coriolis/katabatic/doc/AutoSegment.dox

 // -*- C++ -*-

 namespace Katabatic {

 /*! \class        AutoSegment
  *
  *  \brief        Abstract base class for AutoSegment
  *
  *
  *  \section      secASCreation  Creating AutoHorizontal & AutoVertical
  *
  *                AutoSegment is the abstract base class for AutoHorizontal and
  *                AutoVertical. They are must be created only through the
  *                factory method: AutoSegment::create().
  *
  *
  *  \section      secASCharacteristics  Characteristics of AutoSegments
  *
  *                <ul>
  *                  <li>Unique ID: to ease the enforcing of a deterministic behavior
  *                      and to gain some independance from the pointers, each AutoSegment
  *                      is associated with an unique identifier.
  *                      \red{<b>IDs</b> are now directly taken from the Hurricane::Segment.}
  *                  <li>Source contact is always lesser than Target contact 
  *                      <code>(Xs,Ys) < (Xt,Yt)</code>.
  *                  <li>When assembled through AutoContactVTee or AutoContactHTee,
  *                      AutoSegments became (i.e. must be kept) aligneds. Among a
  *                      set of aligned AutoSegments, we distinguish a representative
  *                      trough which we can manipulate the whole set. This representative
  *                      is called the \e canonical AutoSegment and is the one with the
  *                      lowest \c id).
  *                  <li>When an aligned set contains at least one global, all the segments
  *                      of the set are tagged Katabatic::SegWeakGlobal. This is
  *                      especially useful on local ones to know if they are part of a
  *                      much longer wire.
  *
  *                      Conversely, a set of aligned may contains only local segments and
  *                      thus will not have the flag set.
  *                  <li>To allow some optimization, the Katabatic::SegNotAligned
  *                      tells if a segment is part of an aligned set. It is deduced from
  *                      the type of both source and target contact: not on the parallel
  *                      branch of a tee.
  *                </ul>
  *
  *                <b>The Ever Fragmenting Data Structure</b>
  *
  *                All the transformations applied to the database, after it's initial
  *                building, can be reduced to making new doglegs (and layer changes).
  *                Another way to put it, is that no Tee is ever created after the
  *                initial stage. The consequence is that the segments are only fragmenting
  *                more and more (up to a certain limit). The aligneds sets are progessively
  *                broken apart as needed, and until there remains only one tee per set
  *                (the two segments on the aligned branch).
  *
  *
  *  \section      secASOperations  Operations on AutoSegments
  *
  *                <ul>
  *                  <li><b>Slackening.</b> Constraints transmited through either source
  *                      or target AutoContact are too tight (tighter than the GCell),
  *                      by adding straps in the perpandicular direction, the full slack
  *                      of the segment is restored.
  *                  <li><b>Layer Change.</b> One or two layers above or below the
  *                      current layer. One up/down may means into the perpandicular
  *                      routing direction.
  *                  <li><b>Dogleg Creation.</b> Mean breaking the segment in two.
  *                      This operation is used to slacken the constraints on a segment
  *                      or restore connexity on source/target contact after a layer
  *                      change. The new segment is always created on the source.
  *                  <li><b>Reduction/Raising.</b> When a segment is a short dogleg,
  *                      no greater than one picth, it can use the layer of the
  *                      perpandiculars.
  *                </ul>
  *
  *
  *  \section      secASInvalidate  Invalidate on AutoSegments
  *
  *                The simple invalidation of an AutoSegment <b>do not</b> invalidate
  *                it's source & target contact.
  *
  *                An axis position change or a layer change both invalidate the
  *                AutoSegment <b>and</b> it's source & target contacts.
  *
  *                For the complete invalidation/revalidation mechanism see
  *                \ref secSessionAlgo "Session Algorithm".
  *
  *
  *  \section      secASAttributes  Main Attributes of AutoSegments
  *
  *                AutoSegment retains all attributes from Segment. The Segment itself
  *                beeing accessible through the base() methods.
  *                <ul>
  *                  <li>An unique \c Id (for determinism).
  *                  <li>The GCell from wich it starts from. It is the GCell of the
  *                      source AutoContact.
  *                  <li>A state, combination of flags from Katabatic::AutoSegmentFlag.
  *                  <li>An interval for the optimal range of the AutoSegment axis.
  *                  <li>An interval for user's defined constraint on the axis.
  *                  <li>The interval giving the complete length of the AutoSegment,
  *                      that is, with all extentions cap taken into account.
  *                      This interval is refered as the \e span.
  *                  <li>A small counter, of the number of reduced neighbors (never
  *                      exceed two).
  *                </ul>
  *
  *
  *  \section      secASImplementation  Implementation Details
  *
  *                AutoSegment / AutoHorizontal & AutoVertical are kind of decorators of
  *                Hurricane::Segment (they do not scrictly respect the pattern).
  *
  *                Canonical AutoSegment can should be considered as a kind of Composite.
  *
  *                Thoses objects are created using a Factory method.
  *
  *
  *  \section      secASMethodsClassif  Methods Classification
  *
  *                <ul>
  *                  <li><em>Wrapper methods</em> on the underlying Hurricane::Segment.
  *                </ul>
  *                <ul>
  *                  <li><em>Atomic methods</em> on AutoSegment, that is, which applies exactly
  *                      on the current AutoSegment.
  *                </ul>
  *                <ul>
  *                  <li><em>Canonical methods</em> that applies on the set of aligned AutoSegments.
  *                      There are two kind of those, the methods part of the API, and
  *                      the ones that make the link with the atomic methods. Those
  *                      intermediate methods hide some cumbersome AutoSegment list
  *                      parameters.
  *                      <ul>
  *                        <li>AutoSegment::invalidate()
  *                        <li>AutoSegment::computeOptimal()
  *                        <li>AutoSegment::setAxis()
  *                        <li>AutoSegment::toConstraintAxis()
  *                        <li>AutoSegment::toOptimalAxis()
  *                      </ul>
  *                </ul>
  *                <ul>
  *                  <li><em>Uniform access</em>, to simplify the managment of AutoHorizontal
  *                      and AutoVertical through AutoSegment, a set of uniformized methods is
  *                      introduced. For instance, to avoid to check the dynamic type to choose
  *                      to call getSourceX() or getSourceY(), we may call getSourceU().
  *                      Uniform methods are named by replacing \c X/Y with \c U.
  *                      <ul>
  *                        <li>AutoSegment::getSourceU()
  *                        <li>AutoSegment::getTargetU()
  *                        <li>AutoSegment::getDuSource()
  *                        <li>AutoSegment::getDuTarget()
  *                        <li>AutoSegment::getSpanU()
  *                        <li>AutoSegment::setDuSource()
  *                        <li>AutoSegment::setDuTarget()
  *                      </ul>
  *                </ul>
  */


 //! \enum        AutoSegmentFlag
 //!              Set of flags to describe the internal state of an AutoSegment.

