| Taskflow: A General-purpose Task-parallel Programming System

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Public Types | Public Member Functions | List of all members
tf::DataPipeline< Ps > Class Template Reference

class to create a data-parallel pipeline scheduling framework More...

`#include <taskflow/algorithm/data_pipeline.hpp>`

## Public Types
using | data_t
| internal storage type for each data token (default std::variant)

## Public Member Functions
| DataPipeline (size_t num_lines, Ps &&... ps)
| constructs a data-parallel pipeline object
| DataPipeline (size_t num_lines, std::tuple< Ps... > &&ps)
| constructs a data-parallel pipeline object
size_t | num_lines () const noexcept
| queries the number of parallel lines
constexpr size_t | num_pipes () const noexcept
| queries the number of pipes
void | reset ()
| resets the pipeline
size_t | num_tokens () const noexcept
| queries the number of generated tokens in the pipeline
Graph & | graph ()
| obtains the graph object associated with the pipeline construct

## Detailed Description

template<typename... Ps>
class tf::DataPipeline< Ps >

class to create a data-parallel pipeline scheduling framework

Template Parameters

  Ps | data pipe types

Similar to tf::Pipeline, a tf::DataPipeline is a composable graph object for users to create a data-parallel pipeline scheduling framework using a module task in a taskflow. The only difference is that tf::DataPipeline provides a data abstraction for users to quickly express dataflow in a pipeline. The following example creates a data-parallel pipeline of three stages that generate dataflow from `void` to `int`, `std::string`, and `void`.

#include <taskflow/taskflow.hpp>
#include <taskflow/algorithm/data_pipeline.hpp>
int main() {
// data flow => void -> int -> std::string -> void
tf::Taskflow taskflow("pipeline");
tf::Executor executor;
const size_t num_lines = 4;
tf::DataPipeline pl(num_lines,
tf::make_data_pipe<void, int>(tf::PipeType::SERIAL, [&](tf::Pipeflow& pf) -> int{
if(pf.token() == 5) {
pf.stop();
return 0;
}
else {
return pf.token();
}
}),
tf::make_data_pipe<int, std::string>(tf::PipeType::SERIAL, [](int& input) {
return std::to_string(input + 100);
}),
tf::make_data_pipe<std::string, void>(tf::PipeType::SERIAL, [](std::string& input) {
std::cout << input << std::endl;
})
);
// build the pipeline graph using composition
taskflow.composed_of(pl).name("pipeline");
// dump the pipeline graph structure (with composition)
taskflow.dump(std::cout);
// run the pipeline
executor.run(taskflow).wait();
return 0;
}
tf::DataPipeline
class to create a data-parallel pipeline scheduling framework
Definition data_pipeline.hpp:254
tf::DataPipeline::num_lines
size_t num_lines() const noexcept
queries the number of parallel lines
Definition data_pipeline.hpp:428
tf::Executor
class to create an executor
Definition executor.hpp:62
tf::Executor::run
tf::Future< void > run(Taskflow &taskflow)
runs a taskflow once
tf::Pipeflow
class to create a pipeflow object used by the pipe callable
Definition pipeline.hpp:43
tf::Pipeflow::token
size_t token() const
queries the token identifier
Definition pipeline.hpp:78
tf::Pipeflow::stop
void stop()
stops the pipeline scheduling
Definition pipeline.hpp:88
tf::Taskflow
class to create a taskflow object
Definition taskflow.hpp:64
tf::make_data_pipe
auto make_data_pipe(PipeType d, C &&callable)
function to construct a data pipe (tf::DataPipe)
Definition data_pipeline.hpp:171
tf::PipeType::SERIAL
@ SERIAL
serial type

The pipeline schedules five tokens over four parallel lines in a circular fashion, as depicted below:

o -> o -> o
| | |
v v v
o -> o -> o
| | |
v v v
o -> o -> o
| | |
v v v
o -> o -> o

## Member Typedef Documentation

## ◆ data_t

template<typename... Ps>

using tf::DataPipeline< Ps >::data_t

Initial value:
unique_variant_t<std::variant<std::conditional_t<
std::is_void_v<typename Ps::output_t>,
std::monostate,
std::decay_t<typename Ps::output_t>>...
>>

internal storage type for each data token (default std::variant)

## Constructor & Destructor Documentation

## ◆ DataPipeline() [1/2]

template<typename... Ps>

tf::DataPipeline< Ps >::DataPipeline | ( | size_t | num_lines,
|  | Ps &&... | ps )

constructs a data-parallel pipeline object

Parameters

  num_lines | the number of parallel lines
  ps | a list of pipes

Constructs a data-parallel pipeline of up to `num_lines` parallel lines to schedule tokens through the given linear chain of pipes. The first pipe must define a serial direction (tf::PipeType::SERIAL) or an exception will be thrown.

## ◆ DataPipeline() [2/2]

template<typename... Ps>

tf::DataPipeline< Ps >::DataPipeline | ( | size_t | num_lines,
|  | std::tuple< Ps... > && | ps )

constructs a data-parallel pipeline object

Parameters

  num_lines | the number of parallel lines
  ps | a tuple of pipes

Constructs a data-parallel pipeline of up to `num_lines` parallel lines to schedule tokens through the given linear chain of pipes stored in a std::tuple. The first pipe must define a serial direction (tf::PipeType::SERIAL) or an exception will be thrown.

## Member Function Documentation

## ◆ graph()

template<typename... Ps>

Graph & tf::DataPipeline< Ps >::graph | ( |  | ) |

obtains the graph object associated with the pipeline construct

This method is primarily used as an opaque data structure for creating a module task of this pipeline.

## ◆ num_lines()

template<typename... Ps>

size_t tf::DataPipeline< Ps >::num_lines | ( |  | ) | const
| noexcept

queries the number of parallel lines

The function returns the number of parallel lines given by the user upon the construction of the pipeline. The number of lines represents the maximum parallelism this pipeline can achieve.

## ◆ num_pipes()

template<typename... Ps>

size_t tf::DataPipeline< Ps >::num_pipes | ( |  | ) | const
| constexpr noexcept

queries the number of pipes

The Function returns the number of pipes given by the user upon the construction of the pipeline.

## ◆ num_tokens()

template<typename... Ps>

size_t tf::DataPipeline< Ps >::num_tokens | ( |  | ) | const
| noexcept

queries the number of generated tokens in the pipeline

The number represents the total scheduling tokens that has been generated by the pipeline so far.

## ◆ reset()

template<typename... Ps>

void tf::DataPipeline< Ps >::reset | ( |  | ) |

resets the pipeline

Resetting the pipeline to the initial state. After resetting a pipeline, its token identifier will start from zero as if the pipeline was just constructed.

The documentation for this class was generated from the following file:

- taskflow/algorithm/data_pipeline.hpp