Bitmask Operations

Files
file	null_mask.hpp
	APIs for managing validity bitmasks.

Functions
size_type	cudf::state_null_count (mask_state state, size_type size)
	Returns the null count for a null mask of the specified state representing size elements. More...
std::size_t	cudf::bitmask_allocation_size_bytes (size_type number_of_bits, std::size_t padding_boundary=64)
	Computes the required bytes necessary to represent the specified number of bits with a given padding boundary. More...
size_type	cudf::num_bitmask_words (size_type number_of_bits)
	Returns the number of bitmask_type words required to represent the specified number of bits. More...
rmm::device_buffer	cudf::create_null_mask (size_type size, mask_state state, rmm::mr::device_memory_resource *mr=rmm::mr::get_current_device_resource())
	Creates a device_buffer for use as a null value indicator bitmask of a column. More...
void	cudf::set_null_mask (bitmask_type *bitmask, size_type begin_bit, size_type end_bit, bool valid)
	Sets a pre-allocated bitmask buffer to a given state in the range [begin_bit, end_bit) More...
cudf::size_type	cudf::count_set_bits (bitmask_type const *bitmask, size_type start, size_type stop)
	Given a bitmask, counts the number of set (1) bits in the range [start, stop) More...
cudf::size_type	cudf::count_unset_bits (bitmask_type const *bitmask, size_type start, size_type stop)
	Given a bitmask, counts the number of unset (0) bits in the range [start, stop). More...
std::vector< size_type >	cudf::segmented_count_set_bits (bitmask_type const *bitmask, std::vector< cudf::size_type > const &indices)
	Given a bitmask, counts the number of set (1) bits in every range [indices[2*i], indices[(2*i)+1]) (where 0 <= i < indices.size() / 2). More...
std::vector< size_type >	cudf::segmented_count_unset_bits (bitmask_type const *bitmask, std::vector< cudf::size_type > const &indices)
	Given a bitmask, counts the number of unset (0) bits in every range [indices[2*i], indices[(2*i)+1]) (where 0 <= i < indices.size() / 2). More...
rmm::device_buffer	cudf::copy_bitmask (bitmask_type const *mask, size_type begin_bit, size_type end_bit, rmm::mr::device_memory_resource *mr=rmm::mr::get_current_device_resource())
	Creates a device_buffer from a slice of bitmask defined by a range of indices [begin_bit, end_bit). More...
rmm::device_buffer	cudf::copy_bitmask (column_view const &view, rmm::mr::device_memory_resource *mr=rmm::mr::get_current_device_resource())
	Copies view's bitmask from the bits [view.offset(), view.offset() + view.size()) into a device_buffer More...
rmm::device_buffer	cudf::bitmask_and (table_view const &view, rmm::mr::device_memory_resource *mr=rmm::mr::get_current_device_resource())
	Returns a bitwise AND of the bitmasks of columns of a table. More...

Detailed Description

Function Documentation

bitmask_allocation_size_bytes()

std::size_t cudf::bitmask_allocation_size_bytes	(	size_type	number_of_bits,
		std::size_t	padding_boundary = 64
	)

Computes the required bytes necessary to represent the specified number of bits with a given padding boundary.

Note

The Arrow specification for the null bitmask requires a 64B padding boundary.

Parameters

number_of_bits	The number of bits that need to be represented
padding_boundary	The value returned will be rounded up to a multiple of this value

Returns

std::size_t The necessary number of bytes

bitmask_and()

rmm::device_buffer cudf::bitmask_and	(	table_view const &	view,
		rmm::mr::device_memory_resource *	mr = rmm::mr::get_current_device_resource()
	)

Returns a bitwise AND of the bitmasks of columns of a table.

If any of the columns isn't nullable, it is considered all valid. If no column in the table is nullable, an empty bitmask is returned.

Parameters

view	The table of columns
mr	Device memory resource used to allocate the returned device_buffer

Returns

rmm::device_buffer Output bitmask

copy_bitmask() [1/2]

rmm::device_buffer cudf::copy_bitmask	(	bitmask_type const *	mask,
		size_type	begin_bit,
		size_type	end_bit,
		rmm::mr::device_memory_resource *	mr = rmm::mr::get_current_device_resource()
	)

Creates a device_buffer from a slice of bitmask defined by a range of indices [begin_bit, end_bit).

Returns empty device_buffer if bitmask == nullptr.

