Merge pull request #977 from rust-ndarray/cf-preference

Require len > 1 axis for layout preference

Author: bluss

src/layout/mod.rs

@@ -170,6 +170,34 @@ mod tests {
         }
     }
 
+    #[test]
+    fn no_layouts() {
+        let a = M::zeros((5, 5));
+        let b = M::zeros((5, 5).f());
+
+        // 2D row/column matrixes
+        let arow = a.slice(s![0..1, ..]);
+        let acol = a.slice(s![.., 0..1]);
+        let brow = b.slice(s![0..1, ..]);
+        let bcol = b.slice(s![.., 0..1]);
+        assert_layouts!(arow, CORDER, FORDER);
+        assert_not_layouts!(acol, CORDER, CPREFER, FORDER, FPREFER);
+        assert_layouts!(bcol, CORDER, FORDER);
+        assert_not_layouts!(brow, CORDER, CPREFER, FORDER, FPREFER);
+
+        // 2D row/column matrixes - now made with insert axis
+        for &axis in &[Axis(0), Axis(1)] {
+            let arow = a.slice(s![0, ..]).insert_axis(axis);
+            let acol = a.slice(s![.., 0]).insert_axis(axis);
+            let brow = b.slice(s![0, ..]).insert_axis(axis);
+            let bcol = b.slice(s![.., 0]).insert_axis(axis);
+            assert_layouts!(arow, CORDER, FORDER);
+            assert_not_layouts!(acol, CORDER, CPREFER, FORDER, FPREFER);
+            assert_layouts!(bcol, CORDER, FORDER);
+            assert_not_layouts!(brow, CORDER, CPREFER, FORDER, FPREFER);
+        }
+    }
+
     #[test]
     fn skip_layouts() {
         let a = M::zeros((5, 5));

src/zip/mod.rs

@@ -69,9 +69,9 @@ where
         } else if n > 1 && self.raw_view().reversed_axes().is_standard_layout() {
             Layout::f()
         } else if n > 1 {
-            if self.stride_of(Axis(0)) == 1 {
+            if self.len_of(Axis(0)) > 1 && self.stride_of(Axis(0)) == 1 {
                 Layout::fpref()
-            } else if self.stride_of(Axis(n - 1)) == 1 {
+            } else if self.len_of(Axis(n - 1)) > 1 && self.stride_of(Axis(n - 1)) == 1 {
                 Layout::cpref()
             } else {
                 Layout::none()