Components#

Axis#

class tensorkrowch.Axis(num, name, node=None, node1=True)[source]#

Axes are the objects that stick edges to nodes. Each instance of the AbstractNode class has a list of \(N\) axes, each corresponding to one edge. Each axis stores information that facilitates accessing that edge, such as its name and num (index). Additionally, an axis keeps track of its batch and node1 attributes.

batch: If the axis name contains the word “batch”, the edge will be a batch edge, which means that it cannot be connected to other nodes. Instead, it specifies a dimension that allows for batch operations (e.g., batch contraction). If the name of the axis is changed and no longer contains the word “batch”, the corresponding edge will no longer be a batch edge. Furthermore, instances of the StackNode and ParamStackNode classes always have an axis with name “stack” whose edge is a batch edge.
node1: When two dangling edges are connected the result is a new edge linking two nodes, say nodeA and nodeB. If the connection is performed in the following order:
```
new_edge = nodeA[edgeA] ^ nodeB[edgeB]
```
Then nodeA will be the node1 of new_edge and nodeB, the node2. Hence, to access one of the nodes from new_edge one needs to know if it is node1 or node2.

Even though we can create Axis instances, that will not be usually the case, since axes are automatically created when instantiating a new node.

Other thing one must take into account is the naming of Axes. Since the name of an Axis is used to access it from the Node, the same name cannot be used by more than one Axis. In that case, repeated names get an automatic enumeration of the form "name_{number}" (underscore followed by number).

To add a custom enumeration in a user-defined way, one may use brackets or parenthesis: "name_({number})".

Parameters

num (int) – Index of the axis in the node’s axes list.
name (str) – Axis name, should not contain blank spaces or special characters. If it contains the word “batch”, the axis will correspond to a batch edge. The word “stack” cannot be used in the name, since it is reserved for stacks.
node (AbstractNode, optional) – Node to which the axis belongs.
node1 (bool) – Boolean indicating whether node1 of the edge attached to this axis is the node that contains the axis (True). Otherwise, the node is node2 of the edge (False).

Examples

Although Axis will not be usually explicitly instantiated, it can be done like so:

>>> axis = tk.Axis(0, 'left')
>>> axis
Axis( left (0) )

>>> axis.is_node1()
True

>>> axis.is_batch()
False

Since “batch” is not contained in “left”, axis does not correspond to a batch edge, but that can be changed:

>>> axis.name = 'mybatch'
>>> axis.is_batch()
True

Also, as explained before, knowing if a node is the node1 or node2 of an edge enables users to access that node from the edge:

>>> nodeA = tk.Node(shape=(2, 3), axes_names=('left', 'right'))
>>> nodeB = tk.Node(shape=(3, 4), axes_names=('left', 'right'))
>>> new_edge = nodeA['right'] ^ nodeB['left']
...
>>> # nodeA is node1 and nodeB is node2 of new_edge
>>> nodeA == new_edge.nodes[1 - nodeA.get_axis('right').is_node1()]
True

>>> nodeB == new_edge.nodes[nodeA.get_axis('right').is_node1()]
True

The node1 attribute is extended to resultant nodes that inherit edges.

>>> nodeA = tk.randn(shape=(2, 3), axes_names=('left', 'right'))
>>> nodeB = tk.randn(shape=(3, 4), axes_names=('left', 'right'))
>>> nodeC = tk.randn(shape=(4, 5), axes_names=('left', 'right'))
>>> edge1 = nodeA['right'] ^ nodeB['left']
>>> edge2 = nodeB['right'] ^ nodeC['left']
>>> result = nodeA @ nodeB
...
>>> # result inherits the edges nodeA['left'] and edge2
>>> result['left'] == nodeA['left']
True

>>> result['right'] == edge2
True

>>> # result is still node1 of edge2, since nodeA was
>>> result.is_node1('right')
True

property num#: Index in the node’s axes list.

property name#: Axis name, used to access edges by name of the axis. It cannot contain blank spaces or special characters. If it contains the word “batch”, the axis will correspond to a batch edge. The word “stack” cannot be used in the name, since it is reserved for stacks.

property node#: Node to which the axis belongs.

is_node1()[source]#: Returns boolean indicating whether node1 of the edge attached to this axis is the node that contains the axis. Otherwise, the node is node2 of the edge.

is_batch()[source]#: Returns boolean indicating whether the edge in this axis is used as a batch edge.

Nodes#

AbstractNode#

class tensorkrowch.AbstractNode(shape=None, axes_names=None, name=None, network=None, data=False, virtual=False, override_node=False, tensor=None, edges=None, override_edges=False, node1_list=None, init_method=None, device=None, dtype=None, **kwargs)[source]#

Abstract class for all types of nodes. Defines what a node is and most of its properties and methods. Since it is an abstract class, cannot be instantiated.

Nodes are the elements that make up a TensorNetwork. At its most basic level, a node is a container for a torch.Tensor that stores other relevant information which enables to build any network and operate nodes to contract it (and train it!). Some of the information that is carried by the nodes includes:

Shape: Every node needs a shape to know if connections with other nodes are possible. Even if the tensor is not specified, an empty node needs a shape.
Tensor: The key ingredient of the node. Although the node acts as a container for the tensor, the node does not contain it. Actually, for efficiency purposes, the tensors are stored in a sort of memory that is shared by all the nodes of the TensorNetwork. Therefore, all that nodes contain is a memory address. Furthermore, some nodes can share the same (or a part of the same) tensor, thus containing the same address. Sometimes, to maintain consistency, when two nodes share a tensor, one stores its memory address, and the other one stores a reference to the former.
Axes: A list of Axes that make it easy to access edges just using a name or an index.
Edges: A list of Edges, one for each dimension of the node. Each edge is attached to the node via an Axis. Edges are useful to connect several nodes, creating a TensorNetwork.
Network: The TensorNetwork to which the node belongs. If the network is not specified when creating the node, a new TensorNetwork is created to contain the node. Although the network can be thought of as a graph, it is a torch.nn.Module, so it is much more than that. Actually, the TensorNetwork can contain different types of nodes, not all of them being part of the graph, but being used for different purposes.
Successors: A dictionary with information about the nodes that result from Operations in which the current node was involved. See Successor.

Carrying this information with the node is what makes it easy to:

Perform tensor network Operations such as contraction of two neighbouring nodes, without having to worry about tensor’s shapes, order of axes, etc.
Perform more advanced operations such as stack() or unbind() saving memory and time.
Keep track of operations in which a node has taken place, so that several steps can be skipped in further training iterations. See TensorNetwork.trace().

Also, there are 4 excluding types of nodes that will have different roles in the TensorNetwork:

leaf: These are the nodes that form the TensorNetwork (together with the data nodes). Usually, these will be the trainable nodes. These nodes can store their own tensors or use other node’s tensor.
data: These are similar to leaf nodes, but they are never trainable, and are used to store the temporary tensors coming from input data. These nodes can store their own tensors or use other node’s tensor.
virtual: These nodes are a sort of ancillary, hidden nodes that accomplish some useful task (e.g. in uniform tensor networks a virtual node can store the shared tensor, while all the other nodes in the network just have a reference to it). These nodes always store their own tensors.
resultant: These are nodes that result from an Operation. They are intermediate nodes that (almost always) inherit edges from leaf and data nodes, the ones that really form the network. These nodes can store their own tensors or use other node’s tensor. The names of the resultant nodes are the name of the Operation that originated it.

See TensorNetwork and reset() to learn more about the importance of these 4 types of nodes.

Other thing one should take into account are reserved nodes’ names:

“stack_data_memory”: Name of the virtual StackNode that is created in set_data_nodes() to store the whole data tensor from which each data node might take just one slice. There should be at most one "stack_data_memory" in the network. To learn more about this, see set_data_nodes() and add_data().
“virtual_result”: Name of virtual nodes that are not explicitly part of the network, but are required for some situations during contraction. For instance, the ParamStackNode that results from stacking ParamNodes as the first operation in the network contraction, if auto_stack mode is set to True. To learn more about this, see ParamStackNode.
“virtual_uniform”: Name of the virtual Node or ParamNode that is used in uniform (translationally invariant) tensor networks to store the tensor that will be shared by all leaf nodes. There might be as much "virtual_uniform" nodes as shared memories are used for the leaf nodes in the network (usually just one).

For "virtual_result" and "virtual_uniform", these special behaviours are not restricted to nodes having those names, but also nodes whose names contain those strings.

Although these names can in principle be used for other nodes, this can lead to undesired behaviour.

See reset() to learn more about the importance of these reserved nodes’ names.

Other thing one must take into account is the naming of Nodes. Since the name of a Node is used to access it from the TensorNetwork, the same name cannot be used by more than one Node. In that case, repeated names get an automatic enumeration of the form "name_{number}" (underscore followed by number).

To add a custom enumeration to keep track of the nodes of the network in a user-defined way, one may use brackets or parenthesis: "name_({number})".

The same automatic enumeration of names occurs for Axes’ names in a Node.

Refer to the subclasses of AbstractNode to see how to instantiate nodes:

Node
ParamNode
StackNode
ParamStackNode

property tensor#: Node’s tensor. It can be a torch.Tensor, torch.nn.Parameter or None if the node is empty.

property shape#: Shape of node’s tensor. It is of type torch.Size.

property rank#: Length of node’s shape, that is, number of edges of the node.

property dtype#: torch.dtype of node’s tensor.

property device#: torch.device of node’s tensor.

property axes#: List of nodes’ axes.

property axes_names#: List of names of node’s axes.

property edges#: List of node’s edges.

property network#: TensorNetwork where the node belongs. If the node is moved to another TensorNetwork, the entire connected component of the graph where the node is will be moved.

property successors#: Dictionary with Operations’ names as keys, and dictionaries of Successors of the node as values. The inner dictionaries use as keys the arguments used when the operation was called.

property name#: Node’s name, used to access the node from the tensor network where it belongs. It cannot contain blank spaces.

is_leaf()[source]#: Returns a boolean indicating if the node is a leaf node. These are the nodes that form the TensorNetwork (together with the data nodes). Usually, these will be the trainable nodes. These nodes can store their own tensors or use other node’s tensor.

is_data()[source]#: Returns a boolean indicating if the node is a data node. These nodes are similar to leaf nodes, but they are never trainable, and are used to store the temporary tensors coming from input data. These nodes can store their own tensors or use other node’s tensor.

is_virtual()[source]#

Returns a boolean indicating if the node is a virtual node. These nodes are a sort of ancillary, hidden nodes that accomplish some useful task (e.g. in uniform tensor networks a virtual node can store the shared tensor, while all the other nodes in the network just have a reference to it). These nodes always store their own tensors.

