Add Ugrid1d.is_cyclic. Fixes #328

docs/api.rst

@@ -223,6 +223,7 @@ UGRID1D Topology
     Ugrid1d.directed_node_node_connectivity
     Ugrid1d.directed_edge_edge_connectivity
     Ugrid1d.get_connectivity_matrix
+    Ugrid1d.is_cyclic
 
     Ugrid1d.copy
     Ugrid1d.rename

docs/changelog.rst

@@ -9,6 +9,12 @@ The format is based on `Keep a Changelog`_, and this project adheres to
 Unreleased
 ----------
 
+Added
+~~~~~
+
+- Added :attr:`xugrid.Ugrid1d.is_cyclic` property to check if grid topology
+  contains cycles.
+
 [0.12.3] 2025-02-17
 -------------------
 

tests/test_ugrid1d.py

@@ -301,6 +301,30 @@ def test_meshkernel():
     assert isinstance(grid.meshkernel, mk.MeshKernel)
 
 
+def test_is_cyclic():
+    x = np.array([0.0, 1.0, 2.0])
+    y = np.array([0.0, 1.0, 0.0])
+    edge_nodes = np.array(
+        [
+            [0, 1],
+            [1, 2],
+            [2, 0],
+        ]
+    )
+    cycle = xugrid.Ugrid1d(x, y, -1, edge_nodes)
+    assert cycle.is_cyclic
+
+    edge_nodes = np.array(
+        [
+            [0, 1],
+            [1, 2],
+            [0, 2],
+        ]
+    )
+    dag = xugrid.Ugrid1d(x, y, -1, edge_nodes)
+    assert not dag.is_cyclic
+
+
 def test_from_shapely():
     with pytest.raises(TypeError):
         xy = np.array(

xugrid/ugrid/ugrid1d.py

@@ -353,6 +353,24 @@ def meshkernel(self) -> "mk.MeshKernel":  # type: ignore # noqa
             self._meshkernel.mesh1d_set(self.mesh)
         return self._meshkernel
 
+    @property
+    def is_cyclic(self) -> bool:
+        """
+        Return True if the directed node node connectivity contains cycles. If
+        False, then the directed node node connectivity is a directed acyclic
+        graph (DAG).
+
+        Runs a depth-first-search.
+        """
+        # topological sort returns a ValueError if it detects a cycle.
+        try:
+            self.topological_sort_by_dfs()
+            return False
+        except ValueError as e:
+            if str(e) == "The graph contains at least one cycle":
+                return True
+            raise  # Re-raise any other ValueError
+
     @classmethod
     def from_geodataframe(cls, geodataframe: "geopandas.GeoDataFrame") -> "Ugrid1d":  # type: ignore # noqa
         """