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/********************* */
/*! \file equality_infer.cpp
** \verbatim
** Original author: Andrew Reynolds
** Major contributors: none
** Minor contributors (to current version): none
** This file is part of the CVC4 project.
** Copyright (c) 2009-2014 New York University and The University of Iowa
** See the file COPYING in the top-level source directory for licensing
** information.\endverbatim
**
** \brief Method for inferring equalities between arithmetic equivalence classes,
** inspired by "A generalization of Shostak's method for combining decision procedures" Barrett et al. Figure 1.
**
**/
#include "theory/quantifiers/equality_infer.h"
#include "theory/quantifiers/quant_util.h"
#include "context/context_mm.h"
using namespace CVC4;
using namespace CVC4::kind;
using namespace CVC4::theory;
using namespace CVC4::theory::quantifiers;
using namespace std;
namespace CVC4 {
EqualityInference::EqcInfo::EqcInfo(context::Context* c) : d_rep( c ), d_valid( c, false ) {
}
EqualityInference::EqualityInference( context::Context* c ) : d_c( c ), d_elim_vars( c ), d_rep_to_eqc( c ), d_uselist( c ), d_pending_merges( c ){
d_one = NodeManager::currentNM()->mkConst( Rational( 1 ) );
}
EqualityInference::~EqualityInference(){
for( std::map< Node, EqcInfo * >::iterator it = d_eqci.begin(); it != d_eqci.end(); ++it ){
delete it->second;
}
}
void EqualityInference::eqNotifyNewClass(TNode t) {
if( t.getType().isReal() ){
Trace("eq-infer") << "Notify equivalence class : " << t << std::endl;
EqcInfo * eqci;
std::map< Node, EqcInfo * >::iterator itec = d_eqci.find( t );
if( itec==d_eqci.end() ){
eqci = new EqcInfo( d_c );
d_eqci[t] = eqci;
}else{
eqci = itec->second;
}
std::map< Node, Node > msum;
if( QuantArith::getMonomialSum( t, msum ) ){
eqci->d_valid = true;
bool changed = false;
std::vector< Node > children;
for( std::map< Node, Node >::iterator it = msum.begin(); it != msum.end(); ++it ) {
Node n = it->first;
if( !n.isNull() ){
NodeMap::const_iterator itv = d_elim_vars.find( n );
if( itv!=d_elim_vars.end() ){
changed = true;
n = (*itv).second;
}
if( it->second.isNull() ){
children.push_back( n );
}else{
children.push_back( NodeManager::currentNM()->mkNode( MULT, it->second, n ) );
}
}else{
children.push_back( it->second );
}
}
Node r;
bool mvalid = true;
if( changed ){
r = children.size()==1 ? children[0] : NodeManager::currentNM()->mkNode( PLUS, children );
r = Rewriter::rewrite( r );
msum.clear();
if( !QuantArith::getMonomialSum( r, msum ) ){
mvalid = false;
}
}else{
r = t;
}
Trace("eq-infer") << "...value is " << r << std::endl;
setEqcRep( t, r, eqci );
if( mvalid ){
for( std::map< Node, Node >::iterator it = msum.begin(); it != msum.end(); ++it ){
if( !it->first.isNull() ){
addToUseList( it->first, t );
}
}
}
}else{
eqci->d_valid = false;
}
}
}
void EqualityInference::addToUseList( Node used, Node eqc ) {
NodeListMap::iterator ul_i = d_uselist.find( used );
NodeList* ul;
if( ul_i != d_uselist.end() ){
ul = (*ul_i).second;
}else{
ul = new(d_c->getCMM()) NodeList( true, d_c, false, context::ContextMemoryAllocator<TNode>(d_c->getCMM()) );
d_uselist.insertDataFromContextMemory( used, ul );
}
Trace("eq-infer-debug") << " add to use list : " << used << " -> " << eqc << std::endl;
(*ul).push_back( eqc );
}
void EqualityInference::setEqcRep( Node t, Node r, EqcInfo * eqci ) {
eqci->d_rep = r;
NodeMap::const_iterator itr = d_rep_to_eqc.find( r );
if( itr==d_rep_to_eqc.end() ){
d_rep_to_eqc[r] = t;
}else{
//merge two equivalence classes