 //! \var         AutoSegmentFlag::SegHorizontal
 //!              This AutoSegment is associated to a Hurricane::Horizontal, if not
 //!              set, it is associated to a Hurricane::Vertical. Set when the object
 //!              is constructed.

 //! \var         AutoSegmentFlag::SegFixed
 //!              The Hurricane::Segment associated must/cannot be moved.

 //! \var         AutoSegmentFlag::SegGlobal
 //!              The AutoSegment span between at least two GCells (i.e. not fully enclosed
 //!              in one).

 //! \var         AutoSegmentFlag::SegWeakGlobal
 //!              The AutoSegment is part of an aligned set which contains at least a global.
 //!              The global segment is itself tagged as weak global.

 //! \var         AutoSegmentFlag::SegCanonical
 //!              This AutoSegment is the designated representant of a set of aligned
 //!              AutoSegment.

 //! \var         AutoSegmentFlag::SegBipoint
 //!              This AutoSegment is a straight wire between two terminal AutoContact.

 //! \var         AutoSegmentFlag::SegDogleg
 //!              This AutoSegment has been created as the perpandicular part of a dogleg.

 //! \var         AutoSegmentFlag::SegStrap
 //!              This AutoSegment has been created to to reconnect parts of an AutoSegment
 //!              after slackening.

 //! \var         AutoSegmentFlag::SegSourceTop
 //!              The source contact of this segment is connected to the <em>top</em> layer.

 //! \var         AutoSegmentFlag::SegSourceBottom
 //!              The source contact of this segment is connected to the <em>bottom</em> layer.

 //! \var         AutoSegmentFlag::SegTargetTop
 //!              The target contact of this segment is connected to the <em>top</em> layer.

 //! \var         AutoSegmentFlag::SegTargetBottom
 //!              The target contact of this segment is connected to the <em>bottom</em> layer.

 //! \var         AutoSegmentFlag::SegIsReduced
 //!              This segment is the perpandicular part of a dogleg which will use the
 //!              <em>same</em> layer as the parallels.

 //! \var         AutoSegmentFlag::SegLayerChange
 //!              This AutoSegment has been created to to reconnect parts of an AutoSegment
 //!              after a layer change.

 //! \var         AutoSegmentFlag::SegSlackened
 //!              This AutoSegment has been slackened, that is freed from any constraints from
 //!              source or target through the insertion of straps.

 //! \var         AutoSegmentFlag::SegStrongTerminal
 //!              This AutoSegment directly connected to a terminal.

 //! \var         AutoSegmentFlag::SegWeakTerminal1
 //!              This AutoSegment indirectly connected to a terminal with medium strength.

 //! \var         AutoSegmentFlag::SegWeakTerminal2
 //!              This AutoSegment indirectly connected to a terminal with weak strength.

 //! \var         AutoSegmentFlag::SegNotSourceAligned
 //!              This source contact of the segment is not the aligned part of a tee
 //!              (\c h1 or \c h2 for a \c HTee, \c v1 or \c v2 for a \c VTee).
 //!
 //! \sa          AutoSegmentFlag::SegNotAligned

 //! \var         AutoSegmentFlag::SegNotTargetAligned
 //!              This target contact of the segment is not the aligned part of a tee
 //!              (\c h1 or \c h2 for a \c HTee, \c v1 or \c v2 for a \c VTee).
 //!
 //! \sa          AutoSegmentFlag::SegNotAligned

 //! \var         AutoSegmentFlag::SegAxisSet
 //!              This AutoSegment has been explicitly positionned at least once.

 //! \var         AutoSegmentFlag::SegInvalidated
 //!              This position or topology of this AutoSegment has been changed, needing
 //!              a revalidation.

 //! \var         AutoSegmentFlag::SegInvalidatedLayer
 //!              The segment has been chenged of layer, but the source & target AutoContact
 //!              have not been topologicaly checked yet. This flag \b must be used in
 //!              whith AutoSegmentFlag::SegInvalidated.

 //! \var         AutoSegmentFlag::SegCreated
 //!              The AutoSegment has just been created. This flag is set only from the
 //!              contruction of the object until is \e first revalidation. Used to
 //!              disable some tests that cannot be satisfied initially.

 //! \var         AutoSegmentFlag::SegWeakTerminal
 //!              A mask composed of:
 //!                - Katabatic::SegStrongTerminal
 //!                - Katabatic::SegWeakTerminal1
 //!                - Katabatic::SegWeakTerminal2

 //! \var         AutoSegmentFlag::SegNotAligned
 //!              A mask composed of:
 //!                - Katabatic::SegNotSourceAligned
 //!                - Katabatic::SegNotTargetAligned
 //!
 //!              This mask is a quick way to know if a segment is \b not part of an aligned set.
 //!              It means that the segment is, on both ends, either connected to a terminal,
 //!              a turn <em>or the stem part of a tee</em>.


 //! \function    AutoSegment* AutoSegment::create ( AutoContact* source, AutoContact* target, Segment* hurricaneSegment );
 //! \param       source  The source AutoContact.
 //! \param       target  The target AutoContact.
 //! \param       hurricaneSegment  The Hurricane::Segment to decorate.
 //! \return      The AutoHorizontal/AutoVertical decorator segment.
 //!
 //!              Factory method to create AutoHorizontal or AutoVertical. It is important
 //!              to note that this function may modify the underlying Hurricane::Segment.
 //!                - Layer is set to the default (bottom) routing Layers.
 //!                - Source & target anchor of \c hurricaneSegment are set on \c source 
 //!                  and \c target. If the \c hurricaneSegment is already anchored and
 //!                  \c source or \c target are not the one decorating the anchors, an
 //!                  exception is thrown.

