Requirements on table types

Follows the definition of the dm table concept and its restrictions (e.g., immutability).
Is derived from the
oneapi::dal::table
class. The behavior of this class can be extended, but cannot be weaken.
Is reference-counted.
Every new
oneapi::dal::table
sub-type defines a unique id number - the “kind” that represents objects of that type in runtime.

using namespace onedal;

// Creating homogen_table sub-type.
dal::homogen_table table1 = homogen_table::wrap(queue, data_ptr, row_count, column_count);

// table1 and table2 share the same data (no data copy is performed)
dal::table table2 = table1;

// Creating an empty table
dal::table table3;

std::cout << table1.get_kind()     == table2.get_kind() << std::endl; // true
std::cout << homogen_table::kind() == table2.get_kind() << std::endl; // true
std::cout << table2.get_kind()     == table3.get_kind() << std::endl; // false

// Referring table3 to the table2.
table3 = table2;
std::cout << table2.get_kind() == table3.get_kind() << std::endl; // true

Table types

Programming interface

The instance stores a pointer to table implementation that holds all property values and data
The reference count indicating how many table objects refer to the same implementation.
The table increments the reference count for it to be equal to the number of table objects sharing the same implementation.
The table decrements the reference count when the table goes out of the scope. If the reference count is zero, the table frees its implementation.

class

table

Constructors

table

()

An empty table constructor: creates the table instance with zero number of rows and columns. Implementation is set to the special “empty” object that returns all the property values set to default (see Properties section).

table

(

const

table&) = default

Creates a new table instance that shares the implementation with another one.

table

(table&&)

Creates a new table instance and moves implementation from another one into it.

template<typename

Impl

, typename

ImplType

= std::decay_t<Impl>, typename

None

= std::enable_if_t<detail::is_table_impl_v<ImplType> && !std::is_base_of_v<table, ImplType>>>

table

(Impl &&

impl

)

Public Methods

table &

operator=

(

const

table&) = default

Replaces the implementation by another one.

table &

operator=

(table&&)

Swaps the implementation of this object and another one.

bool

has_data

()

const

noexcept

Indicates whether a table contains non-zero number of rows and columns.

Properties

std::int64_t

column_count

= 0

The number of columns in the table.

Getter & Setter

std::int64_t get_column_count() const

std::int64_t

row_count

= 0

The number of rows in the table.

Getter & Setter

std::int64_t get_row_count() const

const

table_metadata &

metadata

= table_metadata()

The metadata object that holds additional information about the data within the table.

Getter & Setter

const table_metadata & get_metadata() const

std::int64_t

kind

= empty_table_kind

The runtime id of the table type. Each table sub-type has its unique

kind

. An empty table (see the default constructor) has a unique

kind

value as well.

Getter & Setter

std::int64_t get_kind() const

data_layout

data_layout

= data_layout::unknown

The layout of the data within the table.

Getter & Setter

data_layout get_data_layout() const

class

table_metadata

Constructors

table_metadata

()

Creates the metadata instance without information about the features. The

feature_count

sshould be set to zero. The

data_type

and

feature_type

properties should not be initialized.

table_metadata

(

const

array<data_type> &

dtypes

,

const

array<feature_type> &

ftypes

)

Creates the metadata instance from external information about the data types and the feature types.

Parameters

dtypes
– The data types of the features. Assigned into the
data_type
property.
ftypes
– The feature types. Assigned into the
feature_type
property.

Preconditions

dtypes.get_count() == ftypes.get_count()

Properties

std::int64_t

feature_count

The number of features that metadata contains information about.

Getter & Setter

std::int64_t get_feature_count() const

const

feature_type &

feature_type

Feature types in the metadata object. Should be within the range

[0, feature_count)

.

Getter & Setter

const feature_type & get_feature_type(std::int64_t feature_index) const

const

data_type &

data_type

Data types of the features in the metadata object. Should be within the range

[0, feature_count)

.

Getter & Setter

const data_type & get_data_type(std::int64_t feature_index) const

enum class data_layout { unknown, row_major, column_major };

data_layout::unknown
   Represents the :capterm:`data layout` that is undefined or unknown at this moment.

data_layout::row_major
   The data block elements are stored in raw-major layout.

data_layout::column_major
   The data block elements are stored in column_major layout.

enum class feature_type { nominal, ordinal, interval, ratio };

feature_type::nominal
   Represents the type of :capterm:`Nominal feature`.

feature_type::ordinal
   Represents the type of :capterm:`Ordinal feature`.

feature_type::interval
   Represents the type of :capterm:`Interval feature`.

feature_type::ratio
   Represents the type of :capterm:`Ratio feature`.