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/********************* */
/*! \file synth_rew_rules.cpp
** \verbatim
** Top contributors (to current version):
** Andrew Reynolds
** This file is part of the CVC4 project.
** Copyright (c) 2009-2018 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 A technique for synthesizing candidate rewrites of the form t1 = t2,
** where t1 and t2 are subterms of the input.
**/
#include "preprocessing/passes/synth_rew_rules.h"
#include "options/base_options.h"
#include "options/quantifiers_options.h"
#include "preprocessing/preprocessing_pass_registry.h"
#include "printer/printer.h"
#include "theory/quantifiers/candidate_rewrite_database.h"
using namespace std;
namespace CVC4 {
namespace preprocessing {
namespace passes {
// Attribute for whether we have computed rewrite rules for a given term.
// Notice that this currently must be a global attribute, since if
// we've computed rewrites for a term, we should not compute rewrites for the
// same term in a subcall to another SmtEngine (for instance, when using
// "exact" equivalence checking).
struct SynthRrComputedAttributeId
{
};
typedef expr::Attribute<SynthRrComputedAttributeId, bool>
SynthRrComputedAttribute;
SynthRewRulesPass::SynthRewRulesPass(PreprocessingPassContext* preprocContext)
: PreprocessingPass(preprocContext, "synth-rr"){};
PreprocessingPassResult SynthRewRulesPass::applyInternal(
AssertionPipeline* assertionsToPreprocess)
{
Trace("synth-rr-pass") << "Synthesize rewrite rules from assertions..."
<< std::endl;
std::vector<Node>& assertions = assertionsToPreprocess->ref();
// compute the variables we will be sampling
std::vector<Node> vars;
unsigned nsamples = options::sygusSamples();
Options& nodeManagerOptions = NodeManager::currentNM()->getOptions();
// attribute to mark processed terms
SynthRrComputedAttribute srrca;
// initialize the candidate rewrite
std::unique_ptr<theory::quantifiers::CandidateRewriteDatabaseGen> crdg;
std::unordered_map<TNode, bool, TNodeHashFunction> visited;
std::unordered_map<TNode, bool, TNodeHashFunction>::iterator it;
std::vector<TNode> visit;
// two passes: the first collects the variables, the second registers the
// terms
for (unsigned r = 0; r < 2; r++)
{
visited.clear();
visit.clear();
TNode cur;
for (const Node& a : assertions)
{
visit.push_back(a);
do
{
cur = visit.back();
visit.pop_back();
it = visited.find(cur);
// if already processed, ignore
if (cur.getAttribute(SynthRrComputedAttribute()))
{
Trace("synth-rr-pass-debug")
<< "...already processed " << cur << std::endl;
}
else if (it == visited.end())
{
Trace("synth-rr-pass-debug") << "...preprocess " << cur << std::endl;
visited[cur] = false;
Kind k = cur.getKind();
bool isQuant = k == kind::FORALL || k == kind::EXISTS
|| k == kind::LAMBDA || k == kind::CHOICE;
// we recurse on this node if it is not a quantified formula
if (!isQuant)
{
visit.push_back(cur);
for (const Node& cc : cur)
{
visit.push_back(cc);
}
}
}
else if (!it->second)
{
Trace("synth-rr-pass-debug") << "...postprocess " << cur << std::endl;
// check if all of the children are valid
// this ensures we do not register terms that have e.g. quantified
// formulas as subterms
bool childrenValid = true;
for (const Node& cc : cur)
{
Assert(visited.find(cc) != visited.end());
if (!visited[cc])
{
childrenValid = false;
}
}
if (childrenValid)
{
Trace("synth-rr-pass-debug")
<< "...children are valid, check rewrites..." << std::endl;
if (r == 0)
{
if (cur.isVar())
{
vars.push_back(cur);
}
}
else
{
Trace("synth-rr-pass-debug") << "Add term " << cur << std::endl;
// mark as processed
cur.setAttribute(srrca, true);
bool ret = crdg->addTerm(cur, *nodeManagerOptions.getOut());
Trace("synth-rr-pass-debug") << "...return " << ret << std::endl;
// if we want only rewrites of minimal size terms, we would set
// childrenValid to false if ret is false here.
}
}
visited[cur] = childrenValid;
}
} while (!visit.empty());
}
if (r == 0)
{
Trace("synth-rr-pass-debug")
<< "Initialize with " << nsamples
<< " samples and variables : " << vars << std::endl;
crdg = std::unique_ptr<theory::quantifiers::CandidateRewriteDatabaseGen>(
new theory::quantifiers::CandidateRewriteDatabaseGen(vars, nsamples));
}
}
Trace("synth-rr-pass") << "...finished " << std::endl;
return PreprocessingPassResult::NO_CONFLICT;
}
static RegisterPass<SynthRewRulesPass> X("synth-rr");
} // namespace passes
} // namespace preprocessing
} // namespace CVC4
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