From f539a525ca5081f0613a756b8bc3e28f35e13239 Mon Sep 17 00:00:00 2001 From: Andrew Reynolds Date: Mon, 6 Aug 2018 21:44:41 -0500 Subject: Move sygus quantifier elimination step for non-ground-single-invocation to sygus (#2269) --- .../quantifiers/sygus/ce_guided_instantiation.cpp | 129 ++++++++++++++++++++- 1 file changed, 127 insertions(+), 2 deletions(-) (limited to 'src/theory') diff --git a/src/theory/quantifiers/sygus/ce_guided_instantiation.cpp b/src/theory/quantifiers/sygus/ce_guided_instantiation.cpp index f877bcefd..919a8f008 100644 --- a/src/theory/quantifiers/sygus/ce_guided_instantiation.cpp +++ b/src/theory/quantifiers/sygus/ce_guided_instantiation.cpp @@ -16,11 +16,13 @@ #include "theory/quantifiers/sygus/ce_guided_instantiation.h" #include "options/quantifiers_options.h" +#include "smt/smt_engine.h" +#include "smt/smt_engine_scope.h" #include "smt/smt_statistics_registry.h" -#include "theory/theory_engine.h" #include "theory/quantifiers/quantifiers_attributes.h" #include "theory/quantifiers/sygus/term_database_sygus.h" #include "theory/quantifiers/term_util.h" +#include "theory/theory_engine.h" using namespace CVC4::kind; using namespace std; @@ -81,7 +83,130 @@ void CegInstantiation::registerQuantifier( Node q ) { if( d_quantEngine->getOwner( q )==this ){ // && d_eval_axioms.find( q )==d_eval_axioms.end() ){ if( !d_conj->isAssigned() ){ Trace("cegqi") << "Register conjecture : " << q << std::endl; - d_conj->assign( q ); + Node conj = q; + if (options::sygusQePreproc()) + { + // the following does quantifier elimination as a preprocess step + // for "non-ground single invocation synthesis conjectures": + // exists f. forall xy. P[ f(x), x, y ] + // We run quantifier elimination: + // exists y. P[ z, x, y ] ----> Q[ z, x ] + // Where we replace the original conjecture with: + // exists f. forall x. Q[ f(x), x ] + // For more details, see Example 6 of Reynolds et al. SYNT 2017. + Node body = q[1]; + if (body.getKind() == NOT && body[0].getKind() == FORALL) + { + body = body[0][1]; + } + NodeManager* nm = NodeManager::currentNM(); + Trace("cegqi-qep") << "Compute single invocation for " << conj << "..." + << std::endl; + quantifiers::SingleInvocationPartition sip; + std::vector funcs; + funcs.insert(funcs.end(), conj[0].begin(), conj[0].end()); + sip.init(funcs, body); + Trace("cegqi-qep") << "...finished, got:" << std::endl; + sip.debugPrint("cegqi-qep"); + + if (!sip.isPurelySingleInvocation() + && sip.isNonGroundSingleInvocation()) + { + // create new smt engine to do quantifier elimination + SmtEngine smt_qe(nm->toExprManager()); + smt_qe.setLogic(smt::currentSmtEngine()->getLogicInfo()); + Trace("cegqi-qep") << "Property is non-ground single invocation, run " + "QE to obtain single invocation." + << std::endl; + // partition variables + std::vector all_vars; + sip.getAllVariables(all_vars); + std::vector si_vars; + sip.getSingleInvocationVariables(si_vars); + std::vector qe_vars; + std::vector nqe_vars; + for (unsigned i = 0, size = all_vars.size(); i < size; i++) + { + Node v = all_vars[i]; + if (std::find(si_vars.begin(), si_vars.end(), v) == si_vars.end()) + { + qe_vars.push_back(v); + } + else + { + nqe_vars.push_back(v); + } + } + std::vector orig; + std::vector subs; + // skolemize non-qe variables + for (unsigned i = 0, size = nqe_vars.size(); i < size; i++) + { + Node k = nm->mkSkolem("k", + nqe_vars[i].getType(), + "qe for non-ground single invocation"); + orig.push_back(nqe_vars[i]); + subs.push_back(k); + Trace("cegqi-qep") + << " subs : " << nqe_vars[i] << " -> " << k << std::endl; + } + std::vector funcs; + sip.getFunctions(funcs); + for (unsigned i = 0, size = funcs.size(); i < size; i++) + { + Node f = funcs[i]; + Node fi = sip.getFunctionInvocationFor(f); + Node fv = sip.getFirstOrderVariableForFunction(f); + Assert(!fi.isNull()); + orig.push_back(fi); + Node k = + nm->mkSkolem("k", + fv.getType(), + "qe for function in non-ground single invocation"); + subs.push_back(k); + Trace("cegqi-qep") << " subs : " << fi << " -> " << k << std::endl; + } + Node conj_se_ngsi = sip.getFullSpecification(); + Trace("cegqi-qep") + << "Full specification is " << conj_se_ngsi << std::endl; + Node conj_se_ngsi_subs = conj_se_ngsi.substitute( + orig.begin(), orig.end(), subs.begin(), subs.end()); + Assert(!qe_vars.empty()); + conj_se_ngsi_subs = nm->mkNode(EXISTS, + nm->mkNode(BOUND_VAR_LIST, qe_vars), + conj_se_ngsi_subs.negate()); + + Trace("cegqi-qep") << "Run quantifier elimination on " + << conj_se_ngsi_subs << std::endl; + Expr qe_res = smt_qe.doQuantifierElimination( + conj_se_ngsi_subs.toExpr(), true, false); + Trace("cegqi-qep") << "Result : " << qe_res << std::endl; + + // create single invocation conjecture + Node qe_res_n = Node::fromExpr(qe_res); + qe_res_n = qe_res_n.substitute( + subs.begin(), subs.end(), orig.begin(), orig.end()); + if (!nqe_vars.empty()) + { + qe_res_n = nm->mkNode( + EXISTS, nm->mkNode(BOUND_VAR_LIST, nqe_vars), qe_res_n); + } + Assert(conj.getNumChildren() == 3); + qe_res_n = nm->mkNode(FORALL, conj[0], qe_res_n, conj[2]); + Trace("cegqi-qep") + << "Converted conjecture after QE : " << qe_res_n << std::endl; + qe_res_n = Rewriter::rewrite(qe_res_n); + conj = qe_res_n; + // must assert it is equivalent to the original + Node lem = conj.eqNode(q); + Trace("cegqi-lemma") + << "Cegqi::Lemma : qe-preprocess : " << lem << std::endl; + d_quantEngine->getOutputChannel().lemma(lem); + // we've reduced the original to a preprocessed version, return + return; + } + } + d_conj->assign(conj); }else{ Assert( d_conj->getEmbeddedConjecture()==q ); } -- cgit v1.2.3