coriolis/katana/src/Track.cpp

// -*- C++ -*-
//
// This file is part of the Coriolis Software.
// Copyright (c) UPMC 2008-2018, All Rights Reserved
//
// +-----------------------------------------------------------------+
// |                   C O R I O L I S                               |
// |      K i t e  -  D e t a i l e d   R o u t e r                  |
// |                                                                 |
// |  Author      :                    Jean-Paul CHAPUT              |
// |  E-mail      :       Jean-Paul.Chaput@asim.lip6.fr              |
// | =============================================================== |
// |  C++ Module  :       "./Track.cpp"                              |
// +-----------------------------------------------------------------+


#include <cstdlib>
#include <sstream>
#include <memory>
#include <algorithm>
#include "hurricane/DebugSession.h"
#include "hurricane/Warning.h"
#include "hurricane/Bug.h"
#include "hurricane/Layer.h"
#include "hurricane/Net.h"
#include "anabatic/AutoContact.h"
#include "katana/RoutingPlane.h"
#include "katana/Track.h"
#include "katana/TrackMarker.h"
#include "katana/DataNegociate.h"


namespace {

  using namespace std;
  using Hurricane::DebugSession;
  using namespace CRL;
  using namespace Katana;


  struct isDetachedSegment {
      bool operator() ( const TrackElement* s ) { return not s->getTrack(); };
  };


  // DbU::Unit  getPositionByIterator ( const vector<TrackElement*>& v, size_t i )
  // { return (*(v.begin()+i))->getSourceU(); }


  bool  hasSameLayerTurn ( const Layer* layer, TrackElement* segment, Flags flags )
  {
    if (not segment or not segment->base()) return false;
    AutoContact* contact = (flags & Flags::Source) ? segment->base()->getAutoSource()
                                                   : segment->base()->getAutoTarget() ;
    if (contact->getLayer() != layer) return false;
    if (not contact->isTurn()) return false;
    AutoSegment* pp = contact->getPerpandicular( segment->base() );
    return contact->getPerpandicular(segment->base())->getLength();
  }


  DbU::Unit  toFoundryGrid ( DbU::Unit u, DbU::SnapMode mode )
  {
    DbU::Unit oneGrid = DbU::fromGrid( 1.0 );
    return DbU::getOnCustomGrid( u, oneGrid, mode );
  }


  void  expandToMinArea ( TrackElement*   minSegment
                        , TrackElement*   maxSegment
                        , const Interval& segSpan
                        , DbU::Unit       minFree
                        , DbU::Unit       maxFree )
  {
    DebugSession::open( minSegment->getNet(), 150, 160 );
    cdebug_log(155,1) << "Track::expandMinArea() for:" << endl;
    cdebug_log(155,0) << "minSegment:" << minSegment << endl;
    cdebug_log(155,0) << "maxSegment:" << maxSegment << endl;

    const Layer* layer      = minSegment->getLayer();
    double       minArea    = layer->getMinimalArea();
    DbU::Unit    minSpacing = layer->getMinimalSpacing();
    DbU::Unit    minLength
      = DbU::fromPhysical( minArea / DbU::toPhysical( minSegment->getWidth(), DbU::UnitPower::Micro )
                         , DbU::UnitPower::Micro );
    minLength = toFoundryGrid( minLength, DbU::Superior );
    DbU::Unit segLength = segSpan.getSize() - minSpacing;
    cdebug_log(155,0) << "minSpacing:" << DbU::getValueString(minSpacing) << endl;
    cdebug_log(155,0) << " minLength:" << DbU::getValueString(minLength)  << endl;
    cdebug_log(155,0) << " segLenght:" << DbU::getValueString(segLength)  << endl;

