Add uniformity tests and change spawn

src/system/mod.rs

@@ -6,7 +6,7 @@ pub mod model;
 
 pub const DIM: u32 = 2;
 
-#[derive(Clone, Debug)]
+#[derive(Clone, Debug, PartialEq, Eq)]
 pub struct Position(pub i32, pub i32);
 
 impl Position {

src/system/model.rs

@@ -89,7 +89,7 @@ impl<R: Rng, S: Storage, W: Walker<R>> DLASystem<R, S, W> {
         for direction in 0..DIM {
             for sign in [-1, 1] {
                 let neighbour = position.clone() + Position::in_direction(direction, sign);
-                if self.storage.at(&neighbour) && self.rng.gen_range(0.0f32..1.0) < self.stick_probability {
+                if self.storage.at(&neighbour) && self.rng.gen_range(0.0f32..=1.0) < self.stick_probability {
                     return true;
                 }
             }
@@ -101,7 +101,7 @@ impl<R: Rng, S: Storage, W: Walker<R>> DLASystem<R, S, W> {
     fn spawn_particle(&mut self) {
         let theta = self.rng.gen_range(0f32..1.0);
         let (x, y) = (self.add_circle * theta.cos(), self.add_circle * theta.sin());
-        let position = Position(x.round() as i32, y.round() as i32);
+        let position = Position(x as i32, y as i32);
 
         if !self.storage.at(&position) {
             self.active_particle = Some(position);

src/system/walker.rs

@@ -17,3 +17,46 @@ impl<R: Rng> Walker<R> for LocalRandomWalker {
         position.clone() + offset
     }
 }
+
+mod test {
+    use rand::rngs::SmallRng;
+    use rand::{SeedableRng, thread_rng};
+    use crate::system::Position;
+    use crate::system::walker::{LocalRandomWalker, Walker};
+
+    #[test]
+    fn uniformity() {
+        let walker = LocalRandomWalker;
+        let mut rng = SmallRng::from_rng(thread_rng()).unwrap();
+        let mut results: Vec<Position> = vec![];
+
+        let origin = &Position(0, 0);
+
+        let x: u32 = (1_000000_000);
+        for i in 0..x {
+            results.push(walker.walk(&mut rng, origin));
+        }
+
+        let a = results
+            .iter()
+            .filter(|a| **a == Position(0, 1))
+            .count();
+
+        let b = results
+            .iter()
+            .filter(|a| **a == Position(0, -1))
+            .count();
+
+        let c = results
+            .iter()
+            .filter(|a| **a == Position(1, 0))
+            .count();
+
+        let d = results
+            .iter()
+            .filter(|a| **a == Position(-1, 0))
+            .count();
+
+        println!("{} {} {} {}", a as f32 / x as f32, b as f32 / x as f32, c as f32 / x as f32, d as f32 / x as f32);
+    }
+}