pns_diff_pair_placer.cpp

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/*
 * KiRouter - a push-and-(sometimes-)shove PCB router
 *
 * Copyright (C) 2013-2015 CERN
 * Copyright (C) 2016-2021 KiCad Developers, see AUTHORS.txt for contributors.
 * Author: Tomasz Wlostowski <[email protected]>
 *
 * This program is free software: you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation, 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/>.
 */
 
#include "pns_walkaround.h"
#include "pns_shove.h"
#include "pns_router.h"
#include "pns_diff_pair_placer.h"
#include "pns_solid.h"
#include "pns_topology.h"
#include "pns_debug_decorator.h"
 
namespace PNS {
 
DIFF_PAIR_PLACER::DIFF_PAIR_PLACER( ROUTER* aRouter ) :
 PLACEMENT_ALGO( aRouter )
{
 m_state = RT_START;
 m_chainedPlacement = false;
 m_initialDiagonal = false;
 m_startDiagonal = false;
 m_fitOk = false;
 m_netP = 0;
 m_netN = 0;
 m_iteration = 0;
 m_world = nullptr;
 m_shove = nullptr;
 m_currentNode = nullptr;
 m_lastNode = nullptr;
 m_placingVia = false;
 m_viaDiameter = 0;
 m_viaDrill = 0;
 m_currentWidth = 0;
 m_currentNet = 0;
 m_currentLayer = 0;
 m_startsOnVia = false;
 m_orthoMode = false;
 m_snapOnTarget = false;
 m_currentEndItem = nullptr;
 m_currentTraceOk = false;
 m_idle = true;
}
 
DIFF_PAIR_PLACER::~DIFF_PAIR_PLACER()
{}
 
 
void DIFF_PAIR_PLACER::setWorld( NODE* aWorld )
{
 m_world = aWorld;
}
 
 
const VIA DIFF_PAIR_PLACER::makeVia( const VECTOR2I& aP, int aNet )
{
 const LAYER_RANGE layers( m_sizes.GetLayerTop(), m_sizes.GetLayerBottom() );
 
 VIA v( aP, layers, m_sizes.ViaDiameter(), m_sizes.ViaDrill(), -1, m_sizes.ViaType() );
 v.SetNet( aNet );
 
 return v;
}
 
 
void DIFF_PAIR_PLACER::SetOrthoMode ( bool aOrthoMode )
{
 m_orthoMode = aOrthoMode;
 
 if( !m_idle )
 Move( m_currentEnd, nullptr );
}
 
 
bool DIFF_PAIR_PLACER::ToggleVia( bool aEnabled )
{
 m_placingVia = aEnabled;
 
 if( !m_idle )
 Move( m_currentEnd, nullptr );
 
 return true;
}
 
 
bool DIFF_PAIR_PLACER::rhMarkObstacles( const VECTOR2I& aP )
{
 if( !routeHead( aP ) )
 return false;
 
 bool collP = static_cast<bool>( m_currentNode->CheckColliding( &m_currentTrace.PLine() ) );
 bool collN = static_cast<bool>( m_currentNode->CheckColliding( &m_currentTrace.NLine() ) );
 
 m_fitOk = !( collP || collN ) ;
 
 return m_fitOk;
}
 
 
bool DIFF_PAIR_PLACER::propagateDpHeadForces ( const VECTOR2I& aP, VECTOR2I& aNewP )
{
 VIA virtHead = makeVia( aP, -1 );
 
 if( m_placingVia )
 {
 virtHead.SetDiameter( viaGap() + 2 * virtHead.Diameter() );
 }
 else
 {
 virtHead.SetLayer( m_currentLayer );
 virtHead.SetDiameter( m_sizes.DiffPairGap() + 2 * m_sizes.DiffPairWidth() );
 }
 
 bool solidsOnly = true;
 
 if( Settings().Mode() == RM_MarkObstacles )
 {
 aNewP = aP;
 return true;
 }
 else if( Settings().Mode() == RM_Walkaround )
 {
 solidsOnly = false;
 }
 
 // fixme: I'm too lazy to do it well. Circular approximaton will do for the moment.
 
