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# product.hxx

    00001 // product.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, 2007, 2008 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_PRODUCT_HXX
    00018 # define VCSN_ALGORITHMS_PRODUCT_HXX
    00019
    00020 # include <set>
    00021 # include <map>
    00022 # include <queue>
    00023 # include <stack>
    00024
    00025 # include <vaucanson/algorithms/product.hh>
    00026
    00027 # ifndef VCSN_NDEBUG
    00028 #  include <vaucanson/algorithms/realtime.hh>
    00029 # endif // ! VCSN_NDEBUG
    00030
    00031 # include <vaucanson/automata/concept/automata_base.hh>
    00032 # include <vaucanson/misc/usual_macros.hh>
    00033 # include <vaucanson/automata/implementation/geometry.hh>
    00034 # include <vaucanson/misc/static.hh>
    00035
    00036 namespace vcsn
    00037 {
    00038
    00039 /*--------------------------------.
    00040 | Functor for product algorithm.  |
    00041 `--------------------------------*/
    00042 template<typename A, typename T, typename U>
    00043 class Product
    00044 {
    00045   public:
    00046     typedef AutomataBase<A> structure_t;
    00047     typedef Element<A, T> lhs_t;
    00048     typedef Element<A, U> rhs_t;
    00049     typedef lhs_t           output_t;
    00050     typedef std::map<typename output_t::hstate_t,
    00051               std::pair<typename lhs_t::hstate_t, typename rhs_t::hstate_t> >
    00052                           pair_map_t;
    00053
    00054     Product (const structure_t& structure,
    00055              const bool use_geometry)
    00056       : use_geometry_(use_geometry),
    00057         series_(structure.series()),
    00058         monoid_(series_.monoid()),
    00059         semiring_zero_(series_.semiring().zero(SELECT(semiring_elt_value_t)))
    00060     {
    00061     }
    00062
    00063     // returns the product of @c lhs and @c rhs (and put it also in @c output)
    00064     output_t&
    00065     operator() (output_t& output,
    00066                 const lhs_t& lhs,
    00067                 const rhs_t& rhs,
    00068                 pair_map_t& m)
    00069     {
    00070       BENCH_TASK_SCOPED("product");
    00071       visited_.clear();
    00072
    00073       precondition(is_realtime(lhs));
    00074       precondition(is_realtime(rhs));
    00075
    00076       this->initialize_queue(output, lhs, rhs, m);
    00077
    00078       while (not to_process_.empty())
    00079       {
    00080         const pair_hstate_t current_pair = to_process_.front();
    00081         to_process_.pop();
    00082
    00083         const hstate_t lhs_s         = current_pair.first;
    00084         const hstate_t rhs_s         = current_pair.second;
    00085         const hstate_t current_state = visited_[current_pair];
    00086
    00087         output.set_initial(current_state,
    00088                            lhs.get_initial(lhs_s) * rhs.get_initial(rhs_s));
    00089         output.set_final(current_state,
    00090                          lhs.get_final(lhs_s) * rhs.get_final(rhs_s));
    00091
    00092         for (typename lhs_t::delta_iterator l(lhs.value(), lhs_s);
    00093              ! l.done();
    00094              l.next())
    00095           for (typename rhs_t::delta_iterator r(rhs.value(), rhs_s);
    00096                ! r.done();
    00097                r.next())
    00098           {
    00099             series_set_elt_t    prod_series(series_);
    00100
    00101             if (is_product_not_null(lhs, rhs, l, r, prod_series))
    00102             {
    00103               const pair_hstate_t new_pair(lhs.dst_of(*l), rhs.dst_of(*r));
    00104               typename visited_t::const_iterator found = visited_.find(new_pair);
    00105
    00106               hstate_t dst;
    00107               if (found == visited_.end())
    00108               {
    00109                 dst = output.add_state();
    00110
    00111                 this->add_state_to_process(output, lhs, rhs, m, dst, new_pair);
    00112               }
    00113               else
    00114                 dst = found->second;
    00115               output.add_series_transition(current_state, dst, prod_series);
    00116             }
    00117           }
    00118       }
    00119       return output;
    00120     }
    00121
    00122   private:
    00123     // Some little graphic tools
    00124     class grphx
    00125     {
    00126       public:
