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_initialize_raises_error_faulty_arguments(double_node_edge):
node1 = double_node_edge.node1
node2 = double_node_edge.node2
with pytest.raises(ValueError):
Edge(name="edge", node1=node1, node2=node2, axis1=0)
with pytest.raises(ValueError):
Edge(name="edge", node1=node1, axis1=0, axis2=0)
def test_edge_magic_xor(double_node_edge): node1 = double_node_edge.node1 node2 = double_node_edge.node2 edge1 = Edge(name="edge1", node1=node1, axis1=2) edge2 = Edge(name="edge2", node1=node2, axis1=2) edge = edge1 ^ edge2 assert edge.node1 == node1 assert edge.node2 == node2
def fixture_double_node_edge(backend):
net = tensornetwork.TensorNetwork(backend=backend)
tensor = net.backend.convert_to_tensor(np.ones((1, 2, 2)))
node1 = Node(
tensor=tensor, name="test_node1", axis_names=["a", "b", "c"], network=net)
node2 = Node(
tensor=tensor, name="test_node2", axis_names=["a", "b", "c"], network=net)
net.connect(node1["b"], node2["b"])
edge1 = Edge(name="edge", node1=node1, axis1=0)
edge12 = Edge(name="edge", node1=node1, axis1=1, node2=node2, axis2=1)
return DoubleNodeEdgeTensor(node1, node2, edge1, edge12, tensor)
def copy(nodes: Iterable[AbstractNode],
conjugate: bool = False) -> Tuple[dict, dict]:
"""Copy the given nodes and their edges.
This will return a tuple linking original nodes/edges to their copies.
If nodes A and B are connected but only A is passed in to be
copied, the edge between them will become a dangling edge.
Args:
nodes: An Iterable (Usually a `list` or `set`) of `nodes`.
conjugate: Boolean. Whether to conjugate all of the nodes
(useful for calculating norms and reduced density matrices).
Returns:
A tuple containing:
node_dict:
A dictionary mapping the nodes to their copies.
edge_dict:
A dictionary mapping the edges to their copies.
"""
node_dict = {}
for node in nodes:
node_dict[node] = node.copy(conjugate)
edge_dict = {}
for edge in get_all_edges(nodes):
node1 = edge.node1
axis1 = edge.node1.get_axis_number(edge.axis1)
# edge dangling or node2 does not need to be copied
if edge.is_dangling() or edge.node2 not in node_dict:
new_edge = Edge(node_dict[node1], axis1, edge.name)
node_dict[node1].add_edge(new_edge, axis1)
edge_dict[edge] = new_edge
continue
node2 = edge.node2
axis2 = edge.node2.get_axis_number(edge.axis2)
# copy node2 but not node1
if node1 not in node_dict:
new_edge = Edge(node_dict[node2], axis2, edge.name)
node_dict[node2].add_edge(new_edge, axis2)
edge_dict[edge] = new_edge
continue
# both nodes should be copied
new_edge = Edge(node_dict[node1], axis1, edge.name, node_dict[node2],
axis2)
if not edge.is_trace():
node_dict[node2].add_edge(new_edge, axis2)
node_dict[node1].add_edge(new_edge, axis1)
edge_dict[edge] = new_edge
return node_dict, edge_dict
def fixture_double_node_edge(backend):
tensor = np.ones((1, 2, 2))
node1 = Node(tensor=tensor,
name="test_node1",
axis_names=["a", "b", "c"],
backend=backend)
node2 = Node(tensor=tensor,
name="test_node2",
axis_names=["a", "b", "c"],
backend=backend)
tn.connect(node1["b"], node2["b"])
edge1 = Edge(name="edge", node1=node1, axis1=0)
edge12 = Edge(name="edge", node1=node1, axis1=1, node2=node2, axis2=1)
return DoubleNodeEdgeTensor(node1, node2, edge1, edge12, tensor)
def disconnect(
self,
edge: network_components.Edge,
dangling_edge_name_1: Optional[Text] = None,
dangling_edge_name_2: Optional[Text] = None
) -> List[network_components.Edge]:
"""Break a edge into two dangling edges.
Args:
edge: An edge to break.
dangling_edge_name_1: Optional name to give the new dangling edge 1.
dangling_edge_name_2: Optional name to give the new dangling edge 2.
Returns:
dangling_edge_1: A new dangling edge.
dangling_edge_2: A new dangling edge.
Raises:
ValueError: If input edge is a dangling one.