If a virtual node is used as the node storing the shared tensor in a uniform (translationally invariant) TensorNetwork, it is recommended to use the string “virtual_uniform” in the node’s name (e.g. “virtual_uniform_mps”).

is_resultant()[source]#: Returns a boolean indicating if the node is a resultant node. These are nodes that result from an Operation. They are intermediate nodes that (almost always) inherit edges from leaf and data nodes, the ones that really form the network. These nodes can store their own tensors or use other node’s tensor.

is_conj()[source]#: Equivalent to torch.is_conj().

is_complex()[source]#: Equivalent to torch.is_complex().

is_floating_point()[source]#: Equivalent to torch.is_floating_point().

size(axis=None)[source]#

Returns the size of the node’s tensor. If axis is specified, returns the size of that axis; otherwise returns the shape of the node (same as shape).

Parameters: axis (int, str or Axis, optional) – Axis for which to retrieve the size.
Return type: int or torch.Size

is_node1(axis=None)[source]#

Returns node1 attribute of axes of the node. If axis is specified, returns only the node1 of that axis; otherwise returns the node1 of all axes of the node.

Parameters: axis (int, str or Axis, optional) – Axis for which to retrieve the node1.
Return type: bool or list[bool]

neighbours(axis=None)[source]#

Returns the neighbours of the node, the nodes to which it is connected.

If self is a resultant node, this will return the neighbours of the leaf nodes from which self inherits the edges. Therefore, one cannot check if two resultant nodes are connected by looking into their neighbours lists. To do that, use is_connected_to().

Parameters: axis (int, str or Axis, optional) – Axis for which to retrieve the neighbour.
Return type: AbstractNode or list[AbstractNode]

Examples

>>> nodeA = tk.randn(shape=(2, 3), axes_names=('left', 'right'))
>>> nodeB = tk.randn(shape=(3, 4), axes_names=('left', 'right'))
>>> nodeC = tk.randn(shape=(4, 5), axes_names=('left', 'right'))
>>> _ = nodeA['right'] ^ nodeB['left']
>>> _ = nodeB['right'] ^ nodeC['left']
>>> set(nodeB.neighbours()) == {nodeA, nodeC}
True

>>> nodeB.neighbours('right') == nodeC
True

Nodes resultant from operations are still connected to original neighbours.

>>> result = nodeA @ nodeB
>>> result.neighbours('right') == nodeC
True

is_connected_to(other)[source]#: Returns list of tuples of axes where the node is connected to other

get_axis(axis)[source]#: Returns Axis given its name or num.

get_axis_num(axis)[source]#: Returns axis’ num given the Axis or its name.

get_edge(axis)[source]#: Returns Edge given the Axis (or its name or num) where it is attached to the node.

in_which_axis(edge)[source]#: Returns Axis given the Edge that is attached to the node through it.

reattach_edges(axes=None, override=False)[source]#

Substitutes current edges by copies of them that are attached to the node. It can happen that an edge is not attached to the node if it is the result of an Operation and, hence, it inherits edges from the operands. In that case, the new copied edges will be attached to the resultant node, replacing each previous node1 or node2 with it (according to the node1 attribute of each axis).

Used for in-place operations like permute_() or split_() and to (de)parameterize nodes.

Parameters

axis (list[int, str or Axis] or tuple[int, str or Axis], optional) – The edge attached to these axes will be reattached. If None, all edges will be reattached.
override (bool) – Boolean indicating if the new, reattached edges should also replace the corresponding edges in the node’s neighbours (True). Otherwise, the neighbours’ edges will be pointing to the original nodes from which the current node inherits its edges (False).

Examples

>>> nodeA = tk.randn(shape=(2, 3), axes_names=('left', 'right'))
>>> nodeB = tk.randn(shape=(3, 4), axes_names=('left', 'right'))
>>> nodeC = tk.randn(shape=(4, 5), axes_names=('left', 'right'))
>>> _ = nodeA['right'] ^ nodeB['left']
>>> _ = nodeB['right'] ^ nodeC['left']
>>> result = nodeA @ nodeB

Node result inherits its right edge from nodeB.

>>> result['right'] == nodeB['right']
True

However, nodeB['right'] still connects nodeB and nodeC. There is no reference to result.

>>> result in result['right'].nodes
False

One can reattach its edges so that result’s edges do have references to it.

>>> result.reattach_edges()
>>> result in result['right'].nodes
True

If override is True, nodeB['right'] would be replaced by the new result['right'].

disconnect(axis=None)[source]#

Disconnects all edges of the node if they were connected to other nodes. If axis is sepcified, only the corresponding edge is disconnected.

Parameters: axis (int, str or Axis, optional) – Axis whose edge will be disconnected.

Examples

>>> nodeA = tk.Node(shape=(2, 3), axes_names=('left', 'right'))
>>> nodeB = tk.Node(shape=(3, 4), axes_names=('left', 'right'))
>>> nodeC = tk.Node(shape=(4, 5), axes_names=('left', 'right'))
>>> _ = nodeA['right'] ^ nodeB['left']
>>> _ = nodeB['right'] ^ nodeC['left']
>>> set(nodeB.neighbours()) == {nodeA, nodeC}
True

>>> nodeB.disconnect()
>>> nodeB.neighbours() == []
True

make_tensor(shape=None, init_method='zeros', device=None, dtype=None, **kwargs)[source]#

Returns a tensor that can be put in the node, and is initialized according to init_method. By default, it has the same shape as the node.

Parameters

shape (list[int], tuple[int] or torch.Size, optional) – Shape of the tensor. If None, node’s shape will be used.
init_method ({"zeros", "ones", "copy", "rand", "randn"}, optional) – Initialization method.
device (torch.device, optional) – Device where to initialize the tensor.
dtype (torch.dtype, optional) – Dtype of the tensor.
kwargs (float) –
Keyword arguments for the different initialization methods:
- low, high for uniform initialization. See torch.rand()
- mean, std for normal initialization. See torch.randn()

Return type

torch.Tensor

Raises

ValueError – If init_method is not one of “zeros”, “ones”, “copy”, “rand”, “randn”.

set_tensor(tensor=None, init_method='zeros', device=None, dtype=None, **kwargs)[source]#

Sets new node’s tensor or creates one with make_tensor() and sets it. Before setting it, it is cast to the correct type: torch.Tensor for Node and torch.nn.Parameter for ParamNode.

When a tensor is set in the node, it means the node stores it, that is, the node has its own memory address for its tensor, rather than a reference to other node’s tensor. Because of this, set_tensor cannot be applied for nodes that have a reference to other node’s tensor, since that tensor would be changed also in the referenced node. To overcome this issue, see reset_tensor_address().

This can only be used for non resultant``nodes that store their own tensors. For ``resultant nodes, tensors are set automatically when computing Operations.

Although this can also be used for data nodes, input data will be usually automatically set into nodes when calling the TensorNetwork.forward() method of TensorNetwork with a data tensor or a sequence of tensors. This method calls TensorNetwork.add_data(), which can also be used to set data tensors into the data nodes.

Parameters

tensor (torch.Tensor, optional) – Tensor to be set in the node. If None, and init_method is provided, the tensor is created with make_tensor(). Otherwise, a None is set as node’s tensor.
init_method ({"zeros", "ones", "copy", "rand", "randn"}, optional) – Initialization method.
device (torch.device, optional) – Device where to initialize the tensor.
dtype (torch.dtype, optional) – Dtype of the tensor.
kwargs (float) – Keyword arguments for the different initialization methods. See make_tensor().

Raises

ValueError – If the node is a resultant node or if it does not store its own tensor.

Examples

>>> node = tk.Node(shape=(2, 3), axes_names=('left', 'right'))
...
>>> # Call set_tensor without arguments uses the
>>> # default init_method ("zeros")
>>> node.set_tensor()
>>> torch.equal(node.tensor, torch.zeros(node.shape))
True

>>> node.set_tensor(init_method='randn', mean=1., std=2., device='cuda')
>>> torch.equal(node.tensor, torch.zeros(node.shape, device='cuda'))
False

>>> node.device
device(type='cuda', index=0)

>>> tensor = torch.randn(2, 3)
>>> node.set_tensor(tensor)
>>> torch.equal(node.tensor, tensor)
True

unset_tensor()[source]#

Replaces node’s tensor with None. This can only be used for non resultant nodes that store their own tensors.

Examples

>>> node = tk.randn(shape=(2, 3), axes_names=('left', 'right'))
>>> node.tensor is None
False

>>> node.unset_tensor()
>>> node.tensor is None
True

set_tensor_from(other)[source]#

Sets node’s tensor as the tensor used by other node. That is, when setting the tensor this way, the current node will store a reference to the other node’s tensor, instead of having its own tensor.

The node and other should be both the same type (Node or ParamNode). Also, they should be in the same TensorNetwork.

Parameters: other (Node or ParamNode) – Node whose tensor is to be set in current node.
Raises: TypeError – If other is a different type than the current node, or if it is in a different network.

Examples

>>> nodeA = tk.randn(shape=(2, 3),
...                  name='nodeA',
...                  axes_names=('left', 'right'))
>>> nodeB = tk.empty(shape=(2, 3),
...                  name='nodeB',
...                  axes_names=('left', 'right'),
...                  network=nodeA.network)
>>> nodeB.set_tensor_from(nodeA)
>>> print(nodeB.tensor_address())
nodeA

Since nodeB has a reference to nodeA’s tensor, if this one is changed, nodeB will reproduce all the changes.

>>> nodeA.tensor = torch.randn(nodeA.shape)
>>> torch.equal(nodeA.tensor, nodeB.tensor)
True

tensor_address()[source]#: Returns address of the node’s tensor in the network’s memory.

node_ref()[source]#: Returns the node that stores current node’s tensor.

reset_tensor_address()[source]#

Resets memory address of node’s tensor to reference the node itself. Thus, the node will store its own tensor, instead of having a reference to other node’s tensor.

Examples

>>> nodeA = tk.randn(shape=(2, 3),
...                  name='nodeA',
...                  axes_names=('left', 'right'))
>>> nodeB = tk.empty(shape=(2, 3),
...                  name='nodeB',
...                  axes_names=('left', 'right'),
...                  network=nodeA.network)
>>> nodeB.set_tensor_from(nodeA)
>>> print(nodeB.tensor_address())
nodeA

Now one cannot set in nodeB a different tensor from the one in nodeA, unless tensor address is reset in nodeB.

