def _set_up_distributed_communication(self, mpi_communicator, queue):
from_dd = sym.DOFDesc("vol", sym.QTAG_NONE)
from meshmode.distributed import get_connected_partitions
connected_parts = get_connected_partitions(self._volume_discr.mesh)
if mpi_communicator is None and connected_parts:
raise RuntimeError("must supply an MPI communicator when using a "
"distributed mesh")
grp_factory = self.group_factory_for_quadrature_tag(sym.QTAG_NONE)
setup_helpers = {}
boundary_connections = {}
from meshmode.distributed import MPIBoundaryCommSetupHelper
for i_remote_part in connected_parts:
conn = self.connection_from_dds(
from_dd,
sym.DOFDesc(sym.BTAG_PARTITION(i_remote_part), sym.QTAG_NONE))
setup_helper = setup_helpers[
i_remote_part] = MPIBoundaryCommSetupHelper(
mpi_communicator, queue, conn, i_remote_part, grp_factory)
setup_helper.post_sends()
for i_remote_part, setup_helper in six.iteritems(setup_helpers):
boundary_connections[i_remote_part] = setup_helper.complete_setup()
return boundary_connections
def _set_up_distributed_communication(self, mpi_communicator,
array_context):
from_dd = DOFDesc("vol", DISCR_TAG_BASE)
boundary_connections = {}
from meshmode.distributed import get_connected_partitions
connected_parts = get_connected_partitions(self._volume_discr.mesh)
if connected_parts:
if mpi_communicator is None:
raise RuntimeError(
"must supply an MPI communicator when using a "
"distributed mesh")
grp_factory = \
self.group_factory_for_discretization_tag(DISCR_TAG_BASE)
local_boundary_connections = {}
for i_remote_part in connected_parts:
local_boundary_connections[
i_remote_part] = self.connection_from_dds(
from_dd,
DOFDesc(BTAG_PARTITION(i_remote_part), DISCR_TAG_BASE))
from meshmode.distributed import MPIBoundaryCommSetupHelper
with MPIBoundaryCommSetupHelper(mpi_communicator, array_context,
local_boundary_connections,
grp_factory) as bdry_setup_helper:
while True:
conns = bdry_setup_helper.complete_some()
if not conns:
break
for i_remote_part, conn in conns.items():
boundary_connections[i_remote_part] = conn
return boundary_connections
def test_partition_interpolation(actx_factory, dim, mesh_pars, num_parts,
num_groups, part_method):
np.random.seed(42)
group_factory = PolynomialWarpAndBlendGroupFactory
actx = actx_factory()
order = 4
def f(x):
return 10. * actx.np.sin(50. * x)
for n in mesh_pars:
from meshmode.mesh.generation import generate_warped_rect_mesh
base_mesh = generate_warped_rect_mesh(dim, order=order, n=n)
if num_groups > 1:
from meshmode.mesh.processing import split_mesh_groups
# Group every Nth element
element_flags = np.arange(
base_mesh.nelements,
dtype=base_mesh.element_id_dtype) % num_groups
mesh = split_mesh_groups(base_mesh, element_flags)
else:
mesh = base_mesh
if part_method == "random":
part_per_element = np.random.randint(num_parts,
size=mesh.nelements)
else:
pytest.importorskip("pymetis")
from meshmode.distributed import get_partition_by_pymetis
part_per_element = get_partition_by_pymetis(
mesh, num_parts, connectivity=part_method)
from meshmode.mesh.processing import partition_mesh
part_meshes = [
partition_mesh(mesh, part_per_element, i)[0]
for i in range(num_parts)
]
connected_parts = set()
for i_local_part, part_mesh in enumerate(part_meshes):
from meshmode.distributed import get_connected_partitions
neighbors = get_connected_partitions(part_mesh)
for i_remote_part in neighbors:
connected_parts.add((i_local_part, i_remote_part))
from meshmode.discretization import Discretization
vol_discrs = [
Discretization(actx, part_meshes[i], group_factory(order))
for i in range(num_parts)
]
