fixes

Author: pbrubeck

firedrake/cython/dmcommon.pyx

@@ -4328,7 +4328,7 @@ def get_dm_cell_types(PETSc.DM dm):
 
 
 def create_label_intersection(PETSc.DM dm, label_name, label_values):
-    """Return the intersection of the closure of a subdomains of a DMPlex.
+    """Return the intersection of the closure of subdomains of a DMPlex.
 
     Parameters
     ----------
@@ -4341,25 +4341,23 @@ def create_label_intersection(PETSc.DM dm, label_name, label_values):
 
     Returns
     -------
-    tuple
+    PETSc.IS
         A PETSc.IS with the points in the intersection.
 
     """
     cdef:
+        PETSc.IS iout, i1, i2
         PETSc.DMLabel label
-        PETSc.PetscIS is1, is2
-        PetscInt val = label_values[0]
+
+    if len(label_values) == 0:
+        return PETSc.IS().createGeneral([], comm=dm.comm)
 
     label = dm.getLabel(label_name)
     CHKERR(DMPlexLabelComplete(dm.dm, label.dmlabel))
-    CHKERR(DMLabelGetStratumIS(<DMLabel>label.dmlabel, val, &is1))
-
-    for i in range(1, len(label_values)):
+    iout = label.getStratumIS(label_values[0])
+    for val in label_values[1:]:
+        i1 = iout
+        i2 = label.getStratumIS(val)
         iout = PETSc.IS()
-        val = label_values[i]
-        CHKERR(DMLabelGetStratumIS(<DMLabel>label.dmlabel, val, &is2))
-        CHKERR(ISIntersect(is1, is2, &(<PETSc.IS?>iout).iset))
-        CHKERR(ISDestroy(&is1))
-        CHKERR(ISDestroy(&is2))
-        is1 = (<PETSc.IS?>iout).iset
+        CHKERR(ISIntersect(i1.iset, i2.iset, &iout.iset))
     return iout

firedrake/mesh.py

@@ -4890,15 +4890,10 @@ def Submesh(mesh, subdim=None, subdomain_id=None, label_name=None, name=None, ig
 
     if isinstance(subdomain_id, Sequence):
         # Create a temporary DMLabel with the union of the labels in the list
-        icomm = comm or mesh.comm
-        iset = PETSc.IS().createGeneral([], comm=icomm)
+        iset = PETSc.IS().createGeneral([], comm=mesh.comm)
         for sub in subdomain_id:
-            try:
-                sub, = sub
-            except ValueError:
-                pass
             if isinstance(sub, Sequence):
-                # Take the intersection of the (closure of the) labels from nested lists
+                # Take the intersection of the labels from nested lists
                 cur = dmcommon.create_label_intersection(plex, label_name, sub)
             else:
                 cur = plex.getStratumIS(label_name, sub)