>>> nodeB.reset_tensor_address()
>>> nodeB.tensor = torch.randn(nodeB.shape)
>>> torch.equal(nodeA.tensor, nodeB.tensor)
False

move_to_network(network, visited=None)[source]#

Moves node to another network. All other nodes connected to it, or to a node connected to it, etc. are also moved to the new network.

If a node does not store its own tensor, and is moved to other network, it will recover the “ownership” of its tensor.

Parameters

network (TensorNetwork) – Tensor Network to which the nodes will be moved.
visited (list[AbstractNode], optional) – List indicating the nodes that have been already moved to the new network, used by this DFS-like algorithm.

Examples

>>> net = tk.TensorNetwork()
>>> nodeA = tk.Node(shape=(2, 3),
...                 axes_names=('left', 'right'),
...                 network=net)
>>> nodeB = tk.Node(shape=(3, 4),
...                 axes_names=('left', 'right'),
...                 network=net)
>>> nodeC = tk.Node(shape=(5, 5),
...                 axes_names=('left', 'right'),
...                 network=net)
>>> _ = nodeA['right'] ^ nodeB['left']

If nodeA is moved to other network, nodeB will also move, but nodeC will not.

>>> net2 = tk.TensorNetwork()
>>> nodeA.network = net2
>>> nodeA.network == nodeB.network
True

>>> nodeA.network != nodeC.network
True

sum(axis=None)[source]#

Returns the sum of all elements in the node’s tensor. If an axis is specified, the sum is over that axis. If axis is a sequence of axes, reduce over all of them.

This is not a node Operation, hence it returns a torch.Tensor instead of a Node.

Node#

class tensorkrowch.Node(shape=None, axes_names=None, name=None, network=None, data=False, virtual=False, override_node=False, tensor=None, edges=None, override_edges=False, node1_list=None, init_method=None, device=None, dtype=None, **kwargs)[source]#

Base class for non-trainable nodes. Should be subclassed by any class of nodes that are not intended to be trained (e.g. StackNode).

Can be used for fixed nodes of the TensorNetwork, or intermediate nodes that are resultant from an Operation between nodes.

All 4 types of nodes (leaf, data, virtual and resultant) can be Node. In fact, data and resultant nodes can only be of class Node, since they are not intended to be trainable. To learn more about these 4 types of nodes, see AbstractNode.

For a complete list of properties and methods, see also AbstractNode.

Parameters

shape (list[int], tuple[int] or torch.Size, optional) – Node’s shape, that is, the shape of its tensor. If shape and init_method are provided, a tensor will be made for the node. Otherwise, tensor would be required.
axes_names (list[str] or tuple[str], optional) – Sequence of names for each of the node’s axes. Names are used to access the edge that is attached to the node in a certain axis. Hence, they should be all distinct. They cannot contain blank spaces or special characters. By default, axes names will be "axis_0", …, "axis_n", being n the nummber of axes. If an axis’ name contains the word "batch", it will define a batch edge. The word "stack" cannot be used, since it is reserved for the stack edge of StackNode.
name (str, optional) – Node’s name, used to access the node from de TensorNetwork where it belongs. It cannot contain blank spaces. By default, it is the name of the class (e.g. "node", "paramnode").
network (TensorNetwork, optional) – Tensor network where the node should belong. If None, a new tensor network will be created to contain the node.
data (bool) – Boolean indicating if the node is a data node.
virtual (bool) – Boolean indicating if the node is a virtual node.
override_node (bool) – Boolean indicating whether the node should override (True) another node in the network that has the same name (e.g. if a node is parameterized, it would be required that a new ParamNode replaces the non-parameterized node in the network).
tensor (torch.Tensor, optional) – Tensor that is to be stored in the node. If None, shape and init_method will be required.
edges (list[Edge], optional) – List of edges that are to be attached to the node. This can be used in case the node inherits the edges from other node(s), like results from Operations.
override_edges (bool) – Boolean indicating whether the provided edges should be overriden (True) when reattached (e.g. if a node is parameterized, it would be required that the new ParamNode’s edges are indeed connected to it, instead of to the original non-parameterized node).
node1_list (list[bool], optional) – If edges are provided, the list of node1 attributes of each edge should also be provided.
init_method ({"zeros", "ones", "copy", "rand", "randn"}, optional) – Initialization method.
device (torch.device, optional) – Device where to initialize the tensor if init_method is provided.
dtype (torch.dtype, optional) – Dtype of the tensor if init_method is provided.
kwargs (float) – Keyword arguments for the different initialization methods. See AbstractNode.make_tensor().

Examples

>>> node = tk.Node(shape=(2, 5, 2),
...                axes_names=('left', 'input', 'right'),
...                name='my_node',
...                init_method='randn',
...                mean=0.,
...                std=1.)
>>> node
Node(
    name: my_node
    tensor:
            tensor([[[-1.2517, -1.8147],
                     [-0.7997, -0.0440],
                     [-0.2808,  0.3508],
                     [-1.2380,  0.8859],
                     [-0.3585,  0.8815]],
                    [[-0.2898, -2.2775],
                     [ 1.2856, -0.3222],
                     [-0.8911, -0.4216],
                     [ 0.0086,  0.2449],
                     [-2.1998, -1.6295]]])
    axes:
            [left
             input
             right]
    edges:
            [my_node[left] <-> None
             my_node[input] <-> None
             my_node[right] <-> None])

Also, one can use one of the Initializers to simplify:

>>> node = tk.randn((2, 5, 2))
>>> node
Node(
    name: node
    tensor:
            tensor([[[ 0.6545, -0.0445],
                     [-0.9265, -0.2730],
                     [-0.5069, -0.6524],
                     [-0.8227, -1.1211],
                     [ 0.2390,  0.9432]],
                    [[ 0.8633,  0.4402],
                     [-0.6982,  0.4461],
                     [-0.0633, -0.9320],
                     [ 1.6023,  0.5406],
                     [ 0.3489, -0.3088]]])
    axes:
            [axis_0
             axis_1
             axis_2]
    edges:
            [node[axis_0] <-> None
             node[axis_1] <-> None
             node[axis_2] <-> None])

parameterize(set_param=True)[source]#

Replaces the node with a parameterized version of it, that is, turns a fixed Node into a trainable ParamNode.

Since the node is replaced, it will be completely removed from the network, and its neighbours will point to the new parameterized node.

Parameters: set_param (bool) – Boolean indicating whether the node should be parameterized (True). Otherwise (False), the non-parameterized node itself will be returned.
Returns: The original node or a parameterized version of it.
Return type: Node or ParamNode

Examples

>>> nodeA = tk.randn((2, 3))
>>> nodeB = tk.randn((3, 4))
>>> _ = nodeA[1] ^ nodeB[0]
>>> paramnodeA = nodeA.parameterize()
>>> nodeB.neighbours() == [paramnodeA]
True

>>> isinstance(paramnodeA.tensor, torch.nn.Parameter)
True

nodeA still exists and has an edge pointing to nodeB, but the latter does not “see” the former. It should be deleted.

>>> del nodeA

To overcome this issue, one should override nodeA:

>>> nodeA = nodeA.parameterize()

copy(share_tensor=False)[source]#

Returns a copy of the node. That is, returns a node whose tensor is a copy of the original, whose edges are directly inherited (these are not copies, but the exact same edges) and whose name is extended with the suffix "_copy".

To create a copy that has its own (non-inherited) edges, one can use reattach_edges() afterwards.

Parameters: share_tensor (bool) – Boolean indicating whether the copied node should store its own copy of the tensor (False) or share it with the original node (True) storing a reference to it.
Return type: Node

Examples

>>> node = tk.randn(shape=(2, 3), name='node')
>>> copy = node.copy()
>>> node.tensor_address() != copy.tensor_address()
True

>>> torch.equal(node.tensor, copy.tensor)
True

If tensor is shared:

>>> copy = node.copy(True)
>>> node.tensor_address() == copy.tensor_address()
True

>>> torch.equal(node.tensor, copy.tensor)
True

change_type(leaf=False, data=False, virtual=False)[source]#

Changes node type, only if node is not a resultant node.

Parameters

leaf (bool) – Boolean indicating if the new node type is leaf.
data (bool) – Boolean indicating if the new node type is data.
virtual (bool) – Boolean indicating if the new node type is virtual.

ParamNode#

class tensorkrowch.ParamNode(shape=None, axes_names=None, name=None, network=None, virtual=False, override_node=False, tensor=None, edges=None, override_edges=False, node1_list=None, init_method=None, device=None, dtype=None, **kwargs)[source]#

Class for trainable nodes. Should be subclassed by any class of nodes that are intended to be trained (e.g. ParamStackNode).

Should be used as the initial nodes conforming the TensorNetwork, if it is going to be trained. When operating these initial nodes, the resultant nodes will be non-parameterized (e.g. Node, StackNode).

The main difference with Nodes is that ParamNodes have torch.nn.Parameter tensors instead of torch.Tensor. Therefore, a ParamNode is a sort of parameter that is attached to the TensorNetwork (which is itself a torch.nn.Module). That is, the list of parameters of the tensor network module contains the tensors of all ParamNodes.

ParamNodes can only be leaf and virtual (e.g. a virtual node used in a uniform TensorNetwork to store the tensor that is shared by all the trainable nodes must also be a ParamNode, since it stores a torch.nn.Parameter).

For a complete list of properties and methods, see also AbstractNode.

Parameters

shape (list[int], tuple[int] or torch.Size, optional) – Node’s shape, that is, the shape of its tensor. If shape and init_method are provided, a tensor will be made for the node. Otherwise, tensor would be required.
axes_names (list[str] or tuple[str], optional) – Sequence of names for each of the node’s axes. Names are used to access the edge that is attached to the node in a certain axis. Hence, they should be all distinct. They cannot contain blank spaces or special characters. By default, axes names will be "axis_0", …, "axis_n", being n the nummber of axes. If an axis’ name contains the word "batch", it will define a batch edge. The word "stack" cannot be used, since it is reserved for the stack edge of StackNode.
name (str, optional) – Node’s name, used to access the node from de TensorNetwork where it belongs. It cannot contain blank spaces. By default, it is the name of the class (e.g. "node", "paramnode").
network (TensorNetwork, optional) – Tensor network where the node should belong. If None, a new tensor network will be created to contain the node.
virtual (bool) – Boolean indicating if the node is a virtual node.
override_node (bool) – Boolean indicating whether the node should override (True) another node in the network that has the same name (e.g. if a node is parameterized, it would be required that a new ParamNode replaces the non-parameterized node in the network).
tensor (torch.Tensor, optional) – Tensor that is to be stored in the node. If None, shape and init_method will be required.
edges (list[Edge], optional) – List of edges that are to be attached to the node. This can be used in case the node inherits the edges from other node(s), like results from Operations.
override_edges (bool) – Boolean indicating whether the provided edges should be overriden (True) when reattached (e.g. if a node is parameterized, it would be required that the new ParamNode’s edges are indeed connected to it, instead of to the original non-parameterized node).
node1_list (list[bool], optional) – If edges are provided, the list of node1 attributes of each edge should also be provided.
init_method ({"zeros", "ones", "copy", "rand", "randn"}, optional) – Initialization method.
device (torch.device, optional) – Device where to initialize the tensor if init_method is provided.
dtype (torch.dtype, optional) – Dtype of the tensor if init_method is provided.
kwargs (float) – Keyword arguments for the different initialization methods. See AbstractNode.make_tensor().

