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/********************* */
/*! \file symmetry_breaker.h
** \verbatim
** Top contributors (to current version):
** Morgan Deters, Liana Hadarean, Tim King
** This file is part of the CVC4 project.
** Copyright (c) 2009-2018 by the authors listed in the file AUTHORS
** in the top-level source directory) and their institutional affiliations.
** All rights reserved. See the file COPYING in the top-level source
** directory for licensing information.\endverbatim
**
** \brief Implementation of algorithm suggested by Deharbe, Fontaine,
** Merz, and Paleo, "Exploiting symmetry in SMT problems," CADE 2011
**
** Implementation of algorithm suggested by Deharbe, Fontaine, Merz,
** and Paleo, "Exploiting symmetry in SMT problems," CADE 2011.
**
** From the paper:
**
** <pre>
** \f$ P := guess\_permutations(\phi) \f$
** foreach \f$ {c_0, ..., c_n} \in P \f$ do
** if \f$ invariant\_by\_permutations(\phi, {c_0, ..., c_n}) \f$ then
** T := \f$ select\_terms(\phi, {c_0, ..., c_n}) \f$
** cts := \f$ \emptyset \f$
** while T != \f$ \empty \wedge |cts| <= n \f$ do
** \f$ t := select\_most\_promising\_term(T, \phi) \f$
** \f$ T := T \setminus {t} \f$
** cts := cts \f$ \cup used\_in(t, {c_0, ..., c_n}) \f$
** let \f$ c \in {c_0, ..., c_n} \setminus cts \f$
** cts := cts \f$ \cup {c} \f$
** if cts != \f$ {c_0, ..., c_n} \f$ then
** \f$ \phi := \phi \wedge ( \vee_{c_i \in cts} t = c_i ) \f$
** end
** end
** end
** end
** return \f$ \phi \f$
** </pre>
**/
#include "cvc4_private.h"
#ifndef __CVC4__THEORY__UF__SYMMETRY_BREAKER_H
#define __CVC4__THEORY__UF__SYMMETRY_BREAKER_H
#include <iostream>
#include <list>
#include <unordered_map>
#include <vector>
#include "context/cdlist.h"
#include "context/context.h"
#include "expr/node.h"
#include "expr/node_builder.h"
#include "smt/smt_statistics_registry.h"
#include "util/statistics_registry.h"
namespace CVC4 {
namespace theory {
namespace uf {
class SymmetryBreaker : public context::ContextNotifyObj {
class Template {
Node d_template;
NodeBuilder<> d_assertions;
std::unordered_map<TNode, std::set<TNode>, TNodeHashFunction> d_sets;
std::unordered_map<TNode, TNode, TNodeHashFunction> d_reps;
TNode find(TNode n);
bool matchRecursive(TNode t, TNode n);
public:
Template();
bool match(TNode n);
std::unordered_map<TNode, std::set<TNode>, TNodeHashFunction>& partitions() { return d_sets; }
Node assertions() {
switch(d_assertions.getNumChildren()) {
case 0: return Node::null();
case 1: return d_assertions[0];
default: return Node(d_assertions);
}
}
void reset();
};/* class SymmetryBreaker::Template */
public:
typedef std::set<TNode> Permutation;
typedef std::set<Permutation> Permutations;
typedef TNode Term;
typedef std::list<Term> Terms;
typedef std::set<Term> TermEq;
typedef std::unordered_map<Term, TermEq, TNodeHashFunction> TermEqs;
private:
/**
* This class wasn't initially built to be incremental. It should
* be attached to a UserContext so that it clears everything when
* a pop occurs. This "assertionsToRerun" is a set of assertions to
* feed back through assertFormula() when we started getting things
* again. It's not just a matter of effectiveness, but also soundness;
* if some assertions (still in scope) are not seen by a symmetry-breaking
* round, then some symmetries that don't actually exist might be broken,
* leading to unsound results!
*/
context::CDList<Node> d_assertionsToRerun;
bool d_rerunningAssertions;
std::vector<Node> d_phi;
std::set<TNode> d_phiSet;
Permutations d_permutations;
Terms d_terms;
Template d_template;
std::unordered_map<Node, Node, NodeHashFunction> d_normalizationCache;
TermEqs d_termEqs;
TermEqs d_termEqsOnly;
void clear();
void rerunAssertionsIfNecessary();
void guessPermutations();
bool invariantByPermutations(const Permutation& p);
void selectTerms(const Permutation& p);
Terms::iterator selectMostPromisingTerm(Terms& terms);
void insertUsedIn(Term term, const Permutation& p, std::set<Node>& cts);
Node normInternal(TNode phi, size_t level);
Node norm(TNode n);
std::string d_name;
// === STATISTICS ===
/** number of new clauses that come from the SymmetryBreaker */
struct Statistics {
/** number of new clauses that come from the SymmetryBreaker */
IntStat d_clauses;
IntStat d_units;
/** number of potential permutation sets we found */
IntStat d_permutationSetsConsidered;
/** number of invariant permutation sets we found */
IntStat d_permutationSetsInvariant;
/** time spent in invariantByPermutations() */
TimerStat d_invariantByPermutationsTimer;
/** time spent in selectTerms() */
TimerStat d_selectTermsTimer;
/** time spent in initial round of normalization */
TimerStat d_initNormalizationTimer;
Statistics(std::string name);
~Statistics();
};
Statistics d_stats;
protected:
void contextNotifyPop() override
{
Debug("ufsymm") << "UFSYMM: clearing state due to pop" << std::endl;
clear();
}
public:
SymmetryBreaker(context::Context* context, std::string name = "");
void assertFormula(TNode phi);
void apply(std::vector<Node>& newClauses);
};/* class SymmetryBreaker */
}/* CVC4::theory::uf namespace */
}/* CVC4::theory namespace */
std::ostream& operator<<(std::ostream& out, const ::CVC4::theory::uf::SymmetryBreaker::Permutation& p);
}/* CVC4 namespace */
#endif /* __CVC4__THEORY__UF__SYMMETRY_BREAKER_H */
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