from meshmode.mesh import BTAG_PARTITION
from meshmode.discretization.connection import (
make_face_restriction, make_partition_connection, check_connection)
for i_local_part, i_remote_part in connected_parts:
# Mark faces within local_mesh that are connected to remote_mesh
local_bdry_conn = make_face_restriction(
actx, vol_discrs[i_local_part], group_factory(order),
BTAG_PARTITION(i_remote_part))
# Mark faces within remote_mesh that are connected to local_mesh
remote_bdry_conn = make_face_restriction(
actx, vol_discrs[i_remote_part], group_factory(order),
BTAG_PARTITION(i_local_part))
bdry_nelements = sum(grp.nelements
for grp in local_bdry_conn.to_discr.groups)
remote_bdry_nelements = sum(
grp.nelements for grp in remote_bdry_conn.to_discr.groups)
assert bdry_nelements == remote_bdry_nelements, \
"partitions do not have the same number of connected elements"
local_bdry = local_bdry_conn.to_discr
remote_bdry = remote_bdry_conn.to_discr
from meshmode.distributed import make_remote_group_infos
remote_to_local_conn = make_partition_connection(
actx,
local_bdry_conn=local_bdry_conn,
i_local_part=i_local_part,
remote_bdry_discr=remote_bdry,
remote_group_infos=make_remote_group_infos(
actx, remote_bdry_conn))
# Connect from local mesh to remote mesh
local_to_remote_conn = make_partition_connection(
actx,
local_bdry_conn=remote_bdry_conn,
i_local_part=i_remote_part,
remote_bdry_discr=local_bdry,
remote_group_infos=make_remote_group_infos(
actx, local_bdry_conn))
check_connection(actx, remote_to_local_conn)
check_connection(actx, local_to_remote_conn)
true_local_points = f(thaw(actx, local_bdry.nodes()[0]))
remote_points = local_to_remote_conn(true_local_points)
local_points = remote_to_local_conn(remote_points)
err = actx.np.linalg.norm(true_local_points - local_points, np.inf)
# Can't currently expect exact results due to limitations of
# interpolation "snapping" in DirectDiscretizationConnection's
# _resample_point_pick_indices
assert err < 1e-11
def _test_mpi_boundary_swap(dim, order, num_groups):
from meshmode.distributed import MPIMeshDistributor, MPIBoundaryCommSetupHelper
from mpi4py import MPI
mpi_comm = MPI.COMM_WORLD
i_local_part = mpi_comm.Get_rank()
num_parts = mpi_comm.Get_size()
mesh_dist = MPIMeshDistributor(mpi_comm)
if mesh_dist.is_mananger_rank():
np.random.seed(42)
from meshmode.mesh.generation import generate_warped_rect_mesh
meshes = [
generate_warped_rect_mesh(dim, order=order, n=4)
for _ in range(num_groups)
]
if num_groups > 1:
from meshmode.mesh.processing import merge_disjoint_meshes
mesh = merge_disjoint_meshes(meshes)
else:
mesh = meshes[0]
part_per_element = np.random.randint(num_parts, size=mesh.nelements)
local_mesh = mesh_dist.send_mesh_parts(mesh, part_per_element,
num_parts)
else:
local_mesh = mesh_dist.receive_mesh_part()
group_factory = PolynomialWarpAndBlendGroupFactory(order)
from meshmode.array_context import PyOpenCLArrayContext
cl_ctx = cl.create_some_context()
queue = cl.CommandQueue(cl_ctx)
actx = PyOpenCLArrayContext(queue)
from meshmode.discretization import Discretization
vol_discr = Discretization(actx, local_mesh, group_factory)
from meshmode.distributed import get_connected_partitions
connected_parts = get_connected_partitions(local_mesh)
assert i_local_part not in connected_parts
bdry_setup_helpers = {}
local_bdry_conns = {}
from meshmode.discretization.connection import make_face_restriction
from meshmode.mesh import BTAG_PARTITION
for i_remote_part in connected_parts:
local_bdry_conns[i_remote_part] = make_face_restriction(
actx, vol_discr, group_factory, BTAG_PARTITION(i_remote_part))