    DbU::Unit sourceECap = minSegment->base()->getExtensionCap( Flags::Source|Flags::LayerCapOnly );
    DbU::Unit targetECap = maxSegment->base()->getExtensionCap( Flags::Target|Flags::LayerCapOnly );
    cdebug_log(155,0) << "sourceECap:" << DbU::getValueString(sourceECap) << endl;
    cdebug_log(155,0) << "targetECap:" << DbU::getValueString(targetECap) << endl;

    if (segLength < minLength) {
      DbU::Unit marginLeft  = segSpan.getVMin() - minFree;
      DbU::Unit marginRight = maxFree - segSpan.getVMax();
      DbU::Unit expandLeft  = toFoundryGrid( (minLength - segLength)/2 + sourceECap, DbU::Inferior );
      DbU::Unit expandRight = toFoundryGrid( (minLength - segLength)/2 + targetECap, DbU::Superior );
      if ((marginLeft >= expandLeft) and (marginRight >= expandRight)) {
        minSegment->base()->setDuSource( minSegment->base()->getDuSource() - expandLeft  );
        maxSegment->base()->setDuTarget( maxSegment->base()->getDuTarget() + expandRight );
      } else {
        if (marginLeft + marginRight >= expandLeft + expandRight) {
          DbU::Unit shiftLeft = 0;
          if (marginLeft >= expandLeft + expandRight)
            shiftLeft = - expandRight;
          else
            shiftLeft = - marginLeft + expandLeft;
          minSegment->base()->setDuSource( minSegment->base()->getDuSource() - expandLeft  + shiftLeft );
          maxSegment->base()->setDuTarget( maxSegment->base()->getDuTarget() + expandRight + shiftLeft );
        } else {
          cerr << Error( "::expandToMinArea(): Cannot expand %s."
                       , getString(minSegment).c_str() ) << endl;
        }
      }
    }
    cdebug_tabw(155,-1);
    DebugSession::close();
  }


} // Anonymous namespace.


namespace Katana {

  using std::lower_bound;
  using std::remove_if;
  using std::sort;
  using Hurricane::dbo_ptr;
  using Hurricane::tab;
  using Hurricane::DebugSession;
  using Hurricane::Warning;
  using Hurricane::Bug;
  using Hurricane::Layer;
  using Hurricane::Net;


// -------------------------------------------------------------------
// Class  :  "Track".


  const size_t  Track::npos = (size_t)-1;


  Track::Track ( RoutingPlane* routingPlane, unsigned int index )
    : _routingPlane (routingPlane)
    , _index        (index)
    , _axis         (routingPlane->getTrackPosition(index))
    , _min          (routingPlane->getTrackMin())
    , _max          (routingPlane->getTrackMax())
    , _segments     ()
    , _markers      ()
    , _localAssigned(false)
    , _segmentsValid(false)
    , _markersValid (false)
  { }


  void  Track::_postCreate ()
  { }


  Track::~Track ()
  { cdebug_log(155,0) << "Track::~Track() - " << (void*)this << endl; }


  void  Track::_preDestroy ()
  {
    cdebug_log(155,1) << "Track::_preDestroy() - " << (void*)this << " " << this << endl;

    TrackSet dummy;
    for ( size_t i=0 ; i<_segments.size() ; i++ )
      if (_segments[i]) {
        _segments[i]->detach( dummy );
        if (not _segments[i]->getTrackCount()) {
        //cerr << "destroy " << _segments[i] << endl;
          _segments[i]->destroy();
        }
      }

    for ( size_t i=0 ; i<_markers.size() ; i++ )
      if (_markers[i]) _markers[i]->destroy();

    cdebug_tabw(155,-1);
  }


  void  Track::destroy ()
  {
    cdebug_log(155,1) << "Track::destroy() - " << (void*)this << " " << this << endl;

    Track::_preDestroy();
    delete this;

    cdebug_tabw(155,-1);
  }


  KatanaEngine* Track::getKatanaEngine () const
  { return _routingPlane->getKatanaEngine(); }


  uint32_t  Track::getDepth () const
  { return _routingPlane->getDepth(); }


  const Layer* Track::getLayer () const
  { return _routingPlane->getLayer(); }


  const Layer* Track::getBlockageLayer () const
  { return _routingPlane->getBlockageLayer(); }


  Track* Track::getNextTrack () const
  { return getRoutingPlane()->getTrackByIndex( getIndex()+1 ); }


  Track* Track::getPreviousTrack () const
  {
    if (not getIndex()) return NULL;
    return getRoutingPlane()->getTrackByIndex( getIndex()-1 );
  }


