Function _map_graph_network

tensorflow/python/keras/engine/network.py:1653–1834

Validates a network's topology and gather its layers and nodes. Arguments: inputs: List of input tensors. outputs: List of outputs tensors. Returns: A tuple `(nodes, nodes_by_depth, layers, layers_by_depth)`. - nodes: list of Node instances. - nodes_by_depth: dict mapping i

(inputs, outputs)

def _map_graph_network(inputs, outputs):
  """Validates a network's topology and gather its layers and nodes.

  Arguments:
    inputs: List of input tensors.
    outputs: List of outputs tensors.

  Returns:
    A tuple `(nodes, nodes_by_depth, layers, layers_by_depth)`.
    - nodes: list of Node instances.
    - nodes_by_depth: dict mapping ints (depth) to lists of node instances.
    - layers: list of Layer instances.
    - layers_by_depth: dict mapping ints (depth) to lists of layer instances.

  Raises:
    ValueError: In case the network is not valid (e.g. disconnected graph).
  """
  # Network_nodes: set of nodes included in the graph of layers
  # (not all nodes included in the layers are relevant to the current graph).
  network_nodes = set()  # ids of all nodes relevant to the Network
  nodes_depths = {}  # dict {node: depth value}
  layers_depths = {}  # dict {layer: depth value}
  layer_indices = {}  # dict {layer: index in traversal}
  nodes_in_decreasing_depth = []

  def build_map(tensor,
                finished_nodes,
                nodes_in_progress,
                layer,
                node_index,
                tensor_index):
    """Builds a map of the graph of layers.

    This recursively updates the map `layer_indices`,
    the list `nodes_in_decreasing_depth` and the set `network_nodes`.

    Arguments:
        tensor: Some tensor in a graph.
        finished_nodes: Set of nodes whose subgraphs have been traversed
            completely. Useful to prevent duplicated work.
        nodes_in_progress: Set of nodes that are currently active on the
            recursion stack. Useful to detect cycles.
        layer: Layer from which `tensor` comes from. If not provided,
            will be obtained from `tensor._keras_history`.
        node_index: Node index from which `tensor` comes from.
        tensor_index: Tensor_index from which `tensor` comes from.

    Raises:
        ValueError: if a cycle is detected.
    """
    node = layer._inbound_nodes[node_index]  # pylint: disable=protected-access

    # Prevent cycles.
    if node in nodes_in_progress:
      raise ValueError('The tensor ' + str(tensor) + ' at layer "' +
                       layer.name + '" is part of a cycle.')

    # Don't repeat work for shared subgraphs