"""
if edge.is_dangling():
raise ValueError(
"Attempted to break a dangling edge '{}'.".format(edge))
node1 = edge.node1
node2 = edge.node2
dangling_edge_name_1 = self._new_edge_name(dangling_edge_name_1)
dangling_edge_name_2 = self._new_edge_name(dangling_edge_name_2)
dangling_edge_1 = network_components.Edge(dangling_edge_name_1, node1,
edge.axis1)
dangling_edge_2 = network_components.Edge(dangling_edge_name_2, node2,
edge.axis2)
node1.add_edge(dangling_edge_1, edge.axis1, True)
node2.add_edge(dangling_edge_2, edge.axis2, True)
self.edge_order.remove(edge)
return [dangling_edge_1, dangling_edge_2]
def _contract_trace(
self,
edge: network_components.Edge,
name: Optional[Text] = None) -> network_components.Node:
"""Contract a trace edge connecting in the TensorNetwork.
Args:
edge: The edge name or object to contract next.
name: Name to give to the new node. If None, a name will automatically be
generated.
Returns:
new_node: The new node created after the contraction.
Raise:
ValueError: When edge is a dangling edge.
"""
if edge.is_dangling():
raise ValueError(
"Attempted to contract dangling edge '{}'".format(edge))
if edge.node1 is not edge.node2:
raise ValueError(
"Can not take trace of edge '{}'. This edge connects to "
"two different nodes: '{}' and '{}".format(
edge, edge.node1, edge.node2))
axes = sorted([edge.axis1, edge.axis2])
dims = len(edge.node1.tensor.shape)
permutation = sorted(set(range(dims)) - set(axes)) + axes
new_tensor = self.backend.trace(
self.backend.transpose(edge.node1.tensor, perm=permutation))
new_node = self.add_node(new_tensor, name)
self._remove_trace_edge(edge, new_node)
return new_node
def find_parallel(
edge: network_components.Edge
) -> Tuple[Set[network_components.Edge], int]:
"""Finds all edges shared between the nodes connected with the given edge.
Args:
edge: A non-dangling edge between two different nodes.
Returns:
parallel_edges: Edges that are parallel to the given edge.
parallel_dim: Product of sizes of all parallel edges.
"""
if edge.is_dangling():
raise ValueError(
"Cannot find parallel edges for dangling edge {}".format(edge))
nodes = {edge.node1, edge.node2}
parallel_dim = 1
parallel_edges = set()
for e in edge.node1.edges:
if set(e.get_nodes()) == nodes:
parallel_edges.add(e)
edge_size = list(e.node1.get_tensor().shape)[e.axis1]
if edge_size is not None:
parallel_dim *= edge_size
return parallel_edges, parallel_dim
def _remove_edge(self, edge: network_components.Edge,
new_node: network_components.Node) -> None:
"""Collapse an edge in the network.
Collapses an edge and updates the rest of the network.
Args:
edge: The edge to contract.
new_node: The new node that represents the contraction of the two old
nodes.
Raises:
Value Error: If edge isn't in the network.
"""
# Assert that the edge isn't a dangling edge.
if edge.is_dangling():
raise ValueError(
"Attempted to remove dangling edge '{}'.".format(edge))
if edge.node1 is edge.node2:
self._remove_trace_edge(edge, new_node)
# Collapse the nodes into a new node and remove the edge.
node1 = edge.node1
node2 = edge.node2
node1_edges = edge.node1.edges[:]
node2_edges = edge.node2.edges[:]
