.. _helpers_for_expressing_graphs:
Helper Functions for Expressing Graphs
======================================
.. note::
To enable this feature, define the ``TBB_PREVIEW_FLOW_GRAPH_FEATURES`` macro to 1.
Helper functions are intended to make creation of the flow graphs less verbose.
.. contents::
:local:
:depth: 1
Description
***********
This feature adds ``make_edges``, ``make_node_set``,
``follows`` and ``precedes`` functions to ``oneapi::tbb::flow`` namespace.
These functions simplify the process of building flow graphs by allowing to gather nodes
into sets and connect them to other nodes in the graph.
API
***
.. toctree::
:titlesonly:
constructors_for_nodes
follows_and_precedes_functions
make_node_set_function
make_edges_function
Example
*******
Consider the graph depicted below.
.. figure:: ./Resources/fg_api_graph_structure.png
:align: center
In the examples below, C++17 Class Template Argument Deduction is used
to avoid template parameter specification where possible.
**Regular API**
.. code:: cpp
#include <oneapi/tbb/flow_graph.h>
int main() {
using namespace oneapi::tbb::flow;
graph g;
broadcast_node<int> input(g);
function_node doubler(g, unlimited, [](const int& v) { return 2 * v; });
function_node squarer(g, unlimited, [](const int&) { return v * v; });
function_node cuber(g, unlimited, [](const int& v) { return v * v * v; });
join_node<std::tuple<int, int, int>> join(g);
int sum = 0;
function_node summer(g, serial, [&](const std::tuple<int, int, int>& v) {
int sub_sum = std::get<0>(v) + std::get<1>(v) + std::get<2>(v);
sum += sub_sum;
return sub_sum;
});
make_edge(input, doubler);
make_edge(input, squarer);
make_edge(input, cuber);
make_edge(doubler, std::get<0>(join.input_ports()));
make_edge(squarer, std::get<1>(join.input_ports()));
make_edge(cuber, std::get<2>(join.input_ports()));
make_edge(join, summer);
for (int i = 1; i <= 10; ++i) {
input.try_put(i);
}
g.wait_for_all();
}
**Preview API**
.. code:: cpp
#define TBB_PREVIEW_FLOW_GRAPH_FEATURES 1
#include <oneapi/tbb/flow_graph.h>
int main() {
using namespace oneapi::tbb::flow;
graph g;
function_node doubler(g, unlimited, [](const int& v) { return 2 * v; });
function_node squarer(g, unlimited, [](const int&) { return v * v; });
function_node cuber(g, unlimited, [](const int& v) { return v * v * v; });
auto handlers = make_node_set(doubler, squarer, cuber);
broadcast_node input(precedes(handlers));
join_node join(follows(handlers));
int sum = 0;
function_node summer(follows(join), serial,
[&](const std::tuple<int, int, int>& v) {
int sub_sum = std::get<0>(v) + std::get<1>(v) + std::get<2>(v);
sum += sub_sum;
return sub_sum;
});
for (int i = 1; i <= 10; ++i) {
input.try_put(i);
}
g.wait_for_all();
}
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