Add benchmark for reserve()

benches/reserve.rs

@@ -0,0 +1,31 @@
+#![feature(test)]
+
+extern crate test;
+use test::Bencher;
+
+use ndarray::prelude::*;
+
+#[bench]
+fn push_reserve(bench: &mut Bencher)
+{
+    let ones: Array<f32, _> = array![1f32];
+    bench.iter(|| {
+        let mut a: Array<f32, Ix1> = array![];
+        a.reserve(Axis(0), 100);
+        for _ in 0..100 {
+            a.append(Axis(0), ones.view()).unwrap();
+        }
+    });
+}
+
+#[bench]
+fn push_no_reserve(bench: &mut Bencher)
+{
+    let ones: Array<f32, _> = array![1f32];
+    bench.iter(|| {
+        let mut a: Array<f32, Ix1> = array![];
+        for _ in 0..100 {
+            a.append(Axis(0), ones.view()).unwrap();
+        }
+    });
+}

src/impl_owned_array.rs

@@ -764,9 +764,6 @@ where D: Dimension
     pub fn reserve(&mut self, axis: Axis, additional: usize)
     where D: RemoveAxis
     {
-        if additional == 0 {
-            return;
-        }
         let self_dim = self.raw_dim();
         let remaining_shape = self_dim.remove_axis(axis);
         let len_to_append = remaining_shape.size() * additional;