Refactor and other improvements

server-rs/src/aggregation.rs

@@ -0,0 +1,70 @@
+/// Per-cell accumulator for aggregating features (min/max/sum/count).
+/// Uses Box<[T]> instead of Vec<T> to avoid storing capacity (saves 8 bytes per field per cell).
+/// Shared by hexagon and postcode aggregation routes.
+pub struct Aggregator {
+    pub count: u32,
+    pub mins: Box<[f32]>,
+    pub maxs: Box<[f32]>,
+    pub sums: Box<[f64]>,
+    pub feat_counts: Box<[u32]>,
+}
+
+impl Aggregator {
+    pub fn new(num_features: usize) -> Self {
+        Aggregator {
+            count: 0,
+            mins: vec![f32::INFINITY; num_features].into_boxed_slice(),
+            maxs: vec![f32::NEG_INFINITY; num_features].into_boxed_slice(),
+            sums: vec![0.0f64; num_features].into_boxed_slice(),
+            feat_counts: vec![0u32; num_features].into_boxed_slice(),
+        }
+    }
+
+    /// Add a row using row-major feature_data layout.
+    /// feature_data[row * num_features + feat_idx] — all features for one row
+    /// are contiguous, so this reads a single cache line per ~8 features.
+    #[inline]
+    pub fn add_row(&mut self, feature_data: &[f32], row: usize, num_features: usize) {
+        self.count += 1;
+        let base = row * num_features;
+        let row_slice = &feature_data[base..base + num_features];
+        for (feat_index, &value) in row_slice.iter().enumerate() {
+            if value.is_finite() {
+                if value < self.mins[feat_index] {
+                    self.mins[feat_index] = value;
+                }
+                if value > self.maxs[feat_index] {
+                    self.maxs[feat_index] = value;
+                }
+                self.sums[feat_index] += value as f64;
+                self.feat_counts[feat_index] += 1;
+            }
+        }
+    }
+
+    /// Add a row, only aggregating the features at the given indices.
+    #[inline]
+    pub fn add_row_selective(
+        &mut self,
+        feature_data: &[f32],
+        row: usize,
+        num_features: usize,
+        indices: &[usize],
+    ) {
+        self.count += 1;
+        let base = row * num_features;
+        for &feat_index in indices {
+            let value = feature_data[base + feat_index];
+            if value.is_finite() {
+                if value < self.mins[feat_index] {
+                    self.mins[feat_index] = value;
+                }
+                if value > self.maxs[feat_index] {
+                    self.maxs[feat_index] = value;
+                }
+                self.sums[feat_index] += value as f64;
+                self.feat_counts[feat_index] += 1;
+            }
+        }
+    }
+}