node1_axis = edge.axis1
node2_axis = edge.axis2
# Redefine all other edges.
num_added_front_edges = len(node1_edges) - 1
for i, tmp_edge in enumerate(node1_edges[:node1_axis]):
tmp_edge.update_axis(old_axis=i,
old_node=node1,
new_axis=i,
new_node=new_node)
for i, tmp_edge in enumerate(node1_edges[node1_axis + 1:]):
tmp_edge.update_axis(old_axis=i + node1_axis + 1,
old_node=node1,
new_axis=i + node1_axis,
new_node=new_node)
for i, tmp_edge in enumerate(node2_edges[:node2_axis]):
tmp_edge.update_axis(old_axis=i,
old_node=node2,
new_axis=i + num_added_front_edges,
new_node=new_node)
for i, tmp_edge in enumerate(node2_edges[node2_axis + 1:]):
tmp_edge.update_axis(old_axis=i + node2_axis + 1,
old_node=node2,
new_axis=i + node2_axis +
num_added_front_edges,
new_node=new_node)
node1_edges.pop(node1_axis)
node2_edges.pop(node2_axis)
new_edges = node1_edges + node2_edges
for i, e in enumerate(new_edges):
new_node.add_edge(e, i)
# Remove nodes
self.nodes_set.remove(node1)
self.nodes_set.remove(node2)
def test_edge_load(backend, tmp_path, double_node_edge):
edge = double_node_edge.edge12
with h5py.File(tmp_path / 'edge', 'w') as edge_file:
edge_group = edge_file.create_group('edge_data')
edge_group.create_dataset('signature', data=edge.signature)
edge_group.create_dataset('name', data=edge.name)
edge_group.create_dataset('node1', data=edge.node1.name)
edge_group.create_dataset('node2', data=edge.node2.name)
edge_group.create_dataset('axis1', data=edge.axis1)
edge_group.create_dataset('axis2', data=edge.axis2)
ten = np.ones((1, 2, 2))
node1 = Node(
tensor=2 * ten,
name="test_node1",
axis_names=["a", "b", "c"],
backend=backend)
node2 = Node(
tensor=ten,
name="test_node2",
axis_names=["a", "b", "c"],
backend=backend)
loaded_edge = Edge._load_edge(edge_group, {
node1.name: node1,
node2.name: node2
})
assert loaded_edge.name == edge.name
assert loaded_edge.signature == edge.signature
assert loaded_edge.node1.name == edge.node1.name
assert loaded_edge.node2.name == edge.node2.name
assert loaded_edge.axis1 == edge.axis1
assert loaded_edge.axis2 == edge.axis2
np.testing.assert_allclose(loaded_edge.node1.tensor, node1.tensor)
np.testing.assert_allclose(loaded_edge.node2.tensor, node2.tensor)
def redirect_edge(edge: Edge, new_node: AbstractNode,
old_node: AbstractNode) -> None:
"""
Redirect `edge` from `old_node` to `new_node`.
Routine updates `new_node` and `old_node`.
`edge` is added to `new_node`, `old_node` gets a
new Edge instead of `edge`.
Args:
edge: An Edge.
new_node: The new `Node` object.
old_node: The old `Node` object.
Returns:
None
Raises:
ValueError: if `edge` does not point to `old_node`.
"""
if not edge.is_trace():
if edge.is_dangling():
if edge.node1 is not old_node:
raise ValueError(f"edge {edge} is not pointing "
f"to old_node {old_node}")
edge.node1 = new_node
axis = edge.axis1
else:
if edge.node1 is old_node:
edge.node1 = new_node
axis = edge.axis1
elif edge.node2 is old_node:
edge.node2 = new_node
axis = edge.axis2
else:
raise ValueError(f"edge {edge} is not pointing "
f"to old_node {old_node}")
new_node.add_edge(edge, axis, True)
new_edge = Edge(old_node, axis)
old_node.add_edge(new_edge, axis, True)
else:
if edge.node1 is not old_node:
raise ValueError(f"edge {edge} is not pointing "
f"to old_node {old_node}")
edge.node1 = new_node
edge.node2 = new_node
axis1 = edge.axis1
axis2 = edge.axis2
new_node.add_edge(edge, axis1, True)
new_node.add_edge(edge, axis2, True)
new_edge = Edge(old_node, axis1, None, old_node, axis2)
old_node.add_edge(new_edge, axis1, True)
old_node.add_edge(new_edge, axis2, True)
def test_node_add_edge_raises_error_mismatch_rank(single_node_edge):
node = single_node_edge.node
edge = single_node_edge.edge
with pytest.raises(ValueError):
node.add_edge(edge, axis=-1)
edge = Edge(name="edge", node1=node, axis1=0)
with pytest.raises(ValueError):
node.add_edge(edge, axis=3)
def fixture_single_node_edge(backend):
tensor = np.ones((1, 2, 2))
node = Node(tensor=tensor,
name="test_node",
axis_names=["a", "b", "c"],
backend=backend)
edge = Edge(name="edge", node1=node, axis1=0)
return SingleNodeEdgeTensor(node, edge, tensor)
def fixture_single_node_edge(backend):
net = tensornetwork.TensorNetwork(backend=backend)
tensor = np.ones((1, 2, 2))
tensor = net.backend.convert_to_tensor(tensor)
node = Node(
tensor=tensor, name="test_node", axis_names=["a", "b", "c"], network=net)
edge = Edge(name="edge", node1=node, axis1=0)
return SingleNodeEdgeTensor(node, edge, tensor)
def test_node_reorder_edges_raise_error_wrong_edges(single_node_edge):
node = single_node_edge.node
e0 = node[0]
e1 = node[1]
e2 = node[2]
edge = Edge(name="edge", node1=node, axis1=0)
with pytest.raises(ValueError) as e:
node.reorder_edges([e0])
assert "Missing edges that belong to node found:" in str(e.value)
with pytest.raises(ValueError) as e:
node.reorder_edges([e0, e1, e2, edge])
assert "Additional edges that do not belong to node found:" in str(e.value)
def load(path: str):
"""Load a tensor network from disk.