Examples

>>> node = tk.ParamNode(shape=(2, 5, 2),
...                     axes_names=('left', 'input', 'right'),
...                     name='my_paramnode',
...                     init_method='randn',
...                     mean=0.,
...                     std=1.)
>>> node
ParamNode(
    name: my_paramnode
    tensor:
            Parameter containing:
            tensor([[[ 1.8090, -0.1371],
                     [-0.0501, -1.0371],
                     [ 1.4588, -0.8361],
                     [-0.4974, -1.9957],
                     [ 0.3760, -1.0412]],
                    [[ 0.3393, -0.2503],
                     [ 1.7752, -0.0188],
                     [-0.9561, -0.0806],
                     [-1.0465, -0.5731],
                     [ 1.5021,  0.4181]]], requires_grad=True)
    axes:
            [left
             input
             right]
    edges:
            [my_paramnode[left] <-> None
             my_paramnode[input] <-> None
             my_paramnode[right] <-> None])

Also, one can use one of the Initializers to simplify:

>>> node = tk.randn((2, 5, 2),
...                 param_node=True)
>>> node
ParamNode(
    name: paramnode
    tensor:
            Parameter containing:
            tensor([[[-0.8442,  1.4184],
                     [ 0.4431, -1.4385],
                     [-0.5161, -0.6492],
                     [ 0.2095,  0.5760],
                     [-0.9925, -1.5797]],
                    [[-0.8649, -0.5401],
                     [-0.1091,  1.1654],
                     [-0.3821, -0.2477],
                     [-0.7688, -2.4731],
                     [-0.0234,  0.9618]]], requires_grad=True)
    axes:
            [axis_0
             axis_1
             axis_2]
    edges:
            [paramnode[axis_0] <-> None
             paramnode[axis_1] <-> None
             paramnode[axis_2] <-> None])

property grad#

Returns gradient of the param-node’s tensor.

StackNode#

class tensorkrowch.StackNode(nodes=None, axes_names=None, name=None, network=None, override_node=False, tensor=None, edges=None, node1_list=None)[source]#

Class for stacked nodes. StackNodes are nodes that store the information of a list of nodes that are stacked via stack(), although they can also be instantiated directly. To do so, there are two options:

Provide a sequence of nodes: if nodes are provided, their tensors will be stacked and stored in the StackNode. It is necessary that all nodes are of the same class (Node or ParamNode), have the same rank (although dimension of each leg can be different for different nodes; in which case smaller tensors are extended with 0’s to match the dimensions of the largest tensor in the stack), same axes names (to ensure only the “same kind” of nodes are stacked), belong to the same network and have edges with the same type in each axis (Edge or ParamEdge).
Provide a stacked tensor: if the stacked tensor is provided, it is also necessary to specify the axes_names, network, edges and node1_list.

StackNodes have an additional axis for the new stack dimension, which is a batch edge. This way, some contractions can be computed in parallel by first stacking two sequences of nodes (connected pair-wise), performing the batch contraction and finally unbinding the StackNodes to retrieve just one sequence of nodes.

For the rest of the axes, a list of the edges corresponding to all nodes in the stack is stored, so that, when unbinding the stack, it can be inferred to which nodes the unbound nodes have to be connected.

Parameters

nodes (list[AbstractNode] or tuple[AbstractNode], optional) – Sequence of nodes that are to be stacked. They should all be of the same class (Node or ParamNode), have the same rank, same axes names and belong to the same network. They do not need to have equal shapes.
axes_names (list[str], tuple[str], optional) – Sequence of names for each of the node’s axes. Names are used to access the edge that is attached to the node in a certain axis. Hence, they should be all distinct. Necessary if nodes are not provided.
name (str, optional) – Node’s name, used to access the node from de TensorNetwork where it belongs. It cannot contain blank spaces.
network (TensorNetwork, optional) – Tensor network where the node should belong. Necessary if nodes are not provided.
override_node (bool, optional) – Boolean indicating whether the node should override (True) another node in the network that has the same name (e.g. if a node is parameterized, it would be required that a new ParamNode replaces the non-parameterized node in the network).
tensor (torch.Tensor, optional) – Tensor that is to be stored in the node. Necessary if nodes are not provided.
edges (list[Edge], optional) – List of edges that are to be attached to the node. Necessary if nodes are not provided.
node1_list (list[bool], optional) – If edges are provided, the list of node1 attributes of each edge should also be provided. Necessary if nodes are not provided.

Examples

>>> net = tk.TensorNetwork()
>>> nodes = [tk.randn(shape=(2, 4, 2),
...                   axes_names=('left', 'input', 'right'),
...                   network=net)
...          for _ in range(10)]
>>> data = [tk.randn(shape=(4,),
...                  axes_names=('feature',),
...                  network=net)
...         for _ in range(10)]
...
>>> for i in range(10):
...     _ = nodes[i]['input'] ^ data[i]['feature']
...
>>> stack_nodes = tk.stack(nodes)
>>> stack_data = tk.stack(data)
...
>>> # It is necessary to re-connect stacks
>>> _ = stack_nodes['input'] ^ stack_data['feature']
>>> result = tk.unbind(stack_nodes @ stack_data)
>>> print(result[0].name)
unbind_0

>>> result[0].axes
[Axis( left (0) ), Axis( right (1) )]

>>> result[0].shape
torch.Size([2, 2])

property edges_dict#: Returns dictionary where the keys are the axes. For each axis, the value is the list of all the edges (one from each node) that correspond to that axis.

property node1_lists_dict#: Returns dictionary where the keys are the axes. For each axis, the value is the list with the node1 attribute of that axis for all nodes.

reconnect(other)[source]#: Re-connects the StackNode to another (Param)StackNode, in the axes where the original stacked nodes were already connected.

unbind()#

Unbinds a StackNode or ParamStackNode, where the first dimension is assumed to be the stack dimension.

If auto_unbind() is set to False, each resultant node will store its own tensor. Otherwise, they will have only a reference to the corresponding slice of the (Param)StackNode.

See TensorNetwork to learn how the auto_unbind mode affects the computation of unbind().

Nodes resultant from this operation are called "unbind". The node that keeps information about the Successor is self.

Return type: list[Node]

Examples

>>> net = tk.TensorNetwork()
>>> nodes = [tk.randn(shape=(2, 4, 2),
...                   axes_names=('left', 'input', 'right'),
...                   network=net)
...          for _ in range(10)]
>>> data = [tk.randn(shape=(4,),
...                  axes_names=('feature',),
...                  network=net)
...         for _ in range(10)]
...
>>> for i in range(10):
...     _ = nodes[i]['input'] ^ data[i]['feature']
...
>>> stack_nodes = tk.stack(nodes)
>>> stack_data = tk.stack(data)
...
>>> # It is necessary to re-connect stacks
>>> _ = stack_nodes['input'] ^ stack_data['feature']
>>> result = stack_nodes @ stack_data
>>> result = result.unbind()
>>> print(result[0].name)
unbind_0

>>> result[0].axes
[Axis( left (0) ), Axis( right (1) )]

>>> result[0].shape
torch.Size([2, 2])

ParamStackNode#

class tensorkrowch.ParamStackNode(nodes, name=None, virtual=False, override_node=False)[source]#

Class for parametric stacked nodes. They are essentially the same as StackNodes but they are ParamNodes.

They are used to optimize memory usage and save some time when the first operation that occurs to param-nodes in a contraction (that might be computed several times during training) is stack(). If this is the case, the param-nodes no longer store their own tensors, but rather they make reference to a slide of a greater ParamStackNode (if auto_stack attribute of the TensorNetwork is set to True). Hence, that first stack() is never actually computed.

The ParamStackNode that results from this process has the name "virtual_result_stack", which contains the reserved name "virtual_result", as explained here. This node stores the tensor from which all the stacked ParamNodes just take one slice.

This behaviour occurs when stacking param-nodes via stack(), not when instantiating ParamStackNode manually.

ParamStackNodes can only be instantiated by providing a sequence of nodes.

Parameters

nodes (list[AbstractNode] or tuple[AbstractNode]) – Sequence of nodes that are to be stacked. They should all be of the same class (Node or ParamNode), have the same rank, same axes names and belong to the same network. They do not need to have equal shapes.
name (str, optional) – Node’s name, used to access the node from de TensorNetwork where it belongs. It cannot contain blank spaces.
virtual (bool, optional) – Boolean indicating if the node is a virtual node. Since it will be used mainly for the case described here, the node will be virtual, it will not be an effective part of the tensor network.
override_node (bool, optional) – Boolean indicating whether the node should override (True) another node in the network that has the same name (e.g. if a node is parameterized, it would be required that a new ParamNode replaces the non-parameterized node in the network).

Examples

>>> net = tk.TensorNetwork()
>>> net.auto_stack = True
>>> nodes = [tk.randn(shape=(2, 4, 2),
...                   axes_names=('left', 'input', 'right'),
...                   network=net,
...                   param_node=True)
...          for _ in range(10)]
>>> data = [tk.randn(shape=(4,),
...                  axes_names=('feature',),
...                  network=net)
...         for _ in range(10)]
...
>>> for i in range(10):
...     _ = nodes[i]['input'] ^ data[i]['feature']
...
>>> stack_nodes = tk.stack(nodes)
>>> stack_nodes.name = 'my_stack'
>>> print(nodes[0].tensor_address())
my_stack

>>> stack_data = tk.stack(data)
...
>>> # It is necessary to re-connect stacks
>>> _ = stack_nodes['input'] ^ stack_data['feature']
>>> result = tk.unbind(stack_nodes @ stack_data)
>>> print(result[0].name)
unbind_0

>>> print(result[0].axes)
[Axis( left (0) ), Axis( right (1) )]

>>> print(result[0].shape)
torch.Size([2, 2])

property edges_dict#: Returns dictionary where the keys are the axes. For each axis, the value is the list of all the edges (one from each node) that correspond to that axis.

property node1_lists_dict#: Returns dictionary where the keys are the axes. For each axis, the value is the list with the node1 attribute of that axis for all nodes.

reconnect(other)[source]#: Re-connects the StackNode to another (Param)StackNode, in the axes where the original stacked nodes were already connected.

unbind()#

Unbinds a StackNode or ParamStackNode, where the first dimension is assumed to be the stack dimension.

