[Marble-commits] KDE/kdeedu/marble/src/lib/routing

[Dennis Nienhüser]

SVN commit 1207580 by nienhueser:

Introduce a lookup table to bring down RoutingModel::currentInstruction() from O(n^2) to O(n) (worst case), n the number of waypoints. This reduces the computation time by one magnitude for some longer test routes (180 ms => < 20 ms). The previous approach lead to clumsy behavior on the N900 when the worst case was hit (large routes including large motorway parts), evenutally leading to freezes when the computation time exceeds the inverse gps frequency.

 M  +51 -13    RoutingModel.cpp  


--- trunk/KDE/kdeedu/marble/src/lib/routing/RoutingModel.cpp #1207579:1207580
@@ -84,6 +84,7 @@
     QMap<RoutingInstruction::TurnType,QPixmap> m_turnTypePixmaps;
     PositionTracking* m_positionTracking;
     RouteRequest* m_request;
+    QVector<int> m_instructionLookupTable;
 
     void importPlacemark( const GeoDataPlacemark *placemark );
 
@@ -274,6 +275,33 @@
     }
 
     d->m_deviation = RoutingModelPrivate::Unknown;
+
+    // Generate lookup table
+    d->m_instructionLookupTable.clear();
+    GeoDataLineString wayPoints, instructions;
+    foreach( const RouteElement &element, d->m_route ) {
+        if ( element.type == WayPoint ) {
+            wayPoints << element.position;
+        } else if ( element.type == Instruction ) {
+          instructions << element.position;
+        }
+    }
+
+    int const end = wayPoints.size();
+    int j=0;
+    for ( int i=0; i<end; ++i ) {
+      if ( j >= instructions.size() ) {
+        // Towards the end of the route
+        break;
+      }
+
+      if ( wayPoints.at(i) == instructions.at(j) ) {
+        //mDebug() << "Instruction " << j << " => Waypoint " << i;
+        d->m_instructionLookupTable.push_back( i );
+        ++j;
+      }
+    }
+
     reset();
     return true;
 }
@@ -401,6 +429,9 @@
 
 void RoutingModel::currentInstruction( GeoDataCoordinates location, qreal speed )
 {
+    /** @todo FIXME Refactor this method. Shorter, less caching.
+              Switch to a more intelligent underlying data structure */
+
     if( rowCount() != 0 ) {
 
         QList<RouteElement> instructions;
@@ -445,16 +476,22 @@
         //if there is no route but source and destination are specified
         if( wayPoints.size() != 0 ) {
             if( !( wayPoints[waypointIndex] == wayPoints[wayPoints.size()-1] ) ) {
-                int currentWaypointOffset = 0;
-                for( int i = 0; i<instructions.size(); ++i ) {
-                    int instructionSize = instructions[i].instructionPointSet.size();
-                    for ( int j = 0; j<instructionSize; ++j ) {
-                       if( wayPoints[waypointIndex] ==  instructions[i].instructionPointSet.at(j) ) {
-                           d->m_nextInstructionIndex = i + 1;
-                           currentWaypointOffset = j;
+//                int currentWaypointOffset = 0;
+                for ( int k = 0; k<d->m_instructionLookupTable.size(); ++k ) {
+                  if ( d->m_instructionLookupTable.at( k ) > waypointIndex ) {
+                    d->m_nextInstructionIndex = k;
+                    break;
                        }
                     }
-                }
+//                for( int i = 0; i<instructions.size(); ++i ) {
+//                    int instructionSize = instructions[i].instructionPointSet.size();
+//                    for ( int j = 0; j<instructionSize; ++j ) {
+//                       if( wayPoints[waypointIndex] ==  instructions[i].instructionPointSet.at(j) ) {
+//                           d->m_nextInstructionIndex = i + 1;
+//                           currentWaypointOffset = j;
+//                       }
+//                    }
+//                }
 
                 qreal radius = EARTH_RADIUS;
 
@@ -472,13 +509,14 @@
                 }
                 else {
                     GeoDataCoordinates destinationCoord =  instructions[d->m_nextInstructionIndex-1].instructionPointSet.last();
-                    if( !(instructions[d->m_nextInstructionIndex-1].instructionPointSet.at( currentWaypointOffset ) == destinationCoord ) ) {
                         distanceRemaining = distanceSphere( location, destinationCoord ) * radius;
+//                    if( !(instructions[d->m_nextInstructionIndex-1].instructionPointSet.at( currentWaypointOffset ) == destinationCoord ) ) {
+//                        distanceRemaining = distanceSphere( location, destinationCoord ) * radius;
+//                    }
+//                    else {
+//                        distanceRemaining = 0.0;
+//                    }
                     }
-                    else {
-                        distanceRemaining = 0.0;
-                    }
-                }
 
                 d->m_currentInstructionLength = instructions[d->m_nextInstructionIndex-1].instructionDistance;