 // Note: this code is lifted from VIA::PushoutForce and then optimized for this use case and to
 // check proper clearances to the diff pair line. It can be removed if some specialized
 // pushout for traces / diff pairs is implemented. Just calling VIA::PushoutForce does not work
 // as the via may have different resolved clearance to items than the diff pair should.
 int maxIter = 40;
 int iter = 0;
 bool collided = false;
 VECTOR2I force, totalForce;
 std::set<ITEM*> handled;
 
 while( iter < maxIter )
 {
 NODE::OPT_OBSTACLE obs = m_currentNode->CheckColliding( &virtHead, solidsOnly ?
 ITEM::SOLID_T :
 ITEM::ANY_T );
 if( !obs || handled.count( obs->m_item ) )
 break;
 
 int clearance = m_currentNode->GetClearance( obs->m_item, &m_currentTrace.PLine() );
 
 if( obs->m_item->Shape()->Collide( virtHead.Shape(), clearance, &force ) )
 {
 collided = true;
 totalForce += force;
 virtHead.SetPos( virtHead.Pos() + force );
 }
 
 handled.insert( obs->m_item );
 
 iter++;
 }
 
 bool succeeded = ( !collided || iter != maxIter );
 
 if( succeeded )
 {
 aNewP = aP + force;
 return true;
 }
 
 return false;
}
 
 
bool DIFF_PAIR_PLACER::attemptWalk( NODE* aNode, DIFF_PAIR* aCurrent, DIFF_PAIR& aWalk,
 bool aPFirst, bool aWindCw, bool aSolidsOnly )
{
 WALKAROUND walkaround( aNode, Router() );
 WALKAROUND::WALKAROUND_STATUS wf1;
 
 walkaround.SetSolidsOnly( aSolidsOnly );
 walkaround.SetIterationLimit( Settings().WalkaroundIterationLimit() );
 
 SHOVE shove( aNode, Router() );
 LINE walkP, walkN;
 
 aWalk = *aCurrent;
 
 int iter = 0;
 
 DIFF_PAIR cur( *aCurrent );
 
 bool currentIsP = aPFirst;
 
 int mask = aSolidsOnly ? ITEM::SOLID_T : ITEM::ANY_T;
 
 do
 {
 LINE preWalk = ( currentIsP ? cur.PLine() : cur.NLine() );
 LINE preShove = ( currentIsP ? cur.NLine() : cur.PLine() );
 LINE postWalk;
 
 if( !aNode->CheckColliding ( &preWalk, mask ) )
 {
 currentIsP = !currentIsP;
 
 if( !aNode->CheckColliding( &preShove, mask ) )
 break;
 else
 continue;
 }
 
 wf1 = walkaround.Route( preWalk, postWalk, false );
 
 if( wf1 != WALKAROUND::DONE )
 return false;
 
 LINE postShove( preShove );
 
 shove.ForceClearance( true, cur.Gap() - 2 * PNS_HULL_MARGIN );
 
 SHOVE::SHOVE_STATUS sh1;
 
 sh1 = shove.ShoveObstacleLine( postWalk, preShove, postShove );
 
 if( sh1 != SHOVE::SH_OK )
 return false;
 
 postWalk.Line().Simplify();
 postShove.Line().Simplify();
 
 cur.SetShape( postWalk.CLine(), postShove.CLine(), !currentIsP );
 
 currentIsP = !currentIsP;
 
 if( !aNode->CheckColliding( &postShove, mask ) )
 break;
 
 iter++;
 }
 while( iter < 3 );
 
 if( iter == 3 )
 return false;
 
 aWalk.SetShape( cur.CP(), cur.CN() );
 
 return true;
}
 
 
bool DIFF_PAIR_PLACER::tryWalkDp( NODE* aNode, DIFF_PAIR &aPair, bool aSolidsOnly )
{
 DIFF_PAIR best;
 double bestScore = 100000000000000.0;
 
 for( int attempt = 0; attempt <= 3; attempt++ )
 {
 DIFF_PAIR p;
 NODE *tmp = m_currentNode->Branch();
 
 bool pfirst = ( attempt & 1 ) ? true : false;
 bool wind_cw = ( attempt & 2 ) ? true : false;
 
 if( attemptWalk( tmp, &aPair, p, pfirst, wind_cw, aSolidsOnly ) )
 {
 // double len = p.TotalLength();
 double cl = 1 + p.CoupledLength();
 double skew = p.Skew();
 
