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/****************************************************************************** |
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* Top contributors (to current version): |
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* Andrew Reynolds |
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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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* Preprocessor for the theory of quantifiers. |
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*/ |
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#include "theory/quantifiers/quantifiers_preprocess.h" |
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#include "expr/node_algorithm.h" |
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#include "options/quantifiers_options.h" |
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#include "theory/quantifiers/quant_util.h" |
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#include "theory/quantifiers/quantifiers_rewriter.h" |
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#include "theory/quantifiers/skolemize.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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QuantifiersPreprocess::QuantifiersPreprocess(Env& env) : EnvObj(env) {} |
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Node QuantifiersPreprocess::computePrenexAgg( |
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Node n, std::map<Node, Node>& visited) const |
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{ |
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std::map<Node, Node>::iterator itv = visited.find(n); |
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if (itv != visited.end()) |
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{ |
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return itv->second; |
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} |
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if (!expr::hasClosure(n)) |
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{ |
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// trivial |
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return n; |
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} |
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NodeManager* nm = NodeManager::currentNM(); |
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Node ret = n; |
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if (n.getKind() == NOT) |
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{ |
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ret = computePrenexAgg(n[0], visited).negate(); |
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} |
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else if (n.getKind() == FORALL) |
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{ |
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std::vector<Node> children; |
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children.push_back(computePrenexAgg(n[1], visited)); |
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std::vector<Node> args; |
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args.insert(args.end(), n[0].begin(), n[0].end()); |
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// for each child, strip top level quant |
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for (unsigned i = 0; i < children.size(); i++) |
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{ |
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if (children[i].getKind() == FORALL) |
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{ |
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args.insert(args.end(), children[i][0].begin(), children[i][0].end()); |
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children[i] = children[i][1]; |
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} |
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} |
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// keep the pattern |
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std::vector<Node> iplc; |
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if (n.getNumChildren() == 3) |
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{ |
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iplc.insert(iplc.end(), n[2].begin(), n[2].end()); |
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} |
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Node nb = nm->mkOr(children); |
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ret = QuantifiersRewriter::mkForall(args, nb, iplc, true); |
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} |
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else |
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{ |
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std::unordered_set<Node> argsSet; |
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std::unordered_set<Node> nargsSet; |
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Node q; |
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QuantifiersRewriter qrew(options()); |
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Node nn = qrew.computePrenex(q, n, argsSet, nargsSet, true, true); |
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Assert(n != nn || argsSet.empty()); |
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Assert(n != nn || nargsSet.empty()); |
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if (n != nn) |
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{ |
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Node nnn = computePrenexAgg(nn, visited); |
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// merge prenex |
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if (nnn.getKind() == FORALL) |
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{ |
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argsSet.insert(nnn[0].begin(), nnn[0].end()); |
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nnn = nnn[1]; |
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// pos polarity variables are inner |
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if (!argsSet.empty()) |
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{ |
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nnn = QuantifiersRewriter::mkForall( |
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{argsSet.begin(), argsSet.end()}, nnn, true); |
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} |
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argsSet.clear(); |
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} |
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else if (nnn.getKind() == NOT && nnn[0].getKind() == FORALL) |
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{ |
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nargsSet.insert(nnn[0][0].begin(), nnn[0][0].end()); |
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nnn = nnn[0][1].negate(); |
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} |
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if (!nargsSet.empty()) |
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{ |
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nnn = QuantifiersRewriter::mkForall( |
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{nargsSet.begin(), nargsSet.end()}, nnn.negate(), true) |
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.negate(); |
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} |
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if (!argsSet.empty()) |
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{ |
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nnn = QuantifiersRewriter::mkForall( |
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{argsSet.begin(), argsSet.end()}, nnn, true); |
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} |
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ret = nnn; |
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} |
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} |
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visited[n] = ret; |
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return ret; |
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} |
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Node QuantifiersPreprocess::preSkolemizeQuantifiers( |
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Node n, |
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bool polarity, |
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std::vector<TNode>& fvs, |
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std::unordered_map<std::pair<Node, bool>, Node, NodePolPairHashFunction>& |
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visited) const |
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{ |
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std::pair<Node, bool> key(n, polarity); |
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std::unordered_map<std::pair<Node, bool>, Node, NodePolPairHashFunction>:: |
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iterator it = visited.find(key); |
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if (it != visited.end()) |
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{ |
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return it->second; |
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} |
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NodeManager* nm = NodeManager::currentNM(); |
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Trace("pre-sk") << "Pre-skolem " << n << " " << polarity << " " << fvs.size() |
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<< std::endl; |
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if (n.getKind() == FORALL) |
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{ |
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Node ret = n; |
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if (n.getNumChildren() == 3) |