 //! \function    AutoSegment* AutoSegment::create ( AutoContact* source, AutoContact* target, unsigned int dir, size_t depth );
 //! \param       source  The source AutoContact.
 //! \param       target  The target AutoContact.
 //! \param       dir     Specify the segment direction.
 //! \param       depth   The layer, given by it's depth in the RoutingGauge.
 //! \return      The AutoHorizontal/AutoVertical.
 //!
 //!              Factory method to create AutoHorizontal or AutoVertical.
 //!              \c flags indicate the direction (KbHorizontal or KbVertical).
 //!              The underlying Hurricane segment is also created.

 //! \function    Segment* AutoSegment::base() const;
 //! \sreturn     the decorated Hurricane::Segment (const flavor).

 //! \function    Segment* AutoSegment::base();
 //! \sreturn     the decorated Hurricane::Segment.

 //! \function    Horizontal* AutoSegment::getHorizontal();
 //! \sreturn     If the decorated segment is a Hurricane::Horizontal, return it.
 //!              \c NULL otherwise.

 //! \function    Vertical* AutoSegment::getVertical();
 //! \sreturn     If the decorated segment is a Hurricane::Vertical, return it.
 //!              \c NULL otherwise.

 //! \function    Cell* AutoSegment::getCell() const;
 //!              \see Segment::getCell().

 //! \function    Net* AutoSegment::getNet() const;
 //!              \see Segment::getNet().

 //! \function    const Layer* AutoSegment::getLayer() const;
 //!              \see Segment::getLayer().

 //! \function    BoundingBox* AutoSegment::getBoundingBox() const;
 //!              \see Segment::getBoundingBox().

 //! \function    Hook* AutoSegment::getSourceHook();
 //!              \see Segment::getSourceHook().

 //! \function    Hook* AutoSegment::getTargetHook();
 //!              \see Segment::getTargetHook().

 //! \function    Contact* AutoSegment::getSource() const;
 //!              \see Segment::getSource().

 //! \function    Contact* AutoSegment::getTarget() const;
 //!              \see Segment::getTarget().

 //! \function    Component* AutoSegment::getOppositeAnchor( Component* ) const;
 //!              \see Segment::getNet().

 //! \function    Components  AutoSegment::getAnchors() const;
 //!              \see Segment::getAnchors().

 //! \function    DbU::Unit  AutoSegment::getX() const;
 //!              \see Segment::getX().

 //! \function    DbU::Unit  AutoSegment::getY() const;
 //!              \see Segment::getY().

 //! \function    DbU::Unit  AutoSegment::getWidth() const;
 //!              \see Segment::getWidth().

 //! \function    DbU::Unit  AutoSegment::getLength() const;
 //!              \see Segment::getLength().

 //! \function    DbU::Unit  AutoSegment::getSourcePosition() const;
 //!              \see Segment::getSourcePosition().

 //! \function    DbU::Unit  AutoSegment::getTargetPosition() const;
 //!              \see Segment::getTargetPosition().

 //! \function    DbU::Unit  AutoSegment::getSourceX() const;
 //!              \see Segment::getSourceX().

 //! \function    DbU::Unit  AutoSegment::getSourceY() const;
 //!              \see Segment::getSourceY().

 //! \function    DbU::Unit  AutoSegment::getTargetX() const;
 //!              \see Segment::getTargetX().

 //! \function    DbU::Unit  AutoSegment::getTargetY() const;
 //!              \see Segment::getTargetY().

 //! \function    DbU::Unit  AutoSegment::invert();
 //!              \see Segment::invert().

 //! \function    void  AutoSegment::setLayer( const Layer* );
 //!              \see Segment::setLayer().

 //! \function    bool  AutoSegment::isHorizontal() const;
 //! \sreturn     \true if the Hurricane::Segment is Horizontal.

 //! \function    bool  AutoSegment::isVertical() const;
 //! \sreturn     \true if the Hurricane::Segment is Vertical.

 //! \function    bool  AutoSegment::isGlobal() const;
 //! \sreturn     \true if the segment is global (span over more than one GCell).

 //! \function    bool  AutoSegment::isLocal() const;
 //! \sreturn     \true if the segment is local (fully enclosed in one GCell).

 //! \function    bool  AutoSegment::isFixed() const;
 //! \sreturn     \true if segment must not be moved by the router.

 //! \function    bool  AutoSegment::isBipoint() const;
 //! \sreturn     \true if the segment straigh join two terminals.

 //! \function    bool  AutoSegment::isWeakTerminal() const;
 //! \sreturn     \true if segment is indirectly connected to a terminal.

 //! \function    bool  AutoSegment::isStrongTerminal( unsigned int flags=0 ) const;
 //! \sreturn     \true if segment is directly connected to a terminal.

 //! \function    bool  AutoSegment::isLayerChange() const;
 //! \sreturn     \true if segment is a strap used only to connect between two different
 //!              metal layers on the way up or down.

 //! \function    bool  AutoSegment::isSpinTop() const;
 //! \sreturn     \true if segment is connected to turns and both perpandiculars segments
 //!              are in the \e top layer (candidate for reduction).

 //! \function    bool  AutoSegment::isSpinBottom() const;
 //! \sreturn     \true if segment is connected to turns and both perpandiculars segments
 //!              are in the \e bottom layer (candidate for reduction).

 //! \function    bool  AutoSegment::isSpinTopOrBottom() const;
 //! \sreturn     \true if segment is either <em>spin top</em> or <em>spin bottom</em> 
 //!              (candidate for reduction).

 //! \function    bool  AutoSegment::isReduced() const;
 //! \sreturn     \true if segment is actually in a reduced state: it's effective layer
 //!              will be the one of it's perpandiculars.

 //! \function    bool  AutoSegment::isStrap() const;
 //! \sreturn     \true if segment has been created from a slackening operation to
 //!              restore the slack of another segment.

 //! \function    bool  AutoSegment::isDogleg() const;
 //! \sreturn     \true if segment has been created as the perpandicular part of a dogleg.