setup_helper = bdry_setup_helpers[i_remote_part] = \
MPIBoundaryCommSetupHelper(
mpi_comm, actx, local_bdry_conns[i_remote_part],
i_remote_part, bdry_grp_factory=group_factory)
setup_helper.post_sends()
remote_to_local_bdry_conns = {}
from meshmode.discretization.connection import check_connection
while bdry_setup_helpers:
for i_remote_part, setup_helper in bdry_setup_helpers.items():
if setup_helper.is_setup_ready():
assert bdry_setup_helpers.pop(i_remote_part) is setup_helper
conn = setup_helper.complete_setup()
check_connection(actx, conn)
remote_to_local_bdry_conns[i_remote_part] = conn
break
# FIXME: Not ideal, busy-waits
_test_data_transfer(mpi_comm, actx, local_bdry_conns,
remote_to_local_bdry_conns, connected_parts)
logger.debug("Rank %d exiting", i_local_part)
def test_partition_mesh(mesh_size, num_parts, num_groups, dim,
scramble_partitions):
np.random.seed(42)
n = (mesh_size, ) * dim
from meshmode.mesh.generation import generate_regular_rect_mesh
meshes = [
generate_regular_rect_mesh(a=(0 + i, ) * dim, b=(1 + i, ) * dim, n=n)
for i in range(num_groups)
]
from meshmode.mesh.processing import merge_disjoint_meshes
mesh = merge_disjoint_meshes(meshes)
if scramble_partitions:
part_per_element = np.random.randint(num_parts, size=mesh.nelements)
else:
pytest.importorskip("pymetis")
from meshmode.distributed import get_partition_by_pymetis
part_per_element = get_partition_by_pymetis(mesh, num_parts)
from meshmode.mesh.processing import partition_mesh
# TODO: The same part_per_element array must be used to partition each mesh.
# Maybe the interface should be changed to guarantee this.
new_meshes = [
partition_mesh(mesh, part_per_element, i) for i in range(num_parts)
]
assert mesh.nelements == np.sum(
[new_meshes[i][0].nelements for i in range(num_parts)]), \
"part_mesh has the wrong number of elements"
assert count_tags(mesh, BTAG_ALL) == np.sum(
[count_tags(new_meshes[i][0], BTAG_ALL) for i in range(num_parts)]), \
"part_mesh has the wrong number of BTAG_ALL boundaries"
connected_parts = set()
for i_local_part, (part_mesh, _) in enumerate(new_meshes):
from meshmode.distributed import get_connected_partitions
neighbors = get_connected_partitions(part_mesh)
for i_remote_part in neighbors:
connected_parts.add((i_local_part, i_remote_part))
from meshmode.mesh import BTAG_PARTITION, InterPartitionAdjacencyGroup
from meshmode.mesh.processing import find_group_indices
num_tags = np.zeros((num_parts, ))
index_lookup_table = dict()
for ipart, (m, _) in enumerate(new_meshes):
for igrp in range(len(m.groups)):
adj = m.facial_adjacency_groups[igrp][None]
if not isinstance(adj, InterPartitionAdjacencyGroup):
# This group is not connected to another partition.
continue
for i, (elem,
face) in enumerate(zip(adj.elements, adj.element_faces)):
index_lookup_table[ipart, igrp, elem, face] = i
for part_num in range(num_parts):
part, part_to_global = new_meshes[part_num]
for grp_num in range(len(part.groups)):
adj = part.facial_adjacency_groups[grp_num][None]
tags = -part.facial_adjacency_groups[grp_num][None].neighbors
assert np.all(tags >= 0)
if not isinstance(adj, InterPartitionAdjacencyGroup):
# This group is not connected to another partition.
continue
elem_base = part.groups[grp_num].element_nr_base
for idx in range(len(adj.elements)):
if adj.partition_neighbors[idx] == -1:
continue
elem = adj.elements[idx]
face = adj.element_faces[idx]
n_part_num = adj.neighbor_partitions[idx]
n_meshwide_elem = adj.partition_neighbors[idx]
n_face = adj.neighbor_faces[idx]
num_tags[n_part_num] += 1
n_part, n_part_to_global = new_meshes[n_part_num]