Args:
path: path to file where network is saved.
"""
with h5py.File(path, 'r') as net_file:
net = TensorNetwork(backend=net_file["backend"][()])
node_names = list(net_file["nodes"].keys())
edge_names = list(net_file["edges"].keys())
for node_name in node_names:
node_data = net_file["nodes/" + node_name]
node_type = get_component(node_data['type'][()])
node_type._load_node(net, node_data)
nodes_dict = {node.name: node for node in net.nodes_set}
for edge in edge_names:
edge_data = net_file["edges/" + edge]
Edge._load_edge(edge_data, nodes_dict)
return net
def contract_parallel(
self, edge: network_components.Edge) -> network_components.Node:
"""Contract all edges parallel to this edge.
This method calls `contract_between` with the nodes connected by the edge.
Args:
edge: The edge to contract.
Returns:
The new node created after contraction.
"""
if edge.is_dangling():
raise ValueError("Attempted to contract dangling edge: '{}'".format(edge))
return self.contract_between(edge.node1, edge.node2)
def _remove_trace_edge(self, edge: network_components.Edge,
new_node: network_components.Node) -> 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 copy(nodes: Iterable[BaseNode],
conjugate: bool = False) -> Tuple[dict, dict]:
"""Copy the given nodes and their edges.
This will return a dictionary linking original nodes/edges
to their copies.
Args:
nodes: An `Iterable` (Usually a `List` or `Set`) of `Nodes`.
conjugate: Boolean. Whether to conjugate all of the nodes
(useful for calculating norms and reduced density
matrices).
Returns:
A tuple containing:
node_dict: A dictionary mapping the nodes to their copies.
edge_dict: A dictionary mapping the edges to their copies.
"""
#TODO: add support for copying CopyTensor
if conjugate:
node_dict = {
node: Node(node.backend.conj(node.tensor),
name=node.name,
axis_names=node.axis_names,
backend=node.backend.name)
for node in nodes
}
else:
node_dict = {
node: Node(node.tensor,
name=node.name,
axis_names=node.axis_names,
backend=node.backend.name)
for node in nodes
}
edge_dict = {}
for edge in get_all_edges(nodes):
node1 = edge.node1
axis1 = edge.node1.get_axis_number(edge.axis1)
if not edge.is_dangling():
node2 = edge.node2
axis2 = edge.node2.get_axis_number(edge.axis2)
new_edge = Edge(node_dict[node1], axis1, edge.name,
node_dict[node2], axis2)
new_edge.set_signature(edge.signature)
else:
new_edge = Edge(node_dict[node1], axis1, edge.name)
node_dict[node1].add_edge(new_edge, axis1)
if not edge.is_dangling():
node_dict[node2].add_edge(new_edge, axis2)
edge_dict[edge] = new_edge
return node_dict, edge_dict
def nodes_from_json(
json_str: str) -> Tuple[List[AbstractNode], Dict[str, Tuple[Edge]]]:
"""
Create a tensor network from a JSON string representation of a tensor network.
Args:
json_str: A string representing a JSON serialized tensor network.
Returns:
A list of nodes making up the tensor network.
A dictionary of {str -> (edge,)} bindings. All dictionary values are tuples
of Edges.
"""
network_dict = json.loads(json_str)
nodes = []
node_ids = {}
edge_lookup = {}
edge_binding = {}
for n in network_dict['nodes']:
node = Node.from_serial_dict(n['attributes'])
nodes.append(node)
node_ids[n['id']] = node
for e in network_dict['edges']:
e_nodes = [node_ids.get(n_id) for n_id in e['node_ids']]
axes = e['attributes']['axes']
edge = Edge(node1=e_nodes[0],
axis1=axes[0],
node2=e_nodes[1],
axis2=axes[1],
name=e['attributes']['name'])
edge_lookup[e['id']] = edge
for node, axis in zip(e_nodes, axes):
if node is not None:
node.add_edge(edge, axis, override=True)
for k, v in network_dict.get('edge_binding', {}).items():
for e_id in v:
edge_binding[k] = edge_binding.get(k, ()) + (edge_lookup[e_id], )
return nodes, edge_binding
def load_nodes(path: str) -> List[BaseNode]:
"""
Load a set of nodes from disk.