 //! \function    bool  AutoSegment::isInvalidated() const;
 //! \sreturn     \true if segment has been moved or topologicaly altered.

 //! \function    bool  AutoSegment::isInvalidatedLayer() const;
 //! \sreturn     \true if segment has been changed of layer. Source and Target AutoContact
 //!              may need to be altered.

 //! \function    bool  AutoSegment::isCreated() const;
 //! \sreturn     \true if segment has just been created and is not revalidated for the
 //!              first time

 //! \function    bool  AutoSegment::isCanonical() const;
 //! \sreturn     \true if segment is the representant of an aligned set.

 //! \function    bool  AutoSegment::isUnsetAxis() const;
 //! \sreturn     \true if the segment axis has never been set.

 //! \function    bool  AutoSegment::isSlackened() const;
 //! \sreturn     \true if the segment has already been slackened.

 //! \function    unsigned int  AutoSegment::canDogleg( Interval interval );
 //! \sreturn     non-zero if the aligned set of segment can be broken \e outside \c interval.
 //!              The returned value could be zero (failure) or Katabatic::KbDoglegOnLeft
 //!              or Katabatic::KbDoglegOnRight menaing that the aligned set could be broken
 //!              on the left of the \c interval (resp. right of it).

 //  \function    bool  AutoSegment::canDesalignate( AutoContact* contact ) const;
 //  \sreturn     \true if \c contact restrict the slack of the segment.

 //! \function    bool  AutoSegment::canReduce() const;
 //! \sreturn     \true if the segment can be reduced. That is:
 //!                - Source & target are AutoContactTurn.
 //!                - It is either <em>spin top</em> or <em>spin bottom</em>, that is
 //!                  connecting perpandiculars both in the same layer.
 //!                - Has a length less or equal one pitch in the perpandicular direction.
 //!                - Neither of the perpandicular are also reduceds.

 //! \function    bool  AutoSegment::mustRaise() const;
 //! \sreturn     \true if the segment must \e be reduced. That is:
 //!                 - It is in reduced state...
 //!                 - It is no longer <em>spin top</em> or <em>spin bottom</em>.
 //!                 - It's length exceed one pitch in the perpandicular direction.

 //! \function    bool  AutoSegment::canSlacken( unsigned int flags=0 ) const;
 //! \sreturn     \true if the segment can be slackened. That is, source or target constraints
 //!              are less than three pitches.
 //!
 //!              If \c flags contains KbPropagate, look on the whole aligned set.

 //! \function    bool  AutoSegment::_canSlacken() const;
 //! \sreturn     \true if the segment can be slackened. That is, source or target constraints
 //!              are less than three pitches.

 //! \function    bool  AutoSegment::canMoveULeft( float reserve ) const;
 //! \return      \true if the \e global segment can be moved on the left GCell (for a
 //!              vertical) or down (for an horizontal). The move is accepted only if
 //!              it do not change the amount of global wiring. Thus the following
 //!              conditions:
 //!                - The segment mustn't be on the leftmost GCell (obvious...).
 //!                - The segment must be global.
 //!                - The source and target contacts must be AutoContactTurn(s).
 //!                - At least one of the perpandicular must be global \b and connected
 //!                  through the \e target. That is, it's a global which extends toward
 //!                  left.
 //!                - The GCell of maximum density on the left must remains below the
 //!                  current GCell of maximum density, with a margin of \c reserve
 //!                  (expressed in total saturation percentage).

 //! \function    bool  AutoSegment::canMoveURight( float reserve ) const;
 //! \return      \true if the \e global segment can be moved on the right GCell (for a
 //!              vertical) or up (for an horizontal). The move is accepted only if
 //!              it do not change the amount of global wiring. Thus the following
 //!              conditions:
 //!                - The segment mustn't be on the leftmost GCell (obvious...).
 //!                - The segment must be global.
 //!                - The source and target contacts must be AutoContactTurn(s).
 //!                - At least one of the perpandicular must be global \b and connected
 //!                  through the \e source. That is, it's a global which extends toward
 //!                  right.
 //!                - The GCell of maximum density on the left must remains below the
 //!                  current GCell of maximum density, with a margin of \c reserve
 //!                  (expressed in total saturation percentage).

 //! \function    bool  AutoSegment::canMoveUp( float reserve, unsigned int flags ) const;
 //! \param       reserve   Number of track that must remains free \e after the move.
 //! \param       flags     Modificate the method behavior, see below.
 //! \return      \true if the segment can be moved up, that is to the next layer above in
 //!              the same preferred routing direction. This method will check that in
 //!              every GCell of the segment, at least \c reserve tracks are still avalaible
 //!              \e after the segment has been moved up (\c reserve can be less than
 //!              \c 1.0).
 //!
 //!              Possible (bitwise) value for \c flags :
 //!                - \c KbAllowTerminal : allow strong terminal to be moved up.
 //!                - \c KbAllowLocal : allow local segments to be moved up.
 //!                - \c KbPropagate : perform the check on the whole aligned set.
 //!                - \c KbWithPerpands : also check the density on the perpandiculars
 //!                  begin & end GCell, there must be at least a \c 0.5 density
 //!                  reserve on them.

 //! \function    bool  AutoSegment::canPivotUp( float reserve, unsigned int flags ) const;
 //! \param       reserve   Number of track that must remains free \e after the move.
 //! \param       flags     Modificate the method behavior, see below.
 //! 
 //!              Checks of the segment can be \e pivoted up. The difference between
 //!              \c canMoveUp() and \c canPivotUp() lies in the fact that no
 //!              perpandicular segment needs to be altered if the current segment
 //!              is moved up. For example an \b M3 segment connected to only \b M4 can
 //!              be pivoted up (in \b M5), but if connected to \b M2, it cannot.
 //!
 //!              Possible (bitwise) value for \c flags :
 //!                - \c KbPropagate : perform the check on the whole aligned set.
 //!                - \c KbIgnoreContacts : do not check the source & target layers
 //!                  to know if the segment can be pivoted up.

