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# eval.hxx

    00001 // eval.hxx: this file is part of the Vaucanson project.
    00002 //
    00003 // Vaucanson, a generic library for finite state machines.
    00004 //
    00005 // Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006 The Vaucanson Group.
    00006 //
    00007 // This program is free software; you can redistribute it and/or
    00008 // modify it under the terms of the GNU General Public License
    00009 // as published by the Free Software Foundation; either version 2
    00010 // of the License, or (at your option) any later version.
    00011 //
    00012 // The complete GNU General Public Licence Notice can be found as the
    00013 // `COPYING' file in the root directory.
    00014 //
    00015 // The Vaucanson Group consists of people listed in the `AUTHORS' file.
    00016 //
    00017 #ifndef VCSN_ALGORITHMS_EVAL_HXX
    00018 # define VCSN_ALGORITHMS_EVAL_HXX
    00019
    00020 # include <vaucanson/algorithms/eval.hh>
    00021 # include <vaucanson/automata/concept/automata_base.hh>
    00022 # include <vaucanson/misc/selectors.hh>
    00023 # include <vaucanson/misc/usual_macros.hh>
    00024 # include <algorithm>
    00025 # include <vector>
    00026
    00027 namespace vcsn {
    00028
    00029   /*-----.
    00030   | Eval |
    00031   `-----*/
    00032   // precondition : the automaton is realtime
    00033   template <typename auto_t, typename input_t, typename Selt>
    00034   struct eval_functor
    00035   {
    00036       AUTOMATON_TYPES(auto_t);
    00037
    00038       typedef std::vector<semiring_elt_t> weights;
    00039
    00040       const auto_t& a;
    00041       int max_hstate;
    00042
    00043       weights v1, v2;
    00044
    00045       typename weights::const_iterator w;
    00046       typename input_t::const_iterator l;
    00047
    00048       template <typename A>
    00049       eval_functor(const AutomataBase<A>&, const auto_t& aut)
    00050         : a(aut), max_hstate(a.states().max() + 1),
    00051           v1(max_hstate, a.series().semiring().wzero_), v2(max_hstate)
    00052       {}
    00053
    00054       void operator() (htransition_t t)
    00055       {
    00056         v2[a.dst_of(t)] += *w *
    00057           a.series_of(t).get(monoid_elt_t(a.structure().series().monoid(), *l));
    00058       }
    00059
    00060       void execute(const input_t& word, Selt& result)
    00061       {
    00062         const monoid_elt_t empty(a.series().monoid());
    00063
    00064         // Initialize
    00065         for_all_initial_states(i, a)
    00066           v1[*i] = a.get_initial(*i).get(empty);
    00067
    00068         const semiring_elt_t zero = a.series().semiring().wzero_;
    00069
    00070         // Computation
    00071         l = word.begin();
    00072         for (typename input_t::const_iterator w_end = word.end();
    00073              l != w_end; ++l)
    00074         {
    00075           std::fill(v2.begin(), v2.end(), zero);
    00076           int i = 0;
    00077           w = v1.begin();
    00078           for (typename weights::const_iterator v1_end = v1.end();
    00079                w != v1_end; ++w)
    00080           {
    00081             if (*w != zero)
    00082               a.letter_deltaf(*this, i, *l, delta_kind::transitions());
    00083             ++i;
    00084           }
    00085           std::swap(v1, v2);
    00086         }
    00087
    00088         // Result
    00089         result = zero;
    00090         int i = 0;
    00091         for_all_const_ (weights, w, v1)
    00092         {
    00093           if (*w != zero)
    00094             result += *w * a.get_final(i).get(empty);
    00095           ++i;
    00096         }
    00097       }
    00098   };
    00099
    00100   /*----------.
    00101   | Wrapper.  |
    00102   `----------*/
    00103   template<typename A, typename T, typename W>
    00104   typename Element<A, T>::semiring_elt_t
    00105   eval(const Element<A, T>& a, const W& word)
    00106   {
    00107     TIMER_SCOPED("eval");
    00108     typedef Element<A, T> auto_t;
    00109     AUTOMATON_TYPES(auto_t);
    00110     semiring_elt_t ret(a.structure().series().semiring());
    00111     eval_functor<auto_t, W, semiring_elt_t> evalf(a.structure(), a);
    00112
    00113     evalf.execute(word, ret);
    00114     return ret;
    00115   }
    00116
    00117 } // vcsn
    00118
    00119 #endif // ! VCSN_ALGORITHMS_EVAL_HXX