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filter

filter#

[algorithms.parallel_pipeline.filter]

A filter class template represents a strongly-typed filter in a parallel_pipeline algorithm, with its template parameters specifying the filter input and output types. A filter can be constructed from a functor or by composing two filter objects with operator&(). The same filter object can be reused in multiple & expressions.

The filter class should only be used in conjunction with parallel_pipeline functions.

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

namespace oneapi {
    namespace tbb {

        template<typename InputType, typename OutputType>
        class filter {
        public:
            filter() = default;
            filter( const filter& rhs ) = default;
            filter( filter&& rhs ) = default;
            void operator=(const filter& rhs) = default;
            void operator=( filter&& rhs ) = default;

            template<typename Body>
            filter( filter_mode mode, const Body& body );

            filter& operator&=( const filter<OutputType,OutputType>& right );

            void clear();
        }

        template<typename T, typename U, typename Body>
        filter<T,U> make_filter( filter::mode mode, const Body& f );
        template<typename T, typename V, typename U>
        filter<T,U> operator&( const filter<T,V>& left, const filter<V,U>& right );

    } // namespace tbb
} // namespace oneapi

Requirements:

  • If InputType is void, a Body type must meet the FirstFilterBody requirements.

  • If OutputType is void, a Body type must meet the LastFilterBody requirements. Since C++17, Body may also be a pointer to a member function in InputType.

  • If InputType and OutputType are not void, a Body type must meet the MiddleFilterBody requirements. Since C++17, Body may also be a pointer to a member function in InputType that returns OutputType or a pointer to a data member in InputType of type OutputType.

  • If InputType and OutputType are void, a Body type must meet the SingleFilterBody requirements.

filter_mode Enumeration#

Member functions#

filter()#

Constructs an undefined filter.

Caution

The effect of using an undefined filter by operator&() or parallel_pipeline is undefined.

template<typename Body>
filter(filter_mode mode, const Body &body)#

Constructs a filter that uses a copy of a provided body to map an input value of type InputType to an output value of type OutputType, and that operates in the specified mode.

void clear()#

Sets *this to an undefined filter.

Non-member functions#

template<typename T, typename U, typename Func>
filter<T, U> make_filter(filter::mode mode, const Func &f)#

Returns filter<T, U>(mode, f).

template<typename T, typename V, typename U>
filter<T, U> operator&(const filter<T, V> &left, const filter<V, U> &right)#

Returns a filter representing the composition of filters left and right. The composition behaves as if the output value of left becomes the input value of right.

Deduction Guides#

template<typename Body>
filter(filter_mode, Body) -> filter<filter_input<Body>, filter_output<Body>>;

Where:

  • filter_input<Body> is an alias to the Body::operator() input parameter type. If Body::operator() input parameter type is flow_control then filter_input<Body> is void.

  • filter_output<Body> is an alias to the Body::operator() return type.

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