mirror of
https://github.com/ethereum/solidity
synced 2023-10-03 13:03:40 +00:00
97 lines
2.6 KiB
C++
97 lines
2.6 KiB
C++
/*
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This file is part of solidity.
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solidity is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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solidity is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with solidity. If not, see <http://www.gnu.org/licenses/>.
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*/
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// SPDX-License-Identifier: GPL-3.0
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#pragma once
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#include <libsolutil/Numeric.h>
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#include <libsolutil/LinearExpression.h>
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#include <boost/rational.hpp>
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#include <vector>
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#include <variant>
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namespace solidity::util
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{
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/**
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* Constraint of the form
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* - data[1] * x_1 + data[2] * x_2 + ... <= data[0] (equality == false)
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* - data[1] * x_1 + data[2] * x_2 + ... = data[0] (equality == true)
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* The set and order of variables is implied.
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*/
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struct Constraint
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{
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LinearExpression data;
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bool equality = false;
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bool operator<(Constraint const& _other) const;
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bool operator==(Constraint const& _other) const;
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};
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/**
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* State used when solving an LP problem.
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*/
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struct SolvingState
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{
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/// Names of variables, the index zero should be left empty
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/// (because zero corresponds to constants).
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std::vector<std::string> variableNames;
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struct Bounds
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{
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std::optional<rational> lower;
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std::optional<rational> upper;
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bool operator<(Bounds const& _other) const { return make_pair(lower, upper) < make_pair(_other.lower, _other.upper); }
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bool operator==(Bounds const& _other) const { return make_pair(lower, upper) == make_pair(_other.lower, _other.upper); }
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};
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/// Lower and upper bounds for variables (in the sense of >= / <=).
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std::vector<Bounds> bounds;
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std::vector<Constraint> constraints;
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bool operator<(SolvingState const& _other) const;
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bool operator==(SolvingState const& _other) const;
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std::string toString() const;
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};
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enum class LPResult
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{
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Unknown,
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Unbounded,
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Feasible,
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Infeasible
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};
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/**
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* LP solver for rational problems.
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*
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* Does not solve integer problems!
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*
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* Tries to split a given problem into sub-problems and utilizes a cache to quickly solve
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* similar problems.
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*/
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class LPSolver
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{
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public:
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std::pair<LPResult, std::map<std::string, boost::rational<bigint>>> check(SolvingState _state);
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private:
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// TODO check if the model is requested in production. If not, we do not need to cache it.
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std::map<SolvingState, std::pair<LPResult, std::vector<boost::rational<bigint>>>> m_cache;
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};
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}
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