We can create a new single-population model

src/blur.rs

@@ -63,7 +63,7 @@ impl Blur {
             for j in 0..radius {
                 value += src_row[width - radius + j] + src_row[j];
             }
-            // At this point "value" contains the unweighted sum for the right-most row element.
+
             for i in 0..width {
                 let left = (i + width - radius - 1) & (width - 1);
                 let right = (i + radius) & (width - 1);
@@ -82,7 +82,6 @@ impl Blur {
         // We don't replicate the horizontal filter logic because of the cache-unfriendly memory
         // access patterns of sequential iteration over individual columns. Instead, we iterate over
         // rows via loop interchange.
-
         let offset = (height - radius - 1) * width;
         self.row_buffer
             .copy_from_slice(&src[offset..offset + width]);
@@ -97,7 +96,6 @@ impl Blur {
                 *buf += bottom + top;
             }
         }
-        // At this point row_buffer contains the unweighted sum for all top elements.
 
         for (i, dst_row) in dst.chunks_exact_mut(width).enumerate() {
             let bottom_off = ((i + height - radius - 1) & (height - 1)) * width;
@@ -128,7 +126,7 @@ mod tests {
         blur.box_blur_h(&src, &mut dst, 1);
         assert_eq!(
             dst,
-            &[
+            [
                 2.3333335, 2.0, 3.0, 2.6666667, 6.3333335, 6.0, 7.0, 6.666667, 10.333334, 10.0,
                 11.0, 10.666667, 14.333334, 14.0, 15.0, 14.666667
             ]

src/main.rs

@@ -2,4 +2,7 @@ mod blur;
 mod grid;
 mod model;
 
-fn main() {}
+fn main() {
+    let model = model::Model::new(4, 4, 20, 1);
+    println!("{:#?}", model);
+}

src/model.rs

@@ -1,32 +1,97 @@
 use crate::grid::Grid;
 
+use rand::{thread_rng, Rng};
+
 /// A single Physarum agent. The x and y positions are continuous, hence we use floating point
 /// numbers instead of integers.
 #[derive(Debug)]
-pub struct Agent {
+struct Agent {
-    pub x: f32,
+    x: f32,
-    pub y: f32,
+    y: f32,
-    pub angle: f32,
+    angle: f32,
+}
+
+impl Agent {
+    fn new(width: usize, height: usize) -> Self {
+        let mut rng = rand::thread_rng();
+        let (x, y, angle) = rng.gen::<(f32, f32, f32)>();
+        Agent {
+            x: x * width as f32,
+            y: y * height as f32,
+            angle: angle * std::f32::consts::TAU,
+        }
+    }
 }
 
 /// A model configuration. We make it into a separate type, because we will eventually have multiple
 /// configurations in one model.
 #[derive(Debug)]
-pub struct PopulationConfig {
+struct PopulationConfig {
-    pub sensor_angle: f32,
+    sensor_distance: f32,
-    pub sensor_distance: f32,
+    step_distance: f32,
-    pub rotation_angle: f32,
+    decay_factor: f32,
-    pub step_distance: f32,
+    sensor_angle: f32,
-    pub decay_factor: f32,
+    rotation_angle: f32,
 }
 
-impl PopulationConfig {}
+impl PopulationConfig {
+    const SENSOR_ANGLE_MIN: f32 = 0.0;
+    const SENSOR_ANGLE_MAX: f32 = 120.0;
+    const SENSOR_DISTANCE_MIN: f32 = 0.0;
+    const SENSOR_DISTANCE_MAX: f32 = 64.0;
+    const ROTATION_ANGLE_MIN: f32 = 0.0;
+    const ROTATION_ANGLE_MAX: f32 = 120.0;
+    const STEP_DISTANCE_MIN: f32 = 0.2;
+    const STEP_DISTANCE_MAX: f32 = 2.0;
+    const DEPOSITION_AMOUNT_MIN: f32 = 5.0;
+    const DEPOSITION_AMOUNT_MAX: f32 = 5.0;
+    const DECAY_FACTOR_MIN: f32 = 0.1;
+    const DECAY_FACTOR_MAX: f32 = 0.1;
+
+    /// Generate a random configuration.
+    pub fn new() -> Self {
+        let mut rng = rand::thread_rng();
+
+        PopulationConfig {
+            sensor_distance: rng.gen_range(Self::SENSOR_DISTANCE_MIN..=Self::SENSOR_DISTANCE_MAX),
+            step_distance: rng.gen_range(Self::STEP_DISTANCE_MIN..=Self::STEP_DISTANCE_MAX),
+            decay_factor: rng.gen_range(Self::DECAY_FACTOR_MIN..=Self::DECAY_FACTOR_MAX),
+            sensor_angle: rng
+                .gen_range(Self::SENSOR_ANGLE_MIN..=Self::SENSOR_ANGLE_MAX)
+                .to_radians(),
+            rotation_angle: rng
+                .gen_range(Self::ROTATION_ANGLE_MIN..=Self::ROTATION_ANGLE_MAX)
+                .to_radians(),
+        }
+    }
+}
 
 /// Top-level simulation class.
 #[derive(Debug)]
 pub struct Model {
-    grid: Grid,
+    // Physarum agents.
     agents: Vec<Agent>,
 
+    // The grid they move on.
+    grid: Grid,
+
+    // Simulation parameters.
+    diffusivity: usize,
     config: PopulationConfig,
+
+    iteration: i32,
+}
+
+impl Model {
+    pub fn new(width: usize, height: usize, n_particles: usize, diffusivity: usize) -> Self {
+        Model {
+            agents: (0..n_particles)
+                .map(|_| Agent::new(width, height))
+                .collect(),
+            grid: Grid::new(width, height),
+            diffusivity,
+            config: PopulationConfig::new(),
+            iteration: 0,
+        }
+    }
 }