TangencyComputer.ih

/**
 *  This program is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU Lesser General Public License as
 *  published by the Free Software Foundation, either version 3 of the
 *  License, or  (at your option) any later version.
 *
 *  This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 **/
 
/**
 * @file TangencyComputer.ih
 * @author Jacques-Olivier Lachaud (\c jacques-olivier.lachaud@univ-savoie.fr )
 * Laboratory of Mathematics (CNRS, UMR 5127), University of Savoie, France
 *
 * @date 2021/07/16
 *
 * Implementation of inline methods defined in TangencyComputer.h
 *
 * This file is part of the DGtal library.
 */
 
 
//////////////////////////////////////////////////////////////////////////////
#include <cstdlib>
//////////////////////////////////////////////////////////////////////////////
 
///////////////////////////////////////////////////////////////////////////////
// class TangencyComputer
///////////////////////////////////////////////////////////////////////////////
 
//-----------------------------------------------------------------------------
template <typename TKSpace>
DGtal::TangencyComputer<TKSpace>::
TangencyComputer( Clone<KSpace> K )
  : myK( K ), myDConv( myK ), myLatticeCellCover( false )
{
  setUp();
}
 
//-----------------------------------------------------------------------------
template < typename TKSpace >
template < typename PointIterator >
void
DGtal::TangencyComputer<TKSpace>::
init( PointIterator itB, PointIterator itE, bool use_lattice_cell_cover )
{
  myX = std::vector< Point >( itB, itE );
  myUseLatticeCellCover = use_lattice_cell_cover;
  if ( use_lattice_cell_cover )
    myLatticeCellCover = LatticeCellCover( myX.cbegin(), myX.cend() ).starOfPoints();
  else
    myCellCover =
      myDConv.makeCellCover( myX.cbegin(), myX.cend(), 1, KSpace::dimension - 1 );    
  for ( Size i = 0; i < myX.size(); ++i )
    myPt2Index[ myX[ i ] ] = i;
}
 
//-----------------------------------------------------------------------------
template < typename TKSpace >
bool
DGtal::TangencyComputer<TKSpace>::
arePointsCotangent( const Point& a, const Point& b ) const
{
  return myUseLatticeCellCover
    ? myDConv.isFullySubconvex( a, b, myLatticeCellCover )
    : myDConv.isFullySubconvex( a, b, myCellCover );
}
 
//-----------------------------------------------------------------------------
template < typename TKSpace >
bool
DGtal::TangencyComputer<TKSpace>::
arePointsCotangent( const Point& a, const Point& b, const Point& c ) const
{
  std::vector< Point > Z { a, b, c };
  const auto P = myDConv.makePolytope( Z );
  return myUseLatticeCellCover
    ? myDConv.isFullySubconvex( P, myLatticeCellCover )
    : myDConv.isFullySubconvex( P, myCellCover );
}
 
//-----------------------------------------------------------------------------
template < typename TKSpace >
std::vector< typename DGtal::TangencyComputer<TKSpace>::Index >
DGtal::TangencyComputer<TKSpace>::
getCotangentPoints( const Point& a ) const
{
  // Breadth-first traversal from a
  std::vector< Index > R; // result
  std::set   < Index > V; // visited or in queue
  std::queue < Index > Q; // queue for breadth-first traversal
  ASSERT( myPt2Index.find( a ) != myPt2Index.cend() );
  const auto idx_a = myPt2Index.find( a )->second;
  Q.push  ( idx_a );
  V.insert( idx_a );
  while ( ! Q.empty() )
    {
      const auto j = Q.front();
      const auto p = myX[ j ];
      Q.pop();
      for ( auto && v : myN ) {
        const Point q = p + v;
        const auto it = myPt2Index.find( q );
        if ( it == myPt2Index.cend() ) continue; // not in X
        const auto next = it->second;
        if ( V.count( next ) ) continue; // already visited
        if ( arePointsCotangent( a, q ) )
          {
            R.push_back( next );
            V.insert( next );
            Q.push  ( next );
          }
      }
    }
  return R;
}
 
