def split_upper_ranks(partition: RankedPartition, block: _Block):
"""Split the blocks whose `rank` is **greater** than `block.rank` using
`block` as *splitter*.
:param partition: The current partition.
:param block: The splitter block.
"""
block_counterimage = build_block_counterimage(block)
modified_blocks = []
for vertex in block_counterimage:
# if this is an upper-rank node with respect to the collapsed block, we
# need to split. the split is not needed if the block is a singoletto.
if vertex.rank > block.rank and not (
vertex.qblock.split_helper_block is None
and vertex.qblock.size <= 1):
# if needed, create the aux block to help during the splitting
# phase
if vertex.qblock.split_helper_block is None:
vertex.qblock.initialize_split_helper_block()
modified_blocks.append(vertex.qblock)
new_vertex_block = vertex.qblock.split_helper_block
# remove the vertex in the counterimage from its current block
vertex.qblock.remove_vertex(vertex)
# put the vertex in the counterimage in the aux block
new_vertex_block.append_vertex(vertex)
# insert the new blocks in the partition, and then reset aux block for each
# modified block.
for mod_block in modified_blocks:
# we use the rank of aux block because we're sure it's not None
partition.append_at_rank(
block=mod_block.split_helper_block,
rank=mod_block.split_helper_block.rank,
)
mod_block.split_helper_block = None
def test_append_at_rank():
vertexes, _ = decorate_nx_graph(nx.balanced_tree(2, 3))
partition = RankedPartition(vertexes)
block = _QBlock([], None)
partition.append_at_rank(block, 1)
assert partition[2][-1] == block
