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/****************************************************************************** |
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* Top contributors (to current version): |
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* Andrew Reynolds, Mathias Preiner, Morgan Deters |
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* |
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* This file is part of the cvc5 project. |
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* |
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* Copyright (c) 2009-2021 by the authors listed in the file AUTHORS |
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* in the top-level source directory and their institutional affiliations. |
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* All rights reserved. See the file COPYING in the top-level source |
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* directory for licensing information. |
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* **************************************************************************** |
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* |
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* Sygus quantifier elimination preprocessor. |
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*/ |
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#include "theory/quantifiers/sygus/sygus_qe_preproc.h" |
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#include "expr/node_algorithm.h" |
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#include "expr/skolem_manager.h" |
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#include "theory/quantifiers/single_inv_partition.h" |
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#include "theory/rewriter.h" |
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#include "theory/smt_engine_subsolver.h" |
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using namespace cvc5::kind; |
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namespace cvc5 { |
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namespace theory { |
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namespace quantifiers { |
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SygusQePreproc::SygusQePreproc() {} |
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Node SygusQePreproc::preprocess(Node q) |
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{ |
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Node body = q[1]; |
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if (body.getKind() == NOT && body[0].getKind() == FORALL) |
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{ |
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body = body[0][1]; |
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} |
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NodeManager* nm = NodeManager::currentNM(); |
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SkolemManager* sm = nm->getSkolemManager(); |
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Trace("cegqi-qep") << "Compute single invocation for " << q << "..." |
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<< std::endl; |
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quantifiers::SingleInvocationPartition sip; |
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std::vector<Node> funcs0; |
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funcs0.insert(funcs0.end(), q[0].begin(), q[0].end()); |
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sip.init(funcs0, body); |
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Trace("cegqi-qep") << "...finished, got:" << std::endl; |
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sip.debugPrint("cegqi-qep"); |
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if (sip.isPurelySingleInvocation() || !sip.isNonGroundSingleInvocation()) |
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{ |
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return Node::null(); |
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} |
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// create new smt engine to do quantifier elimination |
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std::unique_ptr<SmtEngine> smt_qe; |
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initializeSubsolver(smt_qe); |
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Trace("cegqi-qep") << "Property is non-ground single invocation, run " |
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"QE to obtain single invocation." |
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<< std::endl; |
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// partition variables |
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std::vector<Node> all_vars; |
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sip.getAllVariables(all_vars); |
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std::vector<Node> si_vars; |
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sip.getSingleInvocationVariables(si_vars); |
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std::vector<Node> qe_vars; |
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std::vector<Node> nqe_vars; |
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for (unsigned i = 0, size = all_vars.size(); i < size; i++) |
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{ |
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Node v = all_vars[i]; |
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if (std::find(funcs0.begin(), funcs0.end(), v) != funcs0.end()) |
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{ |
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Trace("cegqi-qep") << "- fun var: " << v << std::endl; |
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} |
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else if (std::find(si_vars.begin(), si_vars.end(), v) == si_vars.end()) |
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{ |
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qe_vars.push_back(v); |
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Trace("cegqi-qep") << "- qe var: " << v << std::endl; |
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} |
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else |
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{ |
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nqe_vars.push_back(v); |
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Trace("cegqi-qep") << "- non qe var: " << v << std::endl; |
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} |
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} |
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std::vector<Node> orig; |
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std::vector<Node> subs; |
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// skolemize non-qe variables |
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for (unsigned i = 0, size = nqe_vars.size(); i < size; i++) |
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{ |
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Node k = sm->mkDummySkolem( |
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"k", nqe_vars[i].getType(), "qe for non-ground single invocation"); |
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orig.push_back(nqe_vars[i]); |
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subs.push_back(k); |
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Trace("cegqi-qep") << " subs : " << nqe_vars[i] << " -> " << k |
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<< std::endl; |
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} |
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std::vector<Node> funcs1; |
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sip.getFunctions(funcs1); |
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for (unsigned i = 0, size = funcs1.size(); i < size; i++) |
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{ |
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Node f = funcs1[i]; |
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Node fi = sip.getFunctionInvocationFor(f); |
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Node fv = sip.getFirstOrderVariableForFunction(f); |
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Assert(!fi.isNull()); |
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orig.push_back(fi); |
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Node k = sm->mkDummySkolem( |
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"k", fv.getType(), "qe for function in non-ground single invocation"); |
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subs.push_back(k); |
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Trace("cegqi-qep") << " subs : " << fi << " -> " << k << std::endl; |
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} |
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Node conj_se_ngsi = sip.getFullSpecification(); |
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Trace("cegqi-qep") << "Full specification is " << conj_se_ngsi << std::endl; |
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Node conj_se_ngsi_subs = conj_se_ngsi.substitute( |
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orig.begin(), orig.end(), subs.begin(), subs.end()); |
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Assert(!qe_vars.empty()); |
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conj_se_ngsi_subs = nm->mkNode( |
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EXISTS, nm->mkNode(BOUND_VAR_LIST, qe_vars), conj_se_ngsi_subs.negate()); |
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Trace("cegqi-qep") << "Run quantifier elimination on " << conj_se_ngsi_subs |
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<< std::endl; |
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Node qeRes = smt_qe->getQuantifierElimination(conj_se_ngsi_subs, true, false); |
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Trace("cegqi-qep") << "Result : " << qeRes << std::endl; |
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// create single invocation conjecture, if QE was successful |
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if (!expr::hasBoundVar(qeRes)) |
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{ |
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qeRes = |
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qeRes.substitute(subs.begin(), subs.end(), orig.begin(), orig.end()); |
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if (!nqe_vars.empty()) |
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{ |
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qeRes = nm->mkNode(EXISTS, nm->mkNode(BOUND_VAR_LIST, nqe_vars), qeRes); |
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} |
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Assert(q.getNumChildren() == 3); |
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qeRes = nm->mkNode(FORALL, q[0], qeRes, q[2]); |
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Trace("cegqi-qep") << "Converted conjecture after QE : " << qeRes |
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<< std::endl; |
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qeRes = Rewriter::rewrite(qeRes); |
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Node nq = qeRes; |
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// must assert it is equivalent to the original |
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Node lem = q.eqNode(nq); |
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Trace("cegqi-lemma") << "Cegqi::Lemma : qe-preprocess : " << lem |
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<< std::endl; |
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return lem; |
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} |
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return Node::null(); |
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} |
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} // namespace quantifiers |
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} // namespace theory |
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} // namespace cvc5 |