Reshaping

Modules
	Transpose

Files
file	explode.hpp
	Column APIs for explore list columns.
file	reshape.hpp
	Column APIs for interleave and tile.

Enumerations
enum class	cudf::flip_endianness : bool { NO , YES }
	Configures whether byte casting flips endianness.

Functions
std::unique_ptr< table >	cudf::explode (table_view const &input_table, size_type explode_column_idx, rmm::device_async_resource_ref mr=rmm::mr::get_current_device_resource())
	Explodes a list column's elements. More...
std::unique_ptr< table >	cudf::explode_position (table_view const &input_table, size_type explode_column_idx, rmm::device_async_resource_ref mr=rmm::mr::get_current_device_resource())
	Explodes a list column's elements and includes a position column. More...
std::unique_ptr< table >	cudf::explode_outer (table_view const &input_table, size_type explode_column_idx, rmm::device_async_resource_ref mr=rmm::mr::get_current_device_resource())
	Explodes a list column's elements retaining any null entries or empty lists inside. More...
std::unique_ptr< table >	cudf::explode_outer_position (table_view const &input_table, size_type explode_column_idx, rmm::device_async_resource_ref mr=rmm::mr::get_current_device_resource())
	Explodes a list column's elements retaining any null entries or empty lists and includes a position column. More...
std::unique_ptr< column >	cudf::interleave_columns (table_view const &input, rmm::device_async_resource_ref mr=rmm::mr::get_current_device_resource())
	Interleave columns of a table into a single column. More...
std::unique_ptr< table >	cudf::tile (table_view const &input, size_type count, rmm::device_async_resource_ref mr=rmm::mr::get_current_device_resource())
	Repeats the rows from input table count times to form a new table. More...
std::unique_ptr< column >	cudf::byte_cast (column_view const &input_column, flip_endianness endian_configuration, rmm::device_async_resource_ref mr=rmm::mr::get_current_device_resource())
	Converts a column's elements to lists of bytes. More...

Detailed Description

Function Documentation

byte_cast()

std::unique_ptr<column> cudf::byte_cast	(	column_view const &	input_column,
		flip_endianness	endian_configuration,
		rmm::device_async_resource_ref	mr = rmm::mr::get_current_device_resource()
	)

Converts a column's elements to lists of bytes.

input<int32>  = [8675, 309]
configuration = flip_endianness::YES
return        = [[0x00, 0x00, 0x21, 0xe3], [0x00, 0x00, 0x01, 0x35]]

Parameters

input_column	Column to be converted to lists of bytes
endian_configuration	Whether to retain or flip the endianness of the elements
mr	Device memory resource used to allocate the returned column's device memory

Returns

The column containing the lists of bytes

explode()

std::unique_ptr<table> cudf::explode	(	table_view const &	input_table,
		size_type	explode_column_idx,
		rmm::device_async_resource_ref	mr = rmm::mr::get_current_device_resource()
	)

Explodes a list column's elements.

Any list is exploded, which means the elements of the list in each row are expanded into new rows in the output. The corresponding rows for other columns in the input are duplicated. Example:

[[5,10,15], 100],
[[20,25],   200],
[[30],      300],
returns
[5,         100],
[10,        100],
[15,        100],
[20,        200],
[25,        200],
[30,        300],

Nulls and empty lists propagate in different ways depending on what is null or empty.

[[5,null,15], 100],
[null,        200],
[[],          300],
returns
[5,           100],
[null,        100],
[15,          100],

Note that null lists are not included in the resulting table, but nulls inside lists and empty lists will be represented with a null entry for that column in that row.

Parameters

input_table	Table to explode.
explode_column_idx	Column index to explode inside the table.
mr	Device memory resource used to allocate the returned column's device memory.

Returns

A new table with explode_col exploded.

explode_outer()

std::unique_ptr<table> cudf::explode_outer	(	table_view const &	input_table,
		size_type	explode_column_idx,
		rmm::device_async_resource_ref	mr = rmm::mr::get_current_device_resource()
	)

Explodes a list column's elements retaining any null entries or empty lists inside.

Any list is exploded, which means the elements of the list in each row are expanded into new rows in the output. The corresponding rows for other columns in the input are duplicated. Example:

[[5,10,15], 100],
[[20,25],   200],
[[30],      300],
returns
[5,         100],
[10,        100],
[15,        100],
[20,        200],
[25,        200],
[30,        300],

Nulls and empty lists propagate as null entries in the result.

