composite_node

[flow_graph.composite_node]

A node that encapsulates a collection of other nodes as a first class graph node.

// Defined in header <tbb/flow_graph.h>

namespace tbb {
namespace flow {

    template< typename InputTuple, typename OutputTuple > class composite_node;

    // composite_node with both input ports and output ports
    template< typename... InputTypes, typename... OutputTypes>
    class composite_node <std::tuple<InputTypes...>, std::tuple<OutputTypes...> > : public graph_node {
    public:
        typedef std::tuple< receiver<InputTypes>&... > input_ports_type;
        typedef std::tuple< sender<OutputTypes>&... > output_ports_type;

        composite_node( graph &g );
        virtual ~composite_node();

        void set_external_ports(input_ports_type&& input_ports_tuple, output_ports_type&& output_ports_tuple);
        input_ports_type& input_ports();
        output_ports_type& output_ports();
    };

    // composite_node with only input ports
    template< typename... InputTypes>
    class composite_node <std::tuple<InputTypes...>, std::tuple<> > : public graph_node{
    public:
        typedef std::tuple< receiver<InputTypes>&... > input_ports_type;

        composite_node( graph &g );
        virtual ~composite_node();

        void set_external_ports(input_ports_type&& input_ports_tuple);
        input_ports_type& input_ports();
    };

    // composite_nodes with only output_ports
    template<typename... OutputTypes>
    class composite_node <std::tuple<>, std::tuple<OutputTypes...> > : public graph_node{
    public:
        typedef std::tuple< sender<OutputTypes>&... > output_ports_type;

        composite_node( graph &g );
        virtual ~composite_node();

        void set_external_ports(output_ports_type&& output_ports_tuple);
        output_ports_type& output_ports();
    };

} // namespace flow
} // namespace tbb
  • The InputTuple and OutputTuple must be instantiations of std::tuple. Each type that these tuples store must meet the CopyConstructible requirements from [copyconstructible] and CopyAssignable requirements from [copyassignable] ISO C++ Standard sections.

composite_node is a graph_node, receiver<T>, and sender<T>.

The composite_node can package any number of other nodes. It maintains input and output port references to nodes in the package that border the composite_node. This allows the references to be used to make edges to other nodes outside of the composite_node. The InputTuple is a tuple of input types. The composite_node has an input port for each type in InputTuple. Likewise, the OutputTuple is a tuple of output types. The composite_node has an output port for each type in OutputTuple.

The composite_node is a multi-port node with three specializations.

  • A multi-port node with multi-input ports and multi-output ports: This specialization has a tuple of input ports, each of which is a receiver of a type in InputTuple. Each input port is a reference to a port of a node that the composite_node encapsulates. Similarly, this specialization also has a tuple of output ports, each of which is a sender of a type in OutputTuple. Each output port is a reference to a port of a node that the composite_node encapsulates.

  • A multi-port node with only input ports and no output ports: This specialization only has a tuple of input ports.

  • A multi-port node with only output ports and no input_ports: This specialization only has a tuple of output ports.

The function template input_port can be used to get a reference to a specific input port and the function template output_port can be used to get a reference to a specific output port.

Construction of a composite_node is done in two stages:

  • Defining the composite_node with specification of InputTuple and OutputTuple.

  • Making aliases from the encapsulated nodes that border the composite_node to the input and output ports of the composite_node. This step is mandatory as without it the composite_node input and output ports are not bound to any actual nodes. Making the aliases is achieved by calling the method set_external_ports.

The composite_node does not meet the CopyConstructible requirements from [copyconstructible] ISO C++ Standard section.

Member functions

composite_node(graph &g)

Constructs a composite_node that belongs to the graph g.

void set_external_ports(input_ports_type &&input_ports_tuple, output_ports_type &&output_ports_tuple)

Creates input and output ports of the composite_node as aliases to the ports referenced by input_ports_tuple and output_ports_tuple, respectively. That is, a port referenced at position N in input_ports_tuple is mapped as the Nth input port of the composite_node, similarly for output ports.

input_ports_type &input_ports()

Returns: A std::tuple of receivers. Each element is a reference to the actual node or input port that was aliased to that position in set_external_ports().

Caution

Calling input_ports() without a prior call to set_external_ports() results in undefined behavior.

output_ports_type &output_ports()

Returns: A std::tuple of senders. Each element is a reference to the actual node or output port that was aliased to that position in set_external_ports().

Caution

Calling output_ports() without a prior call to set_external_ports() results in undefined behavior.

See also: