register_real_images test working

src/metric.rs

@@ -167,13 +167,19 @@ impl Sampling {
     fn index(&self) -> Vec<Vec<f64>> {
         match self {
             Self::Fixed(index) => index.clone(),
-            Self::Random((n_samples, shape, _cached)) => rand::rng()
-                .random_iter::<f64>()
-                .take(n_samples * shape.len())
-                .chunks(shape.len())
-                .into_iter()
-                .map(|c| c.zip_eq(shape.iter()).map(|(i, s)| i * s - 0.5).collect())
-                .collect(),
+            Self::Random((n_samples, shape, cached)) => {
+                let mut cache = cached.borrow_mut();
+                if cache.is_empty() {
+                    *cache = rand::rng()
+                        .random_iter::<f64>()
+                        .take(n_samples * shape.len())
+                        .chunks(shape.len())
+                        .into_iter()
+                        .map(|c| c.zip_eq(shape.iter()).map(|(i, s)| i * s - 0.5).collect())
+                        .collect();
+                }
+                cache.clone()
+            }
         }
     }
 }