Reduce memory usage to improve GC performance

boids.mjs

@@ -1,79 +1,75 @@
 import Vector from './vector.mjs';
 
-const findNeighbors = (boids, boid, radius) =>
-{
-    const neighbors = [];
-
-    for (let otherBoid of boids)
-    {
-        if (boid != otherBoid)
-        {
-            const dist = boid.pos.sub(otherBoid.pos).normSquared();
-
-            if (dist < radius * radius)
-            {
-                neighbors.push(otherBoid);
-            }
-        }
-    }
-
-    return neighbors;
-};
+const meanPos = new Vector(0, 0);
+const meanVel = new Vector(0, 0);
+const repelForce = new Vector(0, 0);
 
 export const update = (boids, params, time) =>
 {
-    for (let boid of boids)
+    const boidsSize = boids.length;
+
+    for (let i = 0; i < boidsSize; ++i)
     {
-        const visible = findNeighbors(boids, boid, params.visibleDist);
-        const close = findNeighbors(boids, boid, params.closeDist);
+        const me = boids[i];
 
-        // Attract towards center of visible flock
-        const center = new Vector(0, 0);
+        meanPos.reset();
+        meanVel.reset();
+        repelForce.reset();
 
-        for (let otherBoid of visible)
+        let visibleSize = 0;
+
+        for (let j = 0; j < boidsSize; ++j)
         {
-            center.addMut(otherBoid.pos);
+            if (i != j)
+            {
+                const you = boids[j];
+                const dist = Vector.distSquared(me.pos, you.pos);
+
+                if (dist < params.visibleDist * params.visibleDist)
+                {
+                    meanPos.add(you.pos);
+                    meanVel.add(you.vel);
+                    visibleSize += 1;
+
+                    if (dist < params.closeDist * params.closeDist)
+                    {
+                        repelForce.add(me.pos).sub(you.pos);
+                    }
+                }
+            }
         }
 
-        if (visible.length >= 1)
+        // Attract towards center of visible flock
+        if (visibleSize >= 1)
         {
-            center.divMut(visible.length);
-            boid.vel.addMut(center.sub(boid.pos).mul(params.centerAccel));
+            me.vel.add(meanPos.div(visibleSize)
+                              .sub(me.pos)
+                              .mul(params.centerAccel));
         }
 
         // Attract toward center of screen
-        boid.vel.addMut(boid.pos.mul(-0.01));
+        me.vel.addMul(me.pos, -0.01);
 
         // Repel away from close boids
-        for (let otherBoid of close)
-        {
-            boid.vel.addMut(boid.pos
-                .sub(otherBoid.pos)
-                .mul(params.repelAccel));
-        }
+        me.vel.add(repelForce.mul(params.repelAccel));
 
         // Match other boids’ velocity
-        const velocity = new Vector(0, 0);
-
-        for (let otherBoid of visible)
+        if (visibleSize >= 1)
         {
-            velocity.addMut(otherBoid.vel);
-        }
-
-        if (visible.length >= 1)
-        {
-            velocity.divMut(visible.length);
-            boid.vel.addMut(velocity.sub(boid.vel).mul(params.matchAccel));
+            me.vel.add(meanVel.div(visibleSize)
+                              .sub(me.vel)
+                              .mul(params.matchAccel));
         }
 
         // Do not surpass maximum speed
-        const speed = boid.vel.normSquared();
+        const speed = me.vel.normSquared();
 
         if (speed > params.maxSpeed * params.maxSpeed)
         {
-            boid.vel.divMut(Math.sqrt(speed)).mulMut(params.maxSpeed);
+            me.vel.div(Math.sqrt(speed)).mul(params.maxSpeed);
         }
 
-        boid.pos.addMut(boid.vel.mul(time));
+        // Integrate speed
+        me.pos.addMul(me.vel, time);
     }
 };

draw.mjs

@@ -7,8 +7,13 @@ const boidShape = [
     new Vector(2, 0),
 ];
 
+const boidShapeSize = boidShape.length;
+const transformed = new Vector(0, 0);
+
 export const boids = (activeBoids, params, ctx, width, height, center) =>
 {
+    const boidsSize = activeBoids.length;
+
     ctx.clearRect(0, 0, width, height);
 
     // // Draw each boid’s visibility and proximity zones
@@ -75,24 +80,31 @@ export const boids = (activeBoids, params, ctx, width, height, center) =>
     ctx.beginPath();
     ctx.fillStyle = 'black';
 
-    for (let boid of activeBoids)
+    for (let i = 0; i < boidsSize; ++i)
     {
+        const boid = activeBoids[i];
         const angle = boid.vel.angle();
         let isFirst = true;
 
-        for (let point of boidShape)
+        for (let j = 0; j < boidShapeSize; ++j)
         {
-            const trans = boid.pos.add(center)
-                .add(point.rotate(angle).mul(params.radius))
+            transformed.x = boidShape[j].x;
+            transformed.y = boidShape[j].y;
+
+            transformed
+                .rotate(angle)
+                .mul(params.radius)
+                .add(center)
+                .add(boid.pos);
 
             if (isFirst)
             {
-                ctx.moveTo(trans.x, trans.y);
+                ctx.moveTo(transformed.x, transformed.y);
                 isFirst = false;
             }
             else
             {
-                ctx.lineTo(trans.x, trans.y);
+                ctx.lineTo(transformed.x, transformed.y);
             }
         }
     }

vector.mjs

@@ -7,23 +7,20 @@ class Vector
     }
 
     add(vector)
-    {
-        return new Vector(this.x + vector.x, this.y + vector.y);
-    }
-
-    addMut(vector)
     {
         this.x += vector.x;
         this.y += vector.y;
         return this;
     }
 
-    sub(vector)
+    addMul(vector, scalar)
     {
-        return new Vector(this.x - vector.x, this.y - vector.y);
+        this.x += vector.x * scalar;
+        this.y += vector.y * scalar;
+        return this;
     }
 
-    subMut(vector)
+    sub(vector)
     {
         this.x -= vector.x;
         this.y -= vector.y;
@@ -31,11 +28,6 @@ class Vector
     }
 
     mul(scalar)
-    {
-        return new Vector(this.x * scalar, this.y * scalar);
-    }
-
-    mulMut(scalar)
     {
         this.x *= scalar;
         this.y *= scalar;
@@ -47,20 +39,16 @@ class Vector
         return this.mul(1 / scalar);
     }
 
-    divMut(scalar)
-    {
-        return this.mulMut(1 / scalar);
-    }
-
     rotate(angle)
     {
         const cos = Math.cos(angle);
         const sin = Math.sin(angle);
+        const nextX = cos * this.x - sin * this.y;
+        const nextY = cos * this.y + sin * this.x;
 
-        return new Vector(
-            cos * this.x - sin * this.y,
-            cos * this.y + sin * this.x,
-        );
+        this.x = nextX;
+        this.y = nextY;
+        return this;
     }
 
     angle()
@@ -72,6 +60,26 @@ class Vector
     {
         return this.x * this.x + this.y * this.y;
     }
+
+    static distSquared(lhs, rhs)
+    {
+        return (
+            (lhs.x - rhs.x) * (lhs.x - rhs.x)
+            + (lhs.y - rhs.y) * (lhs.y - rhs.y)
+        );
+    }
+
+    reset()
+    {
+        this.x = 0;
+        this.y = 0;
+        return this;
+    }
+
+    clone()
+    {
+        return new Vector(this.x, this.y);
+    }
 }
 
 export default Vector;