Enable slate tensors with variable-layers extruded mesh

firedrake/slate/slac/kernel_builder.py

@@ -94,9 +94,6 @@ def __init__(self, expression, tsfc_parameters=None):
         """
         assert isinstance(expression, slate.TensorBase)
 
-        if expression.ufl_domain().variable_layers:
-            raise NotImplementedError("Variable layers not yet handled in Slate.")
-
         # Collect terminals, expressions, and reference counts
         temps = OrderedDict()
         coeff_vecs = OrderedDict()
@@ -429,9 +426,6 @@ def __init__(self, expression, tsfc_parameters=None):
 
         assert isinstance(expression, slate.TensorBase)
 
-        if expression.ufl_domain().variable_layers:
-            raise NotImplementedError("Variable layers not yet handled in Slate.")
-
         self.expression = expression
         self.tsfc_parameters = tsfc_parameters
         self.bag = None

tests/slate/test_scalar_tensors_extr.py

@@ -1,4 +1,5 @@
 import numpy as np
+from math import ceil
 
 from firedrake import *
 
@@ -7,3 +8,48 @@ def test_constant_one_tensor():
     mesh = ExtrudedMesh(UnitIntervalMesh(5), 5)
     one = Constant(1, domain=mesh)
     assert np.allclose(assemble(Tensor(one * dx)), 1.0)
+
+
+def test_mass_matrix_variable_layers_extrusion():
+    # construct variable layer mesh with height increasing from H1 to H2
+    L = 50
+    H1 = 2.
+    H2 = 42.
+    dx_ = 5.0
+    nx = round(L/dx_)
+    dy_ = 2.0
+    tiny_dy = 0.01
+
+    # create mesh
+    mesh1d = IntervalMesh(nx, L)
+    layers = []
+    cell = 0
+    xr = 0
+    for i in range(nx):
+        xr += dx_  # x of rhs of column (assumed to be the higher one)
+        height = H1 + xr/L * (H2-H1)
+        ncells = ceil(height/dy_)
+        layers.append([0, ncells])
+        cell += ncells
+
+    mesh = ExtrudedMesh(mesh1d, layers, layer_height=dy_)
+    # move top nodes to create continuous, piecewise linear top boundary
+    # with height increasing from H1 to H2
+    x = mesh.coordinates.dat.data_ro[:, 0]
+    y = mesh.coordinates.dat.data_ro[:, 1]
+    # left top nodes is moved up from H1 to H1+tiny_dy, to avoid zero edge on boundary
+    height = np.maximum(H1 + x/L * (H2-H1), H1+tiny_dy)
+    mesh.coordinates.dat.data[:, 1] = np.minimum(height, y)
+    V = FunctionSpace(mesh, "DG", 1)
+    v = TestFunction(V)
+    u = TrialFunction(V)
+
+    A1 = assemble(Tensor(v*u*dx)).M.values
+    A2 = assemble(v*u*dx).M.values
+    A3 = assemble(Tensor(v*u*dx).inv).M.values
+
+    # check A1==A2
+    assert np.allclose(A1, A2, rtol=1e-12)
+
+    # check A2*A3==Identity
+    assert np.allclose(np.matmul(A2, A3), np.eye(*A2.shape), rtol=1e-12)