  TrackElement* Track::getSegment ( size_t index ) const
  {
    if ( (index == npos) or (index >= getSize()) ) return NULL;
    return _segments[index];
  }


  TrackElement* Track::getSegment ( DbU::Unit position ) const
  {
    uint32_t  state;
    size_t    begin;

    getBeginIndex( position, begin, state );

    if (state & (BeginIsTrackMin|EndIsTrackMax)) return NULL;
    return getSegment(begin);
  }


  TrackElement* Track::getNext ( size_t& index, Net* net ) const
  {
    for ( index++ ; index < _segments.size() ; index++ ) {
      if (_segments[index]->getNet() == net) continue;
      return _segments[index];
    }
    index = npos;

    return NULL;
  }


  TrackElement* Track::getPrevious ( size_t& index, Net* net ) const
  {
    for ( index-- ; index != npos ; index-- ) {
      cdebug_log(140,0) << index << ":" << _segments[index] << endl;

      if (_segments[index]->getNet() == net) continue;
      return _segments[index];
    }
    index = npos;

    return NULL;
  }


  TrackElement* Track::getNextFixed ( size_t& index ) const
  {
    TrackElement* nextFixed = getNext ( index, NULL );
    for ( ; nextFixed ; nextFixed = getNext(index,NULL) ) {
      if ( nextFixed->base()->isFixed() ) return nextFixed;
    }

    return nextFixed;
  }


  void  Track::getBeginIndex ( DbU::Unit position, size_t& begin, uint32_t& state ) const
  {
    if (_segments.empty()) {
      state = EmptyTrack;
      begin = 0;
      return;
    }

    if (position < _min) {
      cerr << Warning( " Position %s inferior to the lower bound of %s. Returning npos."
                     , DbU::getValueString(position).c_str()
                     , getString(this).c_str() ) << endl;
      state = BeforeFirstElement;
      begin = 0;
      return;
    }

    if (position > _max) {
      cerr << Warning( " Position %s superior to the upper bound of %s. Returning npos."
                     , DbU::getValueString(position).c_str()
                     , getString(this).c_str() ) << endl;
      state = AfterLastElement;
      begin = _segments.size()-1;
      return;
    }

    vector<TrackElement*>::const_iterator  lowerBound
      = lower_bound( _segments.begin(), _segments.end(), position, SourceCompare() );
    begin = lowerBound - _segments.begin();

  // This is suspicious.
  // I guess this has been written for the case of overlapping segments from the same
  // net, we find the first one of the overlapped sets. But what if they are not overlapping
  // but still from the same net?
    size_t sameNetDelta = 0;
    if (begin < _segments.size()) {
      for ( ; (begin > 0) and (_segments[begin-1]->getNet() == _segments[begin]->getNet())
            ; --begin, ++sameNetDelta );
    }

    state = 0;
    if ( (begin == 0) and (position < _segments[0]->getSourceU()) ) {
      state = BeforeFirstElement;
    } else {
      if (begin and not sameNetDelta) begin -= 1;

      size_t   usedBegin    = begin;
      Interval usedInterval = getOccupiedInterval( usedBegin );

      if (position < usedInterval.getVMax())
        state = InsideElement;
      else
        if (begin+1 == _segments.size())
          state = AfterLastElement;
        else
          state = OutsideElement;
    }
  }


  void  Track::getOverlapBounds ( Interval interval, size_t& begin, size_t& end ) const
  {
    uint32_t iState;

    if (  _segments.empty()
       or (interval.getVMax() <= _min)
       or (interval.getVMin() >= _max)) {
      begin = end = npos;
      return;
    }

    getBeginIndex      ( interval.getVMin(), begin, iState );
    getOccupiedInterval( begin );

    getBeginIndex( interval.getVMax(), end, iState );
    for ( ; end < _segments.size() ; ++end ) {
      if (_segments[end]->getSourceU() >= interval.getVMax()) break;
    }

    cdebug_log(155,0) << "Track::getOverlapBounds(): begin:" << begin << " end:" << end << " AfterLastElement:" << (iState == AfterLastElement) << endl;
  }