If auto_unbind() is set to False, each resultant node will store its own tensor. Otherwise, they will have only a reference to the corresponding slice of the (Param)StackNode.

See TensorNetwork to learn how the auto_unbind mode affects the computation of unbind().

Nodes resultant from this operation are called "unbind". The node that keeps information about the Successor is self.

Return type: list[Node]

Examples

>>> net = tk.TensorNetwork()
>>> nodes = [tk.randn(shape=(2, 4, 2),
...                   axes_names=('left', 'input', 'right'),
...                   network=net)
...          for _ in range(10)]
>>> data = [tk.randn(shape=(4,),
...                  axes_names=('feature',),
...                  network=net)
...         for _ in range(10)]
...
>>> for i in range(10):
...     _ = nodes[i]['input'] ^ data[i]['feature']
...
>>> stack_nodes = tk.stack(nodes)
>>> stack_data = tk.stack(data)
...
>>> # It is necessary to re-connect stacks
>>> _ = stack_nodes['input'] ^ stack_data['feature']
>>> result = stack_nodes @ stack_data
>>> result = result.unbind()
>>> print(result[0].name)
unbind_0

>>> result[0].axes
[Axis( left (0) ), Axis( right (1) )]

>>> result[0].shape
torch.Size([2, 2])

Edges#

Edge#

class tensorkrowch.Edge(node1, axis1, node2=None, axis2=None)[source]#

Base class for edges. Should be subclassed by any new class of edges.

An edge is nothing more than an object that wraps references to the nodes it connects. Thus, it stores information like the nodes it connects, the corresponding nodes’ axes it is attached to, whether it is dangling or batch, its size, etc.

Above all, its importance lies in that edges enable to connect nodes, forming any possible graph, and to perform easily Operations like contracting and splitting nodes.

Furthermore, edges have specific operations like contract() or svd() (and its variations), as well as in-place versions of them (contract_(), svd_(), etc.) that allow in-place modification of the TensorNetwork.

Parameters

node1 (AbstractNode) – First node to which the edge is connected.
axis1 (int, str or Axis) – Axis of node1 where the edge is attached.
node2 (AbstractNode, optional) – Second node to which the edge is connected. If None, the edge will be dangling.
axis2 (int, str, Axis, optional) – Axis of node2 where the edge is attached.

Examples

>>> nodeA = tk.randn((2, 3))
>>> nodeB = tk.randn((3, 4))
>>> _ = nodeA[1] ^ nodeB[0]
>>> nodeA[0]
Edge( node_0[axis_0] <-> None )  (Dangling Edge)

>>> nodeA[1]
Edge( node_0[axis_1] <-> node_1[axis_0] )

>>> nodeB[1]
Edge( node_1[axis_1] <-> None )  (Dangling Edge)

property node1#: Returns node1 of the edge.

property node2#: Returns node2 of the edge. If the edge is dangling, it is None.

property nodes#: Returns a list with node1 and node2.

property axis1#: Returns axis where the edge is attached to node1.

property axis2#: Returns axis where the edge is attached to node2. If the edge is dangling, it is None.

property axes#: Returns a list of axes where the edge is attached to node1 and node2, respectively.

property name#

Returns edge’s name. It is formed with the corresponding nodes’ and axes’ names.

Examples

>>> nodeA = tk.Node(shape=(2, 3),
...                 name='nodeA',
...                 axes_names=['left', 'right'])
>>> edge = nodeA['right']
>>> print(edge.name)
nodeA[right] <-> None

>>> nodeB = tk.Node(shape=(3, 4),
...                 name='nodeB',
...                 axes_names=['left', 'right'])
>>> _ = new_edge = nodeA['right'] ^ nodeB['left']
>>> print(new_edge.name)
nodeA[right] <-> nodeB[left]

is_dangling()[source]#: Returns boolean indicating whether the edge is a dangling edge.

is_batch()[source]#: Returns boolean indicating whether the edge is a batch edge.

is_attached_to(node)[source]#: Returns boolean indicating whether the edge is attached to node.

size()[source]#: Returns edge’s size. Equivalent to node’s shape in that axis.

change_size(size)[source]#

Changes size of the edge, thus changing the size of tensors of node1 and node2 at the corresponding axes. If new size is smaller, the tensor will be cropped; if larger, the tensor will be expanded with zeros. In both cases, the process (cropping/expanding) occurs at the “right”, “bottom”, “back”, etc. of each dimension.

Parameters: size (int) – New size of the edge.

Examples

>>> nodeA = tk.ones((2, 3))
>>> nodeB = tk.ones((3, 4))
>>> _ = edge = nodeA[1] ^ nodeB[0]
>>> edge.size()
3

>>> edge.change_size(4)
>>> nodeA.tensor
tensor([[1., 1., 1., 0.],
        [1., 1., 1., 0.]])

>>> nodeB.tensor
tensor([[1., 1., 1., 1.],
        [1., 1., 1., 1.],
        [1., 1., 1., 1.],
        [0., 0., 0., 0.]])

>>> edge.size()
4

>>> edge.change_size(2)
>>> nodeA.tensor
tensor([[1., 1.],
        [1., 1.]])

>>> nodeB.tensor
tensor([[1., 1., 1., 1.],
        [1., 1., 1., 1.]])

>>> edge.size()
2

copy()[source]#

Returns a copy of the edge, that is, a new edge referencing the same nodes at the same axes.

Examples

>>> nodeA = tk.randn((2, 3))
>>> nodeB = tk.randn((3, 4))
>>> _ = edge = nodeA[1] ^ nodeB[0]
>>> copy = edge.copy()
>>> copy != edge
True

>>> copy.is_attached_to(nodeA)
True

>>> copy.is_attached_to(nodeB)
True

connect(other)[source]#

Connects dangling edge to another dangling edge. It is necessary that both edges have the same size so that contractions along that edge can be computed.

Note that this connectes edges from leaf (or data, virtual) nodes, but never from resultant nodes. If one tries to connect one of the inherited edges of a resultant node, the new connected edge will be attached to the original leaf nodes from which the resultant node inherited its edges. Hence, the resultant node will not “see” the connection until the TensorNetwork is reset().

If the nodes that are being connected come from different networks, the node2 (and its connected component) will be moved to node1’s network. See also move_to_network().

Parameters: other (Edge) – The other edge to which current edge will be connected.
Return type: Edge

Examples

To connect two edges, the overloaded operator ^ can also be used.

>>> nodeA = tk.Node(shape=(2, 3),
...                 name='nodeA',
...                 axes_names=('left', 'right'))
>>> nodeB = tk.Node(shape=(3, 4),
...                 name='nodeB',
...                 axes_names=('left', 'right'))
>>> _ = new_edge = nodeA['right'] ^ nodeB['left']  # Same as .connect()
>>> print(new_edge.name)
nodeA[right] <-> nodeB[left]

disconnect()[source]#

Disconnects connected edge, that is, the connected edge is split into two dangling edges, one for each node.

Return type: tuple[Edge, Edge]

Examples

To disconnect an edge, the overloaded operator | can also be used.

>>> nodeA = tk.Node(shape=(2, 3),
...                 name='nodeA',
...                 axes_names=('left', 'right'))
>>> nodeB = tk.Node(shape=(3, 4),
...                 name='nodeB',
...                 axes_names=('left', 'right'))
>>> _ = new_edge = nodeA['right'] ^ nodeB['left']
>>> new_edgeA, new_edgeB = new_edge | new_edge  # Same as .disconnect()
>>> print(new_edgeA.name)
nodeA[right] <-> None

>>> print(new_edgeB.name)
nodeB[left] <-> None

contract()#

Contracts the nodes that are connected through the edge.

This only works if the nodes connected through the edge are leaf nodes. Otherwise, this will perform the contraction between the leaf nodes that were connected through this edge.

Nodes resultant from this operation are called "contract_edges". The node that keeps information about the Successor is self.node1.

Return type: Node

Examples

>>> nodeA = tk.randn(shape=(10, 15, 20),
...                  axes_names=('one', 'two', 'three'),
...                  name='nodeA')
>>> nodeB = tk.randn(shape=(10, 15, 20),
...                  axes_names=('one', 'two', 'three'),
...                  name='nodeB')
...
>>> _ = nodeA['one'] ^ nodeB['one']
>>> _ = nodeA['two'] ^ nodeB['two']
>>> _ = nodeA['three'] ^ nodeB['three']
>>> result = nodeA['one'].contract()
>>> result.shape
torch.Size([15, 20, 15, 20])

contract_()#

In-place version of contract().

Following the PyTorch convention, names of functions ended with an underscore indicate in-place operations.

Nodes resultant from this operation are called "contract_edges_ip".

Return type: Node

Examples

>>> nodeA = tk.randn(shape=(10, 15, 20),
...                  axes_names=('one', 'two', 'three'),
...                  name='nodeA')
>>> nodeB = tk.randn(shape=(10, 15, 20),
...                  axes_names=('one', 'two', 'three'),
...                  name='nodeB')
...
>>> _ = nodeA['one'] ^ nodeB['one']
>>> _ = nodeA['two'] ^ nodeB['two']
>>> _ = nodeA['three'] ^ nodeB['three']
>>> result = nodeA['one'].contract_()
>>> result.shape
torch.Size([15, 20, 15, 20])

nodeA and nodeB have been removed from the network.

>>> nodeA.network is None
True

>>> nodeB.network is None
True

>>> del nodeA
>>> del nodeB

qr()#

Contracts an edge via contract() and splits it via split() using mode = "qr". See split() for a more complete explanation.

This only works if the nodes connected through the edge are leaf nodes. Otherwise, this will perform the contraction between the leaf nodes that were connected through this edge.

