parallel grid deposit

src/grid.rs

@@ -88,6 +88,8 @@ pub struct Grid {
     // Scratch space for the blur operation.
     buf: Vec<f32>,
     blur: Blur,
+
+    pub i: Vec<usize>,
 }
 
 impl Clone for Grid {
@@ -99,13 +101,14 @@ impl Clone for Grid {
             data: self.data.clone(),
             buf: self.buf.clone(),
             blur: self.blur.clone(),
+            i: self.i.clone(),
         }
     }
 }
 
 impl Grid {
     // Create a new grid filled with random floats in the [0.0..1.0) range.
-    pub fn new<R: Rng + ?Sized>(width: usize, height: usize, rng: &mut R) -> Self {
+    pub fn new<R: Rng + ?Sized>(width: usize, height: usize, rng: &mut R, i: Vec<usize>) -> Self {
         if !width.is_power_of_two() || !height.is_power_of_two() {
             panic!("Grid dimensions must be a power of two.");
         }
@@ -119,6 +122,7 @@ impl Grid {
             config: PopulationConfig::new(rng),
             buf: vec![0.0; width * height],
             blur: Blur::new(width),
+            i,
         }
     }