  TrackCost& Track::addOverlapCost ( TrackCost& cost ) const
  {
          size_t    begin    = Track::npos;
          size_t    end      = Track::npos;
    const Interval& interval = cost.getInterval();

    getOverlapBounds( cost.getInterval(), begin, end );
    cost.setTrack( const_cast<Track*>(this), begin, end );

    cdebug_log(155,1) << "addOverlapCost() @" << DbU::getValueString(_axis)
                      << " [" << DbU::getValueString(interval.getVMin())
                      << ":"  << DbU::getValueString(interval.getVMax())
                      << "] <-> [" << begin << ":"  << end << "]"
                      << endl;

    vector<TrackMarker*>::const_iterator lowerBound
      = lower_bound( _markers.begin(), _markers.end(), interval.getVMin(), TrackMarker::Compare() );
    size_t mbegin = lowerBound - _markers.begin();

    for ( ;     (mbegin < _markers.size())
            and (_markers[mbegin]->getSourceU() <= interval.getVMax()) ; mbegin++ ) {
      cdebug_log(155,0) << "| @" << DbU::getValueString(_axis) << " " << _markers[mbegin] << endl;
      if (_markers[mbegin]->getNet() != cost.getNet()) {
        cdebug_log(155,0) << "* Mark: @" << DbU::getValueString(_axis) << " " << _markers[mbegin] << endl;
        cost.incTerminals( _markers[mbegin]->getWeight(this) );

        if ( (_markers[mbegin]->getRefCount() == 1) and (interval.contains(_markers[mbegin]->getSpan())) ) {
          cdebug_log(155,0) << "  Total overlap of a one track terminal: infinite cost." << endl;
          cost.setInfinite();
        }
      }
    }

    if (begin == npos) {
      cdebug_log(155,0) << "  begin == npos (after last TrackElement)." << endl;
      cdebug_tabw(155,-1);
      return cost;
    }

    for ( ; begin < end ; begin++ ) {
      Interval overlap = interval.getIntersection( _segments[begin]->getCanonicalInterval() );
      cdebug_log(155,0) << "overlap:" << overlap << " size:" << overlap.getSize() << endl;
      if (overlap.getSize() == 0) continue;
      
      if (_segments[begin]->getNet() == cost.getNet()) {
        cdebug_log(155,0) << "Same net overlap, increase delta shared." << endl;
        cost.incDeltaShared ( overlap.getSize() );
      }
      _segments[begin]->incOverlapCost( cost );
      cdebug_log(155,0) << "| overlap: " << _segments[begin] << endl;
      cdebug_log(155,0) << "| current cost:" << &cost << endl;

      if (cost.isInfinite()) break;
    }

    cdebug_tabw(155,-1);

    return cost;
  }


  void  Track::getTerminalWeight ( Interval interval, Net* net, size_t& count, uint32_t& weight ) const
  {
    cdebug_log(155,1) << "getTerminalWeight() @" << DbU::getValueString(_axis)
                      << " [" << interval.getVMin() << " " << interval.getVMax() << "]" << endl;

  //count  = 0;
  //weight = 0;

    vector<TrackMarker*>::const_iterator lowerBound
      = lower_bound ( _markers.begin(), _markers.end(), interval.getVMin(), TrackMarker::Compare() );
    size_t mbegin = lowerBound - _markers.begin();

    for ( ;    (mbegin < _markers.size())
            && (_markers[mbegin]->getSourceU() <= interval.getVMax()) ; mbegin++ ) {
      cdebug_log(155,0) << "| @" << DbU::getValueString(_axis) << _markers[mbegin] << endl;
      if ( _markers[mbegin]->getNet() == net ) {
        cdebug_log(155,0) << "* Mark: @" << DbU::getValueString(_axis) << " " << _markers[mbegin] << endl;
        weight += _markers[mbegin]->getWeight(this);
        ++count;
      }
    }
    cdebug_tabw(155,-1);
  }


  size_t  Track::find ( const TrackElement* segment ) const
  {
    if (_segments.empty()) return npos;

    vector<TrackElement*>::const_iterator  lowerBound
      = lower_bound( _segments.begin()
                   , _segments.end()
                   , segment
                   , SegmentCompare()
                   );