Return type: tuple[Node, Node]

Examples

>>> nodeA = tk.randn(shape=(10, 15, 100),
...                  axes_names=('left', 'right', 'batch'),
...                  name='nodeA')
>>> nodeB = tk.randn(shape=(15, 20, 100),
...                  axes_names=('left', 'right', 'batch'),
...                  name='nodeB')
...
>>> new_edge = nodeA['right'] ^ nodeB['left']
>>> new_nodeA, new_nodeB = new_edge.qr()
...
>>> new_nodeA.shape
torch.Size([10, 10, 100])

>>> new_nodeB.shape
torch.Size([10, 20, 100])

>>> print(new_nodeA.axes_names)
['left', 'right', 'batch']

>>> print(new_nodeB.axes_names)
['left', 'right', 'batch']

Original nodes still exist in the network

>>> assert nodeA.network == new_nodeA.network
>>> assert nodeB.network == new_nodeB.network

qr_()#

In-place version of qr().

Contracts an edge in-place via contract_() and splits it in-place via split_() using mode = "qr". See split() for a more complete explanation.

Following the PyTorch convention, names of functions ended with an underscore indicate in-place operations.

Nodes resultant from this operation use the same names as the original nodes connected by self.

Return type: tuple[Node, Node]

Examples

>>> nodeA = tk.randn(shape=(10, 15, 100),
...                  axes_names=('left', 'right', 'batch'),
...                  name='nodeA')
>>> nodeB = tk.randn(shape=(15, 20, 100),
...                  axes_names=('left', 'right', 'batch'),
...                  name='nodeB')
...
>>> new_edge = nodeA['right'] ^ nodeB['left']
>>> nodeA, nodeB = new_edge.qr_()
...
>>> nodeA.shape
torch.Size([10, 10, 100])

>>> nodeB.shape
torch.Size([10, 20, 100])

>>> print(nodeA.axes_names)
['left', 'right', 'batch']

>>> print(nodeB.axes_names)
['left', 'right', 'batch']

rq()#

Contracts an edge via contract() and splits it via split() using mode = "rq". See split() for a more complete explanation.

This only works if the nodes connected through the edge are leaf nodes. Otherwise, this will perform the contraction between the leaf nodes that were connected through this edge.

Return type: tuple[Node, Node]

Examples

>>> nodeA = tk.randn(shape=(10, 15, 100),
...                  axes_names=('left', 'right', 'batch'),
...                  name='nodeA')
>>> nodeB = tk.randn(shape=(15, 20, 100),
...                  axes_names=('left', 'right', 'batch'),
...                  name='nodeB')
...
>>> new_edge = nodeA['right'] ^ nodeB['left']
>>> new_nodeA, new_nodeB = new_edge.rq()
...
>>> new_nodeA.shape
torch.Size([10, 10, 100])

>>> new_nodeB.shape
torch.Size([10, 20, 100])

>>> print(new_nodeA.axes_names)
['left', 'right', 'batch']

>>> print(new_nodeB.axes_names)
['left', 'right', 'batch']

Original nodes still exist in the network

>>> assert nodeA.network == new_nodeA.network
>>> assert nodeB.network == new_nodeB.network

rq_()#

In-place version of rq().

Contracts an edge in-place via contract_() and splits it in-place via split_() using mode = "qr". See split() for a more complete explanation.

Following the PyTorch convention, names of functions ended with an underscore indicate in-place operations.

Nodes resultant from this operation use the same names as the original nodes connected by self.

Return type: tuple[Node, Node]

Examples

>>> nodeA = tk.randn(shape=(10, 15, 100),
...                  axes_names=('left', 'right', 'batch'),
...                  name='nodeA')
>>> nodeB = tk.randn(shape=(15, 20, 100),
...                  axes_names=('left', 'right', 'batch'),
...                  name='nodeB')
...
>>> new_edge = nodeA['right'] ^ nodeB['left']
>>> nodeA, nodeB = tk.rq_(new_edge)
...
>>> nodeA.shape
torch.Size([10, 10, 100])

>>> nodeB.shape
torch.Size([10, 20, 100])

>>> print(nodeA.axes_names)
['left', 'right', 'batch']

>>> print(nodeB.axes_names)
['left', 'right', 'batch']

svd(side='left', rank=None, cum_percentage=None, cutoff=None)#

Contracts an edge via contract() and splits it via split() using mode = "svd". See split() for a more complete explanation.

This only works if the nodes connected through the edge are leaf nodes. Otherwise, this will perform the contraction between the leaf nodes that were connected through this edge.

Parameters

side (str, optional) – Indicates the side to which the diagonal matrix \(S\) should be contracted. If “left”, the first resultant node’s tensor will be \(US\), and the other node’s tensor will be \(V^{\dagger}\). If “right”, their tensors will be \(U\) and \(SV^{\dagger}\), respectively.
rank (int, optional) – Number of singular values to keep.
cum_percentage (float, optional) –
Proportion that should be satisfied between the sum of all singular values kept and the total sum of all singular values.

\[\frac{\sum_{i \in \{kept\}}{s_i}}{\sum_{i \in \{all\}}{s_i}} \ge cum\_percentage\]
cutoff (float, optional) – Quantity that lower bounds singular values in order to be kept.

Return type

tuple[Node, Node]

Examples

>>> nodeA = tk.randn(shape=(10, 15, 100),
...                  axes_names=('left', 'right', 'batch'),
...                  name='nodeA')
>>> nodeB = tk.randn(shape=(15, 20, 100),
...                  axes_names=('left', 'right', 'batch'),
...                  name='nodeB')
...
>>> new_edge = nodeA['right'] ^ nodeB['left']
>>> new_nodeA, new_nodeB = new_edge.svd(rank=7)
...
>>> new_nodeA.shape
torch.Size([10, 7, 100])

>>> new_nodeB.shape
torch.Size([7, 20, 100])

>>> print(new_nodeA.axes_names)
['left', 'right', 'batch']

>>> print(new_nodeB.axes_names)
['left', 'right', 'batch']

Original nodes still exist in the network

>>> assert nodeA.network == new_nodeA.network
>>> assert nodeB.network == new_nodeB.network

svd_(side='left', rank=None, cum_percentage=None, cutoff=None)#

In-place version of svd().

Contracts an edge in-place via contract_() and splits it in-place via split_() using mode = "svd". See split() for a more complete explanation.

Following the PyTorch convention, names of functions ended with an underscore indicate in-place operations.

Nodes resultant from this operation use the same names as the original nodes connected by self.

Parameters

side (str, optional) – Indicates the side to which the diagonal matrix \(S\) should be contracted. If “left”, the first resultant node’s tensor will be \(US\), and the other node’s tensor will be \(V^{\dagger}\). If “right”, their tensors will be \(U\) and \(SV^{\dagger}\), respectively.
rank (int, optional) – Number of singular values to keep.
cum_percentage (float, optional) –
Proportion that should be satisfied between the sum of all singular values kept and the total sum of all singular values.

\[\frac{\sum_{i \in \{kept\}}{s_i}}{\sum_{i \in \{all\}}{s_i}} \ge cum\_percentage\]
cutoff (float, optional) – Quantity that lower bounds singular values in order to be kept.

Return type

tuple[Node, Node]

Examples

>>> nodeA = tk.randn(shape=(10, 15, 100),
...                  axes_names=('left', 'right', 'batch'),
...                  name='nodeA')
>>> nodeB = tk.randn(shape=(15, 20, 100),
...                  axes_names=('left', 'right', 'batch'),
...                  name='nodeB')
...
>>> new_edge = nodeA['right'] ^ nodeB['left']
>>> nodeA, nodeB = new_edge.svd_(rank=7)
...
>>> nodeA.shape
torch.Size([10, 7, 100])

>>> nodeB.shape
torch.Size([7, 20, 100])

>>> print(nodeA.axes_names)
['left', 'right', 'batch']

>>> print(nodeB.axes_names)
['left', 'right', 'batch']

svdr(side='left', rank=None, cum_percentage=None, cutoff=None)#

Contracts an edge via contract() and splits it via split() using mode = "svdr". See split() for a more complete explanation.

This only works if the nodes connected through the edge are leaf nodes. Otherwise, this will perform the contraction between the leaf nodes that were connected through this edge.

Parameters

side (str, optional) – Indicates the side to which the diagonal matrix \(S\) should be contracted. If “left”, the first resultant node’s tensor will be \(US\), and the other node’s tensor will be \(V^{\dagger}\). If “right”, their tensors will be \(U\) and \(SV^{\dagger}\), respectively.
rank (int, optional) – Number of singular values to keep.
cum_percentage (float, optional) –
Proportion that should be satisfied between the sum of all singular values kept and the total sum of all singular values.

\[\frac{\sum_{i \in \{kept\}}{s_i}}{\sum_{i \in \{all\}}{s_i}} \ge cum\_percentage\]
cutoff (float, optional) – Quantity that lower bounds singular values in order to be kept.

Return type

tuple[Node, Node]

Examples

>>> nodeA = tk.randn(shape=(10, 15, 100),
...                  axes_names=('left', 'right', 'batch'),
...                  name='nodeA')
>>> nodeB = tk.randn(shape=(15, 20, 100),
...                  axes_names=('left', 'right', 'batch'),
...                  name='nodeB')
...
>>> new_edge = nodeA['right'] ^ nodeB['left']
>>> new_nodeA, new_nodeB = new_edge.svdr(rank=7)
...
>>> new_nodeA.shape
torch.Size([10, 7, 100])

>>> new_nodeB.shape
torch.Size([7, 20, 100])

>>> print(new_nodeA.axes_names)
['left', 'right', 'batch']

>>> print(new_nodeB.axes_names)
['left', 'right', 'batch']

Original nodes still exist in the network

>>> assert nodeA.network == new_nodeA.network
>>> assert nodeB.network == new_nodeB.network

svdr_(side='left', rank=None, cum_percentage=None, cutoff=None)#

In-place version of svdr().

Contracts an edge in-place via contract_() and splits it in-place via split_() using mode = "svdr". See split() for a more complete explanation.

Following the PyTorch convention, names of functions ended with an underscore indicate in-place operations.

Nodes resultant from this operation use the same names as the original nodes connected by self.

Parameters

side (str, optional) – Indicates the side to which the diagonal matrix \(S\) should be contracted. If “left”, the first resultant node’s tensor will be \(US\), and the other node’s tensor will be \(V^{\dagger}\). If “right”, their tensors will be \(U\) and \(SV^{\dagger}\), respectively.
rank (int, optional) – Number of singular values to keep.
cum_percentage (float, optional) –
Proportion that should be satisfied between the sum of all singular values kept and the total sum of all singular values.

\[\frac{\sum_{i \in \{kept\}}{s_i}}{\sum_{i \in \{all\}}{s_i}} \ge cum\_percentage\]
cutoff (float, optional) – Quantity that lower bounds singular values in order to be kept.

