From 50efeb960e9b133b7a735d834e796fa23472da9a Mon Sep 17 00:00:00 2001
From: hmacdope <hugomacdermott@gmail.com>
Date: Thu, 24 Oct 2024 14:42:14 +1100
Subject: [PATCH] hmmm

---
 package/MDAnalysis/lib/_distopia.py             |  5 +++--
 testsuite/MDAnalysisTests/lib/test_distances.py | 15 +++++++++++++++
 2 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/package/MDAnalysis/lib/_distopia.py b/package/MDAnalysis/lib/_distopia.py
index a467efee2a..f442ed9d19 100644
--- a/package/MDAnalysis/lib/_distopia.py
+++ b/package/MDAnalysis/lib/_distopia.py
@@ -66,7 +66,7 @@ def calc_bond_distance_ortho(
     distopia.calc_bonds_ortho(
         coords1, coords2, box[:3], results=results
     )
-    # upcast is currently required, change for 3.0, see #3927
+
 
 
 def calc_bond_distance(
@@ -75,7 +75,6 @@ def calc_bond_distance(
     distopia.calc_bonds_no_box(
         coords1, coords2, results=results
     )
-    # upcast is currently required, change for 3.0, see #3927
 
 
 def calc_bond_distance_triclinic(
@@ -89,6 +88,7 @@ def calc_angle(
 ) -> None:
     distopia.calc_angles_no_box(coords1, coords2, coords3, results=results)
 
+
 def calc_angle_ortho(
     coords1: np.ndarray, coords2: np.ndarray, coords3: np.ndarray, box: np.ndarray, results: np.ndarray
 ) -> None:
@@ -122,6 +122,7 @@ def calc_distance_array(
 ) -> None:
     distopia.calc_distance_array_no_box(coords1, coords2, results=results)
 
+
 def calc_distance_array_ortho(
     coords1: np.ndarray, coords2: np.ndarray, box: np.ndarray, results: np.ndarray
 ) -> None:
diff --git a/testsuite/MDAnalysisTests/lib/test_distances.py b/testsuite/MDAnalysisTests/lib/test_distances.py
index a2955cbaf4..8c35e1c725 100644
--- a/testsuite/MDAnalysisTests/lib/test_distances.py
+++ b/testsuite/MDAnalysisTests/lib/test_distances.py
@@ -473,6 +473,8 @@ def test_outarray(self, DCD_Universe, backend):
         natoms = len(U.atoms)
         d = np.zeros((natoms, natoms), np.float64)
         distances.distance_array(x0, x1, result=d, backend=backend)
+        print("AFTER")
+        print(d)
         assert_equal(d.shape, (natoms, natoms), "wrong shape, should be"
                      " (Natoms,Natoms) entries")
         assert_almost_equal(d.min(), 0.11981228170520701, self.prec,
@@ -937,6 +939,19 @@ def test_bonds(self, box, backend, dtype, pos, request):
         assert_almost_equal(dists_pbc[3], 3.46410072, self.prec,
                             err_msg="PBC check #w with box")
 
+    @pytest.mark.parametrize("dtype", (np.float32, np.float64))
+    @pytest.mark.parametrize("backend", distopia_conditional_backend())
+    def test_results_inplace_all_backends(self,  backend, dtype,):
+        N = 10
+        c0 = np.ones(3 * N, dtype=dtype).reshape(N, 3) * 2
+        c1 = np.ones(3 * N, dtype=dtype).reshape(N, 3) * 3
+
+        result = np.zeros(N, dtype=np.float64)
+        distances.calc_bonds(c0, c1, result=result, backend=backend)
+        expected = np.ones(N, dtype=dtype) * 3**(1/2)
+        # test the result array is updated in place
+        assert_almost_equal(result, expected, self.prec, err_msg="calc_bonds inplace failed")
+
     @pytest.mark.parametrize("backend", distopia_conditional_backend())
     def test_bonds_badbox(self, positions, backend):
         a, b, c, d = positions