    if (lowerBound != _segments.end()) {
      while ( segment->getSourceU() == (*lowerBound)->getSourceU() ) {
        if (*lowerBound == segment) return (size_t)(lowerBound-_segments.begin());
        lowerBound++;
      }
    }

    return npos;
  }


  Interval  Track::getFreeInterval ( DbU::Unit position, Net* net ) const
  {
    uint32_t  state = 0;
    size_t    begin = 0;
    size_t    end   = 0;

    if (_segments.empty()) return Interval(_min,_max);

    getBeginIndex( position, begin, state );
    if ( (state == InsideElement) and (_segments[begin]->getNet() != net) ) {
      cdebug_log(155,0) << "Track::getFreeInterval(): Inside other element @" << begin
                        << " - " << _segments[begin] << endl;
      return Interval();
    }

    end = begin;
    return expandFreeInterval( begin, end, state, net );
  }


  Interval  Track::expandFreeInterval ( size_t& begin, size_t& end, uint32_t state, Net* net ) const
  {
    cdebug_log(155,1) << "Track::expandFreeInterval() begin:" << begin << " end:" << end
                      << " state:" << state << " " << net << endl;
    cdebug_log(155,0) << _segments[begin] << endl;

    DbU::Unit minFree = _min;
    cdebug_log(155,0) << "minFree:" << DbU::getValueString(minFree) << " (track min)" << endl;

    if (not (state & BeginIsTrackMin) ) {
      if (_segments[begin]->getNet() == net)
        getPrevious( begin, net );

      if (begin != npos) {
        minFree = getOccupiedInterval(begin).getVMax();
        cdebug_log(155,0) << "minFree:" << DbU::getValueString(minFree) << " begin:" << begin << endl;
      }
    }

    if (not (state & EndIsTrackMax) ) {
      if (state & EndIsNextSegmentMin) ++end;
 
      if (_segments[end]->getNet() == net) {
        getNext( end, net );
        if (end != npos) {
          cdebug_log(155,0) << "| same net, end:" << end << " " << _segments[end] << endl;
        } else {
          cdebug_log(155,0) << "| same net, end:" << end << " (after last)" << endl;
        }

        if (end == npos) {
          end  = _segments.size() - 1;
          setMaximalFlags( state, EndIsTrackMax );
        } else {
          setMaximalFlags( state, EndIsSegmentMin );
        }
      } else {
        state = EndIsTrackMax;
        cdebug_log(155,0) << "| already after last" << endl;
      }

      cdebug_log(155,0) << "end:" << end << " state:" << state << endl;
    }

    cdebug_tabw(155,-1);

    return Interval( minFree, getMaximalPosition(end,state) );
  }


  void  Track::invalidate ()
  { _segmentsValid = false; }


  void  Track::insert ( TrackMarker* marker )
  {
    _markers.push_back ( marker );
    _markersValid = false;
  }


  void  Track::insert ( TrackElement* segment )
  {
    // cdebug_log(9000,0) << "Deter| Track::insert() " << getLayer()->getName()
    //             << " @" << DbU::getValueString(getAxis()) << " " << segment << endl;
    cdebug_log(155,1) << "Track::insert() " << getLayer()->getName()
                << " @" << DbU::getValueString(getAxis()) << " " << segment << endl;

    if (   (getLayer()->getMask()         != segment->getLayer()->getMask())
       and (getBlockageLayer()->getMask() != segment->getLayer()->getMask()) ) {
      cerr << Bug("Track::insert(), segment %s has not the right layer."
                 ,getString(segment).c_str()) << endl;
    }

    cdebug_log(159,0) << "Insert in [" << 0 << "] " << this << segment << endl;
    _segments.push_back( segment );
    _segmentsValid = false;

    if (segment->isWide() or segment->isNonPref()) {
      cdebug_log(155,0) << "Segment is wide or non-pref, trackSpan:" << segment->getTrackSpan() << endl;
      Track* wtrack = getNextTrack();
      for ( size_t i=1 ; wtrack and (i<segment->getTrackSpan()) ; ++i ) {
        cdebug_log(159,0) << "Insert in [" << i << "] " << wtrack << segment << endl;
        wtrack->_segments.push_back ( segment );
        wtrack->_segmentsValid = false;
        wtrack = wtrack->getNextTrack();
      }
    }