 double score = cl + fabs( skew ) * 3.0;
 
 if( score < bestScore )
 {
 bestScore = score;
 best = p;
 }
 }
 
 delete tmp;
 }
 
 if( bestScore > 0.0 )
 {
 OPTIMIZER optimizer( m_currentNode );
 
 aPair.SetShape( best );
 optimizer.Optimize( &aPair );
 
 return true;
 }
 
 return false;
}
 
 
bool DIFF_PAIR_PLACER::rhWalkOnly( const VECTOR2I& aP )
{
 if( !routeHead ( aP ) )
 return false;
 
 m_fitOk = tryWalkDp( m_currentNode, m_currentTrace, false );
 
 return m_fitOk;
}
 
 
bool DIFF_PAIR_PLACER::route( const VECTOR2I& aP )
{
 switch( Settings().Mode() )
 {
 case RM_MarkObstacles:
 return rhMarkObstacles( aP );
 case RM_Walkaround:
 return rhWalkOnly( aP );
 case RM_Shove:
 return rhShoveOnly( aP );
 default:
 break;
 }
 
 return false;
}
 
 
bool DIFF_PAIR_PLACER::rhShoveOnly( const VECTOR2I& aP )
{
 m_currentNode = m_shove->CurrentNode();
 
 bool ok = routeHead( aP );
 
 m_fitOk = false;
 
 if( !ok )
 return false;
 
 if( !tryWalkDp( m_currentNode, m_currentTrace, true ) )
 return false;
 
 LINE pLine( m_currentTrace.PLine() );
 LINE nLine( m_currentTrace.NLine() );
 ITEM_SET head;
 
 head.Add( &pLine );
 head.Add( &nLine );
 
 SHOVE::SHOVE_STATUS status = m_shove->ShoveMultiLines( head );
 
 m_currentNode = m_shove->CurrentNode();
 
 if( status == SHOVE::SH_OK )
 {
 m_currentNode = m_shove->CurrentNode();
 
 if( !m_currentNode->CheckColliding( &m_currentTrace.PLine() ) &&
 !m_currentNode->CheckColliding( &m_currentTrace.NLine() ) )
 {
 m_fitOk = true;
 }
 }
 
 return m_fitOk;
}
 
 
const ITEM_SET DIFF_PAIR_PLACER::Traces()
{
 ITEM_SET t;
 
 t.Add( &m_currentTrace.PLine() );
 t.Add( &m_currentTrace.NLine() );
 
 return t;
}
 
 
void DIFF_PAIR_PLACER::FlipPosture()
{
 m_startDiagonal = !m_startDiagonal;
 
 if( !m_idle )
 Move( m_currentEnd, nullptr );
}
 
 
NODE* DIFF_PAIR_PLACER::CurrentNode( bool aLoopsRemoved ) const
{
 if( m_lastNode )
 return m_lastNode;
 
 return m_currentNode;
}
 
 
bool DIFF_PAIR_PLACER::SetLayer( int aLayer )
{
 if( m_idle )
 {
 m_currentLayer = aLayer;
 return true;
 }
 else if( m_chainedPlacement || !m_prevPair )
 {
 return false;
 }
 else if( !m_prevPair->PrimP() || ( m_prevPair->PrimP()->OfKind( ITEM::VIA_T ) &&
 m_prevPair->PrimP()->Layers().Overlaps( aLayer ) ) )
 {
 m_currentLayer = aLayer;
 m_start = *m_prevPair;
 initPlacement();
 Move( m_currentEnd, nullptr );
 return true;
 }
 
 return false;
}
 
 
OPT_VECTOR2I getDanglingAnchor( NODE* aNode, ITEM* aItem )
{
 switch( aItem->Kind() )
 {
 case ITEM::VIA_T:
 case ITEM::SOLID_T:
 return aItem->Anchor( 0 );
 
 case ITEM::ARC_T:
 case ITEM::SEGMENT_T:
 {
 SEGMENT* s = static_cast<SEGMENT*>( aItem );
 
