union_find.hh

// Copyright (C) 2007, 2008, 2009 EPITA Research and Development Laboratory (LRDE)
//
// This file is part of Olena.
//
// Olena 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, version 2 of the License.
//
// Olena 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 Olena.  If not, see <http://www.gnu.org/licenses/>.
//
// As a special exception, you may use this file as part of a free
// software project without restriction.  Specifically, if other files
// instantiate templates or use macros or inline functions from this
// file, or you compile this file and link it with other files to produce
// an executable, this file does not by itself cause the resulting
// executable to be covered by the GNU General Public License.  This
// exception does not however invalidate any other reasons why the
// executable file might be covered by the GNU General Public License.

#ifndef MLN_MORPHO_RECONSTRUCTION_BY_EROSION_UNION_FIND_HH
# define MLN_MORPHO_RECONSTRUCTION_BY_EROSION_UNION_FIND_HH

# include <vector>
# include <mln/core/concept/image.hh>
# include <mln/core/concept/neighborhood.hh>
# include <mln/data/fill.hh>
# include <mln/data/compare.hh>
# include <mln/data/sort_psites.hh>


namespace mln
{

  namespace morpho
  {

    namespace reconstruction
    {

      namespace by_erosion
      {


        template <typename I, typename J, typename N>
        mln_concrete(I)
        union_find(const Image<I>& f, const Image<J>& g,
                   const Neighborhood<N>& nbh);


# ifndef MLN_INCLUDE_ONLY


        // Tests.

        namespace internal
        {

          template <typename I, typename J, typename N>
          inline
          void
          union_find_tests(const Image<I>& f_, const Image<J>& g_,
                           const Neighborhood<N>& nbh_)
          {
            const I& f = exact(f_);
            const J& g = exact(g_);
            const N& nbh = exact(nbh_);

            mln_precondition(f.is_valid());
            mln_precondition(g.is_valid());
            mln_precondition(nbh.is_valid());

            mln_precondition(f.domain() == g.domain()); // FIXME: Relax?
            mln_precondition(f >= g);

            // mlc_equal(mln_value(I), mln_value(J))::check(); // FIXME: Too strong!
            // FIXME: Also check that we have a total ordering for values.

            (void) f;
            (void) g;
            (void) nbh;
          }



          template <typename Par>
          inline
          mln_site(Par) find_root(Par& parent, mln_site(Par) x)
          {
            if (parent(x) == x)
              return x;
            else
              return parent(x) = find_root(parent, parent(x));
          }


        } // end of namespace mln::morpho::reconstruction::by_erosion::internal


        // Implementations.

        namespace impl
        {

          namespace generic
          {

            template <typename I, typename J, typename N>
            inline
            mln_concrete(I)
            union_find(const Image<I>& f_, const Image<J>& g_,
                       const Neighborhood<N>& nbh_)
            {
              trace::entering("morpho::reconstruction::by_erosion::impl::generic::union_find");

              const I& f = exact(f_);
              const J& g = exact(g_);
              const N& nbh = exact(nbh_);

              internal::union_find_tests(f, g, nbh);

              typedef mln_site(I)  P;
              typedef mln_value(I) V;

              // Auxiliary data.
              p_array<P> s;
              mln_ch_value(I, bool) deja_vu;
              mln_ch_value(I, P)    parent;
              mln_concrete(I)       output;

              // Initialization.
              {
                initialize(output, f);
                data::fill(output, f);
                initialize(parent, f);
                initialize(deja_vu, f);
                data::fill(deja_vu, false);

                s = data::sort_psites_increasing(g);
              }

              // First pass.
              {
                for (unsigned i = 0; i < s.nsites(); ++i)
                  {
                    P p = s[i];
                    parent(p) = p; // Make-Set.
                    mln_niter(N) n(nbh, p);
                    for_all(n)
                    {
//                    if (f.domain().has(n))
//                      mln_invariant(deja_vu(n)
//                                    ==
//                                    (g(n) > g(p) || (g(n) == g(p)
//                                                     && util::ord_strict(n, p))));
                      if (f.domain().has(n) && deja_vu(n))
                        {
                          // Do-Union.
                          P r = internal::find_root(parent, n);
                          if (r != p)
                            {
                              if (g(r) == g(p) || g(p) <= output(r)) // Equivalence test.
                                {
                                  parent(r) = p;
                                  if (output(r) < output(p))
                                    output(p) = output(r); // Increasing criterion.
                                }
                              else
                                output(p) = mln_min(V);
                            }
                        }
                    }
                    deja_vu(p) = true;
                  }
              }

              // Second pass.
              {
                for (int i = s.nsites() - 1; i >= 0; --i)
                  {
                    P p = s[i];
                    if (parent(p) == p)
                      {
                        if (output(p) == mln_min(V))
                          output(p) = g(p);
                      }
                    else
                      output(p) = output(parent(p));
                  }
              }

              mln_postcondition(output >= f);
              mln_postcondition(output >= g);

              trace::exiting("morpho::reconstruction::by_erosion::impl::generic::union_find");
              return output;
            }

          } // end of namespace mln::morpho::reconstruction::by_erosion::impl::generic

        } // end of namespace mln::morpho::reconstruction::by_erosion::impl


        // Dispatch.

        namespace internal
        {

          template <typename I, typename J, typename N>
          inline
          mln_concrete(I)
          union_find_dispatch(trait::image::kind::logic,
                              const Image<I>& f, const Image<J>& g,
                              const Neighborhood<N>& nbh)
          {
            // FIXME: Not yet implemented.
          }

          template <typename I, typename J, typename N>
          inline
          mln_concrete(I)
          union_find_dispatch(trait::image::kind::any,
                              const Image<I>& f, const Image<J>& g,
                              const Neighborhood<N>& nbh)
          {
            return impl::generic::union_find(f, g, nbh);
          }

          template <typename I, typename J, typename N>
          inline
          mln_concrete(I)
          union_find_dispatch(const Image<I>& f, const Image<J>& g,
                              const Neighborhood<N>& nbh)
          {
            return union_find_dispatch(mln_trait_image_kind(I)(),
                                       f, g, nbh);
          }

        } // end of namespace mln::morpho::reconstruction::by_erosion::internal


        // Facade.

        template <typename I, typename J, typename N>
        inline
        mln_concrete(I)
        union_find(const Image<I>& f, const Image<J>& g,
                   const Neighborhood<N>& nbh)
        {
          trace::entering("morpho::reconstruction::by_erosion::union_find");

          internal::union_find_tests(f, g, nbh);

          mln_concrete(I) output;
          output = internal::union_find_dispatch(f, g, nbh);

          trace::exiting("morpho::reconstruction::by_erosion::union_find");
          return output;
        }

# endif // ! MLN_INCLUDE_ONLY

      } // end of namespace mln::morpho::reconstruction::by_erosion

    } // end of namespace mln::morpho::reconstruction

  } // end of namespace mln::morpho

} // end of namespace mln


#endif // ! MLN_MORPHO_RECONSTRUCTION_BY_EROSION_UNION_FIND_HH