Every vector holds block data

python/dolfinx/fem/petsc.py

@@ -83,7 +83,7 @@
 def create_vector(
     V: _FunctionSpace | Sequence[_FunctionSpace | None],
     /,
-    kind: str | None = None,
+    kind: str = "mpi",
 ) -> PETSc.Vec:  # type: ignore[name-defined]
     """Create a PETSc vector that is compatible with a linear form(s)
     or functionspace(s).

python/dolfinx/la/petsc.py

@@ -72,9 +72,7 @@ def create_vector_wrap(x: Vector) -> PETSc.Vec:  # type: ignore[name-defined]
     )
 
 
-def create_vector(
-    maps: typing.Sequence[tuple[IndexMap, int]], kind: str | None = None
-) -> PETSc.Vec:  # type: ignore[name-defined]
+def create_vector(maps: typing.Sequence[tuple[IndexMap, int]], kind: str = "mpi") -> PETSc.Vec:  # type: ignore[name-defined]
     """Create a PETSc vector from a sequence of maps and blocksizes.
 
     Three cases are supported:
@@ -118,28 +116,19 @@ def create_vector(
         A PETSc vector with the prescribed layout. The vector is not
         initialised to zero.
     """
-    if len(maps) == 1:
-        # Single space case
-        index_map, bs = maps[0]
-        ghosts = index_map.ghosts.astype(PETSc.IntType)  # type: ignore[attr-defined]
-        size = (index_map.size_local * bs, index_map.size_global * bs)
-        b = PETSc.Vec().createGhost(ghosts, size=size, bsize=bs, comm=index_map.comm)  # type: ignore
-        if kind == PETSc.Vec.Type.MPI:
+    match kind:
+        case PETSc.Vec.Type.MPI:  # type: ignore[attr-defined]
+            b = dolfinx.cpp.fem.petsc.create_vector_block(maps)
             _assign_block_data(maps, b)
-        return b
-
-    if kind is None or kind == PETSc.Vec.Type.MPI:  # type: ignore[attr-defined]
-        b = dolfinx.cpp.fem.petsc.create_vector_block(maps)
-        _assign_block_data(maps, b)
-        return b
-    elif kind == PETSc.Vec.Type.NEST:  # type: ignore[attr-defined]
-        return dolfinx.cpp.fem.petsc.create_vector_nest(maps)
-    else:
-        raise NotImplementedError(
-            "Vector type must be specified for blocked/nested assembly."
-            f"Vector type '{kind}' not supported."
-            "Did you mean 'nest' or 'mpi'?"
-        )
+            return b
+        case PETSc.Vec.Type.NEST:  # type: ignore[attr-defined]
+            return dolfinx.cpp.fem.petsc.create_vector_nest(maps)
+        case _:
+            raise NotImplementedError(
+                "Vector type must be specified for blocked/nested assembly."
+                f"Vector type '{kind}' not supported."
+                "Did you mean 'nest' or 'mpi'?"
+            )
 
 
 @functools.singledispatch

python/test/unit/fem/test_assembler.py

@@ -184,7 +184,7 @@ def test_vector_single_space_as_block():
     mesh = create_unit_square(MPI.COMM_WORLD, 3, 3)
     gdim = mesh.geometry.dim
     V = functionspace(mesh, ("Lagrange", 1, (gdim,)))
-    assert petsc_create_vector(V).getAttr("_blocks") is None
+    # assert petsc_create_vector(V).getAttr("_blocks") is None
     assert petsc_create_vector(V, kind="mpi").getAttr("_blocks") is not None