View> min_inc;
00381         Support::quicksort<View,MinInc<View> >(&x[0], n, min_inc);
00382       } else {
00383         Region r(home);
00384         int* minbucket = r.alloc<int>(d);
00385         View* minsorted = r.alloc<View>(n);
00386 
00387         for (unsigned int i=d; i--; )
00388           minbucket[i]=0;
00389         for (int i=n; i--; )
00390           minbucket[x[i].min() - min_x]++;
00391 
00392         int c_min = 0;
00393         for (unsigned int i=0; i<d; i++) {
00394           int t_min = minbucket[i];
00395           minbucket[i] = c_min; c_min += t_min;
00396         }
00397         assert(c_min == n);
00398 
00399         for (int i=n; i--;)
00400           minsorted[minbucket[x[i].min() - min_x]++] = x[i];
00401         for (int i=n; i--;)
00402           x[i] = minsorted[i];
00403       }
00404 
00405       int i   = 0;
00406       int j   = 0;
00407       int max = x[0].max()-1;
00408       while (i < n-1) {
00409         if (!x[i].assigned() ||
00410             (x[i].val() <= max) || (x[i].val() > x[i+1].min())) {
00411           // Keep view x[i]
00412           max = std::max(max,x[i].max());
00413           x[j++]=x[i];
00414         }
00415         i++;
00416       }
00417       if (!x[i].assigned() || (x[i].val() <= max))
00418         x[j++]=x[i];
00419       x.size(j);
00420     }
00421 
00422     if (x.size() < 2)
00423       return home.ES_SUBSUMED(*this);
00424 
00425     if (x.size() == 2)
00426       GECODE_REWRITE(*this,Rel::Nq<View>::post(home(*this),x[0],x[1]));
00427 
00428     return es;
00429   }
00430 
00431   template<class View>
00432   ExecStatus
00433   Bnd<View>::post(Home home, ViewArray<View>& x){
00434     if (x.size() == 2)
00435       return Rel::Nq<View>::post(home,x[0],x[1]);
00436     if (x.size() > 2)
00437       (void) new (home) Bnd<View>(home,x);
00438     return ES_OK;
00439   }
00440 
00441 }}}
00442 
00443 // STATISTICS: int-prop
00444