bab.cpp
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 * Copyright: 00007 * Christian Schulte, 2009 00008 * 00009 * Last modified: 00010 * $Date: 2015-01-08 15:07:24 +0100 (Thu, 08 Jan 2015) $ by $Author: schulte $ 00011 * $Revision: 14341 $ 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/support.hh> 00039 00040 #ifdef GECODE_HAS_THREADS 00041 00042 #include <gecode/search/parallel/bab.hh> 00043 00044 namespace Gecode { namespace Search { namespace Parallel { 00045 00046 /* 00047 * Statistics 00048 */ 00049 Statistics 00050 BAB::statistics(void) const { 00051 Statistics s; 00052 for (unsigned int i=0; i<workers(); i++) 00053 s += worker(i)->statistics(); 00054 return s; 00055 } 00056 00057 /* 00058 * Actual work 00059 */ 00060 void 00061 BAB::Worker::run(void) { 00062 /* 00063 * The engine maintains the following invariant: 00064 * - If the current space (cur) is not NULL, the path always points 00065 * to exactly that space. 00066 * - If the current space (cur) is NULL, the path always points 00067 * to the next space (if there is any). 00068 * 00069 * This invariant is needed so that no-goods can be extracted properly 00070 * when the engine is stopped or has found a solution. 00071 * 00072 * An additional invariant maintained by the engine is: 00073 * For all nodes stored at a depth less than mark, there 00074 * is no guarantee of betterness. For those above the mark, 00075 * betterness is guaranteed. 00076 * 00077 */ 00078 // Peform initial delay, if not first worker 00079 if (this != engine().worker(0)) 00080 Support::Thread::sleep(Config::initial_delay); 00081 // Okay, we are in business, start working 00082 while (true) { 00083 switch (engine().cmd()) { 00084 case C_WAIT: 00085 // Wait 00086 engine().wait(); 00087 break; 00088 case C_TERMINATE: 00089 // Acknowledge termination request 00090 engine().ack_terminate(); 00091 // Wait until termination can proceed 00092 engine().wait_terminate(); 00093 // Terminate thread 00094 engine().terminated(); 00095 return; 00096 case C_RESET: 00097 // Acknowledge reset request 00098 engine().ack_reset_start(); 00099 // Wait until reset has been performed 00100 engine().wait_reset(); 00101 // Acknowledge that reset cycle is over 00102 engine().ack_reset_stop(); 00103 break; 00104 case C_WORK: 00105 // Perform exploration work 00106 { 00107 m.acquire(); 00108 if (idle) { 00109 m.release(); 00110 // Try to find new work 00111 find(); 00112 } else if (cur != NULL) { 00113 start(); 00114 if (stop(engine().opt())) { 00115 // Report stop 00116 m.release(); 00117 engine().stop(); 00118 } else { 00119 node++; 00120 switch (cur->status(*this)) { 00121 case SS_FAILED: 00122 fail++; 00123 delete cur; 00124 cur = NULL; 00125 path.next(); 00126 m.release(); 00127 break; 00128 case SS_SOLVED: 00129 { 00130 // Deletes all pending branchers 00131 (void) cur->choice(); 00132 Space* s = cur->clone(false); 00133 delete cur; 00134 cur = NULL; 00135 path.next(); 00136 m.release(); 00137 engine().solution(s); 00138 } 00139 break; 00140 case SS_BRANCH: 00141 { 00142 Space* c; 00143 if ((d == 0) || (d >= engine().opt().c_d)) { 00144 c = cur->clone(); 00145 d = 1; 00146 } else { 00147 c = NULL; 00148 d++; 00149 } 00150 const Choice* ch = path.push(*this,cur,c); 00151 cur->commit(*ch,0); 00152 m.release(); 00153 } 00154 break; 00155 default: 00156 GECODE_NEVER; 00157 } 00158 } 00159 } else if (!path.empty()) { 00160 cur = path.recompute(d,engine().opt().a_d,*this,*best,mark); 00161 if (cur == NULL) 00162 path.next(); 00163 m.release(); 00164 } else { 00165 idle = true; 00166 path.ngdl(0); 00167 m.release(); 00168 // Report that worker is idle 00169 engine().idle(); 00170 } 00171 } 00172 break; 00173 default: 00174 GECODE_NEVER; 00175 } 00176 } 00177 } 00178 00179 00180 /* 00181 * Perform reset 00182 * 00183 */ 00184 void 00185 BAB::reset(Space* s) { 00186 // Grab wait lock for reset 00187 m_wait_reset.acquire(); 00188 // Release workers for reset 00189 release(C_RESET); 00190 // Wait for reset cycle started 00191 e_reset_ack_start.wait(); 00192 // All workers are marked as busy again 00193 delete best; 00194 best = NULL; 00195 n_busy = workers(); 00196 for (unsigned int i=1; i<workers(); i++) 00197 worker(i)->reset(NULL,0); 00198 worker(0)->reset(s,opt().nogoods_limit); 00199 // Block workers again to ensure invariant 00200 block(); 00201 // Release reset lock 00202 m_wait_reset.release(); 00203 // Wait for reset cycle stopped 00204 e_reset_ack_stop.wait(); 00205 } 00206 00207 00208 /* 00209 * Create no-goods 00210 * 00211 */ 00212 NoGoods& 00213 BAB::nogoods(void) { 00214 NoGoods* ng; 00215 // Grab wait lock for reset 00216 m_wait_reset.acquire(); 00217 // Release workers for reset 00218 release(C_RESET); 00219 // Wait for reset cycle started 00220 e_reset_ack_start.wait(); 00221 ng = &worker(0)->nogoods(); 00222 // Block workers again to ensure invariant 00223 block(); 00224 // Release reset lock 00225 m_wait_reset.release(); 00226 // Wait for reset cycle stopped 00227 e_reset_ack_stop.wait(); 00228 return *ng; 00229 } 00230 00231 /* 00232 * Termination and deletion 00233 */ 00234 BAB::Worker::~Worker(void) { 00235 delete best; 00236 } 00237 00238 BAB::~BAB(void) { 00239 terminate(); 00240 delete best; 00241 heap.rfree(_worker); 00242 } 00243 00244 }}} 00245 00246 #endif 00247 00248 // STATISTICS: search-parallel