From c27626a6a755be160907c4fab747f36ad6f933f9 Mon Sep 17 00:00:00 2001
From: Dave McDaniel <mcdanieldave@gmail.com>
Date: Mon, 8 Feb 2021 22:01:13 -0500
Subject: [PATCH] add test to sort-axis example to catch issue of swapped
 perm_i and i

also replaced outer iteration with zip directly since it takes slices.
---
 examples/sort-axis.rs | 80 ++++++++++++++++++++++++++++++++++++++-----
 scripts/all-tests.sh  |  1 +
 2 files changed, 72 insertions(+), 9 deletions(-)

diff --git a/examples/sort-axis.rs b/examples/sort-axis.rs
index 09410e819..7ae67fb07 100644
--- a/examples/sort-axis.rs
+++ b/examples/sort-axis.rs
@@ -102,21 +102,27 @@ where
         assert_eq!(axis_len, perm.indices.len());
         debug_assert!(perm.correct());
 
+        if self.is_empty() {
+            return self;
+        }
+
         let mut result = Array::uninit(self.dim());
 
         unsafe {
             // logically move ownership of all elements from self into result
             // the result realizes this ownership at .assume_init() further down
             let mut moved_elements = 0;
-            for i in 0..axis_len {
-                let perm_i = perm.indices[i];
-                Zip::from(result.index_axis_mut(axis, perm_i))
-                    .and(self.index_axis(axis, i))
-                    .for_each(|to, from| {
-                        copy_nonoverlapping(from, to.as_mut_ptr(), 1);
-                        moved_elements += 1;
-                    });
-            }
+            Zip::from(&perm.indices)
+                .and(result.axis_iter_mut(axis))
+                .for_each(|&perm_i, result_pane| {
+                    // possible improvement: use unchecked indexing for `index_axis`
+                    Zip::from(result_pane)
+                        .and(self.index_axis(axis, perm_i))
+                        .for_each(|to, from| {
+                            copy_nonoverlapping(from, to.as_mut_ptr(), 1);
+                            moved_elements += 1;
+                        });
+                });
             debug_assert_eq!(result.len(), moved_elements);
             // panic-critical begin: we must not panic
             // forget moved array elements but not its vec
@@ -129,6 +135,7 @@ where
         }
     }
 }
+
 #[cfg(feature = "std")]
 fn main() {
     let a = Array::linspace(0., 63., 64).into_shape((8, 8)).unwrap();
@@ -143,5 +150,60 @@ fn main() {
     let c = strings.permute_axis(Axis(1), &perm);
     println!("{:?}", c);
 }
+
 #[cfg(not(feature = "std"))]
 fn main() {}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    #[test]
+    fn test_permute_axis() {
+        let a = array![
+            [107998.96, 1.],
+            [107999.08, 2.],
+            [107999.20, 3.],
+            [108000.33, 4.],
+            [107999.45, 5.],
+            [107999.57, 6.],
+            [108010.69, 7.],
+            [107999.81, 8.],
+            [107999.94, 9.],
+            [75600.09, 10.],
+            [75600.21, 11.],
+            [75601.33, 12.],
+            [75600.45, 13.],
+            [75600.58, 14.],
+            [109000.70, 15.],
+            [75600.82, 16.],
+            [75600.94, 17.],
+            [75601.06, 18.],
+        ];
+
+        let perm = a.sort_axis_by(Axis(0), |i, j| a[[i, 0]] < a[[j, 0]]);
+        let b = a.permute_axis(Axis(0), &perm);
+        assert_eq!(
+            b,
+            array![
+                [75600.09, 10.],
+                [75600.21, 11.],
+                [75600.45, 13.],
+                [75600.58, 14.],
+                [75600.82, 16.],
+                [75600.94, 17.],
+                [75601.06, 18.],
+                [75601.33, 12.],
+                [107998.96, 1.],
+                [107999.08, 2.],
+                [107999.20, 3.],
+                [107999.45, 5.],
+                [107999.57, 6.],
+                [107999.81, 8.],
+                [107999.94, 9.],
+                [108000.33, 4.],
+                [108010.69, 7.],
+                [109000.70, 15.],
+            ]
+        );
+    }
+}
diff --git a/scripts/all-tests.sh b/scripts/all-tests.sh
index 22f1d1f94..61dfc56dc 100755
--- a/scripts/all-tests.sh
+++ b/scripts/all-tests.sh
@@ -16,5 +16,6 @@ cargo test --manifest-path=ndarray-rand/Cargo.toml --no-default-features --verbo
 cargo test --manifest-path=ndarray-rand/Cargo.toml --features quickcheck --verbose
 cargo test --manifest-path=serialization-tests/Cargo.toml --verbose
 cargo test --manifest-path=blas-tests/Cargo.toml --verbose
+cargo test --examples
 CARGO_TARGET_DIR=target/ cargo test --manifest-path=numeric-tests/Cargo.toml --verbose
 ([ "$CHANNEL" != "nightly" ] || cargo bench --no-run --verbose --features "$FEATURES")