 JOINT* jA = aNode->FindJoint( aItem->Anchor( 0 ), aItem );
 JOINT* jB = aNode->FindJoint( aItem->Anchor( 1 ), aItem );
 
 if( jA && jA->LinkCount() == 1 )
 return s->Seg().A;
 else if( jB && jB->LinkCount() == 1 )
 return s->Seg().B;
 else
 return OPT_VECTOR2I();
 }
 
 default:
 return OPT_VECTOR2I();
 }
}
 
 
 
bool DIFF_PAIR_PLACER::FindDpPrimitivePair( NODE* aWorld, const VECTOR2I& aP, ITEM* aItem,
 DP_PRIMITIVE_PAIR& aPair, wxString* aErrorMsg )
{
 int netP, netN;
 
 bool result = aWorld->GetRuleResolver()->DpNetPair( aItem, netP, netN );
 
 if( !result )
 {
 if( aErrorMsg )
 {
 *aErrorMsg = _( "Unable to find complementary differential pair "
 "nets. Make sure the names of the nets belonging "
 "to a differential pair end with either N/P or +/-." );
 }
 return false;
 }
 
 int refNet = aItem->Net();
 int coupledNet = ( refNet == netP ) ? netN : netP;
 
 OPT_VECTOR2I refAnchor = getDanglingAnchor( aWorld, aItem );
 ITEM* primRef = aItem;
 
 if( !refAnchor )
 {
 if( aErrorMsg )
 {
 *aErrorMsg = _( "Can't find a suitable starting point. If starting "
 "from an existing differential pair make sure you are "
 "at the end." );
 }
 
 return false;
 }
 
 std::set<ITEM*> coupledItems;
 
 aWorld->AllItemsInNet( coupledNet, coupledItems );
 double bestDist = std::numeric_limits<double>::max();
 bool found = false;
 
 for( ITEM* item : coupledItems )
 {
 if( item->Kind() == aItem->Kind() )
 {
 OPT_VECTOR2I anchor = getDanglingAnchor( aWorld, item );
 
 if( !anchor )
 continue;
 
 double dist = ( *anchor - *refAnchor ).EuclideanNorm();
 
 bool shapeMatches = true;
 
 if( item->OfKind( ITEM::SOLID_T | ITEM::VIA_T ) && item->Layers() != aItem->Layers() )
 {
 shapeMatches = false;
 }
 
 if( dist < bestDist && shapeMatches )
 {
 found = true;
 bestDist = dist;
 
 if( refNet != netP )
 {
 aPair = DP_PRIMITIVE_PAIR ( item, primRef );
 aPair.SetAnchors( *anchor, *refAnchor );
 }
 else
 {
 aPair = DP_PRIMITIVE_PAIR( primRef, item );
 aPair.SetAnchors( *refAnchor, *anchor );
 }
 }
 }
 }
 
 if( !found )
 {
 if( aErrorMsg )
 {
 *aErrorMsg = wxString::Format( _( "Can't find a suitable starting point "
 "for coupled net \"%s\"." ),
 aWorld->GetRuleResolver()->NetName( coupledNet ) );
 }
 
 return false;
 }
 
 return true;
}
 
 
int DIFF_PAIR_PLACER::viaGap() const
{
 return std::max( m_sizes.DiffPairViaGap(),
 m_sizes.GetHoleToHole() + m_sizes.ViaDrill() - m_sizes.ViaDiameter() );
}
 
 
int DIFF_PAIR_PLACER::gap() const
{
 return m_sizes.DiffPairGap() + m_sizes.DiffPairWidth();
}
 
 
bool DIFF_PAIR_PLACER::Start( const VECTOR2I& aP, ITEM* aStartItem )
{
 VECTOR2I p( aP );
 
 setWorld( Router()->GetWorld() );
 m_currentNode = m_world;
 
 wxString err_msg;
 
 if( !FindDpPrimitivePair( m_currentNode, aP, aStartItem, m_start, &err_msg ) )
 {
 Router()->SetFailureReason( err_msg );
 return false;
 }
 
 m_netP = m_start.PrimP()->Net();
 m_netN = m_start.PrimN()->Net();
 
 m_currentStart = p;
 m_currentEnd = p;
 m_placingVia = false;
 m_chainedPlacement = false;
 m_currentTraceOk = false;
 m_currentTrace = DIFF_PAIR();
 m_currentTrace.SetNets( m_netP, m_netN );
 
 initPlacement();
 
 return true;
}
 
 
void DIFF_PAIR_PLACER::initPlacement()
{
 m_idle = false;
 m_orthoMode = false;
 m_currentEndItem = nullptr;
 m_startDiagonal = m_initialDiagonal;
 
