Type Dispatcher

Files
file	type_dispatcher.hpp
	Defines the mapping between cudf::type_id runtime type information and concrete C++ types.

Classes
struct	cudf::dispatch_storage_type< Id >
	Use this specialization on type_dispatcher whenever you only need to operate on the underlying stored type. More...

Macros
#define	CUDF_TYPE_MAPPING(Type, Id)
	Macro used to define a mapping between a concrete C++ type and a cudf::type_id enum. More...
#define	MAP_NUMERIC_SCALAR(Type)
	Macro used to define scalar type and scalar device type for cudf::numeric_scalar template class for numeric C++ types. More...
#define	MAP_TIMESTAMP_SCALAR(Type)
	Macro used to define scalar type and scalar device type for cudf::timestamp_scalar template class for timestamp C++ types. More...
#define	MAP_DURATION_SCALAR(Type)
	Macro used to define scalar type and scalar device type for cudf::duration_scalar template class for duration C++ types. More...

Typedefs
template<cudf::type_id Id>
using	cudf::id_to_type = typename id_to_type_impl< Id >::type
	Maps a cudf::type_id to its corresponding concrete C++ type. More...
template<typename T >
using	cudf::device_storage_type_t = std::conditional_t< std::is_same_v< numeric::decimal32, T >, int32_t, std::conditional_t< std::is_same_v< numeric::decimal64, T >, int64_t, std::conditional_t< std::is_same_v< numeric::decimal128, T >, __int128_t, T > >>
	"Returns" the corresponding type that is stored on the device when using cudf::column More...
template<typename T >
using	cudf::scalar_type_t = typename type_to_scalar_type_impl< T >::ScalarType
	Maps a C++ type to the scalar type required to hold its value. More...
template<typename T >
using	cudf::scalar_device_type_t = typename type_to_scalar_type_impl< T >::ScalarDeviceType
	Maps a C++ type to the scalar device type required to hold its value. More...

Functions
template<typename T >
constexpr type_id	cudf::type_to_id ()
	Maps a C++ type to its corresponding cudf::type_id More...
template<typename T >
constexpr bool	cudf::type_id_matches_device_storage_type (type_id id)
	Checks if fixed_point-like types have template type T matching the column's stored type id. More...
template<template< cudf::type_id > typename IdTypeMap = id_to_type_impl, typename Functor , typename... Ts>
CUDF_HOST_DEVICE constexpr decltype(auto) __forceinline__	cudf::type_dispatcher (cudf::data_type dtype, Functor f, Ts &&... args)
	Invokes an operator() template with the type instantiation based on the specified cudf::data_type's id(). More...
template<template< cudf::type_id > typename IdTypeMap = id_to_type_impl, typename F , typename... Ts>
CUDF_HOST_DEVICE constexpr decltype(auto) __forceinline__	cudf::double_type_dispatcher (cudf::data_type type1, cudf::data_type type2, F &&f, Ts &&... args)
	Dispatches two type template parameters to a callable. More...
std::string	cudf::type_to_name (data_type type)
	Return a name for a given type. More...

Detailed Description

Macro Definition Documentation

CUDF_TYPE_MAPPING

#define CUDF_TYPE_MAPPING	(		Type,
			Id
	)

Value:

  template <>                                              \
  constexpr inline type_id type_to_id<Type>()              \
  {                                                        \
    return Id;                                             \
  }                                                        \
  template <>                                              \
  inline std::string type_to_name_impl::operator()<Type>() \
  {                                                        \
    return CUDF_STRINGIFY(Type);                           \
  }                                                        \
  template <>                                              \
  struct id_to_type_impl<Id> {                             \
    using type = Type;                                     \
  };

Macro used to define a mapping between a concrete C++ type and a cudf::type_id enum.

Parameters

Type	The concrete C++ type
Id	The cudf::type_id enum

Definition at line 142 of file type_dispatcher.hpp.

MAP_DURATION_SCALAR

#define MAP_DURATION_SCALAR

(

Type

)

Value:

  template <>                                                         \
  struct type_to_scalar_type_impl<Type> {                             \
    using ScalarType       = cudf::duration_scalar<Type>;             \
    using ScalarDeviceType = cudf::duration_scalar_device_view<Type>; \
  };

Macro used to define scalar type and scalar device type for cudf::duration_scalar template class for duration C++ types.