    00127         template <typename Output, typename Lhs, typename Rhs>
    00128         static void
    00129         setcoordfrom (Output& a,
    00130                       const Lhs& lhs,
    00131                       const Rhs& rhs,
    00132                       const typename Output::hstate_t state,
    00133                       const typename Lhs::hstate_t x_state,
    00134                       const typename Rhs::hstate_t y_state)
    00135         {
    00136           typename std::map<typename Lhs::hstate_t,
    00137             typename Lhs::geometry_t::coords_t>::const_iterator iter;
    00138           typename std::map<typename Rhs::hstate_t,
    00139             typename Rhs::geometry_t::coords_t>::const_iterator iter2;
    00140           double x = 0, y = 0;
    00141
    00142           iter = lhs.geometry().states().find(x_state);
    00143           if (iter != lhs.geometry().states().end())
    00144             x = iter->second.first;
    00145
    00146           iter2 = rhs.geometry().states().find(y_state);
    00147           if (iter2 != rhs.geometry().states().end())
    00148             y = iter2->second.second;
    00149
    00150           a.geometry().states()[state] = std::make_pair(x, y);
    00151         }
    00152       private:
    00153         // Diagonal alignement with a depth-first traversal
    00154         template<typename I>
    00155         void
    00156         align (const I& a)
    00157         {
    00158           AUTOMATON_TYPES(I);
    00159           std::map<hstate_t,bool> visited;
    00160           std::stack<hstate_t> stack;
    00161
    00162           for_all_const_states(i, a)
    00163             {
    00164               visited[*i] = false;
    00165               // ensure inaccessible states will be visited
    00166               stack.push(*i);
    00167             }
    00168
    00169           for_all_const_initial_states(i, a)
    00170             stack.push(*i);
    00171
    00172           int x = 0;
    00173           while (!stack.empty())
    00174           {
    00175             hstate_t i = stack.top();
    00176             stack.pop();
    00177
    00178             if (!visited[i])
    00179             {
    00180               visited[i] = true;
    00181
    00182               a.geometry()[i] = std::make_pair(x, x);
    00183               x++;
    00184
    00185               for (delta_iterator j(a.value(), i);
    00186                    ! j.done();
    00187                    j.next())
    00188                 stack.push(a.dst_of(*j));
    00189             }
    00190           }
    00191         }
    00192
    00193     };
    00194     class no_grphx
    00195     {
    00196       public:
    00197         template <typename Output, typename Lhs, typename Rhs>
    00198         static void
    00199         setcoordfrom (Output& a,
    00200                       const Lhs& lhs,
    00201                       const Rhs& rhs,
    00202                       const typename Output::hstate_t state,
    00203                       const typename Lhs::hstate_t x_state,
    00204                       const typename Rhs::hstate_t y_state) {};
    00205     };
    00206
    00207     // useful typedefs
    00208     AUTOMATON_TYPES(output_t);
    00209
    00210     typedef std::pair<typename lhs_t::hstate_t, typename rhs_t::hstate_t>
    00211                                                       pair_hstate_t;
    00212     typedef std::list<htransition_t>                    delta_ret_t;
    00213     typedef std::map<pair_hstate_t, hstate_t>           visited_t;
    00214     typedef typename series_set_elt_t::support_t        support_t;
    00215
    00216     // add a @c new_state in the queue
    00217     inline void
    00218     add_state_to_process (output_t& output,
    00219                           const lhs_t& lhs,
    00220                           const rhs_t& rhs,
    00221                           pair_map_t& m,
    00222                           const hstate_t& new_state,
    00223                           const pair_hstate_t& new_pair)
    00224     {
    00225       m[new_state] = new_pair;
    00226       visited_[new_pair] = new_state;
    00227       to_process_.push(new_pair);
    00228
    00229 # define if_(Cond, ThenClause, ElseClause)                      \
    00230 misc::static_if_simple<Cond, ThenClause, ElseClause>::t
    00231 # define eq_(Type1, Type2)                      \
    00232 misc::static_eq<Type1, Type2>::value
    00233 # define DECLARE_GEOMETRY(Type) \
