cpp-taskflow/example/dataflow.hpp at master · Hopobcn/cpp-taskflow · GitHub

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// 2019/02/25 - contributed by Paolo Bolzoni

// - a generic wrapper for dataflow

#ifndef DATAFLOW_HPP

#define DATAFLOW_HPP 1

#include <taskflow/taskflow.hpp>

#include <utility>

#include <vector>

#include <functional>

namespace df {

// "pads" are the object where functions on nodes can read from or write to;

// pads are all of the same compile time type T.

// Class hierarchies and virtual functions can be used to have different types

// of pads. In those cases, T would be probably a std::unique_ptr

template <typename T>

using Pad_id = typename std::vector<T>::size_type;

// "nodes" corresponds to taskflow tasks, but are agumented with input and

// output pads.

template <typename T>

class Node;

template <typename T>

using Node_id = typename std::vector< Node<T> >::size_type;

// each node executes a "functor" of type Tranform_f passing itself as a

// argument; the functor is expected to read from input pads and write to

// output pads.

template <typename T>

using Transform_f = std::function<void(Node<T>& element)>;

// "Dataflow_generator" is the type that keeps track of the relations between

// nodes and their pads. See below for the interface.

template <typename T>

class Dataflow_generator;

// Node interface, gives access to input and output pads.

// For convenience output pads can be accessed with the [] operator

template <typename T>

class Node {

public:

// get input pad

T const& ipad(Pad_id<T> id) const;

// get output pad

T& opad(Pad_id<T> id);

T& operator[](Pad_id<T>);

// get all the input pad ids

std::vector< Pad_id<T> > const& ipad_list() const;

// get all the output pad ids

std::vector< Pad_id<T> > const& opad_list() const;

private:

std::vector<T>& pads_;

std::vector< Pad_id<T> > ipads_;

std::vector< Pad_id<T> > opads_;

Transform_f<T> compute_;

explicit Node(std::vector<T>& pads)

: pads_{pads},

ipads_{},

opads_{},

compute_{ nullptr } {}

friend class Dataflow_generator<T>;

};

// Dataflow generator interface, allows to:

// . create nodes

// . set up what each node executes

// . create arcs

// . execute the dag

// nodes are basically taskflow tasks agumented with input and output pads

// edges are taskflow precedences

// execution is done via taskflow taskflow.run_until

template <typename T>

class Dataflow_generator {

public:

// creates a new node

Node_id<T> create_node();

// creates a new node and set up its functor

Node_id<T> create_node(Transform_f<T> f);

// creates a new arc ensuring that source output pads become the target

// input pads

Pad_id<T> create_arc(Node_id<T> source, Node_id<T> target);

// Set up the functor for an existing node

void set_function(Node_id<T> id, Transform_f<T> f);

// Peek to a node, it might be useful to see how many input or output pads

// it has

Node<T> const& node(Node_id<T> id) const;

// Executes the flow repeatly until the functor Cond returns true

template <typename Cond>

void start_flow(Cond && cond);

// Executes the flow once

void start_flow_once();

Dataflow_generator() = default;

private:

std::vector<T> pads_;

std::vector< Node<T> > nodes_;

std::vector<tf::Task> tasks_;

tf::Framework executor_;

};

// Implementations

template <typename T>

T const& Node<T>::

ipad(Pad_id<T> id) const {

return pads_[id];

}

template <typename T>

T& Node<T>::

opad(Pad_id<T> id) {

return pads_[id];

}

template <typename T>

std::vector<Pad_id<T>> const& Node<T>::

ipad_list() const {

return ipads_;

}

template <typename T>

std::vector<Pad_id<T>> const& Node<T>::

opad_list() const {

return opads_;

}

template <typename T>

T& Node<T>::

operator[](Pad_id<T> id) {

return pads_[id];

}

template <typename T>

Node_id<T> Dataflow_generator<T>::

create_node() {

Node_id<T> node_id { nodes_.size() };

nodes_.emplace_back( Node(pads_) );

tasks_.emplace_back( executor_.emplace([this, node_id]() { this->nodes_[node_id].compute_( this->nodes_[node_id] ); }) );

return node_id;

}

template <typename T>

Node_id<T> Dataflow_generator<T>::

create_node(Transform_f<T> f) {

Node_id<T> node_id { create_node() };

set_function(node_id, f);

return node_id;

}

template <typename T>

Pad_id<T> Dataflow_generator<T>::

create_arc(Node_id<T> source, Node_id<T> target) {

Pad_id<T> pad_id { pads_.size() };

pads_.emplace_back( T{} );

nodes_[source].opads_.push_back(pad_id);

nodes_[target].ipads_.push_back(pad_id);

tasks_[source].precede(tasks_[target]);

return pad_id;

}

template <typename T>

template <typename Cond>

void Dataflow_generator<T>::

start_flow(Cond && cond) {

tf::Taskflow taskflow{};

taskflow.run_until(executor_, cond);

}

template <typename T>

void Dataflow_generator<T>::

start_flow_once() {

bool leave{true};

start_flow( [&leave]() { leave = !leave; return leave;} );

}

template <typename T>

Node<T> const& Dataflow_generator<T> ::

node(Node_id<T> id) const {

return nodes_[id];

}

template <typename T>

void Dataflow_generator<T> ::

set_function(Node_id<T> id, Transform_f<T> f) {

nodes_[id].compute_ = f;

}

#endif

cpp-taskflow/example/dataflow.hpp at master · Hopobcn/cpp-taskflow · GitHub

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