bab.hh
Go to the documentation of this file.
00001 /* -*- mode: C++; c-basic-offset: 2; indent-tabs-mode: nil -*- */ 00002 /* 00003 * Main authors: 00004 * Christian Schulte <schulte@gecode.org> 00005 * 00006 * Contributing authors: 00007 * Guido Tack <tack@gecode.org> 00008 * 00009 * Copyright: 00010 * Christian Schulte, 2004 00011 * Guido Tack, 2004 00012 * 00013 * Last modified: 00014 * $Date: 2009-08-26 21:10:00 +0200 (Wed, 26 Aug 2009) $ by $Author: schulte $ 00015 * $Revision: 9632 $ 00016 * 00017 * This file is part of Gecode, the generic constraint 00018 * development environment: 00019 * http://www.gecode.org 00020 * 00021 * Permission is hereby granted, free of charge, to any person obtaining 00022 * a copy of this software and associated documentation files (the 00023 * "Software"), to deal in the Software without restriction, including 00024 * without limitation the rights to use, copy, modify, merge, publish, 00025 * distribute, sublicense, and/or sell copies of the Software, and to 00026 * permit persons to whom the Software is furnished to do so, subject to 00027 * the following conditions: 00028 * 00029 * The above copyright notice and this permission notice shall be 00030 * included in all copies or substantial portions of the Software. 00031 * 00032 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 00033 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF 00034 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND 00035 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE 00036 * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION 00037 * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION 00038 * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. 00039 * 00040 */ 00041 00042 #ifndef __GECODE_SEARCH_SEQUENTIAL_BAB_HH__ 00043 #define __GECODE_SEARCH_SEQUENTIAL_BAB_HH__ 00044 00045 #include <gecode/search.hh> 00046 #include <gecode/search/support.hh> 00047 #include <gecode/search/worker.hh> 00048 #include <gecode/search/sequential/path.hh> 00049 00050 namespace Gecode { namespace Search { namespace Sequential { 00051 00053 class BAB : public Worker { 00054 private: 00056 Options opt; 00058 Path path; 00060 Space* cur; 00062 unsigned int d; 00064 int mark; 00066 Space* best; 00067 public: 00069 BAB(Space* s, size_t sz, const Options& o); 00071 Space* next(void); 00073 Statistics statistics(void) const; 00075 ~BAB(void); 00076 }; 00077 00078 forceinline 00079 BAB::BAB(Space* s, size_t sz, const Options& o) 00080 : Worker(sz), opt(o), d(0), mark(0), best(NULL) { 00081 cur = (s->status(*this) == SS_FAILED) ? NULL : snapshot(s,opt); 00082 current(s); 00083 current(NULL); 00084 current(cur); 00085 if (cur == NULL) 00086 fail++; 00087 } 00088 00089 forceinline Space* 00090 BAB::next(void) { 00091 /* 00092 * The invariant maintained by the engine is: 00093 * For all nodes stored at a depth less than mark, there 00094 * is no guarantee of betterness. For those above the mark, 00095 * betterness is guaranteed. 00096 * 00097 * The engine maintains the path on the stack for the current 00098 * node to be explored. 00099 * 00100 */ 00101 start(); 00102 while (true) { 00103 while (cur) { 00104 if (stop(opt,path.size())) 00105 return NULL; 00106 node++; 00107 switch (cur->status(*this)) { 00108 case SS_FAILED: 00109 fail++; 00110 delete cur; 00111 cur = NULL; 00112 Worker::current(NULL); 00113 break; 00114 case SS_SOLVED: 00115 // Deletes all pending branchers 00116 (void) cur->choice(); 00117 delete best; 00118 best = cur; 00119 cur = NULL; 00120 mark = path.entries(); 00121 Worker::current(NULL); 00122 return best->clone(); 00123 case SS_BRANCH: 00124 { 00125 Space* c; 00126 if ((d == 0) || (d >= opt.c_d)) { 00127 c = cur->clone(); 00128 d = 1; 00129 } else { 00130 c = NULL; 00131 d++; 00132 } 00133 const Choice* ch = path.push(*this,cur,c); 00134 Worker::push(c,ch); 00135 cur->commit(*ch,0); 00136 break; 00137 } 00138 default: 00139 GECODE_NEVER; 00140 } 00141 } 00142 // Recompute and add constraint if necessary 00143 do { 00144 if (!path.next(*this)) 00145 return NULL; 00146 cur = path.recompute(d,opt.a_d,*this,best,mark); 00147 } while (cur == NULL); 00148 Worker::current(cur); 00149 } 00150 GECODE_NEVER; 00151 return NULL; 00152 } 00153 00154 forceinline Statistics 00155 BAB::statistics(void) const { 00156 Statistics s = *this; 00157 s.memory += path.size(); 00158 return s; 00159 } 00160 00161 forceinline 00162 BAB::~BAB(void) { 00163 path.reset(); 00164 delete best; 00165 delete cur; 00166 } 00167 00168 }}} 00169 00170 #endif 00171 00172 // STATISTICS: search-sequential