    segment->setTrack ( this );
    cdebug_tabw(155,-1);
  }


  void  Track::setSegment ( TrackElement* segment, size_t index )
  {
    if ( index >= _segments.size() ) return;
    _segments[index] = segment;
  }


  bool  Track::check ( uint32_t& overlaps, const char* message ) const
  {
    bool coherency = true;
    bool holes     = false;

    if (message) cerr << "     o  Checking Track - " << message << endl;
    cdebug_log(155,0) << /*(void*)this << ":" <<*/ this << endl;

    for ( size_t i=0 ; i<_segments.size() ; i++ ) {
      if (_segments[i]) {
        bool inTrackRange = false;

        if (_segments[i]->isNonPref()) {
          DbU::Unit min = 0;
          DbU::Unit max = 0;
          _segments[i]->base()->getCanonical( min, max );
          inTrackRange = Interval(min,max).contains( _axis );
        } else {
          Interval trackRange ( _segments[i]->getAxis() - (_segments[i]->getTrackSpan()*_segments[i]->getPitch())/2
                              , _segments[i]->getAxis() + (_segments[i]->getTrackSpan()*_segments[i]->getPitch())/2 );
          inTrackRange = trackRange.contains( _axis );
        }
        
        if (i) {
          if (_segments[i-1] == _segments[i]) {
            cerr << "[CHECK] incoherency at " << i << " "
                 << _segments[i] << " is duplicated. " << endl;
            coherency = false;
          }
        }
        if (not _segments[i]->getTrack()) {
          cerr << "[CHECK] incoherency at " << i << " "
               << _segments[i] << " is detached." << endl;
          coherency = false;
        } else { 
          if ( (_segments[i]->getTrack() != this) and not inTrackRange ) {
            cerr << "[CHECK] incoherency at " << i << " "
                 << _segments[i] << " is in track "
                 << _segments[i]->getTrack() << endl;
            coherency = false;
            cerr << _segments[i]->getTrackSpan() << endl;
          }
        }
        if ( (_segments[i]->getAxis() != getAxis()) and not inTrackRange ) {
          cerr << "[CHECK] incoherency at " << i << " "
               << _segments[i] << " is not on Track axis "
               << DbU::getValueString(getAxis()) << "." << endl;
          coherency = false;
        } 
        
        coherency = _segments[i]->_check() and coherency;
      } else {
        cerr << "[CHECK] Hole at position " << i << "." << endl;
        holes     = true;
        coherency = false;
      }
    }

    if (not holes)
      coherency = (checkOverlap(overlaps) == 0) and coherency;

    return coherency;
  }


  DbU::Unit  Track::getSourcePosition ( size_t  i ) const
  {
    if ( i == npos) return 0;

    return _segments[i]->getSourceU();
  }


  DbU::Unit  Track::getSourcePosition ( vector<TrackElement*>::iterator isegment ) const
  {
    if ( isegment == _segments.end() ) return 0;

    return (*isegment)->getSourceU();
  }


  DbU::Unit  Track::getMinimalPosition ( size_t index, uint32_t state ) const
  {
    Interval  canonical;

    switch ( state & BeginMask ) {
      case BeginIsTrackMin:   return _min;
      case BeginIsSegmentMin: return _segments[index]->getSourceU ();
      case BeginIsSegmentMax: return _segments[index]->getTargetU ();
    }

    cerr << Bug( " Track::getMinimalPosition(size_t,uint32_t) :"
                 " invalid state value %ud.", state ) << endl;

    return _min;
  }


  DbU::Unit  Track::getMaximalPosition ( size_t index, uint32_t state ) const
  {
    Interval  canonical;

    switch ( state & EndMask ) {
      case EndIsTrackMax:       return _max;
      case EndIsSegmentMin:     return _segments[index  ]->getSourceU ();
      case EndIsNextSegmentMin: if (index+1 >= getSize()) return _max;
                                return _segments[index+1]->getSourceU ();
      case EndIsSegmentMax:     return _segments[index  ]->getTargetU ();
    }

    cerr << Bug( " Track::getMaximalPosition(size_t,uint32_t) :"
                 " invalid state value %ud.", state ) << endl;

    return _min;
  }


  Interval  Track::getNextFree ( size_t index, Net* net )
  {
    if (_segments.empty()) return Interval( _min, _max );

    if (index >= _segments.size()) {
      size_t last = _segments.size()-1;
      return Interval( getOccupiedInterval(last).getVMax(), _max );
    }

