Add some PETSc destroy to avoid MPICH leak messages (#3036)

* Add some PETSc `destroy` to avoid MPICH leak messages

* Tidy up

* Syntax fix

* Re-enable test

python/test/unit/fem/test_assembler.py

@@ -594,7 +594,6 @@ def nested_solve():
         ksp_p.setType("preonly")
 
         def monitor(ksp, its, rnorm):
-            # print("Num it, rnorm:", its, rnorm)
             pass
 
         ksp.setTolerances(rtol=1.0e-8, max_it=50)
@@ -603,8 +602,11 @@ def monitor(ksp, its, rnorm):
         x = b.copy()
         ksp.solve(b, x)
         assert ksp.getConvergedReason() > 0
-        ksp.destroy()
-        return b.norm(), x.norm(), nest_matrix_norm(A), nest_matrix_norm(P)
+        norms = (b.norm(), x.norm(), nest_matrix_norm(A), nest_matrix_norm(P))
+        pc.destroy(), ksp.destroy()
+        A.destroy()
+        b.destroy(), x.destroy()
+        return norms
 
     def blocked_solve():
         """Blocked (monolithic) solver"""
@@ -800,11 +802,10 @@ def bc(V):
 @pytest.mark.parametrize("mode", [GhostMode.none, GhostMode.shared_facet])
 @pytest.mark.parametrize("dtype", [np.float32, np.float64, np.complex64, np.complex128])
 def test_basic_assembly_constant(mode, dtype):
-    """Tests assembly with Constant
+    """Tests assembly with Constant.
 
     The following test should be sensitive to order of flattening the
     matrix-valued constant.
-
     """
     xtype = dtype(0).real.dtype
     mesh = create_unit_square(MPI.COMM_WORLD, 5, 5, ghost_mode=mode, dtype=xtype)
@@ -867,7 +868,7 @@ def mat_insert(rows, cols, vals):
 
 
 def test_pack_coefficients():
-    """Test packing of form coefficients ahead of main assembly call"""
+    """Test packing of form coefficients ahead of main assembly call."""
     mesh = create_unit_square(MPI.COMM_WORLD, 12, 15)
     V = functionspace(mesh, ("Lagrange", 1))
 

python/test/unit/fem/test_nonlinear_assembler.py

@@ -564,9 +564,9 @@ def nested():
         Jnorm = nest_matrix_norm(Jmat)
         Fnorm = Fvec.norm()
         xnorm = x.norm()
-        Jmat.destroy()
-        Fvec.destroy()
+        Jmat.destroy(), Fvec.destroy()
         x.destroy()
+        Pmat.destroy()
         return Jnorm, Fnorm, xnorm
 
     def monolithic():

python/test/unit/la/test_nullspace.py

@@ -103,6 +103,8 @@ def test_nullspace_orthogonal(mesh, degree):
     assert not la.is_orthonormal(nullspace, eps=1.0e-4)
     la.orthonormalize(nullspace)
     assert la.is_orthonormal(nullspace, eps=1.0e-3)
+    for x in nullspace:
+        x.destroy()
 
 
 @pytest.mark.parametrize("mesh", [
@@ -144,3 +146,5 @@ def sigma(w, gdim):
     la.orthonormalize(nullspace)
     ns = PETSc.NullSpace().create(vectors=nullspace)
     assert not ns.test(A)
+    for x in nullspace:
+        x.destroy()