Args:
path: path to file where network is saved.
Returns:
An iterable of `Node` objects
"""
nodes_list = []
edges_list = []
with h5py.File(path, 'r') as net_file:
nodes = list(net_file["nodes"].keys())
node_names = {
'node{}'.format(n): v
for n, v in enumerate(net_file["node_names"]['names'][()])
}
edge_names = {
'edge{}'.format(n): v
for n, v in enumerate(net_file["edge_names"]['names'][()])
}
edges = list(net_file["edges"].keys())
for node_name in nodes:
node_data = net_file["nodes/" + node_name]
node_type = get_component(node_data['type'][()])
nodes_list.append(
node_type._load_node(net=None, node_data=node_data))
nodes_dict = {node.name: node for node in nodes_list}
for edge in edges:
edge_data = net_file["edges/" + edge]
edges_list.append(Edge._load_edge(edge_data, nodes_dict))
for edge in edges_list:
edge.set_name(edge_names[edge.name])
for node in nodes_list:
node.set_name(node_names[node.name])
return nodes_list
def test_edge_set_name_throws_type_error(single_node_edge, name):
edge = Edge(node1=single_node_edge.node, axis1=0)
with pytest.raises(TypeError):
edge.set_name(name)
def copy(nodes: Iterable[BaseNode],
conjugate: bool = False) -> Tuple[dict, dict]:
"""Copy the given nodes and their edges.
This will return a dictionary linking original nodes/edges
to their copies. If nodes A and B are connected but only A is passed in to be
copied, the edge between them will become a dangling edge.
Args:
nodes: An `Iterable` (Usually a `List` or `Set`) of `Nodes`.
conjugate: Boolean. Whether to conjugate all of the nodes
(useful for calculating norms and reduced density
matrices).
Returns:
A tuple containing:
node_dict: A dictionary mapping the nodes to their copies.
edge_dict: A dictionary mapping the edges to their copies.
"""
#TODO: add support for copying CopyTensor
if conjugate:
node_dict = {
node: Node(
node.backend.conj(node.tensor),
name=node.name,
axis_names=node.axis_names,
backend=node.backend) for node in nodes
}
else:
node_dict = {
node: Node(
node.tensor,
name=node.name,
axis_names=node.axis_names,
backend=node.backend) for node in nodes
}
edge_dict = {}
for edge in get_all_edges(nodes):
node1 = edge.node1
axis1 = edge.node1.get_axis_number(edge.axis1)
# edge dangling or node2 does not need to be copied
if edge.is_dangling() or edge.node2 not in node_dict:
new_edge = Edge(node_dict[node1], axis1, edge.name)
node_dict[node1].add_edge(new_edge, axis1)
edge_dict[edge] = new_edge
continue
node2 = edge.node2
axis2 = edge.node2.get_axis_number(edge.axis2)
# copy node2 but not node1
if node1 not in node_dict:
new_edge = Edge(node_dict[node2], axis2, edge.name)
node_dict[node2].add_edge(new_edge, axis2)
edge_dict[edge] = new_edge
continue
# both nodes should be copied
new_edge = Edge(node_dict[node1], axis1, edge.name, node_dict[node2], axis2)
new_edge.set_signature(edge.signature)
node_dict[node2].add_edge(new_edge, axis2)
node_dict[node1].add_edge(new_edge, axis1)
edge_dict[edge] = new_edge
return node_dict, edge_dict
def test_edge_signature_setter_disabled_throws_error(single_node_edge):
edge = Edge(node1=single_node_edge.node, axis1=0)
edge.is_disabled = True
with pytest.raises(ValueError):
edge.signature = "signature"
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()
def test_edge_is_trace_true(single_node_edge): node = single_node_edge.node edge = Edge(name="edge", node1=node, axis1=1, node2=node, axis2=2) assert edge.is_trace()
def test_edge_name_throws_type_error(single_node_edge, name):
with pytest.raises(TypeError):
Edge(node1=single_node_edge.node, axis1=0, name=name)
def test_edge_node1_throws_value_error(single_node_edge):
edge = Edge(node1=single_node_edge.node, axis1=0, name="edge")
edge._node1 = None
err_msg = "node1 for edge 'edge' no longer exists."
with pytest.raises(ValueError, match=err_msg):
edge.node1