    Interval occupied = getOccupiedInterval( index );
    return getFreeInterval( occupied.getVMax()+1, net );
  }


  Interval  Track::getPreviousFree ( size_t index, Net* net )
  {
    cdebug_log(155,1) << "Track::getPreviousFree() index:" << index << " " << net << endl;

    if (_segments.empty()) { cdebug_tabw(155,-1); return Interval( _min, _max ); }

    if (index == 0) {
      size_t   first = 0;
      Interval free  = Interval( _min, getOccupiedInterval(first).getVMin() );
      cdebug_tabw(155,-1);
      return free;
    }

    Interval occupied = getOccupiedInterval( index );
    cdebug_log(155,0) << "Previous occupied:" << occupied << endl;
    Interval free = getFreeInterval( occupied.getVMin()-1, net );
    cdebug_tabw(155,-1);
    return free;
  }


  Interval  Track::getOccupiedInterval ( size_t& begin ) const
  {
    if (begin == npos) return Interval();

    size_t  seed  = begin;
    Net*    owner = _segments[seed]->getNet();

    Interval  segmentInterval;
    Interval  mergedInterval;
    _segments[seed]->getCanonical( mergedInterval );

    cdebug_log(155,0) << "| seed:" << mergedInterval << " " << _segments[seed] << endl;

    size_t i = seed;
    while ( --i != npos ) {
      if (_segments[i]->getNet() != owner) break;

      _segments[i]->getCanonical ( segmentInterval );
      if (segmentInterval.getVMax() >= mergedInterval.getVMin()) {
        cdebug_log(155,0) << "| merge (prev):" << segmentInterval << " " << _segments[i] << endl;

        mergedInterval.merge( segmentInterval );
        begin = i;
      }
    }

    i = seed;
    while ( ++i < _segments.size() ) {
      if (_segments[i]->getNet() != owner) break;

      _segments[i]->getCanonical( segmentInterval );
      if (segmentInterval.getVMin() > mergedInterval.getVMax()) break;

      cdebug_log(155,0) << "| merge (next):" << _segments[i] << endl;

      mergedInterval.merge( segmentInterval );
    }

    return mergedInterval;
  }


  size_t  Track::doRemoval ()
  {
    cdebug_log(155,1) << "Track::doRemoval() - " << this << endl;

    size_t  size = _segments.size();

    vector<TrackElement*>::iterator  beginRemove
      = remove_if( _segments.begin(), _segments.end(), isDetachedSegment() );

    _segments.erase( beginRemove, _segments.end() );

    cdebug_log(155,0) << "After doRemoval " << this << endl;
    cdebug_tabw(155,-1);

    return size - _segments.size();
  }


  void  Track::doReorder ()
  {
    cdebug_log(155,0) << "Track::doReorder() " << this << endl;

    if (not _segmentsValid) {
      std::sort( _segments.begin(), _segments.end(), SegmentCompare() );
      _segmentsValid = true;
    }

    if (not _markersValid) {
      std::sort( _markers.begin(), _markers.end(), TrackMarker::Compare() );
      _markersValid = true;
    }
  }


  uint32_t  Track::checkOverlap ( uint32_t& overlaps ) const
  {
    if ( !_segments.size() ) return 0;

    size_t j = 0;
    for ( size_t i=0 ; i<_segments.size()-1 ; i++ ) {
      if (not _segments[i]->isBlockage() and (_segments[i]->getLayer() != getLayer()) ) {
        cerr << Error( " Track vs. Segment Layer discrepency:\n  %s\n  %s  "
                     , getString(this).c_str()
                     , getString(_segments[i]).c_str() ) << endl;
      }

