Hot-fix for broken Stokes tests

tests/firedrake/macro/test_macro_solve.py

@@ -6,10 +6,11 @@
 @pytest.fixture(params=("square", "cube"))
 def mh(request):
     if request.param == "square":
-        base_msh = UnitSquareMesh(3, 3)
+        return [UnitSquareMesh(2**r, 2**r) for r in range(1, 4)]
     elif request.param == "cube":
-        base_msh = UnitCubeMesh(2, 2, 2)
-    return MeshHierarchy(base_msh, 2)
+        return [UnitCubeMesh(2**r, 2**r, 2**r) for r in range(1, 4)]
+    else:
+        raise ValueError("Unexpected mesh type")
 
 
 @pytest.fixture(params=["iso", "alfeld", "th"])
@@ -33,35 +34,27 @@ def mixed_element(mh, variant):
     return Vel, Pel
 
 
-def mesh_sizes(mh):
-    mesh_size = []
-    for msh in mh:
-        DG0 = FunctionSpace(msh, "DG", 0)
-        h = Function(DG0).interpolate(CellDiameter(msh))
-        with h.dat.vec as hvec:
-            _, maxh = hvec.max()
-        mesh_size.append(maxh)
-    return mesh_size
-
-
-def conv_rates(x, h):
+def conv_rates(x, h=None):
     x = np.asarray(x)
-    h = np.asarray(h)
-    return np.log2(x[:-1] / x[1:]) / np.log2(h[:-1] / h[1:])
+    rates = np.log2(x[:-1] / x[1:])
+    if h is not None:
+        h = np.asarray(h)
+        rates /= np.log2(h[:-1] / h[1:])
+    return rates
 
 
 @pytest.fixture
 def convergence_test(variant):
     if variant == "iso":
-        def check(uerr, perr, h):
-            return (conv_rates(uerr, h)[-1] >= 1.9
+        def check(uerr, perr):
+            return (conv_rates(uerr)[-1] >= 1.9
                     and np.allclose(perr, 0, atol=1.e-8))
     elif variant == "alfeld":
-        def check(uerr, perr, h):
+        def check(uerr, perr):
             return (np.allclose(uerr, 0, atol=5.e-9)
                     and np.allclose(perr, 0, atol=5.e-7))
     elif variant == "th":
-        def check(uerr, perr, h):
+        def check(uerr, perr):
             return (np.allclose(uerr, 0, atol=1.e-10)
                     and np.allclose(perr, 0, atol=1.e-8))
     return check
@@ -112,7 +105,7 @@ def test_riesz(mh, variant, mixed_element, convergence_test):
         u_err.append(errornorm(as_vector(zexact[:dim]), uh))
         p_err.append(errornorm(zexact[-1], ph))
 
-    assert convergence_test(u_err, p_err, mesh_sizes(mh))
+    assert convergence_test(u_err, p_err)
 
 
 def stokes_mms(Z, zexact):
@@ -121,7 +114,7 @@ def stokes_mms(Z, zexact):
     u, p = split(trial)
     v, q = split(test)
 
-    a = (inner(grad(u), grad(v)) * dx
+    a = (inner(grad(u) + grad(u).T, grad(v)) * dx
          - inner(p, div(v)) * dx
          - inner(div(u), q) * dx)
 
@@ -131,9 +124,8 @@ def stokes_mms(Z, zexact):
 
 def errornormL2_0(pexact, ph):
     msh = ph.function_space().mesh()
-    vol = assemble(1*dx(domain=msh))
-    err = pexact - ph
-    return sqrt(abs(assemble(inner(err, err)*dx) - (1/vol)*abs(assemble(err*dx))**2))
+    p0 = assemble((pexact - ph) * dx) / assemble(1*dx(domain=msh))
+    return errornorm(pexact - Constant(p0), ph)
 
 
 def test_stokes(mh, variant, mixed_element, convergence_test):
@@ -156,17 +148,22 @@ def test_stokes(mh, variant, mixed_element, convergence_test):
         a, L = stokes_mms(Z, as_vector(zexact))
         bcs = DirichletBC(Z[0], as_vector(zexact[:dim]), "on_boundary")
 
+        pconst = VectorSpaceBasis(constant=True, comm=Z.comm)
+        nullspace = MixedVectorSpaceBasis(Z, [Z.sub(0), pconst])
         zh = Function(Z)
-        nullspace = MixedVectorSpaceBasis(
-            Z,
-            [Z.sub(0), VectorSpaceBasis(constant=True, comm=COMM_WORLD)]
-        )
-        solve(a == L, zh, bcs=bcs, nullspace=nullspace, solver_parameters={"ksp_type": "gmres"})
+        solve(a == L, zh, bcs=bcs,
+              nullspace=nullspace,
+              solver_parameters={
+                  "mat_type": "nest",
+                  "ksp_type": "gmres",
+                  "ksp_pc_side": "right",
+                  "pc_type": "lu"})
+
         uh, ph = zh.subfunctions
         u_err.append(errornorm(as_vector(zexact[:dim]), uh))
         p_err.append(errornormL2_0(zexact[-1], ph))
 
-    assert convergence_test(u_err, p_err, mesh_sizes(mh))
+    assert convergence_test(u_err, p_err)
 
 
 def test_div_free(mh, variant, mixed_element, div_test):
@@ -179,7 +176,7 @@ def test_div_free(mh, variant, mixed_element, div_test):
         V = VectorFunctionSpace(msh, el1)
         Q = FunctionSpace(msh, el2)
         Z = V * Q
-        a, L = stokes_mms(Z, Constant([0] * (dim+1)))
+        a, L = stokes_mms(Z, zero((dim+1, )))
 
         f = as_vector([1] + [0] * (dim-1))
         for k in range(1, dim):

tests/firedrake/regression/test_stokes_hdiv_parallel.py

@@ -132,6 +132,6 @@ def test_stokes_hdiv_parallel(mat_type, element_pair):
     err_p = numpy.asarray(err_p)
     err_div = numpy.asarray(err_div)
 
-    assert numpy.allclose(err_div, 0, atol=1e-7, rtol=1e-5)
+    assert numpy.allclose(err_div, 0, atol=2e-7, rtol=1e-5)
     assert (numpy.log2(err_u[:-1] / err_u[1:]) > 2.8).all()
     assert (numpy.log2(err_p[:-1] / err_p[1:]) > 1.8).all()