reduced allocations for drag vectors, see #191

phetsims · Jan 29, 2019 · c6deed6 · c6deed6
1 parent f0851ed
commit c6deed6
Showing 1 changed file with 8 additions and 10 deletions.
diff --git a/js/common/model/EnergyChunkDistributor.js b/js/common/model/EnergyChunkDistributor.js
@@ -461,6 +461,7 @@ define( function( require ) {
     updateVelocitiesNew: function( slices, energyChunks, energyChunkForces, dt ) {
 
       var maxEnergy = 0;
+      var dragForce = Vector2.dirtyFromPool();
 
       for ( var sliceIndex = 0; sliceIndex < slices.length; sliceIndex++ ) {
         for ( var ecIndex = 0; ecIndex < slices[ sliceIndex ].energyChunkList.length; ecIndex++ ) {
@@ -480,14 +481,13 @@ define( function( require ) {
           // calculate drag force using standard drag equation
           var velocityMagnitudeSquared = velocity.magnitudeSquared();
           var dragMagnitude = 0.5 * FLUID_DENSITY * DRAG_COEFFICIENT * ENERGY_CHUNK_CROSS_SECTIONAL_AREA * velocityMagnitudeSquared;
-          var dragForce = ZERO_VECTOR;
           if ( dragMagnitude > 0 ) {
-            dragForce = Vector2.createFromPool(
-              -velocity.x,
-              -velocity.y
-            );
+            dragForce.setXY( -velocity.x, -velocity.y );
             dragForce.setMagnitude( dragMagnitude );
           }
+          else {
+            dragForce.setXY( 0, 0 );
+          }
           assert && assert( !_.isNaN( dragForce.x ) && !_.isNaN( dragForce.y ), 'drag force contains NaN value' );
 
           // update velocity based on the sum of forces acting on the particle
@@ -499,14 +499,12 @@ define( function( require ) {
           if ( totalParticleEnergy > maxEnergy ) {
             maxEnergy = totalParticleEnergy;
           }
-
-          // free allocations
-          if ( dragForce !== ZERO_VECTOR ) {
-            dragForce.freeToPool();
-          }
         }
       }
 
+      // free allocations
+      dragForce.freeToPool();
+
       return maxEnergy;
     },