      if ( _segments[i]->getNet() == _segments[i+1]->getNet() ) {
        if ( _segments[i]->getSourceU() == _segments[i+1]->getSourceU() ) {
          if ( _segments[i]->getTargetU() < _segments[i+1]->getTargetU() ) {
            cerr << Error(" Invalid sorting length order in %s:\n  %s\n  %s  "
                         ,getString(this).c_str()
                         ,getString(_segments[i  ]).c_str()
                         ,getString(_segments[i+1]).c_str()) << endl;
          }
        }
        for ( j=i+1 ; (j<_segments.size()) && (_segments[i]->getNet() == _segments[j]->getNet()) ; j++ );
      } else {
        j = i+1;
      }

      if (   (j<_segments.size())
          && (_segments[i]->getTargetU() > _segments[j]->getSourceU()) ) {
        cerr << Error("Overlap in %s between:\n  %s\n  %s\n  TargetU:%s SourceU:%s"
                     ,getString(this).c_str()
                     ,getString(_segments[i]).c_str()
                     ,getString(_segments[j]).c_str()
                     ,DbU::getValueString(_segments[i]->getTargetU()).c_str()
                     ,DbU::getValueString(_segments[j]->getSourceU()).c_str() ) << endl;
        overlaps++;
      }
    }

    return overlaps;
  }


  void  Track::expandMinArea ()
  {
    if (_segments.empty()) return;

    double minArea = getLayer()->getMinimalArea();
    if (minArea == 0.0) return;
    
    DbU::Unit     prevSpanMin = getMin();
    TrackElement* minSegment  = NULL;
    TrackElement* maxSegment  = NULL;
    Interval      span;
    bool          hasTurn     = false;
    for ( size_t j=0 ; j<_segments.size() ; ) {
      if (not _segments[j]->base() or not (_segments[j]->getDirection() & getDirection())) {
        ++j;
        continue;
      }

      if (not minSegment) {
        minSegment  = _segments[j];
        maxSegment  = _segments[j];
        if (not span.isEmpty()) prevSpanMin = span.getVMax();
        span.makeEmpty();
        span = _segments[j]->getCanonicalInterval();
        hasTurn =    hasSameLayerTurn( getLayer(), _segments[j], Flags::Source )
                  or hasSameLayerTurn( getLayer(), _segments[j], Flags::Target );
        ++j;
        continue;
      }
      
      if (   (_segments[j]->getNet() == minSegment->getNet())
         and (span.getVMax() >= _segments[j]->getSourceU()) ) {
        if (_segments[j]->getTargetU() > span.getVMax()) {
          maxSegment = _segments[j];
          span.merge( _segments[j]->getTargetU() );
          hasTurn = hasTurn or hasSameLayerTurn( getLayer(), _segments[j], Flags::Target );
        }
        ++j;
        continue;
      }
    
      if (not hasTurn and minSegment->base())
        expandToMinArea( minSegment, maxSegment, span, prevSpanMin, _segments[j]->getSourceU() );

      minSegment = NULL;
    }

    if (not hasTurn and minSegment and minSegment->base())
      expandToMinArea( minSegment, maxSegment, span, prevSpanMin, getMax() );
  }


  string  Track::_getString () const
  {
    return "<" + _getTypeName() + " "
               + "[" + getString(_index) + "] "
               + getString(getLayer()->getName()) + " @"
               + DbU::getValueString(_axis) + " ["
               + DbU::getValueString(_min) + ":"
               + DbU::getValueString(_max) + "] ["
               + getString(_segments.size()) + "/"
               + getString(_segments.capacity())
               + "]>";
  }


  Record* Track::_getRecord () const
  {
    Record* record = new Record ( _getString() );
    record->add ( getSlot           ( "_routingPlane",  _routingPlane ) );
    record->add ( getSlot           ( "_index"       , &_index        ) );
    record->add ( DbU::getValueSlot ( "_axis"        , &_axis         ) );
    record->add ( getSlot           ( "_segments"    , &_segments     ) );
                                     
    return record;
  }


} // Katana namespace.