 //! \function    bool  AutoSegment::canPivotDown( float reserve, unsigned int flags ) const;
 //! \param       reserve   Number of track that must remains free \e after the move.
 //! \param       flags     Modificate the method behavior, see below.
 //!
 //!              Checks of the segment can be \e pivoted down. The difference between
 //!              \c canMoveDown() and \c canPivotDown() lies in the fact that no
 //!              perpandicular segment needs to be altered if the current segment
 //!              is moved down.
 //!
 //!              Possible (bitwise) value for \c flags :
 //!                - \c KbPropagate : perform the check on the whole aligned set.

 //! \function    bool  AutoSegment::checkPositions() const;
 //! \sreturn     \true if the relative positions of source & target are coherent.
 //!              (source <= target).

 //! \function    bool  AutoSegment::checkConstraints() const;
 //! \sreturn     \true if the constraint intervel is coherent (non-empty or
 //!              punctual in the worst case).

 //! \function    unsigned long  AutoSegment::getId() const;
 //! \sreturn     The AutoSegment unique identifier.

 //! \function    unsigned int  AutoSegment::getDirection() const;
 //! \sreturn     Katabatic::KbHorizontal or Katabatic::KbVertical according to the decorated segment.

 //! \function    GCell* AutoSegment::getGCell() const;
 //! \sreturn     The GCell into which the AutoSegment starts (the one of the source).

 //! \function    size_t  AutoSegment::getGCells( vector<GCell*>& gcells ) const;
 //! \param       gcells   A vector that will be filled by all the GCells that the
 //!                       segment overlap. In increasing order, from source to target.
 //! \return      The vector's size.

 //! \function    AutoContact* AutoSegment::getAutoSource() const;
 //! \sreturn     The source AutoContact.

 //! \function    AutoContact* AutoSegment::getAutoTarget() const;
 //! \sreturn     The target AutoContact.

 //! \function    AutoContact* AutoSegment::getOppositeAnchor( AutoContact* contact ) const;
 //! \sreturn     The source or target AutoContact opposite to \c contact.

 //! \function    size_t  AutoSegment::getPerpandicularsBound( set<AutoSegment*>& bounds );
 //! \param       bounds   A vector that will be filled by all the AutoSegments perpandicular
 //!                       to this one that induce a constraint.
 //! \return      The vector's size.

 //! \function    AutoSegment* AutoSegment::getParent() const;
 //! \sreturn     If this segment has been created by a dogleg operation, the parent is
 //!              the one from which we fragmented.

 //! \function    DbU::Unit  AutoSegment::getAxis() const;
 //! \sreturn     The AutoSegment axis position.

 //! \function    DbU::Unit  AutoSegment::getSourceU() const;
 //! \sreturn     The AutoSegment \e uniform source position. (X for an horizontal and
 //!              Y for a Vertical).

 //! \function    DbU::Unit  AutoSegment::getTargetU() const;
 //! \sreturn     The AutoSegment \e uniform target position. (X for an horizontal and
 //!              Y for a Vertical).

 //! \function    DbU::Unit  AutoSegment::getDuSource() const;
 //! \sreturn     The AutoSegment \e uniform delta from source. (dX for an horizontal and
 //!              dY for a Vertical).

 //! \function    DbU::Unit  AutoSegment::getDuTarget() const;
 //! \sreturn     The AutoSegment \e uniform delta from source. (dX for an horizontal and
 //!              dY for a Vertical).

 //! \function    DbU::Unit  AutoSegment::getOrigin() const;
 //! \sreturn     The AutoSegment \e uniform source (lowest) GCell coordinate. (dX for an horizontal and
 //!              dY for a Vertical).

 //! \function    DbU::Unit  AutoSegment::getExtremity() const;
 //! \sreturn     The AutoSegment \e uniform target (greatest) GCell coordinate. (dX for an horizontal and
 //!              dY for a Vertical).

 //! \function    Interval  AutoSegment::getSpanU() const;
 //! \sreturn     The AutoSegment \e uniform occupying interval (on X for horizontal and
 //!              on Y for vertical).

 //! \function    Interval  AutoSegment::getSourceConstraints( unsigned int flags ) const;
 //! \return      The Interval into witch the source AutoContact can vary. By default
 //!              all deduced constraints and user constraints are took into account.
 //!              If \c flags contains \c KbNativeConstraints the constraint returned is
 //!              only the enclosing GCell.

 //! \function    Interval  AutoSegment::getTargetConstraints( unsigned int flags ) const;
 //! \return      The Interval into witch the target AutoContact can vary. By default
 //!              all deduced constraints and user constraints are took into account.
 //!              If \c flags contains \c KbNativeConstraints the constraint returned is
 //!              only the enclosing GCell.

 //! \function    bool  AutoSegment::getConstraints( DbU::Unit& min, DbU::Unit& max ) const;
 //! \sreturn     in \c min & \c max the allowed range for the segment axis.

 //! \function    bool  AutoSegment::getConstraints( Interval& i ) const;
 //! \sreturn     in \c i the allowed range for the segment axis.

 //! \function    const Interval& AutoSegment::getUserConstraints() const;
 //! \sreturn     A reference to the additional constraints added to the axis of the segment.

 //! \function    DbU::Unit  AutoSegment::getSlack() const;
 //! \sreturn     The length of the axis constraint interval.

 //! \function    DbU::Unit  AutoSegment::getOptimalMin() const;
 //! \sreturn     The AutoSegment minimum axis optimal range.

 //! \function    DbU::Unit  AutoSegment::getOptimalMax() const;
 //! \sreturn     The AutoSegment maximum axis optimal range.

 //! \function    Interval& AutoSegment::getOptimal( Interval& i ) const;
 //!              Inialize \c i with the AutoSegment axis optimal range.

 //! \function    DbU::Unit  AutoSegment::getCost( DbU::Unit axis ) const;
 //! \return      The cost if this segment is placed at \c axis. The cost is null if
 //!              \c axis is inside the optimal interval and is the distance toward
 //!              the nearest bound outside.

 //! \function    AutoSegment* AutoSegment::getCanonical( Interval& i );
 //! \return      The canonical segment associated to this one. Additionnaly compute
 //!              the source & target position of the whole set of aligned segments.             

 //! \function    AutoSegment* AutoSegment::getCanonical( DbU::Unit& min, DbU::Unit& max );
 //! \return      The canonical segment associated to this one. Additionnaly compute
 //!              the source & target position of the whole set of aligned segments.             

