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/********************* */
/*! \file trust_substitutions.cpp
** \verbatim
** Top contributors (to current version):
** Andrew Reynolds, Gereon Kremer
** This file is part of the CVC4 project.
** Copyright (c) 2009-2021 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 Trust substitutions
**/
#include "theory/trust_substitutions.h"
#include "theory/rewriter.h"
namespace cvc5 {
namespace theory {
TrustSubstitutionMap::TrustSubstitutionMap(context::Context* c,
ProofNodeManager* pnm,
std::string name,
PfRule trustId,
MethodId ids)
: d_ctx(c),
d_subs(c),
d_pnm(pnm),
d_tsubs(c),
d_tspb(pnm ? new TheoryProofStepBuffer(pnm->getChecker()) : nullptr),
d_subsPg(
pnm ? new LazyCDProof(pnm, nullptr, c, "TrustSubstitutionMap::subsPg")
: nullptr),
d_applyPg(pnm ? new LazyCDProof(
pnm, nullptr, c, "TrustSubstitutionMap::applyPg")
: nullptr),
d_helperPf(pnm, c),
d_currentSubs(c),
d_name(name),
d_trustId(trustId),
d_ids(ids)
{
}
void TrustSubstitutionMap::addSubstitution(TNode x, TNode t, ProofGenerator* pg)
{
Trace("trust-subs") << "TrustSubstitutionMap::addSubstitution: add " << x
<< " -> " << t << std::endl;
d_subs.addSubstitution(x, t);
if (isProofEnabled())
{
TrustNode tnl = TrustNode::mkTrustRewrite(x, t, pg);
d_tsubs.push_back(tnl);
// current substitution node is no longer valid.
d_currentSubs = Node::null();
// add to lazy proof
d_subsPg->addLazyStep(tnl.getProven(), pg, d_trustId);
}
}
void TrustSubstitutionMap::addSubstitution(TNode x,
TNode t,
PfRule id,
const std::vector<Node>& args)
{
if (!isProofEnabled())
{
addSubstitution(x, t, nullptr);
return;
}
LazyCDProof* stepPg = d_helperPf.allocateProof(nullptr, d_ctx);
Node eq = x.eqNode(t);
stepPg->addStep(eq, id, {}, args);
addSubstitution(x, t, stepPg);
}
ProofGenerator* TrustSubstitutionMap::addSubstitutionSolved(TNode x,
TNode t,
TrustNode tn)
{
Trace("trust-subs") << "TrustSubstitutionMap::addSubstitutionSolved: add "
<< x << " -> " << t << " from " << tn.getProven()
<< std::endl;
if (!isProofEnabled() || tn.getGenerator() == nullptr)
{
// no generator or not proof enabled, nothing to do
addSubstitution(x, t, nullptr);
Trace("trust-subs") << "...no proof" << std::endl;
return nullptr;
}
Node eq = x.eqNode(t);
Node proven = tn.getProven();
// notice that this checks syntactic equality, not CDProof::isSame since
// tn.getGenerator() is not necessarily robust to symmetry.