//-----------------------------------------------------------------------------
template < typename TKSpace >
std::vector< typename DGtal::TangencyComputer<TKSpace>::Index >
DGtal::TangencyComputer<TKSpace>::
getCotangentPoints( const Point& a,
                    const std::vector< bool > & to_avoid ) const
{
  // Breadth-first traversal from a
  std::vector< Index > R; // result
  std::set   < Index > V; // visited or in queue
  std::queue < Index > Q; // queue for breadth-first traversal
  ASSERT( myPt2Index.find( a ) != myPt2Index.cend() );
  const auto idx_a = myPt2Index.find( a )->second;
  Q.push  ( idx_a );
  V.insert( idx_a );
  while ( ! Q.empty() )
    {
      const auto  j = Q.front();
      const auto  p = myX[ j ];
      const auto ap = p - a;
      Q.pop();
      for ( auto && v : myN ) {
        if ( ap.dot( v ) < 0.0 ) continue;
        const Point q = p + v;
        const auto it = myPt2Index.find( q );
        if ( it == myPt2Index.cend() ) continue; // not in X
        const auto next = it->second;
        if ( to_avoid[ next ] ) continue; // to avoid
        if ( V.count( next ) )  continue; // already visited
        if ( arePointsCotangent( a, q ) )
          {
            R.push_back( next );
            V.insert( next );
            Q.push  ( next );
          }
      }
    }
  return R;
}
 
//-----------------------------------------------------------------------------
template < typename TKSpace >
std::vector< typename DGtal::TangencyComputer<TKSpace>::Index >
DGtal::TangencyComputer<TKSpace>::ShortestPaths::
getCotangentPoints( Index idx_a ) const
{
  bool use_secure = mySecure <= sqrt( KSpace::dimension );
  // Breadth-first traversal from a
  std::vector< Index > R; // result
  std::set   < Index > V; // visited or in queue
  std::queue < Index > Q; // queue for breadth-first traversal
  const auto a = point( idx_a );
  Q.push  ( idx_a );
  V.insert( idx_a );
  while ( ! Q.empty() )
    {
      const auto  j = Q.front();
      const auto  p = point( j );
      const auto ap = p - a;
      Q.pop();
      for ( int i = 0; i < myTgcyComputer->myN.size(); i++ ) {
        const auto & v = myTgcyComputer->myN[ i ];
        if ( ap.dot( v ) < 0.0 ) continue; // going backward
        const Point q = p + v;
        const auto it = myTgcyComputer->myPt2Index.find( q );
        if ( it == myTgcyComputer->myPt2Index.cend() ) continue; // not in X
        const auto next = it->second;
        if ( myVisited[ next ] ) continue; // to avoid
        if ( V.count( next ) )   continue; // already visited
        const auto d_a = myDistance[ idx_a ] + ( q - a ).norm();
        if ( d_a >= ( myDistance[ next ]
                      + ( use_secure ? mySecure : myTgcyComputer->myDN[ i ] )  ) )
          continue; // only if distance is better.
        if ( myTgcyComputer->arePointsCotangent( a, q ) )
          {
            R.push_back( next );
            V.insert( next );
            Q.push  ( next );
          }
      }
    }
  return R;
}
 
//-----------------------------------------------------------------------------
template < typename TKSpace >
typename DGtal::TangencyComputer<TKSpace>::ShortestPaths
DGtal::TangencyComputer<TKSpace>::
makeShortestPaths( double secure ) const
{
  return ShortestPaths( *this, secure );
}
 
 
//-----------------------------------------------------------------------------
template < typename TKSpace >
std::vector< typename DGtal::TangencyComputer<TKSpace>::Path >
DGtal::TangencyComputer<TKSpace>::
shortestPaths( const std::vector< Index >& sources,
               const std::vector< Index >& targets,
               double secure, bool verbose ) const
{
  auto SP = makeShortestPaths( secure );
  SP.init( targets.cbegin(), targets.cend() );
  std::vector< Path > paths( sources.size() );
  while ( ! SP.finished() )
    {
      auto n = SP.current();
      SP.expand();
      if ( verbose )
        trace.info() << "Point " << point( std::get<0>( n ) )
                     << " at distance " << std::get<2>( n ) << std::endl;
    }
  for ( auto i = 0; i < sources.size(); i++ )
    paths[ i ] = SP.pathToSource( sources[ i ] );
  return paths;
}
 