 //! \function    unsigned int  AutoSegment::_getFlags () const;
 //!              Sets \c flags given as arguments.

 //! \function    void  AutoSegment::setFlags ( unsigned int flags );
 //!              Sets \c flags given as arguments.

 //! \function    void  AutoSegment::unsetFlags ( unsigned int flags );
 //!              Unsets \c flags given as arguments.

 //! \function    void  AutoSegment::setDuSource( DbU::Unit du );
 //!              Set the \e uniform \c dU from source anchor (dX for Horizontal,
 //!              dY for Vertical).

 //! \function    void  AutoSegment::setDuTarget( DbU::Unit du );
 //!              Set the \e uniform \c dU from target anchor (dX for Horizontal,
 //!              dY for Vertical).

 //! \function    void  AutoSegment::updateOrient ();
 //!              Ensure that source is lower than target. Swap them if needed.
 //!              Swap never occurs on global segment because their source and target
 //!              anchors are from different GCell, which are already ordered.

 //! \function    void  AutoSegment::computeTerminal ();
 //!              Recompute the terminal status of an AutoSegment. Initially, a
 //!              segment which source or target is a terminal is flagged as
 //!              SegStrongTerminal. After a topological modification, if the
 //!              segment is no longer directly attached to a terminal, the
 //!              status is progessively weakened. Once it reaches the weakest
 //!              level, it stays on it so the algorithm can work out which
 //!              segments is a start to a path toward a terminal.
 //!              
 //!              Status from stronger to weaker:
 //!                - Katabatic::SegStrongTerminal.
 //!                - Katabatic::SegWeakTerminal1
 //!                - Katabatic::SegWeakTerminal2
 //!              
 //! \remark      The weakening is poorly done. After making a dogleg we do not
 //!              know which of the segment must be weakened if not directly attached
 //!              on a terminal. We must examinate source & target.

 //! \function    void  AutoSegment::updatePositions();
 //!              Update the segment begenning and ending positions. The positions
 //!              takes into account the extension caps and reflect the real space
 //!              used by the segment under it's long axis.

 //! \function    void  AutoSegment::mergeUserConstraints( const Interval& constraints );
 //!              Constraints applies on the valid axis interval.
 //!              Merge in \c constraints with the user's constraints. The resulting
 //!              constraints is the intersection of the former user's contraints and
 //!              the one given as argument.

 //! \function    void  AutoSegment::resetUserConstraints();
 //!              Constraints applies on the valid axis interval.
 //!              Suppress all user's constraints.

 //! \function    void  AutoSegment::setOptimalMin( DbU::Unit min );
 //!              Sets the lower bound of the optimal axis interval.

 //! \function    void  AutoSegment::setOptimalMax( DbU::Unit max );
 //!              Sets the lower bound of the optimal axis interval.

 //! \function    Interval  AutoSegment::_invalidate();
 //!              Invalidate this segment. The segment is scheduled into the Session
 //!              revalidation mechanism.

 //! \function    Interval  AutoSegment::revalidate();
 //!              Mark this segment as valid (unset the Invalidated flag) and update
 //!              positions. Unlike AutoSegment::invalidate(), it's an atomic method.

 //! \function    Interval  AutoSegment::getMinSpanU() const;
 //! \return      The AutoSegment \e uniform minimum occupying interval, computed from the
 //!              constraints of all the supporting aligned AutoContacts.
 //!              (on X for horizontal and on Y for vertical).

 //! \function    AutoSegment* AutoSegment::canonize ( unsigned int flags=KbNoFlags );
 //!              Find and set the canonical AutoSegment from a set of aligneds. For the
 //!              time beeing we assumes that there is no merging process, so the Segments
 //!              will only gets more and more fragmented. This implies that a segment can
 //!              become canonical but it will never revert to normal status.
 //!
 //!              The canonical AutoSegment is the one with the lowest \c Id. This a way
 //!              of ensuring reproductible results. Note that the canonical one may not
 //!              be the \e geometrically lowest one.
 //!
 //! \remark      Canonical aware method.

 //! \function    Interval  AutoSegment::computeOptimal( set<AutoSegment*>& processeds );
 //! \param       processeds  A set of already processeds AutoSegment. Used by the
 //!                          caller function to avoid doing again the computation
 //!                          on an AutoSegment from an already proccessed aligned set.
 //!              Compute the optimal axis interval for the aligned set.
 //!
 //! \remark      Canonical aware method.

 //! \function    void  AutoSegment::invalidate( unsigned int flags=KbPropagate );
 //!              Invalidate this AutoSegment, or if the Katabatic::KbPropagate flags
 //!              is set, the whole set of aligned segments.
 //!
 //! \remark      If Katabatic is in the destruction stage, this function does nothing.
 //! \remark      Canonical aware method.

 //! \function    void  AutoSegment::setAxis( DbU::Unit axis, unsigned int flags=0 );
 //! \param       axis    The new position of the axis.
 //! \param       flags   See KbRealignate.
 //!              
 //!              Set the axis of an aligned set. This method does nothing if not called
 //!              on the canonical AutoSegment of the set. If the new value of the axis
 //!              is equal to the previous one, nothing is done (non-canonical AutoSegment
 //!              are not looked after). To force an actual axis set, with invalidation of
 //!              the whole AutoSegment set, set the KbRealignate flag.
 //!
 //! \remark      Canonical aware method.

 //! \function    bool  AutoSegment::toConstraintAxis();
 //!              If the AutoSegment axis is outside the constraint interval, put it on
 //!              nearest bound. This method is active only on canonical AutoSegments.
 //!
 //! \return      \true if an actual axis change is made.
 //!
 //! \remark      Canonical aware method.

 //! \function    bool  AutoSegment::toOptimalAxis();
 //!              If the AutoSegment axis is outside the optimal interval, put it on
 //!              nearest bound. This method is active only on canonical AutoSegments.
 //!
 //! \return      \true if an actual axis change is made.
 //!
 //! \remark      Canonical aware method.

 //! \function    AutoSegments  AutoSegment::getAligneds ( unsigned int flags );
 //!              The Collection of AutoSegments that are aligned on this one
 //!              through AutoContactHTee or AutoContactVTee. If the \c flags
 //!              contains Katabatic::KbWithPerpands, the Collection will also
 //!              includes the AutoSegments directly perpandiculars to the whole
 //!              aligned set.