if (eq == proven)
{
// no rewrite required, just use the generator
addSubstitution(x, t, tn.getGenerator());
Trace("trust-subs") << "...use generator directly" << std::endl;
return tn.getGenerator();
}
LazyCDProof* solvePg = d_helperPf.allocateProof(nullptr, d_ctx);
// Try to transform tn.getProven() to (= x t) here, if necessary
if (!d_tspb->applyPredTransform(proven, eq, {}))
{
// failed to rewrite
addSubstitution(x, t, nullptr);
Trace("trust-subs") << "...failed to rewrite" << std::endl;
return nullptr;
}
Trace("trust-subs") << "...successful rewrite" << std::endl;
solvePg->addSteps(*d_tspb.get());
d_tspb->clear();
// link the given generator
solvePg->addLazyStep(proven, tn.getGenerator());
addSubstitution(x, t, solvePg);
return solvePg;
}
void TrustSubstitutionMap::addSubstitutions(TrustSubstitutionMap& t)
{
if (!isProofEnabled())
{
// just use the basic utility
d_subs.addSubstitutions(t.get());
return;
}
// call addSubstitution above in sequence
for (const TrustNode& tns : t.d_tsubs)
{
Node proven = tns.getProven();
addSubstitution(proven[0], proven[1], tns.getGenerator());
}
}
TrustNode TrustSubstitutionMap::apply(Node n, bool doRewrite)
{
Trace("trust-subs") << "TrustSubstitutionMap::addSubstitution: apply " << n
<< std::endl;
Node ns = d_subs.apply(n, doRewrite);
Trace("trust-subs") << "...subs " << ns << std::endl;
if (n == ns)
{
// no change
return TrustNode::null();
}
if (!isProofEnabled())
{
// no proofs, use null generator
return TrustNode::mkTrustRewrite(n, ns, nullptr);
}
Node cs = getCurrentSubstitution();
Trace("trust-subs")
<< "TrustSubstitutionMap::addSubstitution: current substitution is " << cs
<< std::endl;
// Easy case: if n is in the domain of the substitution, maybe it is already
// a proof in the substitution proof generator. This is moreover required
// to avoid cyclic proofs below. For example, if { x -> 5 } is a substitution,
// and we are asked to transform x, resulting in 5, we hence must provide
// a proof of (= x 5) based on the substitution. However, it must be the
// case that (= x 5) is a proven fact of the substitution generator. Hence
// we avoid a proof that looks like:
// ---------- from d_subsPg
// (= x 5)
// ---------- MACRO_SR_EQ_INTRO{x}
// (= x 5)
// by taking the premise proof directly.
Node eq = n.eqNode(ns);
if (d_subsPg->hasStep(eq) || d_subsPg->hasGenerator(eq))
{
return TrustNode::mkTrustRewrite(n, ns, d_subsPg.get());
}
Assert(eq != cs);
std::vector<Node> pfChildren;
if (!cs.isConst())
{
// note we will get more proof reuse if we do not special case AND here.
if (cs.getKind() == kind::AND)
{
for (const Node& csc : cs)
{
pfChildren.push_back(csc);
// connect substitution generator into apply generator
d_applyPg->addLazyStep(csc, d_subsPg.get());
}
}
else
{
pfChildren.push_back(cs);
// connect substitution generator into apply generator
d_applyPg->addLazyStep(cs, d_subsPg.get());
}
}
if (!d_tspb->applyEqIntro(n, ns, pfChildren, d_ids))
{
// if we fail for any reason, we must use a trusted step instead
d_tspb->addStep(PfRule::TRUST_SUBS_MAP, pfChildren, {eq}, eq);
}
// ------- ------- from external proof generators
// x1 = t1 ... xn = tn
// ----------------------- AND_INTRO
// ...
// --------- MACRO_SR_EQ_INTRO (or TRUST_SUBS_MAP if we failed above)
// n == ns
// add it to the apply proof generator.
//
// Notice that we use a single child to MACRO_SR_EQ_INTRO here. This is an
// optimization motivated by the fact that n may be large and reused many
// time. For instance, if this class is being used to track substitutions
// derived during non-clausal simplification during preprocessing, it is
// a fixed (possibly) large substitution applied to many terms. Having
// a single child saves us from creating many proofs with n children, where
// notice this proof is reused.
d_applyPg->addSteps(*d_tspb.get());
d_tspb->clear();
return TrustNode::mkTrustRewrite(n, ns, d_applyPg.get());
}
SubstitutionMap& TrustSubstitutionMap::get() { return d_subs; }
bool TrustSubstitutionMap::isProofEnabled() const
{
return d_subsPg != nullptr;
}
Node TrustSubstitutionMap::getCurrentSubstitution()
{
Assert(isProofEnabled());
if (!d_currentSubs.get().isNull())
{
return d_currentSubs;
}
std::vector<Node> csubsChildren;
for (const TrustNode& tns : d_tsubs)
{
csubsChildren.push_back(tns.getProven());
}
std::reverse(csubsChildren.begin(),csubsChildren.end());
d_currentSubs = NodeManager::currentNM()->mkAnd(csubsChildren);
if (d_currentSubs.get().getKind() == kind::AND)
{
d_subsPg->addStep(d_currentSubs, PfRule::AND_INTRO, csubsChildren, {});
}
return d_currentSubs;
}
} // namespace theory
} // namespace cvc5
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