MinimizeVerbose.h

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/*
 * This file is part of Algorithms library toolkit.
 * Copyright (C) 2017 Jan Travnicek (jan.travnicek@fit.cvut.cz)
 
 * Algorithms library toolkit is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 
 * Algorithms library toolkit is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 
 * You should have received a copy of the GNU General Public License
 * along with Algorithms library toolkit.  If not, see <http://www.gnu.org/licenses/>.
 */
 
#pragma once
 
#include <automaton/FSM/DFA.h>
#include <automaton/TA/DFTA.h>
 
#include <alib/map>
#include <alib/set>
 
#include <global/GlobalData.h>
 
namespace automaton {
 
namespace simplify {
 
class MinimizeVerbose {
public:
    template < class SymbolType, class StateType >
    static ext::vector < ext::map < std::pair < StateType, StateType >, ext::map < SymbolType, StateType > > > minimize(const automaton::DFA < SymbolType, StateType >& dfa );
 
private:
    template < class SymbolType, class StateType >
    static ext::map < std::pair < StateType, StateType >, ext::map < SymbolType, StateType > > print_progress ( const ext::map<std::pair<StateType, ext::set<std::pair<SymbolType, StateType> > >, ext::set<StateType> >& minimizedTransitionFunction);
};
 
template < class SymbolType, class StateType >
ext::vector < ext::map < std::pair < StateType, StateType >, ext::map < SymbolType, StateType > > > MinimizeVerbose::minimize(const automaton::DFA < SymbolType, StateType >& dfa ) {
    ext::vector < ext::map < std::pair < StateType, StateType >, ext::map < SymbolType, StateType > > > res;
 
    ext::map<StateType, ext::map<SymbolType, StateType > > refactor;
 
    for(const StateType& state : dfa.getStates())
        refactor.insert(std::make_pair(state, ext::map<SymbolType, StateType>()));
 
    for(const std::pair<const ext::pair<StateType, SymbolType>, StateType>& transition : dfa.getTransitions())
        refactor[transition.first.first].insert(std::make_pair(transition.first.second, transition.second));
 
    ext::map<StateType, StateType> toEquivalentStates; //original state to equivalent state
    ext::map<std::pair<StateType, ext::set<std::pair<SymbolType, StateType> > >, ext::set<StateType> > minimizedTransitionFunction; //mapped to the original state
 
    const StateType *firstFinal = nullptr;
    const StateType *firstNonfinal = nullptr;
    for(const StateType& state : dfa.getStates()) {
        if(dfa.getFinalStates().count(state) == 0) { // not a final state
            if(!firstNonfinal)
                firstNonfinal = &state;
            toEquivalentStates.insert(std::pair<StateType, StateType>(state, *firstNonfinal));
        } else {
            if(!firstFinal)
                firstFinal = &state;
            toEquivalentStates.insert(std::pair<StateType, StateType>(state, *firstFinal));
        }
    }
 
    unsigned prevSize = 0;
    while ( true ) {
        for(const std::pair<const StateType, ext::map<SymbolType, StateType> >& transition : refactor) {
            const StateType& from = toEquivalentStates.find(transition.first)->second;
            ext::set<std::pair<SymbolType, StateType> > transitionFunction;
 
            for(const std::pair<const SymbolType, StateType> & transitionFromState : transition.second)
                transitionFunction.insert(std::make_pair(transitionFromState.first, toEquivalentStates.find(transitionFromState.second)->second));
 
            minimizedTransitionFunction[std::make_pair(from, transitionFunction)].insert(transition.first);
        }
 
        res.push_back ( print_progress ( minimizedTransitionFunction) );
 
        if (minimizedTransitionFunction.size() == prevSize)
            break;
 
        prevSize = minimizedTransitionFunction.size();
        toEquivalentStates.clear();
 
        for(const std::pair<const std::pair<StateType, ext::set<std::pair<SymbolType, StateType> > >, ext::set<StateType> >& transition : minimizedTransitionFunction)
            for(const StateType& target : transition.second)
                toEquivalentStates.insert(std::make_pair(target, *(transition.second.begin())));
 
        minimizedTransitionFunction.clear();
    }
 
    return res;
}
 
#define RESETSS(x) {(x).clear(); (x).str("");}
 
template < class SymbolType, class StateType >
ext::map<std::pair<StateType, StateType>, ext::map<SymbolType, StateType>> MinimizeVerbose::print_progress ( const ext::map<std::pair<StateType, ext::set<std::pair<SymbolType, StateType> > >, ext::set<StateType> >& minimizedTransitionFunction) {
    /* need to restruct this first so we have table like:   orig state | new state | trans_symb_1 | trans_symb_2 | ... | trans_symb_n */
    // we surely have DFA here (transition map hence)
    ext::map<std::pair<StateType, StateType>, ext::map<SymbolType, StateType>> printMap;
    for(const auto& kv: minimizedTransitionFunction) {
        for(const auto& state : kv.second) {
            ext::map<SymbolType, StateType> stateTransMap;
            for(const auto& transition : kv.first.second) {
                stateTransMap.insert(std::make_pair(transition.first, transition.second));
            }
            printMap.insert(std::make_pair(std::make_pair(state, kv.first.first), stateTransMap));
        }
    }
    return printMap;
}
 
} /* namespace simplify */
 
} /* namespace automaton */