 //! \function    AutoSegments  AutoSegment::getPerpandiculars ();
 //!              The Collection of all AutoSegments directly perpandiculars to the
 //!              whole aligned set.

 //! \function    AutoSegments  AutoSegment::getOnSourceContact ( unsigned int direction );
 //! \sreturn     The Collection of AutoSegment in \c direction that are on this segment
 //!              source contact.

 //! \function    AutoSegments  AutoSegment::getOnTargetContact ( unsigned int direction );
 //! \sreturn     The Collection of AutoSegment in \c direction that are on this segment
 //!              target contact.

 //! \function    AutoSegment::~AutoSegment ()
 //!              AutoSegment destructor. It is not directly accessible, instead use
 //!              one flavor of the AutoSegment::create().

 //! \function    AutoSegment::AutoSegment ( Segment* segment );
 //!              AutoSegment constructor. It is not directly accessible, instead use
 //!              one flavor of the AutoSegment::create().

 //! \function    void  AutoSegment::_preCreate( AutoContact* source, AutoContact* target );
 //!              Perform sanity checks before allowing the actual creation of an
 //!              AutoSegment. If an error occurs throw an exception.
 //!              
 //!              Check for:
 //!                - \c source and \c target must not be \NULL.
 //!                - \c source and \c target must be different.

 //! \function    void  AutoSegment::_postCreate ();
 //!              Perform operations that, given the data structure cannot be done
 //!              in the constructor. Also allows for sharing code with the derived
 //!              classes. Currently:
 //!                - Invalidate the whole net (topology change).
 //!                - Insert the AutoSegment in the lookup/Session machanism.
 //!                - Call AutoSegment::invalidate().
 //!                - Call AutoSegment::updateOrient().
 //!                - Call AutoSegment::updatePositions().

 //! \function    void  AutoSegment::_preDestroy ();
 //!              Perform operations that must be done before the actual destructor is
 //!              called. Merely whidrawn the AutoSegment from the lookup/Session mechanism.

 //! \function    bool  AutoSegment::reduce ();
 //!              Sets the segment into reduced state.
 //!  
 //! \sreturn     \true if the operation did succeed. The layer will not be actually changed
 //!              until the Katabatic database is saved/destroyed.
 //!
 //!              A segment can be reduced if:
 //!                - Source & target are AutoContactTurn.
 //!                - It is either <em>spin top</em> or <em>spin bottom</em>, that is
 //!                  connecting perpandiculars both in the same layer.
 //!                - Has a length less or equal one pitch in the perpandicular direction.
 //!                - Neither of the perpandicular are also reduceds.
 //!              
 //!              \image html  reduce-1.png "Reduce Example"
 //!
 //!              If segment \c id:12 is reduced, it prevents \c id:10 & \c id:14 to
 //!              be also reduced, by increasing the \c _reduced counter. In this
 //!              example \c id:14 is <em>spin top</em> and \c id:12 is <em>spin bottom</em>.
 //!
 //!              If we reduce two adjacent segments, one will go up while the other
 //!              will go down (they will actually exchange their layers), it will
 //!              thus defeat the purpose of creating a <em>same layer</em> dogleg.
 //!              Besides, the turn contact between them will be changed into a pure
 //!              metal one, generating a disconnexion...
 //!
 //! \see         AutoSegment::raise()

 //! \function    bool  AutoSegment::raise ();
 //!              Get a segment out of \e reduced state.
 //! 
 //! \sreturn     \true if a state change did really take place.
 //!
 //! \see         AutoSegment::reduce()

 //! \function    AutoSegment* AutoSegment::makeDogleg ( AutoContact* from );
 //! \param       from   The AutoContact \e from which we want to make a dogleg.
 //!
 //!              This method is dedicated for the restauration of topology connexity on
 //!              AutoContcact after a layer change on one of their connected AutoSegment.
 //!
 //!              It perform three operations:
 //!                -# Create a dogleg on the AutoSegment (using the normal GCell variant).
 //!                -# Adjust the layers of the dogleg according whether we are going \e up
 //!                   or \e down from the AutoContact \c from to the segment.
 //!                -# Returns the new AutoSegment connected to \c from (it may be the
 //!                   same as before, \b if the AutoContact is the source of the
 //!                   segment).

 //! \function    unsigned int  AutoSegment::makeDogleg ( GCell* doglegGCell, unsigned int flags=KbNoFlags );
 //!              Make a dogleg <em>in a set of aligned segments</em>, thus the dogleg
 //!              may not be created on \c this segment but in the one which is under
 //!              \c doglegGCell.
 //!
 //! \sreturn     A flag telling if the above or below layer was used for the
 //!              perpandicular segment (Katabatic::KbUseAboveLayer or
 //!              Katabatic::KbUseBelowLayer).

 //! \function    unsigned int  AutoSegment::makeDogleg ( Interval interval, unsigned int flags=KbNoFlags );
 //!              Make a dogleg <em>in a set of aligned segments</em>, thus the dogleg
 //!              may not be created on \c this segment but in one which span intersect
 //!              \c interval.
 //!
 //! \sreturn     A set of flags telling if the break has occured on the left candidate
 //!              (Katabatic::KbDoglegOnLeft) or right (Katabatic::KbDoglegOnRight).
 //!              it is combined with the flag telling if the above or below layer was
 //!              used for the dogleg. In case of failure, zero is returned.
 //!
 //!              Break the set of aligned segments so the break point is \e outside
 //!              \c interval. The break point so can occurs on the \e left of the
 //!              interval (Katabatic::KbDoglegOnLeft) or on the \e right of the
 //!              interval (Katabatic::KbDoglegOnRight). When the set of aligned
 //!              segments fully enclose \c interval, a choice has to be made between
 //!              the left and right candidate. The rules are as follow:
 //!                - A \e left candidate include the \e min of the interval into
 //!                  it's span.
 //!                - A \e right candidate include the \e max of the interval into
 //!                  it's span.
 //!                - In certain topologies, there can be more than left or right
 //!                  candidates (more than one segment of the set intersect the
 //!                  bounds of the interval). Thoses candidates are ecludeds.
 //!                - If the two candidates are avalaibles, we choose the one
 //!                  with the greated \e native constraints.
 //!                - In case of strict equality, the left candidate is choosen.
 //!              
 //!              \image html  _makeDogleg-4.png "Example Case 4"