# Hack: find_igrps expects a numpy.ndarray and returns
# a numpy.ndarray. But if a single integer is fed
# into find_igrps, an integer is returned.
n_grp_num = int(
find_group_indices(n_part.groups, n_meshwide_elem))
n_adj = n_part.facial_adjacency_groups[n_grp_num][None]
n_elem_base = n_part.groups[n_grp_num].element_nr_base
n_elem = n_meshwide_elem - n_elem_base
n_idx = index_lookup_table[n_part_num, n_grp_num, n_elem,
n_face]
assert (part_num == n_adj.neighbor_partitions[n_idx]
and elem + elem_base == n_adj.partition_neighbors[n_idx]
and face == n_adj.neighbor_faces[n_idx]),\
"InterPartitionAdjacencyGroup is not consistent"
_, n_part_to_global = new_meshes[n_part_num]
p_meshwide_elem = part_to_global[elem + elem_base]
p_meshwide_n_elem = n_part_to_global[n_elem + n_elem_base]
p_grp_num = find_group_indices(mesh.groups, p_meshwide_elem)
p_n_grp_num = find_group_indices(mesh.groups,
p_meshwide_n_elem)
p_elem_base = mesh.groups[p_grp_num].element_nr_base
p_n_elem_base = mesh.groups[p_n_grp_num].element_nr_base
p_elem = p_meshwide_elem - p_elem_base
p_n_elem = p_meshwide_n_elem - p_n_elem_base
f_groups = mesh.facial_adjacency_groups[p_grp_num]
for p_bnd_adj in f_groups.values():
for idx in range(len(p_bnd_adj.elements)):
if (p_elem == p_bnd_adj.elements[idx]
and face == p_bnd_adj.element_faces[idx]):
assert p_n_elem == p_bnd_adj.neighbors[idx],\
"Tag does not give correct neighbor"
assert n_face == p_bnd_adj.neighbor_faces[idx],\
"Tag does not give correct neighbor"
for i_remote_part in range(num_parts):
tag_sum = 0
for i_local_part, (mesh, _) in enumerate(new_meshes):
if (i_local_part, i_remote_part) in connected_parts:
tag_sum += count_tags(mesh, BTAG_PARTITION(i_remote_part))
assert num_tags[i_remote_part] == tag_sum,\
"part_mesh has the wrong number of BTAG_PARTITION boundaries"
def connected_ranks(dcoll: DiscretizationCollection):
from meshmode.distributed import get_connected_partitions
return get_connected_partitions(dcoll._volume_discr.mesh)
def _test_mpi_boundary_swap(dim, order, num_groups):
from meshmode.distributed import MPIMeshDistributor, MPIBoundaryCommSetupHelper
from mpi4py import MPI
mpi_comm = MPI.COMM_WORLD
i_local_part = mpi_comm.Get_rank()
num_parts = mpi_comm.Get_size()
mesh_dist = MPIMeshDistributor(mpi_comm)
if mesh_dist.is_mananger_rank():
np.random.seed(42)
from meshmode.mesh.generation import generate_warped_rect_mesh
meshes = [generate_warped_rect_mesh(dim, order=order, nelements_side=4)
for _ in range(num_groups)]
if num_groups > 1:
from meshmode.mesh.processing import merge_disjoint_meshes
mesh = merge_disjoint_meshes(meshes)
else:
mesh = meshes[0]
part_per_element = np.random.randint(num_parts, size=mesh.nelements)
local_mesh = mesh_dist.send_mesh_parts(mesh, part_per_element, num_parts)
else:
local_mesh = mesh_dist.receive_mesh_part()
group_factory = PolynomialWarpAndBlendGroupFactory(order)
from arraycontext import PyOpenCLArrayContext
cl_ctx = cl.create_some_context()
queue = cl.CommandQueue(cl_ctx)
actx = PyOpenCLArrayContext(queue)
from meshmode.discretization import Discretization
vol_discr = Discretization(actx, local_mesh, group_factory)
from meshmode.distributed import get_connected_partitions
connected_parts = get_connected_partitions(local_mesh)
# Check that the connectivity makes sense before doing any communication
_test_connected_parts(mpi_comm, connected_parts)
from meshmode.discretization.connection import make_face_restriction
from meshmode.mesh import BTAG_PARTITION
local_bdry_conns = {}
for i_remote_part in connected_parts:
local_bdry_conns[i_remote_part] = make_face_restriction(
actx, vol_discr, group_factory, BTAG_PARTITION(i_remote_part))
remote_to_local_bdry_conns = {}
with MPIBoundaryCommSetupHelper(mpi_comm, actx, local_bdry_conns,
bdry_grp_factory=group_factory) as bdry_setup_helper:
from meshmode.discretization.connection import check_connection
while True:
conns = bdry_setup_helper.complete_some()
