From cf9106d9142a8dda298e6e0c73dc0875233179bf Mon Sep 17 00:00:00 2001
From: Drew Johnson <anjohnson@terrapower.com>
Date: Mon, 3 Feb 2025 11:20:04 -0800
Subject: [PATCH] Loosening tolerance on HexGrid roughly equal check (#2058)

---
 armi/reactor/grids/hexagonal.py        |  4 ++--
 armi/reactor/grids/tests/test_grids.py | 11 +++++++++++
 doc/release/0.5.rst                    |  3 ++-
 3 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/armi/reactor/grids/hexagonal.py b/armi/reactor/grids/hexagonal.py
index 262307826..a8a823d1c 100644
--- a/armi/reactor/grids/hexagonal.py
+++ b/armi/reactor/grids/hexagonal.py
@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 from collections import deque
-from math import sqrt
+from math import isclose, sqrt
 from typing import List, Optional, Tuple
 
 import numpy as np
@@ -639,6 +639,6 @@ def _roughlyEqual(self, other) -> bool:
             return True
         return (
             isinstance(other, HexGrid)
-            and other.pitch == self.pitch
+            and isclose(self.pitch, other.pitch, rel_tol=1e-4)
             and other.cornersUp == self.cornersUp
         )
diff --git a/armi/reactor/grids/tests/test_grids.py b/armi/reactor/grids/tests/test_grids.py
index 8cfa5c492..3f0d10759 100644
--- a/armi/reactor/grids/tests/test_grids.py
+++ b/armi/reactor/grids/tests/test_grids.py
@@ -772,6 +772,17 @@ def test_rotatedIndexGridAssignment(self):
             postRotate = base.rotateIndex(loc, rotations=2)
             self.assertIs(postRotate.grid, loc.grid)
 
+    def test_rotatedIndexRoughEqualPitch(self):
+        """Test indices can be rotated in close but not exactly equal grids."""
+        base = grids.HexGrid.fromPitch(1.345)
+        other = grids.HexGrid.fromPitch(base.pitch * 1.00001)
+
+        for i, j in ((0, 0), (1, 1), (2, 1), (-1, 3)):
+            loc = grids.IndexLocation(i, j, k=0, grid=base)
+            fromBase = base.rotateIndex(loc, rotations=2)
+            fromOther = other.rotateIndex(loc, rotations=2)
+            self.assertEqual((fromBase.i, fromBase.j), (fromOther.i, fromOther.j))
+
 
 class TestBoundsDefinedGrid(unittest.TestCase):
     def test_positions(self):
diff --git a/doc/release/0.5.rst b/doc/release/0.5.rst
index f3f5eefd4..33051845a 100644
--- a/doc/release/0.5.rst
+++ b/doc/release/0.5.rst
@@ -21,7 +21,8 @@ Bug Fixes
 ---------
 #. Fixing check for jagged arrays during ``_writeParams``. (`PR#2051 <https://github.com/terrapower/armi/pull/2051>`_)
 #. Fixing BP-section ignoring tool in ``PassiveDBLoadPlugin``. (`PR#2055 <https://github.com/terrapower/armi/pull/2055>`_)
-#. Fixing scaling of volume-integrated parameters on edge assembleis. (`PR#2060 <https://github.com/terrapower/armi/pull/2060>`_)
+#. Fixing scaling of volume-integrated parameters on edge assemblies. (`PR#2060 <https://github.com/terrapower/armi/pull/2060>`_)
+#. Fixing strictness of ``HexGrid`` rough equality check. (`PR#2058 <https://github.com/terrapower/armi/pull/2058>`_)
 #. TBD
 
 Quality Work