Alternative implementation for sum_axis

Author: LukeMathWalker

src/numeric/impl_numeric.rs

@@ -103,22 +103,11 @@ impl<A, S, D> ArrayBase<S, D>
         where A: Clone + Zero + Add<Output=A>,
               D: RemoveAxis,
     {
-        let n = self.len_of(axis);
-        let stride = self.strides()[axis.index()];
-        let mut res = Array::zeros(self.raw_dim().remove_axis(axis));
-        if self.ndim() == 2 && stride == 1 {
-            // contiguous along the axis we are summing
-            let ax = axis.index();
-            for (i, elt) in enumerate(&mut res) {
-                *elt = self.index_axis(Axis(1 - ax), i).sum();
-            }
-            res
-        } else {
-            numeric_util::array_pairwise_sum(
-                (0..n).map(|i| self.index_axis(axis, i)),
-                || res.clone()
-            )
-        }
+        let mut out = Array::zeros(self.dim.remove_axis(axis));
+        Zip::from(&mut out)
+            .and(self.lanes(axis))
+            .apply(|out, lane| *out = lane.sum());
+        out
     }
 
     /// Return mean along `axis`.