TiledArray::detail::ReduceTask< opT > Class Template Reference

Documentation

template<typename opT>
class TiledArray::detail::ReduceTask< opT >

Reduce task.

This task will reduce an arbitrary number of objects. It is optimized for reduction of data that is the result of other tasks or remote data. Also, it is assumed that individual reduction operations require a substantial amount of work (i.e. your reduction operation should reduce a vector of data, not two numbers). The reduction arguments are reduced as they become ready, which results in non-deterministic reduction order. This is much faster than a simple binary tree reduction since the reduction tasks do not have to wait for specific pairs of data. Though data that is not stored in a future can be used, it may not be the best choice in that case.

The reduction operation must have the following form:

struct ReductionOp {
    // typedefs
    typedef ... result_type;
    typedef ... argument_type;
 
    // Constructors
    ReductionOp();
    ReductionOp(const ReductionOp&);
    ReductionOp& operator=(const ReductionOp&);
 
    // Reduction functions
 
    // Make an empty result object
    result_type operator()() const;
 
    // Post process the result
    result_type operator()(const result_type&) const;
 
    // Reduce two result objects
    void operator()(result_type&, const result_type&) const;
 
    // Reduce an argument
    void operator()(result_type&, const argument_type&) const;
 
}; // struct ReductionOp

For example, a vector sum function might look like:

struct VectorSum {
    // typedefs
    typedef double result_type;
    typedef std::vector<double> argument_type;
 
    // Compiler generated constructors and assignment operators are OK here
 
    // Reduction functions
 
    // Make an empty result object
    result_type operator()() const { return 0; }
 
    // Post process the result (no operation, passthrough)
    const result_type& operator()(const result_type& result) const {
      return result;
    }
 
    void operator()(result_type& result, const result_type& arg) const {
        result += arg;
    }
 
    void operator()(result_type& result, const argument_type& arg) const {
        for(std::size_t i = 0ul; i < first.size(); ++i)
            result += arg[i];
    }
}; // struct VectorProduct

Note

There is no need to add this object to the MADNESS task queue. It will be handled internally by the object. Simply call submit() to add this task to the task queue.

Template Parameters

opT	The reduction operation type

Definition at line 200 of file reduce_task.h.

Public Member Functions
	ReduceTask ()
	Default constructor. More...
	ReduceTask (World &world, const opT &op=opT(), madness::CallbackInterface *callback=nullptr)
	Constructor. More...
	ReduceTask (ReduceTask< opT > &&other) noexcept
	Move constructor. More...
	~ReduceTask ()
	Destructor. More...
ReduceTask< opT > &	operator= (ReduceTask< opT > &&other) noexcept
	Move assignment operator. More...
	ReduceTask (const ReduceTask< opT > &)=delete
ReduceTask< opT > &	operator= (const ReduceTask< opT > &)=delete
template<typename Arg >
int	add (const Arg &arg, madness::CallbackInterface *callback=nullptr)
	Add an argument to the reduction task. More...
int	count () const
	Argument count. More...
Future< result_type >	submit ()
	Submit the reduction task to the task queue. More...
	operator bool () const
	Type conversion operator. More...

Constructor & Destructor Documentation

ReduceTask() [1/4]

template<typename opT >

TiledArray::detail::ReduceTask< opT >::ReduceTask ( )

inline

Default constructor.

Definition at line 734 of file reduce_task.h.

ReduceTask() [2/4]

template<typename opT >

TiledArray::detail::ReduceTask< opT >::ReduceTask ( World &  world, const opT &  op = opT(), madness::CallbackInterface *  callback = nullptr  )

inline

Constructor.

Parameters

world	The world that owns this task
op	The reduction operation [ default = opT() ]
callback	The callback that will be invoked when this task is complete

Definition at line 742 of file reduce_task.h.

ReduceTask() [3/4]

template<typename opT >

TiledArray::detail::ReduceTask< opT >::ReduceTask ( ReduceTask< opT > &&  other )

inlinenoexcept

Move constructor.

Parameters

other

The object to be moved

Definition at line 749 of file reduce_task.h.

~ReduceTask()

template<typename opT >

TiledArray::detail::ReduceTask< opT >::~ReduceTask ( )

inline

Destructor.

If the reduction has not been submitted or destroy() has not been called, it will be submitted when the destructor is called.

Definition at line 759 of file reduce_task.h.

ReduceTask() [4/4]

template<typename opT >

TiledArray::detail::ReduceTask< opT >::ReduceTask ( const ReduceTask< opT > &  )

delete

Member Function Documentation

add()

template<typename opT >

template<typename Arg >

int TiledArray::detail::ReduceTask< opT >::add ( const Arg &  arg, madness::CallbackInterface *  callback = nullptr  )

inline

Add an argument to the reduction task.

arg may be of the argument type of opT, a Future to the argument type, or RemoteReference<FutureImpl> to the argument type.

Template Parameters

Arg	The argument type

Parameters

arg	The argument that will be reduced
callback	The callback that will be invoked when this argument pair has been reduced [ default = nullptr ]

Definition at line 786 of file reduce_task.h.

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count()

template<typename opT >

int TiledArray::detail::ReduceTask< opT >::count ( ) const

inline

Argument count.

Returns

The total number of arguments added to this task

Definition at line 796 of file reduce_task.h.

operator bool()

template<typename opT >

TiledArray::detail::ReduceTask< opT >::operator bool ( ) const

inline

Type conversion operator.

Returns

true if the task object is initialized.

Definition at line 821 of file reduce_task.h.

operator=() [1/2]

template<typename opT >

ReduceTask<opT>& TiledArray::detail::ReduceTask< opT >::operator= ( const ReduceTask< opT > &  )

delete

operator=() [2/2]

template<typename opT >

ReduceTask<opT>& TiledArray::detail::ReduceTask< opT >::operator= ( ReduceTask< opT > &&  other )

inlinenoexcept

Move assignment operator.

Parameters

other

The object to be moved

Definition at line 764 of file reduce_task.h.

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submit()

template<typename opT >

Future<result_type> TiledArray::detail::ReduceTask< opT >::submit ( )

inline

Submit the reduction task to the task queue.

Returns

The result of the reduction

Note

Arguments can no longer be added to the reduction after calling submit().

Definition at line 803 of file reduce_task.h.

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

• TiledArray/reduce_task.h