Parameters

Type	The duration C++ type

Definition at line 312 of file type_dispatcher.hpp.

MAP_NUMERIC_SCALAR

#define MAP_NUMERIC_SCALAR

(

Type

)

Value:

  template <>                                                        \
  struct type_to_scalar_type_impl<Type> {                            \
    using ScalarType       = cudf::numeric_scalar<Type>;             \
    using ScalarDeviceType = cudf::numeric_scalar_device_view<Type>; \
  };

Macro used to define scalar type and scalar device type for cudf::numeric_scalar template class for numeric C++ types.

Parameters

Type	The numeric C++ type

Definition at line 214 of file type_dispatcher.hpp.

MAP_TIMESTAMP_SCALAR

#define MAP_TIMESTAMP_SCALAR

(

Type

)

Value:

  template <>                                                          \
  struct type_to_scalar_type_impl<Type> {                              \
    using ScalarType       = cudf::timestamp_scalar<Type>;             \
    using ScalarDeviceType = cudf::timestamp_scalar_device_view<Type>; \
  };

Macro used to define scalar type and scalar device type for cudf::timestamp_scalar template class for timestamp C++ types.

Parameters

Type	The timestamp C++ type

Definition at line 291 of file type_dispatcher.hpp.

Typedef Documentation

device_storage_type_t

template<typename T >

using cudf::device_storage_type_t = typedef std::conditional_t<std::is_same_v<numeric::decimal32, T>, int32_t, std::conditional_t<std::is_same_v<numeric::decimal64, T>, int64_t, std::conditional_t<std::is_same_v<numeric::decimal128, T>, __int128_t, T> >>

"Returns" the corresponding type that is stored on the device when using cudf::column

For decimal32, the storage type is an int32_t. For decimal64, the storage type is an int64_t. For decimal128, the storage type is an __int128_t.

Use this "type function" with the using type alias:

using Type = device_storage_type_t<Element>;

Template Parameters

T	The literal type that is stored on the host

Definition at line 111 of file type_dispatcher.hpp.

id_to_type

template<cudf::type_id Id>

using cudf::id_to_type = typedef typename id_to_type_impl<Id>::type

Maps a cudf::type_id to its corresponding concrete C++ type.

Example:

static_assert(std::is_same<int32_t, id_to_type<id_type::INT32>);

Template Parameters

t	The cudf::type_id to map

Definition at line 93 of file type_dispatcher.hpp.

scalar_device_type_t

template<typename T >

using cudf::scalar_device_type_t = typedef typename type_to_scalar_type_impl<T>::ScalarDeviceType

Maps a C++ type to the scalar device type required to hold its value.

Template Parameters

T	The concrete C++ type to map

Definition at line 340 of file type_dispatcher.hpp.

scalar_type_t

template<typename T >

using cudf::scalar_type_t = typedef typename type_to_scalar_type_impl<T>::ScalarType

Maps a C++ type to the scalar type required to hold its value.

Template Parameters

T	The concrete C++ type to map

Definition at line 332 of file type_dispatcher.hpp.

Function Documentation

double_type_dispatcher()

template<template< cudf::type_id > typename IdTypeMap = id_to_type_impl, typename F , typename... Ts>

CUDF_HOST_DEVICE constexpr decltype(auto) __forceinline__ cudf::double_type_dispatcher ( cudf::data_type  type1, cudf::data_type  type2, F &&  f, Ts &&...  args  )

constexpr

Dispatches two type template parameters to a callable.

This function expects a callable f with an operator() template accepting two typename template parameters T1 and T2.

Parameters

type1	The data_type used to dispatch a type for the first template parameter of the callable F
type2	The data_type used to dispatch a type for the second template parameter of the callable F
f	The callable whose operator() template is invoked
args	Parameter pack forwarded to the operator() invocation F.

Returns

The result of invoking f.template operator<T1, T2>(args)

Definition at line 593 of file type_dispatcher.hpp.

type_dispatcher()

template<template< cudf::type_id > typename IdTypeMap = id_to_type_impl, typename Functor , typename... Ts>

CUDF_HOST_DEVICE constexpr decltype(auto) __forceinline__ cudf::type_dispatcher ( cudf::data_type  dtype, Functor  f, Ts &&...  args  )

constexpr

Invokes an operator() template with the type instantiation based on the specified cudf::data_type's id().