//-----------------------------------------------------------------------------
template < typename TKSpace >
typename DGtal::TangencyComputer<TKSpace>::Path
DGtal::TangencyComputer<TKSpace>::
shortestPath( Index source, Index target,
              double secure, bool verbose ) const
{
  auto SP0 = makeShortestPaths( secure );
  auto SP1 = makeShortestPaths( secure );
  SP0.init( source ); 
  SP1.init( target );
  Path Q;
  while ( ! SP0.finished() && ! SP1.finished() )
    {
      auto n0 = SP0.current();
      auto n1 = SP1.current();
      auto p0 = std::get<0>( n0 );
      auto p1 = std::get<0>( n1 );
      SP0.expand();
      SP1.expand();
      if ( SP0.isVisited( p1 ) )
        {
          auto c0 = SP0.pathToSource( p1 );
          auto c1 = SP1.pathToSource( p1 );
          std::copy(c0.rbegin(), c0.rend(), std::back_inserter(Q));
          Q.pop_back();
          std::copy(c1.begin(), c1.end(), std::back_inserter(Q)); 
          break;
        }
      if ( verbose )
        {
          double last_distance = std::get<2>( n0 ) + std::get<2>( n1 );
          trace.info() << p0 << " " << p1 << " last_d=" << last_distance << std::endl;
        }
    }
  return Q;
}
 
//-----------------------------------------------------------------------------
template <typename TKSpace>
void
DGtal::TangencyComputer<TKSpace>::
setUp()
{
  myN.clear();
  myDN.clear();
  const Point zero = Point::zero;
  Domain neighborhood( Point::diagonal( -1 ), Point::diagonal( 1 ) );
  for ( auto&& v : neighborhood )
    {
      if ( v != zero )
        {
          myN .push_back( v );
          myDN.push_back( v.norm() );
        }
    }
}
 
///////////////////////////////////////////////////////////////////////////////
// class TangencyComputer::Shortestpaths
///////////////////////////////////////////////////////////////////////////////
 
//-----------------------------------------------------------------------------
template <typename TKSpace>
void
DGtal::TangencyComputer<TKSpace>::ShortestPaths::
expand()
{
  ASSERT( ! finished() );
  auto elem = myQ.top();
  myQ.pop();
  propagate( std::get<0>( elem ) );
  Index current;
  double d;
  int nb = 0;
  while ( ! finished() )
    {
      elem = myQ.top();
      nb += 1;
      current = std::get<0>( elem );
      d = std::get<2>( elem );
      ASSERT( ( ! ( myVisited[ current ] && ( d < myDistance[ current ] ) ) )
              && "Already visited node and smaller distance" );
      if ( ! myVisited[ current ] ) break;
      myQ.pop();
    }
  if ( ! finished() )
    {
      myAncestor[ current ] = std::get<1>( elem );
      myDistance[ current ] = d;
      myVisited [ current ] = true;
    }
}
 
//-----------------------------------------------------------------------------
template <typename TKSpace>
void
DGtal::TangencyComputer<TKSpace>::ShortestPaths::
propagate( Index current )
{
  auto eucl_d = [] ( const Point& p, const Point& q )
  { return ( p - q ).norm(); };
 
  if ( ! myVisited[ current ] )
    trace.warning() << "Propagate from unvisited node " << current << std::endl;
  const Point  q = myTgcyComputer->point( current );
  std::vector< Index > N = getCotangentPoints( current );
  for ( auto next : N )
    {
      if ( ! myVisited[ next ] )
        {
          const Point p = myTgcyComputer->point( next );
          double next_d = myDistance[ current ] + eucl_d( q, p );
          if ( next_d < myDistance[ next ] )
            {
              myDistance[ next ] = next_d;
              myQ.push( std::make_tuple( next, current, next_d ) );
            }
        }
    }
}
 
 
///////////////////////////////////////////////////////////////////////////////
// Implementation of inline functions                                        //
 
//-----------------------------------------------------------------------------
template <typename TKSpace>
inline
std::ostream&
DGtal::operator<< ( std::ostream & out,
                    const TangencyComputer<TKSpace> & object )
{
  object.selfDisplay( out );
  return out;
}
 
//                                                                           //
///////////////////////////////////////////////////////////////////////////////