 NODE* world = Router()->GetWorld();
 
 world->KillChildren();
 NODE* rootNode = world->Branch();
 
 setWorld( rootNode );
 
 m_lastNode = nullptr;
 m_currentNode = rootNode;
 
 m_shove = std::make_unique<SHOVE>( m_currentNode, Router() );
}
 
 
bool DIFF_PAIR_PLACER::routeHead( const VECTOR2I& aP )
{
 m_fitOk = false;
 
 DP_GATEWAYS gwsEntry( gap() );
 DP_GATEWAYS gwsTarget( gap() );
 
 if( !m_prevPair )
 m_prevPair = m_start;
 
 gwsEntry.BuildFromPrimitivePair( *m_prevPair, m_startDiagonal );
 
 DP_PRIMITIVE_PAIR target;
 
 if( FindDpPrimitivePair( m_currentNode, aP, m_currentEndItem, target ) )
 {
 gwsTarget.BuildFromPrimitivePair( target, m_startDiagonal );
 m_snapOnTarget = true;
 }
 else
 {
 VECTOR2I fp;
 
 if( !propagateDpHeadForces( aP, fp ) )
 return false;
 
 VECTOR2I midp, dirV;
 m_prevPair->CursorOrientation( fp, midp, dirV );
 
 VECTOR2I fpProj = SEG( midp, midp + dirV ).LineProject( fp );
 
 // compute 'leader point' distance from the cursor (project cursor position
 // on the extension of the starting segment pair of the DP)
 int lead_dist = ( fpProj - fp ).EuclideanNorm();
 
 gwsTarget.SetFitVias( m_placingVia, m_sizes.ViaDiameter(), viaGap() );
 
 // far from the initial segment extension line -> allow a 45-degree obtuse turn
 if( lead_dist > ( m_sizes.DiffPairGap() + m_sizes.DiffPairWidth() ) / 2 )
 {
 gwsTarget.BuildForCursor( fp );
 }
 else
 {
 // close to the initial segment extension line -> keep straight part only, project
 // as close as possible to the cursor.
 gwsTarget.BuildForCursor( fpProj );
 gwsTarget.FilterByOrientation( DIRECTION_45::ANG_STRAIGHT | DIRECTION_45::ANG_HALF_FULL,
 DIRECTION_45( dirV ) );
 }
 
 m_snapOnTarget = false;
 }
 
 m_currentTrace.SetGap( gap() );
 m_currentTrace.SetLayer( m_currentLayer );
 
 bool result = gwsEntry.FitGateways( gwsEntry, gwsTarget, m_startDiagonal, m_currentTrace );
 
 if( result )
 {
 m_currentTraceOk = true;
 m_currentTrace.SetNets( m_netP, m_netN );
 m_currentTrace.SetWidth( m_sizes.DiffPairWidth() );
 m_currentTrace.SetGap( m_sizes.DiffPairGap() );
 
 if( m_placingVia )
 {
 m_currentTrace.AppendVias ( makeVia( m_currentTrace.CP().CPoint( -1 ), m_netP ),
 makeVia( m_currentTrace.CN().CPoint( -1 ), m_netN ) );
 }
 else
 {
 m_currentTrace.RemoveVias();
 }
 
 return true;
 }
 
 return m_currentTraceOk;
}
 
 
bool DIFF_PAIR_PLACER::Move( const VECTOR2I& aP , ITEM* aEndItem )
{
 m_currentEndItem = aEndItem;
 m_fitOk = false;
 
 delete m_lastNode;
 m_lastNode = nullptr;
 
 bool retval = route( aP );
 