Example usage with a functor that returns the size of the dispatched type:

struct size_of_functor{
 template <typename T>
 int operator()(){
   return sizeof(T);
 }
};
cudf::data_type t{INT32};
cudf::type_dispatcher(t, size_of_functor{});  // returns 4

The type_dispatcher uses cudf::type_to_id<t> to provide a default mapping of cudf::type_ids to dispatched C++ types. However, this mapping may be customized by explicitly specifying a user-defined trait struct for the IdTypeMap. For example, to always dispatch int32_t

template<cudf::type_id t> struct always_int{ using type = int32_t; }
 
// This will always invoke operator()<int32_t>
cudf::type_dispatcher<always_int>(data_type, f);

It is sometimes necessary to customize the dispatched functor's operator() for different types. This can be done in several ways.

The first method is to use explicit template specialization. This is useful for specializing behavior for single types. For example, a functor that prints int32_t or double when invoked with either of those types, else it prints unhandled type:

struct type_printer {
  template <typename ColumnType>
  void operator()() { std::cout << "unhandled type\n"; }
};
 
// Due to a bug in g++, explicit member function specializations need to be
// defined outside of the class definition
template <>
void type_printer::operator()<int32_t>() { std::cout << "int32_t\n"; }
 
template <>
void type_printer::operator()<double>() { std::cout << "double\n"; }

A second method is to use SFINAE with std::enable_if_t. This is useful for specializing for a set of types that share some property. For example, a functor that prints integral or floating point for integral or floating point types:

struct integral_or_floating_point {
  template <typename ColumnType,
            std::enable_if_t<not std::is_integral_v<ColumnType>  and
                             not std::is_floating_point_v<ColumnType> >* = nullptr>
  void operator()() {
    std::cout << "neither integral nor floating point\n "; }
 
  template <typename ColumnType,
            std::enable_if_t<std::is_integral_v<ColumnType> >* = nullptr>
  void operator()() { std::cout << "integral\n"; }
 
  template <typename ColumnType,
            std::enable_if_t<std::is_floating_point_v<ColumnType> >* = nullptr>
  void operator()() { std::cout << "floating point\n"; }
};

For more info on SFINAE and std::enable_if, see https://eli.thegreenplace.net/2014/sfinae-and-enable_if/

The return type for all template instantiations of the functor's "operator()" lambda must be the same, else there will be a compiler error as you would be trying to return different types from the same function.

Template Parameters

id_to_type_impl	Maps a cudf::type_id its dispatched C++ type
Functor	The callable object's type
Ts	Variadic parameter pack type

Parameters

dtype	The cudf::data_type whose id() determines which template instantiation is invoked
f	The callable whose operator() template is invoked
args	Parameter pack of arguments forwarded to the operator() invocation

Returns

Whatever is returned by the callable's operator()

Definition at line 442 of file type_dispatcher.hpp.

type_id_matches_device_storage_type()

template<typename T >

constexpr bool cudf::type_id_matches_device_storage_type ( type_id  id )

constexpr

Checks if fixed_point-like types have template type T matching the column's stored type id.

Template Parameters

T	The type that is stored on the device

Parameters

id	The data_type::id of the column

Returns

true If T matches the stored column type_id

false If T does not match the stored column type_id

Definition at line 127 of file type_dispatcher.hpp.

type_to_id()

template<typename T >

constexpr type_id cudf::type_to_id ( )

inlineconstexpr

Maps a C++ type to its corresponding cudf::type_id

When explicitly passed a template argument of a given type, returns the appropriate type_id enum for the specified C++ type.

For example:

return cudf::type_to_id<int32_t>();        // Returns INT32

Template Parameters

T	The type to map to a cudf::type_id

Returns

The cudf::type_id corresponding to the specified type

Definition at line 57 of file type_dispatcher.hpp.

type_to_name()

std::string cudf::type_to_name

(

data_type

type

)

Return a name for a given type.

The returned type names are intended for error messages and are not guaranteed to be stable.

Parameters

type	The data_type

Returns

Name of the type