if not conns:
break
for i_remote_part, conn in conns.items():
check_connection(actx, conn)
remote_to_local_bdry_conns[i_remote_part] = conn
_test_data_transfer(mpi_comm,
actx,
local_bdry_conns,
remote_to_local_bdry_conns,
connected_parts)
logger.debug("Rank %d exiting", i_local_part)
def process_sym_operator(discrwb, sym_operator, post_bind_mapper=None,
dumper=lambda name, sym_operator: None):
orig_sym_operator = sym_operator
import grudge.symbolic.mappers as mappers
dumper("before-bind", sym_operator)
sym_operator = mappers.OperatorBinder()(sym_operator)
mappers.ErrorChecker(discrwb.mesh)(sym_operator)
sym_operator = \
mappers.OppositeInteriorFaceSwapUniqueIDAssigner()(sym_operator)
# {{{ broadcast root rank's symn_operator
# also make sure all ranks had same orig_sym_operator
if discrwb.mpi_communicator is not None:
(mgmt_rank_orig_sym_operator, mgmt_rank_sym_operator) = \
discrwb.mpi_communicator.bcast(
(orig_sym_operator, sym_operator),
discrwb.get_management_rank_index())
from pytools.obj_array import is_equal as is_oa_equal
if not is_oa_equal(mgmt_rank_orig_sym_operator, orig_sym_operator):
raise ValueError("rank %d received a different symbolic "
"operator to bind from rank %d"
% (discrwb.mpi_communicator.Get_rank(),
discrwb.get_management_rank_index()))
sym_operator = mgmt_rank_sym_operator
# }}}
if post_bind_mapper is not None:
dumper("before-postbind", sym_operator)
sym_operator = post_bind_mapper(sym_operator)
dumper("before-empty-flux-killer", sym_operator)
sym_operator = mappers.EmptyFluxKiller(discrwb.mesh)(sym_operator)
dumper("before-cfold", sym_operator)
sym_operator = mappers.CommutativeConstantFoldingMapper()(sym_operator)
dumper("before-qcheck", sym_operator)
sym_operator = mappers.QuadratureCheckerAndRemover(
discrwb.quad_tag_to_group_factory)(sym_operator)
# Work around https://github.com/numpy/numpy/issues/9438
#
# The idea is that we need 1j as an expression to survive
# until code generation time. If it is evaluated and combined
# with other constants, we will need to determine its size
# (as np.complex64/128) within the expression. But because
# of the above numpy bug, sized numbers are not likely to survive
# expression building--so that's why we step in here to fix that.
dumper("before-csize", sym_operator)
sym_operator = mappers.ConstantToNumpyConversionMapper(
real_type=discrwb.real_dtype.type,
complex_type=discrwb.complex_dtype.type,
)(sym_operator)
dumper("before-global-to-reference", sym_operator)
sym_operator = mappers.GlobalToReferenceMapper(discrwb.ambient_dim)(sym_operator)
dumper("before-distributed", sym_operator)
volume_mesh = discrwb.discr_from_dd("vol").mesh
from meshmode.distributed import get_connected_partitions
connected_parts = get_connected_partitions(volume_mesh)
if connected_parts:
sym_operator = mappers.DistributedMapper(connected_parts)(sym_operator)
dumper("before-imass", sym_operator)
sym_operator = mappers.InverseMassContractor()(sym_operator)
dumper("before-cfold-2", sym_operator)
sym_operator = mappers.CommutativeConstantFoldingMapper()(sym_operator)
# FIXME: Reenable derivative joiner
# dumper("before-derivative-join", sym_operator)
# sym_operator = mappers.DerivativeJoiner()(sym_operator)
dumper("process-finished", sym_operator)
return sym_operator
def test_partition_interpolation(ctx_factory, dim, mesh_pars,
num_parts, num_groups, part_method):
np.random.seed(42)
group_factory = PolynomialWarpAndBlendGroupFactory
cl_ctx = ctx_factory()
queue = cl.CommandQueue(cl_ctx)
actx = PyOpenCLArrayContext(queue)
order = 4
def f(x):
return 10.*actx.np.sin(50.*x)
for n in mesh_pars:
from meshmode.mesh.generation import generate_warped_rect_mesh
base_mesh = generate_warped_rect_mesh(dim, order=order, n=n)
if num_groups > 1:
from meshmode.mesh.processing import split_mesh_groups
# Group every Nth element
element_flags = np.arange(base_mesh.nelements,
dtype=base_mesh.element_id_dtype) % num_groups