Return type

tuple[Node, Node]

Examples

>>> nodeA = tk.randn(shape=(10, 15, 100),
...                  axes_names=('left', 'right', 'batch'),
...                  name='nodeA')
>>> nodeB = tk.randn(shape=(15, 20, 100),
...                  axes_names=('left', 'right', 'batch'),
...                  name='nodeB')
...
>>> new_edge = nodeA['right'] ^ nodeB['left']
>>> nodeA, nodeB = new_edge.svdr_(rank=7)
...
>>> nodeA.shape
torch.Size([10, 7, 100])

>>> nodeB.shape
torch.Size([7, 20, 100])

>>> print(nodeA.axes_names)
['left', 'right', 'batch']

>>> print(nodeB.axes_names)
['left', 'right', 'batch']

StackEdge#

class tensorkrowch.StackEdge(edges, node1_list, node1, axis1, node2=None, axis2=None)[source]#

Class for stacked edges. They are just like Edges but used when stacking a collection of nodes into a StackNode. When doing this, all edges of the stacked nodes must be kept, since they have the information regarding the nodes’ neighbours, which will be used when :func: unbinding <unbind> the stack.

Parameters

edges (list[Edge]) – List of edges (one from each node that is being stacked) that are attached to the equivalent of axis1 in each node.
node1_list (list[bool]) – List of axis1 attributes (one from each node that is being stacked) of the equivalent of axis1 in each node.
node1 (StackNode or ParamStackNode) – First node to which the edge is connected.
axis1 (int, str or Axis) – Axis of node1 where the edge is attached.
node2 (StackNode or ParamStackNode, optional) – Second node to which the edge is connected. If None, the edge will be dangling.
axis2 (int, str, Axis, optional) – Axis of node2 where the edge is attached.

property edges#: Returns list of stacked edges corresponding to this axis.

property node1_list#: Returns list of node1’s corresponding to this axis.

connect(other)[source]#

Same as connect() but it is first verified that all stacked edges() corresponding to both StackEdges are the same.

That is, this is a redundant operation to re-connect a list of edges that should be already connected. However, this is mandatory, since when stacking two sequences of nodes independently it cannot be inferred that the resultant StackNodes had to be connected.

Parameters: other (StackEdge) – The other edge to which current edge will be connected.
Return type: StackEdge

Examples

To connect two stack-edges, the overloaded operator ^ can also be used.

>>> net = tk.TensorNetwork()
>>> nodes = [tk.randn(shape=(2, 4, 2),
...                   axes_names=('left', 'input', 'right'),
...                   network=net)
...          for _ in range(10)]
>>> data = [tk.randn(shape=(4,),
...                  axes_names=('feature',),
...                  network=net)
...         for _ in range(10)]
...
>>> for i in range(10):
...     _ = nodes[i]['input'] ^ data[i]['feature']
...
>>> stack_nodes = tk.stack(nodes)
>>> stack_data = tk.stack(data)
...
>>> # It is necessary to re-connect stacks to be able to contract
>>> _ = new_edge = stack_nodes['input'] ^ stack_data['feature']
>>> print(new_edge.name)
stack_0[input] <-> stack_1[feature]

Successor#

class tensorkrowch.Successor(node_ref, index, child, hints=None)[source]#

Class for successors. This is a sort of cache memory for Operations that have been already computed.

For instance, when contracting two nodes, the result gives a new node that stores the tensor resultant from contracting both nodes’ tensors. However, when training a TensorNetwork, the tensors inside the nodes will change every epoch, but there is actually no need to create a new resultant node every time. Instead, it is more efficient to keep track of which node arose as the result of an operation, and simply change its tensor.

Hence, a Successor is instantiated providing details to get the operand nodes’ tensors, as well as a reference to the resultant node, and some hints that might help accelerating the computations the next time the operation is performed.

These properties can be accessed via successor.node_ref, successor.index, successor.child and successor.hints.

See the different operations to learn which resultant node keeps the Successor information.

Parameters

node_ref (Node, ParamNode, or list[Node, ParamNode]) – For the nodes that are involved in an operation, this are the corresponding nodes that store their tensors.
index (list[int, slice] or list[list[int, slice]], optional) – For the nodes that are involved in an operation, this are the corresponding indices used to access their tensors.
child (Node or list[Node]) – The node or list of nodes that result from an operation.
hints (any, optional) – A dictionary of hints created the first time an operation is computed in order to save some computation in the next calls of the operation.

Examples

When contracting two nodes, a Successor is created and added to the list of successors of the first node (left operand).

>>> nodeA = tk.randn(shape=(2, 3), axes_names=('left', 'right'))
>>> nodeB = tk.randn(shape=(3, 4), axes_names=('left', 'right'))
>>> _ = nodeA['right'] ^ nodeB['left']
...
>>> # Contract nodes
>>> result = nodeA @ nodeB
>>> print(result.name)
contract_edges

>>> # To get a successor, the name of the operation and the arguments have
>>> # to be provided as keys of the successors dictionary
>>> nodeA.successors['contract_edges'][(None, nodeA, nodeB)].child == result
True

Tensor Network#

class tensorkrowch.TensorNetwork(name=None)[source]#

Class for arbitrary Tensor Networks. Subclass of PyTorch torch.nn.Module.

Tensor Networks are the central objects of TensorKrowch. Basically, a tensor network is a graph with vertices (Nodes) connected by Edges. In these models, nodes’ tensors will be trained so that the contraction of the whole network approximates a certain function. Hence, TensorNetwork’s are the trainable objects of TensorKrowch, very much like torch.nn.Module’s are the trainable objects of PyTorch.

Recall that the common way of defining models out of torch.nn.Module is by defining a subclass where the __init__ and forward methods are overriden:

__init__: Defines the model itself (its layers, attributes, etc.).
forward: Defines the way the model operates, that is, how the different parts of the model might combine to get an output from a particular input.

With TensorNetwork, the workflow is similar, though there are other methods that should be overriden:

__init__: Defines the graph of the tensor network and initializes the tensors of the nodes. See AbstractNode and Edge to learn how to create nodes and connect them.
set_data_nodes (optional): Creates the data nodes where the data tensor(s) will be placed. Usually, it will just select the edges to which the data nodes should be connected, and call the parent method. See set_data_nodes() to learn good practices to override it. See also add_data().
add_data (optional): Adds new data tensors that will be stored in data nodes. Usually it will not be necessary to override this method, but if one wants to customize how data is set into the data nodes, add_data() can be overriden.
contract: Defines the contraction algorithm of the whole tensor network, thus returning a single node. Very much like forward this is the main method that describes how the components of the network are combined. Hence, in TensorNetwork the forward() method shall not be overriden, since it will just call set_data_nodes(), if needed, add_data() and contract() and then it will return the tensor corresponding to the last resultant node. Hence, the order in which Operations are called from contract is important. The last operation must be the one returning the final node.

Although one can define how the network is going to be contracted, there are a couple of modes that can change how this contraction behaves at a lower level:

auto_stack (False by default): This mode indicates whether the operation stack() can take control of the memory management of the network to skip some steps in future computations. If auto_stack is set to True and a collection of ParamNodes are stacked (as the first operation in which these nodes are involved), then those nodes will no longer store their own tensors, but rather a virtual ParamStackNode will store the stacked tensor, avoiding the computation of that first stack() in every contraction. This behaviour is not possible if auto_stack is set to False, in which case all nodes will always store their own tensors.

Setting auto_stack to True will be faster for both inference and training. However, while experimenting with TensorNetwork’s one might want that all nodes store their own tensors to avoid problems.
auto_unbind (False by default): This mode indicates whether the operation unbind() has to actually unbind the stacked tensor or just generate a collection of references. That is, if auto_unbind is set to False, unbind() creates a collection of nodes, each of them storing the corresponding slice of the stacked tensor. If auto_unbind is set to True, unbind() just creates the nodes and gives each of them an index to reference the stacked tensor, so that each node’s tensor would be retrieved by indexing the stack. This avoids performing the operation, since these indices will be the same in subsequent iterations.

Setting auto_unbind to True will be faster for inference, but slower for training.

Once the training algorithm starts, these modes should not be changed (very often at least), since changing them entails first resetting the whole network, which is a costly method.

When the TensorNetwork is defined, it has a bunch of leaf, data and virtual nodes that make up the network structure, each of them storing its own tensor. However, when the network is contracted, several resultant nodes become new members of the network, even modifying its memory (depending on the auto_stack and auto_unbind modes).

Therefore, if one wants to reset() the network to its initial state after performing some operations, all the resultant nodes should be deleted, and all the tensors should return to its nodes (each node stores its own tensor). This is exactly what reset() does. Besides, since auto_stack and auto_unbind can change how the tensors are stored, if one wants to change these modes, the network should be first reset (this is already done automatically when changing the modes).

See AbstractNode to learn about the 4 excluding types of nodes, and reset() to learn about how these nodes are treated differently.

There are also some special nodes that one should take into account. These are specified by name. See AbstractNode to learn about reserved nodes’ names, and reset() to learn about how these nodes are treated differently.

To add a custom enumeration to keep track of the nodes of the network in a user-defined way, one may use brackets or parenthesis: "name_({number})".

For an example, check this tutorial.

Parameters: name (str, optional) – Network’s name. By default, it is the name of the class (e.g. "tensornetwork").

property nodes#: Returns dictionary with all the nodes belonging to the network (leaf, data, virtual and resultant).

property nodes_names#: Returns list of names of all the nodes belonging to the network (leaf, data, virtual and resultant).

property leaf_nodes#: Returns dictionary of leaf nodes of the network.

property data_nodes#: Returns dictionary of data nodes of the network.

property virtual_nodes#: Returns dictionary of virtual nodes of the network.

property resultant_nodes#: Returns dictionary of resultant nodes of the network.

property edges#: Returns list of dangling, non-batch edges of the network. Dangling edges from virtual nodes are not included.

property auto_stack#

Returns boolean indicating whether auto_stack mode is active. By default, it is True.

This mode indicates whether the operation stack() can take control of the memory management of the network to skip some steps in future computations. If auto_stack is set to True and a collection of ParamNodes are stacked (as the first operation in which these nodes are involved), then those nodes will no longer store their own tensors, but rather a virtual ParamStackNode will store the stacked tensor, avoiding the computation of that first stack() in every contraction. This behaviour is not possible if auto_stack is set to False, in which case all nodes will always store their own tensors.