    00234   typedef geometry<typename Type::hstate_t, typename Type::htransition_t, typename Type::geometry_coords_t> geometry_ ## Type ;
    00235
    00236       DECLARE_GEOMETRY(output_t)
    00237       DECLARE_GEOMETRY(lhs_t)
    00238       DECLARE_GEOMETRY(rhs_t)
    00239       if (use_geometry_)
    00240         if_(eq_(typename output_t::geometry_t, geometry_output_t)  and \
    00241             eq_(typename rhs_t::geometry_t, geometry_rhs_t) and \
    00242             eq_(typename lhs_t::geometry_t, geometry_lhs_t),    \
    00243             grphx, no_grphx)
    00244           ::setcoordfrom(output, lhs, rhs,
    00245                          new_state, new_pair.first, new_pair.second);
    00246 # undef if_
    00247 # undef eq_
    00248     }
    00249
    00250     // initialize queue with all pairs of intials states from @c lhs and @c rhs
    00251     inline void
    00252     initialize_queue (output_t& output,
    00253                       const lhs_t& lhs,
    00254                       const rhs_t& rhs,
    00255                       pair_map_t& m)
    00256     {
    00257       for_all_const_initial_states(lhs_s, lhs)
    00258         for_all_const_initial_states(rhs_s, rhs)
    00259         {
    00260           const pair_hstate_t   new_pair(*lhs_s, *rhs_s);
    00261           const hstate_t        new_state = output.add_state();
    00262
    00263           this->add_state_to_process(output, lhs, rhs, m, new_state, new_pair);
    00264         }
    00265     }
    00266
    00267     inline bool
    00268     is_product_not_null (const lhs_t& lhs,
    00269                          const rhs_t& rhs,
    00270                          const typename lhs_t::delta_iterator& l,
    00271                          const typename rhs_t::delta_iterator& r,
    00272                          series_set_elt_t&  prod_series) const
    00273     {
    00274       const series_set_elt_t    left_series  = lhs.series_of(*l);
    00275       const series_set_elt_t    right_series = rhs.series_of(*r);
    00276
    00277       bool                      prod_is_not_null = false;
    00278       for_all_(support_t, supp, left_series.supp())
    00279         {
    00280           const monoid_elt_t     supp_elt (monoid_, *supp);
    00281           const semiring_elt_t l = left_series.get(supp_elt);
    00282           const semiring_elt_t r = right_series.get(supp_elt);
    00283           const semiring_elt_t p = l * r;
    00284           if (p != semiring_zero_)
    00285           {
    00286             prod_series.assoc(*supp, p.value());
    00287             prod_is_not_null = true;
    00288           }
    00289         }
    00290       return (prod_is_not_null);
    00291     }
    00292
    00293     // If set to true, <geometry> tags of the result automaton should be filled
    00294     const bool  use_geometry_;
    00295
    00296     // keep traces of new states created
    00297     visited_t                   visited_;
    00298     // @c to_process_ stores all states of output that needs are not
    00299     std::queue<pair_hstate_t>   to_process_;
    00300
    00301     // frequently used objects in computation
    00302     const series_set_t& series_;
    00303     const monoid_t&             monoid_;
    00304     // This variable's type must not be set to a reference.
    00305     const semiring_elt_t        semiring_zero_;
    00306 };
    00307
    00308 /*-----------.
    00309 | Wrappers.  |
    00310 `-----------*/
    00311
    00312 template<typename A, typename T, typename U>
    00313 Element<A, T>
    00314 product (const Element<A, T>& lhs, const Element<A, U>& rhs,
    00315          std::map<typename T::hstate_t,
    00316          std::pair<typename T::hstate_t, typename U::hstate_t> >& m,
    00317          const bool use_geometry)
    00318 {
    00319   Element<A, T> ret(rhs.structure());
    00320   Product<A, T, U> do_product(ret.structure(), use_geometry);
    00321   return do_product (ret, lhs, rhs, m);
    00322 }
    00323
    00324 template<typename A, typename T, typename U>
    00325 Element<A, T>
    00326 product (const Element<A, T>& lhs, const Element<A, U>& rhs,
    00327          const bool use_geometry)
    00328 {
    00329   std::map<typename T::hstate_t,
    00330     std::pair<typename T::hstate_t, typename U::hstate_t> > m;
    00331   return product (lhs, rhs, m, use_geometry);
    00332 }
    00333
    00334 } // End of namespace vcsn.
    00335
    00336 #endif // ! VCSN_ALGORITHMS_PRODUCT_HXX