add test for time-varying point data

src/meshio/exodus/_exodus.py

@@ -291,6 +291,12 @@ def write(filename, mesh):
     import netCDF4
 
     with netCDF4.Dataset(filename, "w") as rootgrp:
+        # if time-dependent, pass in mesh and time_step as list
+        if type(mesh) is list:
+            mesh, time_step = mesh
+        else:
+            time_step = None
+
         # set global data
         now = datetime.datetime.now().isoformat()
         rootgrp.title = f"Created by meshio v{__version__}, {now}"
@@ -308,7 +314,7 @@ def write(filename, mesh):
         rootgrp.createDimension("len_string", 33)
         rootgrp.createDimension("len_line", 81)
         rootgrp.createDimension("four", 4)
-        rootgrp.createDimension("time_step", None)
+        rootgrp.createDimension("time_step", time_step)
 
         # dummy time step
         data = rootgrp.createVariable("time_whole", "f4", ("time_step",))
@@ -377,6 +383,9 @@ def write(filename, mesh):
                     fill_value=False,
                 )
                 node_data[0] = data
+                if time_step is not None:
+                    for time_index in range(1, time_step):
+                        node_data[time_index] = data
 
         # node sets
         num_point_sets = len(mesh.point_sets)

tests/helpers.py

@@ -605,6 +605,18 @@ def add_point_data(mesh, dim, num_tags=2, seed=0, dtype=float):
     return mesh2
 
 
+def add_timevarying_point_data(mesh, dim, time_step=2, num_tags=2, seed=0, dtype=float):
+    rng = np.random.default_rng(seed)
+
+    mesh2 = copy.deepcopy(mesh)
+
+    shape = (len(mesh.points),) if dim == 1 else (len(mesh.points), dim)
+    data = [(100 * rng.random(shape)).astype(dtype) for _ in range(num_tags)]
+
+    for k, d in enumerate(data):
+        mesh2.point_data[string.ascii_lowercase[k]] = d
+    return [mesh2, time_step]
+
 def add_cell_data(mesh, specs: list[tuple[str, tuple[int, ...], type]]):
     mesh2 = copy.deepcopy(mesh)
 
@@ -653,11 +665,20 @@ def add_cell_sets(mesh):
 
 def write_read(tmp_path, writer, reader, input_mesh, atol, extension=".dat"):
     """Write and read a file, and make sure the data is the same as before."""
-    in_mesh = copy.deepcopy(input_mesh)
+    if type(input_mesh) is list:
+        in_mesh = copy.deepcopy(input_mesh[0])
+    else:
+        in_mesh = copy.deepcopy(input_mesh)
 
     p = tmp_path / ("test" + extension)
     print(input_mesh)
     writer(p, input_mesh)
+    # when using time-varying data, we pass time_step in list with 
+    # mesh to avoid excessive code changes
+    if type(input_mesh) is list:
+        input_mesh, time_step = input_mesh
+    else:
+        time_step = None
     mesh = reader(p)
 
     # Make sure the output is writeable
@@ -718,10 +739,20 @@ def cell_sorter(cell):
             print("b", cells1.data)
             assert np.array_equal(cells0.data, cells1.data)
 
-    for key in input_mesh.point_data.keys():
-        assert np.allclose(
-            input_mesh.point_data[key], mesh.point_data[key], atol=atol, rtol=0.0
-        )
+    if time_step is None:
+        for key in input_mesh.point_data.keys():
+            assert np.allclose(
+                input_mesh.point_data[key], mesh.point_data[key], atol=atol, rtol=0.0
+            )
+    else:
+        # we cannot write time-dependent data to input_mesh.point_data 
+        # (as far as I can see). So for testing we set all times equal
+        for key in input_mesh.point_data.keys():
+            for time_index in range(time_step):
+                time_dep_key = f"{key}_time{time_index}"
+                assert np.allclose(
+                    input_mesh.point_data[key], mesh.point_data[time_dep_key], atol=atol, rtol=0.0
+                )
 
     print(input_mesh.cell_data)
     print()

tests/test_exodus.py

@@ -23,6 +23,7 @@
     helpers.add_point_data(helpers.tri_mesh, 2),
     helpers.add_point_data(helpers.tri_mesh, 3),
     helpers.add_cell_data(helpers.tri_mesh, [("a", (3,), np.float64)]),
+    helpers.add_timevarying_point_data(helpers.tri_mesh, 1, 2),
     helpers.add_point_sets(helpers.tri_mesh),
     helpers.add_point_sets(helpers.tet_mesh),
 ]