Node t2 = (*itr).second;
//check if it is valid
std::map< Node, EqcInfo * >::iterator itc = d_eqci.find( t2 );
if( itc!=d_eqci.end() && itc->second->d_valid ){
Trace("eq-infer") << "Infer two equivalence classes are equal : " << t << " " << t2 << std::endl;
Trace("eq-infer") << " since they both normalize to : " << r << std::endl;
d_pending_merges.push_back( t.eqNode( t2 ) );
}
}
}
void EqualityInference::eqNotifyMerge(TNode t1, TNode t2) {
Assert( !t1.isNull() );
Assert( !t2.isNull() );
std::map< Node, EqcInfo * >::iterator itv1 = d_eqci.find( t1 );
if( itv1!=d_eqci.end() ){
std::map< Node, EqcInfo * >::iterator itv2 = d_eqci.find( t2 );
if( itv2!=d_eqci.end() ){
Trace("eq-infer") << "Merge equivalence classes : " << t2 << " into " << t1 << std::endl;
Node tr1 = itv1->second->d_rep;
Node tr2 = itv2->second->d_rep;
itv2->second->d_valid = false;
Trace("eq-infer") << "Representatives : " << tr2 << " into " << tr1 << std::endl;
if( tr1!=tr2 ){
Node eq = tr1.eqNode( tr2 );
std::map< Node, Node > msum;
if( QuantArith::getMonomialSumLit( eq, msum ) ){
Node v_solve;
//solve for variables with no coefficient
for( std::map< Node, Node >::iterator it = msum.begin(); it != msum.end(); ++it ) {
Node n = it->first;
if( !n.isNull() && it->second.isNull() ){
v_solve = n;
break;
}
}
if( !v_solve.isNull() ){
//solve for v_solve
Node veq;
if( QuantArith::isolate( v_solve, msum, veq, kind::EQUAL, true )==1 ){
Node v_value = veq[1];
Trace("eq-infer") << "...solved " << v_solve << " == " << v_value << std::endl;
Assert( d_elim_vars.find( v_solve )==d_elim_vars.end() );
d_elim_vars[v_solve] = v_value;
std::vector< Node > new_use;
for( std::map< Node, Node >::iterator itmm = msum.begin(); itmm != msum.end(); ++itmm ){
Node n = itmm->first;
if( !n.isNull() && n!=v_solve ){
new_use.push_back( n );
}
}
//go through all equivalence classes that may refer to v_solve
std::map< Node, bool > processed;
NodeListMap::iterator ul_i = d_uselist.find( v_solve );
if( ul_i != d_uselist.end() ){
NodeList* ul = (*ul_i).second;
Trace("eq-infer-debug") << " use list size = " << ul->size() << std::endl;
for( unsigned j=0; j<ul->size(); j++ ){
Node r = (*ul)[j];
if( processed.find( r )==processed.end() ){
processed[r] = true;
std::map< Node, EqcInfo * >::iterator itt = d_eqci.find( r );
if( itt!=d_eqci.end() && itt->second->d_valid ){
std::map< Node, Node > msum2;
if( QuantArith::getMonomialSum( itt->second->d_rep.get(), msum2 ) ){
std::map< Node, Node >::iterator itm = msum2.find( v_solve );
if( itm!=msum2.end() ){
//substitute in solved form
std::map< Node, Node >::iterator itm2 = msum2.find( v_value );
if( itm2 == msum2.end() ){
msum2[v_value] = itm->second;
}else{
msum2[v_value] = NodeManager::currentNM()->mkNode( PLUS, itm2->second.isNull() ? d_one : itm2->second,
itm->second.isNull() ? d_one : itm->second );
}
msum2.erase( itm );
Node rr = QuantArith::mkNode( msum2 );
rr = Rewriter::rewrite( rr );
Trace("eq-infer") << "......update " << itt->first << " => " << rr << std::endl;
setEqcRep( itt->first, rr, itt->second );
//update use list
for( unsigned i=0; i<new_use.size(); i++ ){
addToUseList( new_use[i], r );
}
}
}else{
itt->second->d_valid = false;
}
}
}
}
}
Trace("eq-infer") << "...finished solved." << std::endl;
}
}
}
}
}else{
//no information to merge
}
}else{
//carry information (this might happen for non-linear t1 and linear t2?)
std::map< Node, EqcInfo * >::iterator itv2 = d_eqci.find( t2 );
if( itv2!=d_eqci.end() ){
d_eqci[t1] = d_eqci[t2];
d_eqci[t2] = NULL;
}
}
}
}
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