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/******************************************************************************
* Top contributors (to current version):
* Gereon Kremer
*
* 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.
* ****************************************************************************
*
* Extract bounds on variables from theory atoms.
*/
#include "theory/arith/bound_inference.h"
#include "theory/arith/normal_form.h"
#include "theory/rewriter.h"
using namespace cvc5::kind;
namespace cvc5 {
namespace theory {
namespace arith {
std::ostream& operator<<(std::ostream& os, const Bounds& b) {
return os << (b.lower_strict ? '(' : '[') << b.lower_value << " .. "
<< b.upper_value << (b.upper_strict ? ')' : ']');
}
void BoundInference::reset() { d_bounds.clear(); }
Bounds& BoundInference::get_or_add(const Node& lhs)
{
auto it = d_bounds.find(lhs);
if (it == d_bounds.end())
{
it = d_bounds.emplace(lhs, Bounds()).first;
}
return it->second;
}
Bounds BoundInference::get(const Node& lhs) const
{
auto it = d_bounds.find(lhs);
if (it == d_bounds.end())
{
return Bounds();
}
return it->second;
}
const std::map<Node, Bounds>& BoundInference::get() const { return d_bounds; }
bool BoundInference::add(const Node& n, bool onlyVariables)
{
Node tmp = Rewriter::rewrite(n);
if (tmp.getKind() == Kind::CONST_BOOLEAN)
{
return false;
}
// Parse the node as a comparison
auto comp = Comparison::parseNormalForm(tmp);
auto dec = comp.decompose(true);
if (onlyVariables && !std::get<0>(dec).isVariable())
{
return false;
}
Node lhs = std::get<0>(dec).getNode();
Kind relation = std::get<1>(dec);
if (relation == Kind::DISTINCT) return false;
Node bound = std::get<2>(dec).getNode();
// has the form lhs ~relation~ bound
if (lhs.getType().isInteger())
{
Rational br = bound.getConst<Rational>();
auto* nm = NodeManager::currentNM();
switch (relation)
{
case Kind::LEQ:
bound = nm->mkConst<Rational>(CONST_RATIONAL, br.floor());
break;
case Kind::LT:
bound = nm->mkConst<Rational>(CONST_RATIONAL, (br - 1).ceiling());
relation = Kind::LEQ;
break;
case Kind::GT:
bound = nm->mkConst<Rational>(CONST_RATIONAL, (br + 1).floor());
relation = Kind::GEQ;
break;
case Kind::GEQ:
bound = nm->mkConst<Rational>(CONST_RATIONAL, br.ceiling());
break;
default:;
}
Trace("bound-inf") << "Strengthened " << n << " to " << lhs << " "
<< relation << " " << bound << std::endl;
}
switch (relation)
{
case Kind::LEQ: update_upper_bound(n, lhs, bound, false); break;
case Kind::LT: update_upper_bound(n, lhs, bound, true); break;
case Kind::EQUAL:
update_lower_bound(n, lhs, bound, false);
update_upper_bound(n, lhs, bound, false);
break;
case Kind::GT: update_lower_bound(n, lhs, bound, true); break;
case Kind::GEQ: update_lower_bound(n, lhs, bound, false); break;
default: Assert(false);
}
return true;
}
void BoundInference::replaceByOrigins(std::vector<Node>& nodes) const
{
std::vector<Node> toAdd;
for (auto& n : nodes)
{
for (const auto& b : d_bounds)
{
if (n == b.second.lower_bound && n == b.second.upper_bound)
{
if (n != b.second.lower_origin && n != b.second.upper_origin)
{
Trace("bound-inf")
<< "Replace " << n << " by origins " << b.second.lower_origin
<< " and " << b.second.upper_origin << std::endl;
n = b.second.lower_origin;
toAdd.emplace_back(b.second.upper_origin);
}
}
else if (n == b.second.lower_bound)
{
if (n != b.second.lower_origin)
{
Trace("bound-inf") << "Replace " << n << " by origin "
<< b.second.lower_origin << std::endl;
n = b.second.lower_origin;
}
}
else if (n == b.second.upper_bound)
{
if (n != b.second.upper_origin)
{
Trace("bound-inf") << "Replace " << n << " by origin "
<< b.second.upper_origin << std::endl;
n = b.second.upper_origin;
}
}
}
}
nodes.insert(nodes.end(), toAdd.begin(), toAdd.end());
}
void BoundInference::update_lower_bound(const Node& origin,
const Node& lhs,
const Node& value,
bool strict)
{
// lhs > or >= value because of origin
Trace("bound-inf") << "\tNew bound " << lhs << (strict ? ">" : ">=") << value
<< " due to " << origin << std::endl;
Bounds& b = get_or_add(lhs);
if (b.lower_value.isNull()
|| b.lower_value.getConst<Rational>() < value.getConst<Rational>())
{
auto* nm = NodeManager::currentNM();
b.lower_value = value;
b.lower_strict = strict;
b.lower_origin = origin;
if (!b.lower_strict && !b.upper_strict && b.lower_value == b.upper_value)
{
b.lower_bound = b.upper_bound =
Rewriter::rewrite(nm->mkNode(Kind::EQUAL, lhs, value));
}
else
{
b.lower_bound = Rewriter::rewrite(
nm->mkNode(strict ? Kind::GT : Kind::GEQ, lhs, value));
}
}
else if (strict && b.lower_value == value)
{
auto* nm = NodeManager::currentNM();
b.lower_strict = strict;
b.lower_bound = Rewriter::rewrite(nm->mkNode(Kind::GT, lhs, value));
b.lower_origin = origin;
}
}
void BoundInference::update_upper_bound(const Node& origin,
const Node& lhs,
const Node& value,
bool strict)
{
// lhs < or <= value because of origin
Trace("bound-inf") << "\tNew bound " << lhs << (strict ? "<" : "<=") << value
<< " due to " << origin << std::endl;
Bounds& b = get_or_add(lhs);
if (b.upper_value.isNull()
|| b.upper_value.getConst<Rational>() > value.getConst<Rational>())
{
auto* nm = NodeManager::currentNM();
b.upper_value = value;
b.upper_strict = strict;
b.upper_origin = origin;
if (!b.lower_strict && !b.upper_strict && b.lower_value == b.upper_value)
{
b.lower_bound = b.upper_bound =
Rewriter::rewrite(nm->mkNode(Kind::EQUAL, lhs, value));
}
else
{
b.upper_bound = Rewriter::rewrite(
nm->mkNode(strict ? Kind::LT : Kind::LEQ, lhs, value));
}
}
else if (strict && b.upper_value == value)
{
auto* nm = NodeManager::currentNM();
b.upper_strict = strict;
b.upper_bound = Rewriter::rewrite(nm->mkNode(Kind::LT, lhs, value));
b.upper_origin = origin;
}
}
std::ostream& operator<<(std::ostream& os, const BoundInference& bi)
{
os << "Bounds:" << std::endl;
for (const auto& b : bi.get())
{
os << "\t" << b.first << " -> " << b.second.lower_value << ".."
<< b.second.upper_value << std::endl;
}
return os;
}
std::map<Node, std::pair<Node,Node>> getBounds(const std::vector<Node>& assertions) {
BoundInference bi;
for (const auto& a: assertions) {
bi.add(a);
}
std::map<Node, std::pair<Node,Node>> res;
for (const auto& b : bi.get())
{
res.emplace(b.first,
std::make_pair(b.second.lower_value, b.second.upper_value));
}
return res;
}
} // namespace arith
} // namespace theory
} // namespace cvc5
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