def _remove_trace_edge(self, edge: network_components.Edge,
new_node: network_components.BaseNode) -> None:
"""Collapse a trace edge.
Collapses a trace edge and updates the network.
Args:
edge: The edge to contract.
new_node: The new node created after contraction.
Returns:
The node that had the contracted edge.
Raises:
ValueError: If edge is not a trace edge.
"""
if edge.is_dangling():
raise ValueError("Attempted to remove dangling edge '{}'.".format(edge))
if edge.node1 is not edge.node2:
raise ValueError("Edge '{}' is not a trace edge.".format(edge))
axes = sorted([edge.axis1, edge.axis2])
node_edges = edge.node1.edges[:]
node_edges.pop(axes[0])
node_edges.pop(axes[1] - 1)
seen_edges = set()
for tmp_edge in node_edges:
if tmp_edge in seen_edges:
continue
else:
seen_edges.add(tmp_edge)
if tmp_edge.node1 is edge.node1:
to_reduce = 0
to_reduce += 1 if tmp_edge.axis1 > axes[0] else 0
to_reduce += 1 if tmp_edge.axis1 > axes[1] else 0
tmp_edge.axis1 -= to_reduce
tmp_edge.node1 = new_node
if tmp_edge.node2 is edge.node1:
to_reduce = 0
to_reduce += 1 if tmp_edge.axis2 > axes[0] else 0
to_reduce += 1 if tmp_edge.axis2 > axes[1] else 0
tmp_edge.axis2 -= to_reduce
tmp_edge.node2 = new_node
# Update edges for the new node.
for i, e in enumerate(node_edges):
new_node.add_edge(e, i)
self.nodes_set.remove(edge.node1)
def _remove_edges(self, edges: Set[network_components.Edge],
node1: network_components.BaseNode,
node2: network_components.BaseNode,
new_node: network_components.BaseNode) -> None:
"""Collapse a list of edges shared by two nodes in the network.
Collapses the edges and updates the rest of the network.
The nodes that currently share the edges in `edges` must be supplied as
`node1` and `node2`. The ordering of `node1` and `node2` must match the
axis ordering of `new_node` (as determined by the contraction procedure).
Args:
edges: The edges to contract.
node1: The old node that supplies the first edges of `new_node`.
node2: The old node that supplies the last edges of `new_node`.
new_node: The new node that represents the contraction of the two old
nodes.
Raises:
Value Error: If edge isn't in the network.
"""
if node1 is node2:
raise ValueError(
"node1 and node2 are the same ('{}' == '{}'), but trace edges cannot "
"be removed by _remove_edges.".format(node1, node2))
node1_edges = node1.edges[:]
node2_edges = node2.edges[:]
nodes_set = set([node1, node2])
for edge in edges:
if edge.is_dangling():
raise ValueError("Attempted to remove dangling edge '{}'.".format(edge))
if set([edge.node1, edge.node2]) != nodes_set:
raise ValueError(
"Attempted to remove edges belonging to different node pairs: "
"'{}' != '{}'.".format(nodes_set, set([edge.node1, edge.node2])))
remaining_edges = []
for (i, edge) in enumerate(node1_edges):
if edge not in edges: # NOTE: Makes the cost quadratic in # edges
edge.update_axis(
old_node=node1,
old_axis=i,
new_axis=len(remaining_edges),
new_node=new_node)
remaining_edges.append(edge)
for (i, edge) in enumerate(node2_edges):
if edge not in edges:
edge.update_axis(
old_node=node2,
old_axis=i,
new_axis=len(remaining_edges),
new_node=new_node)
remaining_edges.append(edge)
for (i, edge) in enumerate(remaining_edges):
new_node.add_edge(edge, i)
# Remove nodes
self.nodes_set.remove(node1)
self.nodes_set.remove(node2)