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{ |
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// Do not pre-skolemize quantified formulas with three children. |
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// This includes non-standard quantified formulas |
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// like recursive function definitions, or sygus conjectures, and |
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// quantified formulas with triggers. |
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} |
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else if (polarity) |
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{ |
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if (options().quantifiers.preSkolemQuant |
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&& options().quantifiers.preSkolemQuantNested) |
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{ |
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std::vector<Node> children; |
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children.push_back(n[0]); |
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// add children to current scope |
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std::vector<TNode> fvss; |
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fvss.insert(fvss.end(), fvs.begin(), fvs.end()); |
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fvss.insert(fvss.end(), n[0].begin(), n[0].end()); |
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// process body in a new context |
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std::unordered_map<std::pair<Node, bool>, Node, NodePolPairHashFunction> |
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visitedSub; |
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Node pbody = preSkolemizeQuantifiers(n[1], polarity, fvss, visitedSub); |
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children.push_back(pbody); |
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// return processed quantifier |
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ret = nm->mkNode(FORALL, children); |
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} |
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} |
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else |
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{ |
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// will skolemize current, process body |
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Node nn = preSkolemizeQuantifiers(n[1], polarity, fvs, visited); |
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std::vector<Node> sk; |
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Node sub; |
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std::vector<unsigned> sub_vars; |
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// return skolemized body |
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ret = Skolemize::mkSkolemizedBody(n, nn, fvs, sk, sub, sub_vars); |
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} |
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visited[key] = ret; |
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return ret; |
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} |
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// check if it contains a quantifier as a subterm |
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// if so, we may preprocess this node |
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if (!expr::hasClosure(n)) |
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{ |
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visited[key] = n; |
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return n; |
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} |
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Kind k = n.getKind(); |
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Node ret = n; |
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Assert(n.getType().isBoolean()); |
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if (k == ITE || (k == EQUAL && n[0].getType().isBoolean())) |
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{ |
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if (options().quantifiers.preSkolemQuantAgg) |
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{ |
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Node nn; |
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// must remove structure |
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if (k == ITE) |
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{ |
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nn = nm->mkNode(AND, |
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nm->mkNode(OR, n[0].notNode(), n[1]), |
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nm->mkNode(OR, n[0], n[2])); |
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} |
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else if (k == EQUAL) |
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{ |
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nn = nm->mkNode(AND, |
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nm->mkNode(OR, n[0].notNode(), n[1]), |
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nm->mkNode(OR, n[0], n[1].notNode())); |
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} |
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ret = preSkolemizeQuantifiers(nn, polarity, fvs, visited); |
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} |
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} |
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else if (k == AND || k == OR || k == NOT || k == IMPLIES) |
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{ |
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std::vector<Node> children; |
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for (size_t i = 0, nchild = n.getNumChildren(); i < nchild; i++) |
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{ |
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bool newHasPol; |
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bool newPol; |
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QuantPhaseReq::getPolarity(n, i, true, polarity, newHasPol, newPol); |
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Assert(newHasPol); |
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children.push_back(preSkolemizeQuantifiers(n[i], newPol, fvs, visited)); |
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} |
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ret = nm->mkNode(k, children); |
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} |
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visited[key] = ret; |
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return ret; |
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} |
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TrustNode QuantifiersPreprocess::preprocess(Node n, bool isInst) const |
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{ |
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Node prev = n; |
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if (options().quantifiers.preSkolemQuant) |
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{ |
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if (!isInst || !options().quantifiers.preSkolemQuantNested) |
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{ |
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Trace("quantifiers-preprocess-debug") |
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<< "Pre-skolemize " << n << "..." << std::endl; |
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// apply pre-skolemization to existential quantifiers |
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std::vector<TNode> fvs; |
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std::unordered_map<std::pair<Node, bool>, Node, NodePolPairHashFunction> |
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visited; |
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n = preSkolemizeQuantifiers(prev, true, fvs, visited); |
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} |
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} |
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// pull all quantifiers globally |
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if (options().quantifiers.prenexQuant == options::PrenexQuantMode::NORMAL) |
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{ |
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Trace("quantifiers-prenex") << "Prenexing : " << n << std::endl; |
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std::map<Node, Node> visited; |
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n = computePrenexAgg(n, visited); |
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n = rewrite(n); |
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Trace("quantifiers-prenex") << "Prenexing returned : " << n << std::endl; |
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} |
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if (n != prev) |
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{ |
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Trace("quantifiers-preprocess") << "Preprocess " << prev << std::endl; |
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Trace("quantifiers-preprocess") << "..returned " << n << std::endl; |
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return TrustNode::mkTrustRewrite(prev, n, nullptr); |
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} |
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return TrustNode::null(); |
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} |
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} // namespace quantifiers |
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} // namespace theory |
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} // namespace cvc5 |