def contract(self,
edge: network_components.Edge,
name: Optional[Text] = None) -> network_components.Node:
"""Contract an edge connecting two nodes in the TensorNetwork.
Args:
edge: The edge contract next.
name: Name of the new node created.
Returns:
new_node: The new node created after the contraction.
Raises:
ValueError: When edge is a dangling edge or if it already has been
contracted.
"""
if not edge.is_being_used() or edge.node1 not in self.nodes_set:
raise ValueError(
"Attempting to contract edge '{}' that is not part of "
"the network.".format(edge))
if edge.is_dangling():
raise ValueError("Attempting to contract dangling edge")
if edge.node1 is edge.node2:
return self._contract_trace(edge, name)
new_tensor = self.backend.tensordot(edge.node1.tensor,
edge.node2.tensor,
[[edge.axis1], [edge.axis2]])
new_node = self.add_node(new_tensor, name)
self._remove_edges(set([edge]), edge.node1, edge.node2, new_node)
return new_node
def test_edge_is_being_used_false(single_node_edge): node = single_node_edge.node edge2 = Edge(name="edge", node1=node, axis1=0) assert not edge2.is_being_used()