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/******************************************************************************
* Top contributors (to current version):
* Haniel Barbosa, Andrew Reynolds, Aina Niemetz
*
* This file is part of the cvc5 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.
* ****************************************************************************
*
* Implementation of theory proof step buffer utility.
*/
#include "proof/theory_proof_step_buffer.h"
#include "proof/proof.h"
using namespace cvc5::kind;
namespace cvc5 {
namespace theory {
TheoryProofStepBuffer::TheoryProofStepBuffer(ProofChecker* pc)
: ProofStepBuffer(pc)
{
}
bool TheoryProofStepBuffer::applyEqIntro(Node src,
Node tgt,
const std::vector<Node>& exp,
MethodId ids,
MethodId ida,
MethodId idr)
{
std::vector<Node> args;
args.push_back(src);
builtin::BuiltinProofRuleChecker::addMethodIds(args, ids, ida, idr);
Node res = tryStep(PfRule::MACRO_SR_EQ_INTRO, exp, args);
if (res.isNull())
{
// failed to apply
return false;
}
// should have concluded the expected equality
Node expected = src.eqNode(tgt);
if (res != expected)
{
// did not provide the correct target
popStep();
return false;
}
// successfully proved src == tgt.
return true;
}
bool TheoryProofStepBuffer::applyPredTransform(Node src,
Node tgt,
const std::vector<Node>& exp,
MethodId ids,
MethodId ida,
MethodId idr)
{
// symmetric equalities
if (CDProof::isSame(src, tgt))
{
return true;
}
std::vector<Node> children;
children.push_back(src);
std::vector<Node> args;
// try to prove that tgt rewrites to src
children.insert(children.end(), exp.begin(), exp.end());
args.push_back(tgt);
builtin::BuiltinProofRuleChecker::addMethodIds(args, ids, ida, idr);
Node res = tryStep(PfRule::MACRO_SR_PRED_TRANSFORM, children, args);
if (res.isNull())
{
// failed to apply
return false;
}
// should definitely have concluded tgt
Assert(res == tgt);
return true;
}
bool TheoryProofStepBuffer::applyPredIntro(Node tgt,
const std::vector<Node>& exp,
MethodId ids,
MethodId ida,
MethodId idr)
{
std::vector<Node> args;
args.push_back(tgt);
builtin::BuiltinProofRuleChecker::addMethodIds(args, ids, ida, idr);
Node res = tryStep(PfRule::MACRO_SR_PRED_INTRO, exp, args);
if (res.isNull())
{
return false;
}
Assert(res == tgt);
return true;
}
Node TheoryProofStepBuffer::applyPredElim(Node src,
const std::vector<Node>& exp,
MethodId ids,
MethodId ida,
MethodId idr)
{
std::vector<Node> children;
children.push_back(src);
children.insert(children.end(), exp.begin(), exp.end());
std::vector<Node> args;
builtin::BuiltinProofRuleChecker::addMethodIds(args, ids, ida, idr);
Node srcRew = tryStep(PfRule::MACRO_SR_PRED_ELIM, children, args);
if (CDProof::isSame(src, srcRew))
{
popStep();
}
return srcRew;
}
Node TheoryProofStepBuffer::factorReorderElimDoubleNeg(Node n)
{
if (n.getKind() != kind::OR)
{
return elimDoubleNegLit(n);
}
NodeManager* nm = NodeManager::currentNM();
std::vector<Node> children{n.begin(), n.end()};
std::vector<Node> childrenEqs;
// eliminate double neg for each lit. Do it first because it may expose
// duplicates
bool hasDoubleNeg = false;
for (unsigned i = 0; i < children.size(); ++i)
{
if (children[i].getKind() == kind::NOT
&& children[i][0].getKind() == kind::NOT)
{
hasDoubleNeg = true;
childrenEqs.push_back(children[i].eqNode(children[i][0][0]));
addStep(PfRule::MACRO_SR_PRED_INTRO,
{},
{childrenEqs.back()},
childrenEqs.back());
// update child
children[i] = children[i][0][0];
}
else
{
childrenEqs.push_back(children[i].eqNode(children[i]));
addStep(PfRule::REFL, {}, {children[i]}, childrenEqs.back());
}
}
if (hasDoubleNeg)
{
Node oldn = n;
n = nm->mkNode(kind::OR, children);
// Create a congruence step to justify replacement of each doubly negated
// literal. This is done to avoid having to use MACRO_SR_PRED_TRANSFORM
// from the old clause to the new one, which, under the standard rewriter,
// may not hold. An example is
//
// ---------------------------------------------------------------------
// (or (or (not x2) x1 x2) (not (not x2))) = (or (or (not x2) x1 x2) x2)
//
// which fails due to factoring not happening after flattening.
//
// Using congruence only the
//
// ------------------ MACRO_SR_PRED_INTRO
// (not (not t)) = t
//
// steps are added, which, since double negation is eliminated in a
// pre-rewrite in the Boolean rewriter, will always hold under the
// standard rewriter.
Node congEq = oldn.eqNode(n);
addStep(PfRule::CONG,
childrenEqs,
{ProofRuleChecker::mkKindNode(kind::OR)},
congEq);
// add an equality resolution step to derive normalize clause
addStep(PfRule::EQ_RESOLVE, {oldn, congEq}, {}, n);
}
children.clear();
// remove duplicates while keeping the order of children
std::unordered_set<TNode> clauseSet;
unsigned size = n.getNumChildren();
for (unsigned i = 0; i < size; ++i)
{
if (clauseSet.count(n[i]))
{
continue;
}
children.push_back(n[i]);
clauseSet.insert(n[i]);
}
// if factoring changed
if (children.size() < size)
{
Node factored = children.empty()
? nm->mkConst<bool>(false)
: children.size() == 1 ? children[0]
: nm->mkNode(kind::OR, children);
// don't overwrite what already has a proof step to avoid cycles
addStep(PfRule::FACTORING, {n}, {}, factored);
n = factored;
}
// nothing to order
if (children.size() < 2)
{
return n;
}
// order
std::sort(children.begin(), children.end());
Node ordered = nm->mkNode(kind::OR, children);
// if ordering changed
if (ordered != n)
{
// don't overwrite what already has a proof step to avoid cycles
addStep(PfRule::REORDERING, {n}, {ordered}, ordered);
}
return ordered;
}
Node TheoryProofStepBuffer::elimDoubleNegLit(Node n)
{
// eliminate double neg
if (n.getKind() == kind::NOT && n[0].getKind() == kind::NOT)
{
addStep(PfRule::NOT_NOT_ELIM, {n}, {}, n[0][0]);
return n[0][0];
}
return n;
}
} // namespace theory
} // namespace cvc5
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