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/****************************************************************************** |
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* Top contributors (to current version): |
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* Andrew Reynolds, Mathias Preiner |
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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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* Substitution minimization. |
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*/ |
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#include "cvc5_private.h" |
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#ifndef CVC5__THEORY__SUBS_MINIMIZE_H |
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#define CVC5__THEORY__SUBS_MINIMIZE_H |
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#include <vector> |
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#include "expr/node.h" |
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#include "smt/env_obj.h" |
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namespace cvc5 { |
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namespace theory { |
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/** SubstitutionMinimize |
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* |
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* This class is used for finding a minimal substitution under which an |
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* evaluation holds. |
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*/ |
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class SubstitutionMinimize : protected EnvObj |
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{ |
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public: |
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SubstitutionMinimize(Env& env); |
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~SubstitutionMinimize() {} |
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/** find |
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* |
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* If t { vars -> subs } rewrites to target, this method returns true, and |
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* vars[i_1], ..., vars[i_n] are added to reqVars, such that i_1, ..., i_n are |
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* distinct, and t { vars[i_1] -> subs[i_1], ..., vars[i_n] -> subs[i_n] } |
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* rewrites to target. |
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* |
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* If t { vars -> subs } does not rewrite to target, this method returns |
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* false. |
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*/ |
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bool find(Node t, |
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Node target, |
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const std::vector<Node>& vars, |
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const std::vector<Node>& subs, |
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std::vector<Node>& reqVars); |
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/** find with implied |
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* |
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* This method should be called on a formula t. |
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* |
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* If t { vars -> subs } rewrites to true, this method returns true, |
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* vars[i_1], ..., vars[i_n] are added to reqVars, and |
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* vars[i_{n+1}], ..., vars[i_{n+m}] are added to impliedVars such that |
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* i_1...i_{n+m} are distinct, i_{n+1} < ... < i_{n+m}, and: |
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* |
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* (1) t { vars[i_1]->subs[i_1], ..., vars[i_{n+k}]->subs[i_{n+k}] } implies |
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* vars[i_{n+k+1}] = subs[i_{n+k+1}] for k = 0, ..., m-1. |
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* |
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* (2) t { vars[i_1] -> subs[i_1], ..., vars[i_{n+m}] -> subs[i_{n+m}] } |
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* rewrites to true. |
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* |
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* For example, given (x>0 ^ x = y ^ y = z){ x -> 1, y -> 1, z -> 1, w -> 0 }, |
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* this method may add { x } to reqVars, and { y, z } to impliedVars. |
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* |
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* Notice that the order of variables in vars matters. By the semantics above, |
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* variables that appear earlier in the variable list vars are more likely |
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* to appear in reqVars, whereas those later in the vars are more likely to |
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* appear in impliedVars. |
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*/ |
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bool findWithImplied(Node t, |
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const std::vector<Node>& vars, |
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const std::vector<Node>& subs, |
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std::vector<Node>& reqVars, |
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std::vector<Node>& impliedVars); |
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private: |
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/** Common helper function for the above functions. */ |
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bool findInternal(Node t, |
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Node target, |
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const std::vector<Node>& vars, |
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const std::vector<Node>& subs, |
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std::vector<Node>& reqVars); |
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/** is singular arg |
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* |
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* Returns true if |
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* <k>( ... t_{arg-1}, n, t_{arg+1}...) = c |
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* always holds for some constant c. |
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*/ |
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bool isSingularArg(Node n, Kind k, unsigned arg); |
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}; |
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} // namespace theory |
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} // namespace cvc5 |
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#endif /* CVC5__THEORY__SUBS_MINIMIZE_H */ |