follows and precedes functions

[flow_graph.helper_functions.follows_and_precedes]

Note

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The follows and precedes helper functions aid in expressing dependencies between nodes when building oneTBB flow graphs. These helper functions can only be used while constructing the node.

The follows helper function specifies that the node being constructed is the successor of the set of nodes passed as an argument.

The precedes helper function specifies that the node being constructed is the predecessor of the set of nodes passed as an argument.

Functions follows and precedes are meant to replace the graph argument, which is passed as the first argument to the constructor of the node. The graph argument for the node being constructed is obtained either from the specified node set or the sequence of nodes passed to follows or precedes.

If the nodes passed to follows or precedes belong to different graphs, the behavior is undefined.

Syntax

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

namespace oneapi {
    namespace tbb {
        namespace flow {

        // node_set is an exposition-only name for the type returned from make_node_set function

        template <typename NodeType, typename... NodeTypes>
        /*unspecified*/ follows( node_set<NodeType, NodeTypes...>& set );

        template <typename NodeType, typename... NodeTypes>
        /*unspecified*/ follows( NodeType& node, NodeTypes&... nodes );

        template <typename NodeType, typename... NodeTypes>
        /*unspecified*/ precedes( node_set<NodeType, NodeTypes...>& set );

        template <typename NodeType, typename... NodeTypes>
        /*unspecified*/ precedes( NodeType& node, NodeTypes&... nodes );

        } // namespace flow
    } // namespace tbb
} // namespace oneapi

Input Parameters

Either a set or a sequence of nodes can be used as arguments for follows and precedes. The following expressions are equivalent:

A set of nodes as an input

auto handlers = make_node_set(n1, n2, n3);
broadcast_node<int> input(precedes(handlers));

A sequence of nodes as an input

broadcast_node<int> input(precedes(n1, n2, n3));