Setting auto_stack to True will be faster for both inference and training. However, while experimenting with TensorNetwork’s one might want that all nodes store their own tensors to avoid problems.

Be aware that changing auto_stack mode entails resetting the network, which will modify its nodes. This has to be done manually in order to avoid undesired behaviour.

property auto_unbind#

Returns boolean indicating whether auto_unbind mode is active. By default, it is False.

This mode indicates whether the operation unbind() has to actually unbind the stacked tensor or just generate a collection of references. That is, if auto_unbind is set to False, unbind() creates a collection of nodes, each of them storing the corresponding slice of the stacked tensor. If auto_unbind is set to True, unbind() just creates the nodes and gives each of them an index to reference the stacked tensor, so that each node’s tensor would be retrieved by indexing the stack. This avoids performing the operation, since these indices will be the same in subsequent iterations.

Setting auto_unbind to True will be faster for inference, but slower for training.

Be aware that changing auto_unbind mode entails resetting the network, which will modify its nodes. Thus, this mode has to be changed manually in order to avoid undesired behaviour.

delete_node(node, move_names=True)[source]#

Disconnects node from all its neighbours and removes it from the network. To completely get rid of the node, do not forget to delete it:

>>> del node

or override it:

>>> node = node.copy()  # .copy() calls to .delete_node()

Parameters

node (Node or ParamNode) – Node to be deleted.
move_names (bool) – Boolean indicating whether names’ enumerations should be decreased when removing a node (True) or kept as they are (False). This is useful when several nodes are being modified at once, and each resultant node has the same enumeration as the corresponding original node.

Examples

>>> nodeA = tk.randn((2, 3))
>>> nodeB = tk.randn((3, 4))
>>> _ = nodeA[1] ^ nodeB[0]
>>> print(nodeA.name, nodeB.name)
node_0 node_1

>>> nodeB.network.delete_node(nodeB)
>>> nodeA.neighbours() == []
True

>>> print(nodeA.name)
node

If move_names is set to False, enumeration is not removed. Useful to avoid managing enumeration of a list of nodes that are all going to be deleted.

>>> nodeA = tk.randn((2, 3))
>>> nodeB = tk.randn((3, 4))
>>> _ = nodeA[1] ^ nodeB[0]
>>> nodeB.network.delete_node(nodeB, False)
>>> print(nodeA.name)
node_0

copy()[source]#: Copies the tensor network (via copy.deepcopy).

parameterize(set_param=True, override=False)[source]#

Parameterizes all leaf nodes of the network. If there are resultant nodes in the TensorNetwork, it will be first reset().

Parameters

set_param (bool) – Boolean indicating whether the tensor network has to be parameterized (True) or de-parameterized (False).
override (bool) – Boolean indicating whether the tensor network should be parameterized in-place (True) or copied and then parameterized (False).

set_data_nodes(input_edges, num_batch_edges)[source]#

Creates data nodes with as many batch edges as num_batch_edges and one feature edge. Then it connects each of these nodes’ feature edges to an edge from the list input_edges (following the provided order). Thus, edges in input_edges need to be dangling. Also, if there are already data nodes (or the "stack_data_memory") in the network, they should be unset() first.

If all the data nodes have the same shape, a virtual node will contain all the tensors stacked in one, what will save some memory and time in computations. This node is "stack_data_memory". See AbstractNode to learn more about this node.

If this method is overriden in subclasses, it can be done in two flavours:

def set_data_nodes(self):
    # Collect input edges
    input_edges = [node_1[i], ..., node_n[j]]

    # Define number of batches
    num_batch_edges = m

    # Call parent method
    super().set_data_nodes(input_edges, num_batch_edges)

def set_data_nodes(self):
    # Create data nodes directly
    data_nodes = [
        tk.Node(shape=(batch_1, ..., batch_m, feature_dim),
                       axes_names=('batch_1', ..., 'batch_m', 'feature')
                       network=self,
                       data=True)
        for _ in range(n)]

    # Connect them with the leaf nodes
    for i, data_node in enumerate(data_nodes):
        data_node['feature'] ^ self.my_nodes[i]['input']

If this method is overriden, there is no need to call it explicitly during training, since it will be done in the forward() call.

On the other hand, if one does not override set_data_nodes, it should be called before starting training.

Parameters

input_edges (list[Edge]) – List of edges to which the data nodes’ feature edges will be connected.
num_batch_edges (int) – Number of batch edges in the data nodes.

Examples

>>> nodeA = tk.Node(shape=(2, 5, 2),
...                 axes_names=('left', 'input', 'right'),
...                 name='nodeA',
...                 init_method='randn')
>>> nodeB = tk.Node(shape=(2, 5, 2),
...                 axes_names=('left', 'input', 'right'),
...                 name='nodeB',
...                 init_method='randn')
>>> _ = nodeA['right'] ^ nodeB['left']
...
>>> net = nodeA.network
>>> input_edges = [nodeA['input'], nodeB['input']]
>>> net.set_data_nodes(input_edges, 1)
>>> list(net.data_nodes.keys())
['data_0', 'data_1']

>>> net['data_0']
Node(
    name: data_0
    tensor:
            None
    axes:
            [batch
             feature]
    edges:
            [data_0[batch] <-> None
             data_0[feature] <-> nodeA[input]])

unset_data_nodes()[source]#: Deletes all data nodes (including the "stack_data_memory" when this node exists).

add_data(data)[source]#

Adds data tensor(s) to data nodes, that is, changes their tensors by new data tensors when a new batch is provided.

If all data nodes have the same shape, thus having its tensor stored in "stack_data_memory", the whole data tensor will be stored by this node. The data nodes will just store a reference to a slice of that tensor.

Otherwise, each tensor in the list (data) will be stored by each data node in the network, in the order they appear in data_nodes().

If one wants to customize how data is set into the data nodes, this method can be overriden.

Parameters

data (torch.Tensor or list[torch.Tensor]) –

If all data nodes have the same shape, thus having its tensor stored in "stack_data_memory", data should be a tensor of shape

\[batch\_size_{0} \times ... \times batch\_size_{n} \times n_{features} \times feature\_dim\]

Otherwise, it should be a list with \(n_{features}\) elements, each of them being a tensor with shape

\[batch\_size_{0} \times ... \times batch\_size_{n} \times feature\_dim\]

Examples

>>> nodeA = tk.Node(shape=(3, 5, 3),
...                 axes_names=('left', 'input', 'right'),
...                 name='nodeA',
...                 init_method='randn')
>>> nodeB = tk.Node(shape=(3, 5, 3),
...                 axes_names=('left', 'input', 'right'),
...                 name='nodeB',
...                 init_method='randn')
>>> _ = nodeA['right'] ^ nodeB['left']
...
>>> net = nodeA.network
>>> input_edges = [nodeA['input'], nodeB['input']]
>>> net.set_data_nodes(input_edges, 1)
...
>>> net.add_data(torch.randn(100, 2, 5))
>>> net['data_0'].shape
torch.Size([100, 5])

reset()[source]#

Resets the TensorNetwork to its initial state, before computing any non-in-place Operation. Different actions apply to different types of nodes:

leaf: These nodes retrieve their tensors in case they were just referencing a slice of the tensor in the ParamStackNode that is created when stacking ParamNodes (if auto_stack mode is active). If there is a "virtual_uniform" node in the network from which all leaf nodes take their tensor, this is not modified.
virtual: Only virtual nodes created in operations are deleted. This only includes nodes using the reserved name "virtual_result".
resultant: These nodes are deleted from the network.

Also, the dictionaries of Successors of all leaf and data nodes are emptied.

The TensorNetwork is automatically reset when parameterizing it, changing auto_stack() or auto_unbind() modes, or tracing.

See AbstractNode to learn more about the 4 types of nodes and the reserved names.

For an example, check this tutorial.

trace(example=None, *args, **kwargs)[source]#

Traces the tensor network contraction algorithm with two purposes:

Create all the intermediate resultant nodes that result from Operations so that in the next contractions only the tensor operations have to be computed, thus saving a lot of time.
Keep track of the tensors that are used to compute operations, so that intermediate results that are not useful anymore can be deleted, thus saving a lot of memory. This is achieved by constructing an inverse_memory that, given a memory address, stores the nodes that use the tensor located in that address of the network’s memory.

To trace a tensor network, it is necessary to provide the same arguments that would be required in the forward call. In case the tensor network is contracted with some input data, an example tensor with batch dimension 1 and filled with zeros would be enough to trace the contraction.

For an example, check this tutorial.

Parameters

example (torch.Tensor, optional) – Example tensor used to trace the contraction of the tensor network. In case the tensor network is contracted with some input data, an example tensor with batch dimension 1 and filled with zeros would be enough to trace the contraction.
args – Arguments that might be used in contract().
kwargs – Keyword arguments that might be used in contract().

contract()[source]#: Contracts the whole tensor network returning a single Node. This method is not implemented and subclasses of TensorNetwork should override it to define the contraction algorithm of the network.

forward(data=None, *args, **kwargs)[source]#

Contracts TensorNetwork with input data. It can be called using the __call__ operator ().

Overrides the forward method of PyTorch’s torch.nn.Module. Sets data nodes automatically whenever set_data_nodes() is overriden, adds data tensor(s) to these nodes, and contracts the whole network according to contract(), returning a single torch.Tensor.

Furthermore, to optimize the contraction algorithm during training, once the TensorNetwork is traced, all that forward does is calling the different Operations used in contract() in the same order they appeared in the code. Hence, the last operation in contract() should be the one that returns the single output Node.

For an example, check this tutorial.

Parameters

data (torch.Tensor or list[torch.Tensor], optional) –
If all data nodes have the same shape, thus having its tensor stored in "stack_data_memory", data should be a tensor of shape

\[batch\_size_{0} \times ... \times batch\_size_{n} \times n_{features} \times feature\_dim\]

Otherwise, it should be a list with \(n_{features}\) elements, each of them being a tensor with shape

\[batch\_size_{0} \times ... \times batch\_size_{n} \times feature\_dim\]

Also, it is not necessary that the network has data nodes, thus None is also valid.
args – Arguments that might be used in contract().
kwargs – Keyword arguments that might be used in contract().

Components

Contents

Components#

Axis#

Nodes#

AbstractNode#

Node#

ParamNode#

StackNode#

ParamStackNode#

Edges#

Edge#

StackEdge#

Successor#

Tensor Network#