mesh = split_mesh_groups(base_mesh, element_flags)
else:
mesh = base_mesh
if part_method == "random":
part_per_element = np.random.randint(num_parts, size=mesh.nelements)
else:
pytest.importorskip('pymetis')
from meshmode.distributed import get_partition_by_pymetis
part_per_element = get_partition_by_pymetis(mesh, num_parts,
connectivity=part_method)
from meshmode.mesh.processing import partition_mesh
part_meshes = [
partition_mesh(mesh, part_per_element, i)[0] for i in range(num_parts)]
connected_parts = set()
for i_local_part, part_mesh in enumerate(part_meshes):
from meshmode.distributed import get_connected_partitions
neighbors = get_connected_partitions(part_mesh)
for i_remote_part in neighbors:
connected_parts.add((i_local_part, i_remote_part))
from meshmode.discretization import Discretization
vol_discrs = [Discretization(actx, part_meshes[i], group_factory(order))
for i in range(num_parts)]
from meshmode.mesh import BTAG_PARTITION
from meshmode.discretization.connection import (make_face_restriction,
make_partition_connection,
check_connection)
for i_local_part, i_remote_part in connected_parts:
# Mark faces within local_mesh that are connected to remote_mesh
local_bdry_conn = make_face_restriction(actx, vol_discrs[i_local_part],
group_factory(order),
BTAG_PARTITION(i_remote_part))
# Mark faces within remote_mesh that are connected to local_mesh
remote_bdry_conn = make_face_restriction(actx, vol_discrs[i_remote_part],
group_factory(order),
BTAG_PARTITION(i_local_part))
bdry_nelements = sum(
grp.nelements for grp in local_bdry_conn.to_discr.groups)
remote_bdry_nelements = sum(
grp.nelements for grp in remote_bdry_conn.to_discr.groups)
assert bdry_nelements == remote_bdry_nelements, \
"partitions do not have the same number of connected elements"
# Gather just enough information for the connection
local_bdry = local_bdry_conn.to_discr
local_mesh = part_meshes[i_local_part]
local_adj_groups = [local_mesh.facial_adjacency_groups[i][None]
for i in range(len(local_mesh.groups))]
local_batches = [local_bdry_conn.groups[i].batches
for i in range(len(local_mesh.groups))]
local_from_elem_faces = [[batch.to_element_face
for batch in grp_batches]
for grp_batches in local_batches]
local_from_elem_indices = [[batch.to_element_indices.get(queue=queue)
for batch in grp_batches]
for grp_batches in local_batches]
remote_bdry = remote_bdry_conn.to_discr
remote_mesh = part_meshes[i_remote_part]
remote_adj_groups = [remote_mesh.facial_adjacency_groups[i][None]
for i in range(len(remote_mesh.groups))]
remote_batches = [remote_bdry_conn.groups[i].batches
for i in range(len(remote_mesh.groups))]
remote_from_elem_faces = [[batch.to_element_face
for batch in grp_batches]
for grp_batches in remote_batches]
remote_from_elem_indices = [[batch.to_element_indices.get(queue=queue)
for batch in grp_batches]
for grp_batches in remote_batches]
# Connect from remote_mesh to local_mesh
remote_to_local_conn = make_partition_connection(
actx, local_bdry_conn, i_local_part, remote_bdry,
remote_adj_groups, remote_from_elem_faces,
remote_from_elem_indices)
# Connect from local mesh to remote mesh
local_to_remote_conn = make_partition_connection(
actx, remote_bdry_conn, i_remote_part, local_bdry,
local_adj_groups, local_from_elem_faces,
local_from_elem_indices)
check_connection(actx, remote_to_local_conn)
check_connection(actx, local_to_remote_conn)
true_local_points = f(thaw(actx, local_bdry.nodes()[0]))
remote_points = local_to_remote_conn(true_local_points)
local_points = remote_to_local_conn(remote_points)
err = flat_norm(true_local_points - local_points, np.inf)
# Can't currently expect exact results due to limitations of
# interpolation 'snapping' in DirectDiscretizationConnection's
# _resample_point_pick_indices
assert err < 1e-11
def connected_ranks(self):
from meshmode.distributed import get_connected_partitions
return get_connected_partitions(self._volume_discr.mesh)