 NODE* latestNode = m_currentNode;
 m_lastNode = latestNode->Branch();
 
 assert( m_lastNode != nullptr );
 m_currentEnd = aP;
 
 updateLeadingRatLine();
 
 return retval;
}
 
 
void DIFF_PAIR_PLACER::UpdateSizes( const SIZES_SETTINGS& aSizes )
{
 m_sizes = aSizes;
 
 if( !m_idle )
 {
 m_currentTrace.SetWidth( m_sizes.DiffPairWidth() );
 m_currentTrace.SetGap( m_sizes.DiffPairGap() );
 
 if( m_currentTrace.EndsWithVias() )
 {
 m_currentTrace.SetViaDiameter( m_sizes.ViaDiameter() );
 m_currentTrace.SetViaDrill( m_sizes.ViaDrill() );
 }
 }
}
 
 
bool DIFF_PAIR_PLACER::FixRoute( const VECTOR2I& aP, ITEM* aEndItem, bool aForceFinish )
{
 if( !m_fitOk && !Settings().AllowDRCViolations() )
 return false;
 
 if( m_currentTrace.CP().SegmentCount() < 1 || m_currentTrace.CN().SegmentCount() < 1 )
 return false;
 
 if( m_currentTrace.CP().SegmentCount() > 1 )
 m_initialDiagonal = !DIRECTION_45( m_currentTrace.CP().CSegment( -2 ) ).IsDiagonal();
 
 TOPOLOGY topo( m_lastNode );
 
 if( !m_snapOnTarget && !m_currentTrace.EndsWithVias() && !aForceFinish &&
 !Settings().GetFixAllSegments() )
 {
 SHAPE_LINE_CHAIN newP( m_currentTrace.CP() );
 SHAPE_LINE_CHAIN newN( m_currentTrace.CN() );
 
 if( newP.SegmentCount() > 1 && newN.SegmentCount() > 1 )
 {
 newP.Remove( -1, -1 );
 newN.Remove( -1, -1 );
 }
 
 m_currentTrace.SetShape( newP, newN );
 }
 
 if( m_currentTrace.EndsWithVias() )
 {
 m_lastNode->Add( Clone( m_currentTrace.PLine().Via() ) );
 m_lastNode->Add( Clone( m_currentTrace.NLine().Via() ) );
 m_chainedPlacement = false;
 }
 else
 {
 m_chainedPlacement = !m_snapOnTarget && !aForceFinish;
 }
 
 LINE lineP( m_currentTrace.PLine() );
 LINE lineN( m_currentTrace.NLine() );
 
 m_lastNode->Add( lineP );
 m_lastNode->Add( lineN );
 
 topo.SimplifyLine( &lineP );
 topo.SimplifyLine( &lineN );
 
 m_prevPair = m_currentTrace.EndingPrimitives();
 
 CommitPlacement();
 m_placingVia = false;
 
 if( m_snapOnTarget || aForceFinish )
 {
 m_idle = true;
 return true;
 }
 else
 {
 initPlacement();
 return false;
 }
}
 
 
bool DIFF_PAIR_PLACER::AbortPlacement()
{
 m_world->KillChildren();
 return true;
}
 
 
bool DIFF_PAIR_PLACER::HasPlacedAnything() const
{
 return m_currentTrace.CP().SegmentCount() > 0 || m_currentTrace.CN().SegmentCount() > 0;
}
 
 
bool DIFF_PAIR_PLACER::CommitPlacement()
{
 if( m_lastNode )
 Router()->CommitRouting( m_lastNode );
 
 m_lastNode = nullptr;
 m_currentNode = nullptr;
 return true;
}
 
 
void DIFF_PAIR_PLACER::GetModifiedNets( std::vector<int> &aNets ) const
{
 aNets.push_back( m_netP );
 aNets.push_back( m_netN );
}
 
 
void DIFF_PAIR_PLACER::updateLeadingRatLine()
{
 SHAPE_LINE_CHAIN ratLineN, ratLineP;
 TOPOLOGY topo( m_lastNode );
 
 if( topo.LeadingRatLine( &m_currentTrace.PLine(), ratLineP ) )
 m_router->GetInterface()->DisplayRatline( ratLineP, m_netP );
 
 if( topo.LeadingRatLine ( &m_currentTrace.NLine(), ratLineN ) )
 m_router->GetInterface()->DisplayRatline( ratLineN, m_netN );
}
 
 
const std::vector<int> DIFF_PAIR_PLACER::CurrentNets() const
{
 std::vector<int> rv;
 rv.push_back( m_netP );
 rv.push_back( m_netN );
 return rv;
}
 
}