significantly improve performance

src/main.rs

@@ -50,7 +50,7 @@ impl App {
     }
 }
 
-fn calc_amount(vec: &mut Vec<f64>) -> f64 {
+fn calc_amount(vec: &Vec<f64>) -> f64 {
     (vec[0].powi(2) + vec[1].powi(2)).sqrt()
 }
 
@@ -111,8 +111,8 @@ impl Object {
 
     fn mouse_attract(&mut self, mouse_pos: [f64; 2]) {
         let pos: Vec<f64> = self.get_pos();
-        let mut dist: Vec<f64> = vec![pos[0] - mouse_pos[0], pos[1] - mouse_pos[1]];
-        let amount = calc_amount(&mut dist);
+        let dist: Vec<f64> = vec![pos[0] - mouse_pos[0], pos[1] - mouse_pos[1]];
+        let amount = calc_amount(&dist);
         for (i, d) in dist.iter().enumerate() {
             self.vel[i] -= 0.2 * d / amount.max(0.1);
             self.vel[i] = self.vel[i].min(10.0).max(-10.0);
@@ -121,16 +121,22 @@ impl Object {
 
     fn attract(&mut self, objs: &mut Vec<Vec<f64>>) {
         let this_pos: Vec<f64> = self.get_pos();
-        let mut distances: Vec<Vec<f64>> = Vec::new();
-        for obj_pos in objs {
-            let mut dist_vec: Vec<f64> = Vec::new();
-            for (i, op) in obj_pos.iter().enumerate() {
-                dist_vec.push(op - this_pos[i]);
-            }
-            distances.push(dist_vec);
-        }
-        for mut dist in distances {
-            let amount = calc_amount(&mut dist);
+        let distances: Vec<Vec<f64>> = objs
+            .iter()
+            .map(
+                |obj_pos|
+                    {
+                        obj_pos
+                            .iter()
+                            .zip(&this_pos)
+                            .map(
+                                |(obj, this)|
+                                    { obj - this }
+                            ).collect()
+                    }
+            ).collect();
+        for dist in distances {
+            let amount = calc_amount(&dist);
             for (i, d) in dist.iter().enumerate() {
                 self.vel[i] += 1.0 * (d / amount.max(0.01));
             }
@@ -144,7 +150,7 @@ impl Object {
             for i in 0..2 {
                 dist_vec.push(this_pos[i] - pos[i]);
             }
-            let amount = calc_amount(&mut dist_vec);
+            let amount = calc_amount(&dist_vec);
 
             for (i, d) in dist_vec.iter().enumerate() {
                 self.vel[i] += 1.5 * d.min(150.0).max(-150.0) / (amount).max(0.01);
@@ -170,7 +176,7 @@ impl Object {
         for (i, d) in new_vel.iter().enumerate() {
             self.vel[i] = ((self.vel[i] + d) / 2.0).max(-10.0).min(10.0);
         }
-        let amount = calc_amount(&mut self.vel);
+        let amount = calc_amount(&self.vel);
         for i in 0..2 {
             self.vel[i] *= 10.0 / amount;
         }
@@ -191,7 +197,7 @@ impl Object {
     }
 
     fn calc_direction(&mut self) -> f64 {
-        let mut dir = (self.vel[0] / calc_amount(&mut self.vel)).acos();
+        let mut dir = (self.vel[0] / calc_amount(&self.vel)).acos();
         if self.vel[1].signum() < 0.0 {
             dir = 2.0 * PI - dir;
         }
@@ -223,7 +229,7 @@ fn main() {
 
     let opengl = OpenGL::V3_2;
 
-    let num_objs = 12;
+    let num_objs = 512;
 
     let mut window: Window = WindowSettings::new("Test", [200, 200])
         .opengl(opengl)
@@ -243,16 +249,15 @@ fn main() {
                 .expect("Color failure!"),
         ))
     }
-
-    let mut positions: Vec<Vec<f64>> = Vec::new();
+    let mut positions: Vec<Vec<f64>> = vec![vec![0.0; 2]; objects.len()];
 
     let mut events = Events::new(EventSettings::new());
     while let Some(e) = events.next(&mut window) {
         if let Some(r) = e.render_args() {
-            for obj in &mut objects {
-                obj.update_border_dist(&r);
-                obj.update();
-                positions.push(obj.get_pos());
+            for i in 0..objects.len() {
+                objects[i].update_border_dist(&r);
+                objects[i].update();
+                positions[i] = objects[i].get_pos();
             }
             app.render(&objects, &r);
         }
@@ -262,7 +267,7 @@ fn main() {
                 obj.attract(&mut positions);
                 obj.repel(&mut positions);
             }
-            positions.clear()
+            // positions.clear()
         }
 
         if let Some(p) = e.press_args() {