bab.hpp
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/* -*- mode: C++; c-basic-offset: 2; indent-tabs-mode: nil -*- */
/*
* Main authors:
* Christian Schulte <schulte@gecode.org>
*
* Contributing authors:
* Guido Tack <tack@gecode.org>
*
* Copyright:
* Christian Schulte, 2004
* Guido Tack, 2004
*
* This file is part of Gecode, the generic constraint
* development environment:
* http://www.gecode.org
*
* Permission is hereby granted, free of charge, to any person obtaining
* a copy of this software and associated documentation files (the
* "Software"), to deal in the Software without restriction, including
* without limitation the rights to use, copy, modify, merge, publish,
* distribute, sublicense, and/or sell copies of the Software, and to
* permit persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
* LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
* OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
* WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*
*/
namespace Gecode { namespace Search { namespace Seq {
template<class Tracer>
forceinline
BAB<Tracer>::BAB(Space* s, const Options& o)
: tracer(o.tracer), opt(o), path(opt.nogoods_limit), d(0), mark(0),
best(NULL) {
if (tracer) {
tracer.engine(SearchTracer::EngineType::BAB, 1U);
tracer.worker();
}
if ((s == NULL) || (s->status(*this) == SS_FAILED)) {
fail++;
cur = NULL;
if (!o.clone)
delete s;
} else {
cur = snapshot(s,opt);
}
}
template<class Tracer>
forceinline Space*
BAB<Tracer>::next(void) {
/*
* The engine maintains the following invariant:
* - If the current space (cur) is not NULL, the path always points
* to exactly that space.
* - If the current space (cur) is NULL, the path always points
* to the next space (if there is any).
*
* This invariant is needed so that no-goods can be extracted properly
* when the engine is stopped or has found a solution.
*
* An additional invariant maintained by the engine is:
* For all nodes stored at a depth less than mark, there
* is no guarantee of betterness. For those above the mark,
* betterness is guaranteed.
*
*/
start();
while (true) {
if (stop(opt))
return NULL;
// Recompute and add constraint if necessary
while (cur == NULL) {
if (path.empty())
return NULL;
cur = path.recompute(d,opt.a_d,*this,*best,mark,tracer);
if (cur != NULL)
break;
path.next();
}
node++;
SearchTracer::EdgeInfo ei;
if (tracer && (path.entries() > 0)) {
typename Path<Tracer>::Edge& top = path.top();
ei.init(tracer.wid(), top.nid(), top.truealt(), *cur, *top.choice());
}
unsigned int nid = tracer.nid();
switch (cur->status(*this)) {
case SS_FAILED:
if (tracer) {
SearchTracer::NodeInfo ni(SearchTracer::NodeType::FAILED,
tracer.wid(), nid, *cur);
tracer.node(ei,ni);
}
fail++;
delete cur;
cur = NULL;
path.next();
break;
case SS_SOLVED:
{
if (tracer) {
SearchTracer::NodeInfo ni(SearchTracer::NodeType::SOLVED,
tracer.wid(), nid, *cur);
tracer.node(ei,ni);
}
// Deletes all pending branchers
(void) cur->choice();
delete best;
best = cur;
cur = NULL;
path.next();
mark = path.entries();
}
return best->clone();
case SS_BRANCH:
{
Space* c;
if ((d == 0) || (d >= opt.c_d)) {
c = cur->clone();
d = 1;
} else {
c = NULL;
d++;
}
const Choice* ch = path.push(*this,cur,c,nid);
if (tracer) {
SearchTracer::NodeInfo ni(SearchTracer::NodeType::BRANCH,
tracer.wid(), nid, *cur, ch);
tracer.node(ei,ni);
}
cur->commit(*ch,0);
break;
}
default:
GECODE_NEVER;
}
}
GECODE_NEVER;
return NULL;
}
template<class Tracer>
forceinline Statistics
BAB<Tracer>::statistics(void) const {
return *this;
}
template<class Tracer>
forceinline void
BAB<Tracer>::constrain(const Space& b) {
if (best != NULL) {
// Check whether b is in fact better than best
best->constrain(b);
if (best->status(*this) != SS_FAILED)
return;
else
delete best;
}
best = b.clone();
if (cur != NULL)
cur->constrain(b);
mark = path.entries();
}
template<class Tracer>
forceinline void
BAB<Tracer>::reset(Space* s) {
tracer.round();
delete best;
best = NULL;
path.reset();
d = 0;
mark = 0;
delete cur;
if ((s == NULL) || (s->status(*this) == SS_FAILED)) {
delete s;
cur = NULL;
} else {
cur = s;
}
Worker::reset();
}
template<class Tracer>
forceinline NoGoods&
BAB<Tracer>::nogoods(void) {
return path;
}
template<class Tracer>
forceinline
BAB<Tracer>::~BAB(void) {
tracer.done();
path.reset();
delete best;
delete cur;
}
}}}
// STATISTICS: search-seq
Gecode::Choice
Choice for performing commit
Definition core.hpp:1412
Gecode::NoGoods
No-goods recorded from restarts.