 //! \function    unsigned int  AutoSegment::_makeDogleg ( GCell* doglegGCell, unsigned int flags );
 //!              <b>This method is the workhorse for the various dogleg and topology
 //!              restauration methods.</b> It is the atomic method that actually
 //!              make the dogleg on \b this segment.
 //!
 //! \sreturn     Katabatic::KbUseAboveLayer if the dogleg is using the \e above layer
 //!              (Katabatic::KbUseBelowLayer for the below layer).
 //!
 //!              Break the current segment in two (a.k.a. making a dogleg).
 //!                - The segment is broken inside \c doglegGCell.
 //!                - Two new segments are createds, one perpandicular and one parallel.
 //!                - The original segment is always kept attached to the \e source.
 //!                  (the new parallel fragment is attached to the \e target).
 //!                - The perpandicular segment is in the layer \e above by default.
 //!                  If we are already on the topmost routing layer, the \e below
 //!                  layer is used.
 //!                - If the segment pass through the breaking GCell, it's axis is set
 //!                  into the center. If the segment is local, the axis is the middle
 //!                  of the segment.
 //!                - The Local/Global kind of the original segment is updated.
 //!                  The local/global status is computed by the constructor of the AutoSegment
 //!                  for the perpandicular and the new parallel.
 //!                - The terminal state is updated. If the segment is a strong terminal
 //!                  the part that is no longer directly connected to the terminal is
 //!                  demoted to Katabatic::SegWeakTerminal1.
 //!                - The perpandicular is obviously a canonical. If the broken segment
 //!                  is canonical, the original \b is left canonical and only the new parallel
 //!                  is re-canonized. Otherwise, we re-canonise both sets of aligned segments
 //!                  (the one on the source and the one on the target).
 //!                - The three segments are added to the session dogleg stack.
 //!
 //!              \red{After this method call the net topology is guarantee to be valid.}
 //!
 //!              \image html  _makeDogleg-1.png "Example Case 1"
 //!              \image html  _makeDogleg-2.png "Example Case 2"

 //! \function    bool  AutoSegment::moveULeft ();
 //!              <b>This function do not manage an aligned set. It applies on \c this
 //!              segment only.</b>
 //!
 //!              Displace an Horizontal or Vertical segment to the GCell below (a.k.a.
 //!              lower or inferior). Rules for displacement:
 //!                - The segment must be connected at both end to a turn contact
 //!                  (we do not want to manage more complex cases for the time beeing).
 //!                - And, of course, the segment must not already by on the bottomost
 //!                  GCell...
 //!
 //!              The displacement take care of:
 //!                - Managing the status of the various perpandiculars. The stretched
 //!                  one are made global if needed. The shrinked one made local, if
 //!                  needed.
 //!                - The supporting AutoContact (source & target) are changed of
 //!                  GCell.
 //!                - If the segment is global, the go-through GCells are updateds.
 //!
 //! \sreturn     \true if the move has succeeded.
 //!
 //!              \image html  moveULeft-1.png "moveULeft() for an Horizontal"

 //! \function    bool  AutoSegment::moveURight ();
 //!              <b>This function do not manage an aligned set. It applies on \c this
 //!              segment only.</b>
 //!
 //!              Displace an Horizontal or Vertical segment to the GCell above (a.k.a.
 //!              upper or superior). Rules for displacement:
 //!
 //! \sa          AutoSegment::moveULeft() for a complete description.

 //! \function    void  AutoSegment::slacken ( unsigned int flags );
 //!
 //!              If the the AutoSegment is attached trough source and/or target to a
 //!              terminal with too tight constraints, create a dogleg on overconstrained
 //!              extremities.
 //!
 //!              If \c flags contains Katabatic::KbPropagate, not only the current segment will be
 //!              looked up, but the whole aligned set. Note that due to the structure of
 //!              the database, there can be no more than two terminal connected segments
 //!              on the whole set (one on each extremity).
 //!
 //!              If \c flags contains Katabatic::KbHalfSlacken, the number of tracks under which
 //!              the constraints are considered too tight is 3. Otherwise it is 10, that is a
 //!              whole GCell side span. This flag should be used when a long set of global
 //!              wire is overconstrained by only one of it's terminal, the other one offering
 //!              sufficient slack (typically: 8).
 //!
 //!              The segment will also be slackened from it's terminal if the difference
 //!              between the current slack (resulting from all the constraints of the
 //!              aligned set) and the native slack is less than 3 tracks. This case means
 //!              that we are already near the native slack and it not sufficent enough
 //!              a degree of freedom.
 //!
 //!              \image html  _slacken-1.png "slacken() for an Horizontal"
 //!
 //!              The \c slacken() method reject the slackening of short locals as shown in
 //!              figure \b 2.a. One way or another, we must connect to the terminal through
 //!              \b this short local. If we cannot place it, breaking it in two other
 //!              short local wouldn't help. In fact, it will only clutter more the GCell
 //!              and make subsequent routing more difficult.
 //!
 //!              The figures \b 2.b and \b 2.c shows the special case of slackening an
 //!              horizontal from an \e horizontal terminal. In the original configuration,
 //!              the slack on segment \c id:10 is null, it's only choice is to be aligned
 //!              with the terminal. If a slackening is requested, it generally implies that
 //!              the horizontal track is blocked, and close to the terminal. Based on thoses
 //!              hypothesis, when we slacken the segment \c id:10 we impose that the
 //!              \e source contact is \b fixed on the terminal itself. That is, the segment
 //!              \c id:10 will be reduced to a zero-length and we made an immediate turn 
 //!              (see \b 2.c ).
 //!
 //!              \image html  _slacken-2.png "slacken() for an Horizontal (special cases)"

 //! \function    bool  AutoSegment::reduceDoglegLayer ();
 //!
 //!              Perform the actual layer change on a reduced segment. This method is to
 //!              be called juste before destroying the Katabatic database.
 //!
 //! \sreturn     \true if a change occurs.

}