[[5,null,15], 100],
[null,        200],
[[],          300],
returns
[5,           100],
[null,        100],
[15,          100],
[null,        200],
[null,        300],

Parameters

input_table	Table to explode.
explode_column_idx	Column index to explode inside the table.
mr	Device memory resource used to allocate the returned column's device memory.

Returns

A new table with explode_col exploded.

explode_outer_position()

std::unique_ptr<table> cudf::explode_outer_position	(	table_view const &	input_table,
		size_type	explode_column_idx,
		rmm::device_async_resource_ref	mr = rmm::mr::get_current_device_resource()
	)

Explodes a list column's elements retaining any null entries or empty lists and includes a position column.

Any list is exploded, which means the elements of the list in each row are expanded into new rows in the output. The corresponding rows for other columns in the input are duplicated. A position column is added that has the index inside the original list for each row. Example:

[[5,10,15], 100],
[[20,25],   200],
[[30],      300],
returns
[0,   5,    100],
[1,  10,    100],
[2,  15,    100],
[0,  20,    200],
[1,  25,    200],
[0,  30,    300],

Nulls and empty lists propagate as null entries in the result.

[[5,null,15], 100],
[null,        200],
[[],          300],
returns
[0,     5,    100],
[1,  null,    100],
[2,    15,    100],
[0,  null,    200],
[0,  null,    300],

Parameters

input_table	Table to explode.
explode_column_idx	Column index to explode inside the table.
mr	Device memory resource used to allocate the returned column's device memory.

Returns

A new table with explode_col exploded.

explode_position()

std::unique_ptr<table> cudf::explode_position	(	table_view const &	input_table,
		size_type	explode_column_idx,
		rmm::device_async_resource_ref	mr = rmm::mr::get_current_device_resource()
	)

Explodes a list column's elements and includes a position column.

Any list is exploded, which means the elements of the list in each row are expanded into new rows in the output. The corresponding rows for other columns in the input are duplicated. A position column is added that has the index inside the original list for each row. Example:

[[5,10,15], 100],
[[20,25],   200],
[[30],      300],
returns
[0,   5,     100],
[1,   10,    100],
[2,   15,    100],
[0,   20,    200],
[1,   25,    200],
[0,   30,    300],

Nulls and empty lists propagate in different ways depending on what is null or empty.

[[5,null,15], 100],
[null,        200],
[[],          300],
returns
[0,     5,    100],
[1,  null,    100],
[2,    15,    100],

Note that null lists are not included in the resulting table, but nulls inside lists and empty lists will be represented with a null entry for that column in that row.

Parameters

input_table	Table to explode.
explode_column_idx	Column index to explode inside the table.
mr	Device memory resource used to allocate the returned column's device memory.

Returns

A new table with exploded value and position. The column order of return table is [cols before explode_input, explode_position, explode_value, cols after explode_input].

interleave_columns()

std::unique_ptr<column> cudf::interleave_columns	(	table_view const &	input,
		rmm::device_async_resource_ref	mr = rmm::mr::get_current_device_resource()
	)

Interleave columns of a table into a single column.

Converts the column major table input into a row major column. Example:

in     = [[A1, A2, A3], [B1, B2, B3]]
return = [A1, B1, A2, B2, A3, B3]

Exceptions

cudf::logic_error	if input contains no columns.
cudf::logic_error	if input columns dtypes are not identical.

Parameters

[in]	input	Table containing columns to interleave
[in]	mr	Device memory resource used to allocate the returned column's device memory

Returns

The interleaved columns as a single column

tile()

std::unique_ptr<table> cudf::tile	(	table_view const &	input,
		size_type	count,
		rmm::device_async_resource_ref	mr = rmm::mr::get_current_device_resource()
	)

Repeats the rows from input table count times to form a new table.

output.num_columns() == input.num_columns() output.num_rows() == input.num_rows() * count

input  = [[8, 4, 7], [5, 2, 3]]
count  = 2
return = [[8, 4, 7, 8, 4, 7], [5, 2, 3, 5, 2, 3]]

Parameters

[in]	input	Table containing rows to be repeated
[in]	count	Number of times to tile "rows". Must be non-negative
[in]	mr	Device memory resource used to allocate the returned table's device memory

Returns

The table containing the tiled "rows"