Definition core.hpp:1588
Gecode::SearchTracer::EdgeInfo
Edge information.
Definition search.hh:242
Gecode::SearchTracer::EdgeInfo::init
void init(unsigned int wid, unsigned int nid, unsigned int a)
Initialize.
Definition tracer.hpp:107
Gecode::SearchTracer::EdgeInfo::nid
unsigned int nid(void) const
Return parent node id.
Definition tracer.hpp:142
Gecode::SearchTracer::NodeInfo
Node information.
Definition search.hh:282
Gecode::SearchTracer::FAILED
@ FAILED
A solution node.
Definition search.hh:278
Gecode::SearchTracer::BRANCH
@ BRANCH
A failed node.
Definition search.hh:279
Gecode::SearchTracer::SOLVED
@ SOLVED
Definition search.hh:277
Gecode::SearchTracer::BAB
@ BAB
Engine is a BAB engine.
Definition search.hh:195
Gecode::Search::Options
Search engine options
Definition search.hh:746
Gecode::Search::Seq::BAB::BAB
BAB(Space *s, const Options &o)
Initialize with space s and search options o.
Definition bab.hpp:42
Gecode::Search::Seq::BAB::~BAB
~BAB(void)
Destructor.
Definition bab.hpp:203
Gecode::Search::Seq::BAB::nogoods
NoGoods & nogoods(void)
Return no-goods.
Definition bab.hpp:197
Gecode::Search::Seq::BAB::next
Space * next(void)
Search for next better solution
Definition bab.hpp:61
Gecode::Search::Seq::BAB::constrain
void constrain(const Space &b)
Constrain future solutions to be better than b.
Definition bab.hpp:161
Gecode::Search::Seq::BAB::statistics
Statistics statistics(void) const
Return statistics.
Definition bab.hpp:155
Gecode::Search::Seq::Path::Edge
Search tree edge for recomputation
Definition path.hh:66
Gecode::Search::Seq::Path::Edge::truealt
unsigned int truealt(void) const
Return true number for alternatives (excluding lao optimization).
Definition path.hpp:67
Gecode::Search::Seq::Path::Edge::nid
unsigned int nid(void) const
Return node identifier.
Definition path.hpp:99
Gecode::Search::Seq::Path::Edge::choice
const Choice * choice(void) const
Return choice.
Definition path.hpp:93
Gecode::Search::Statistics
Search engine statistics
Definition search.hh:147
Gecode::Search::Statistics::fail
unsigned long int fail
Number of failed nodes in search tree.
Definition search.hh:150
Gecode::Search::Statistics::node
unsigned long int node
Number of nodes expanded.
Definition search.hh:152
Gecode::Search::Worker::start
void start(void)
Reset stop information.
Definition worker.hh:74
Gecode::Search::Worker::stop
bool stop(const Options &o)
Check whether engine must be stopped.
Definition worker.hh:79
Gecode::Space
Computation spaces.
Definition core.hpp:1742
Gecode::StatusStatistics::reset
void reset(void)
Reset information.
Definition core.hpp:4690
Gecode::Space::status
SpaceStatus status(StatusStatistics &stat=unused_status)
Query space status.
Definition core.cpp:252
Gecode::SS_BRANCH
@ SS_BRANCH
Space must be branched (at least one brancher left)
Definition core.hpp:1684
Gecode::SS_SOLVED
@ SS_SOLVED
Space is solved (no brancher left)
Definition core.hpp:1683
Gecode::SS_FAILED
@ SS_FAILED
Space is failed
Definition core.hpp:1682
Gecode::Search::Seq
Definition pbs.cpp:36
Gecode::Search
Search engines
Gecode
Gecode toplevel namespace
forceinline
#define forceinline
Definition config.hpp:187
GECODE_NEVER
#define GECODE_NEVER
Assert that this command is never executed.
Definition macros.hpp:56