Exceptions

cudf::logic_error	if begin_bit > end_bit
cudf::logic_error	if begin_bit < 0

Parameters

mask	Bitmask residing in device memory whose bits will be copied
begin_bit	Index of the first bit to be copied (inclusive)
end_bit	Index of the last bit to be copied (exclusive)
mr	Device memory resource used to allocate the returned device_buffer

Returns

rmm::device_buffer A device_buffer containing the bits [begin_bit, end_bit) from mask.

copy_bitmask() [2/2]

rmm::device_buffer cudf::copy_bitmask	(	column_view const &	view,
		rmm::mr::device_memory_resource *	mr = rmm::mr::get_current_device_resource()
	)

Copies view's bitmask from the bits [view.offset(), view.offset() + view.size()) into a device_buffer

Returns empty device_buffer if the column is not nullable

Parameters

view	Column view whose bitmask needs to be copied
mr	Device memory resource used to allocate the returned device_buffer

Returns

rmm::device_buffer A device_buffer containing the bits [view.offset(), view.offset() + view.size()) from view's bitmask.

count_set_bits()

cudf::size_type cudf::count_set_bits	(	bitmask_type const *	bitmask,
		size_type	start,
		size_type	stop
	)

Given a bitmask, counts the number of set (1) bits in the range [start, stop)

Returns 0 if bitmask == nullptr.

Exceptions

cudf::logic_error	if start > stop
cudf::logic_error	if start < 0

Parameters

bitmask	Bitmask residing in device memory whose bits will be counted
start_bit	Index of the first bit to count (inclusive)
stop_bit	Index of the last bit to count (exclusive)

Returns

The number of non-zero bits in the specified range

count_unset_bits()

cudf::size_type cudf::count_unset_bits	(	bitmask_type const *	bitmask,
		size_type	start,
		size_type	stop
	)

Given a bitmask, counts the number of unset (0) bits in the range [start, stop).

Returns 0 if bitmask == nullptr.

Exceptions

cudf::logic_error	if start > stop
cudf::logic_error	if start < 0

Parameters

bitmask	Bitmask residing in device memory whose bits will be counted
start_bit	Index of the first bit to count (inclusive)
stop_bit	Index of the last bit to count (exclusive)

Returns

The number of zero bits in the specified range

create_null_mask()

rmm::device_buffer cudf::create_null_mask	(	size_type	size,
		mask_state	state,
		rmm::mr::device_memory_resource *	mr = rmm::mr::get_current_device_resource()
	)

Creates a device_buffer for use as a null value indicator bitmask of a column.

Parameters

size	The number of elements to be represented by the mask
state	The desired state of the mask
mr	Device memory resource used to allocate the returned device_buffer.

Returns

rmm::device_buffer A device_buffer for use as a null bitmask satisfying the desired size and state

num_bitmask_words()

size_type cudf::num_bitmask_words

(

size_type

number_of_bits

)

Returns the number of bitmask_type words required to represent the specified number of bits.

Unlike bitmask_allocation_size_bytes, which returns the number of bytes needed for a bitmask allocation (including padding), this function returns the actual number bitmask_type elements necessary to represent number_of_bits. This is useful when one wishes to process all of the bits in a bitmask and ignore the padding/slack bits.

Parameters

number_of_bits

The number of bits that need to be represented

Returns

size_type The necessary number of bitmask_type elements

segmented_count_set_bits()

std::vector<size_type> cudf::segmented_count_set_bits	(	bitmask_type const *	bitmask,
		std::vector< cudf::size_type > const &	indices
	)

Given a bitmask, counts the number of set (1) bits in every range [indices[2*i], indices[(2*i)+1]) (where 0 <= i < indices.size() / 2).

Returns an empty vector if bitmask == nullptr.

Exceptions

cudf::logic_error	if indices.size() % 2 != 0
cudf::logic_error	if indices[2*i] < 0 or indices[2*i] > indices[(2*i)+1]

Parameters

[in]	bitmask	Bitmask residing in device memory whose bits will be counted
[in]	indices	A vector of indices used to specify ranges to count the number of set bits

Returns

std::vector<size_type> A vector storing the number of non-zero bits in the specified ranges

segmented_count_unset_bits()

std::vector<size_type> cudf::segmented_count_unset_bits	(	bitmask_type const *	bitmask,
		std::vector< cudf::size_type > const &	indices
	)

Given a bitmask, counts the number of unset (0) bits in every range [indices[2*i], indices[(2*i)+1]) (where 0 <= i < indices.size() / 2).

Returns an empty vector if bitmask == nullptr.

Exceptions

cudf::logic_error	if indices.size() % 2 != 0
cudf::logic_error	if indices[2*i] < 0 or indices[2*i] > indices[(2*i)+1]

Parameters

[in]	bitmask	Bitmask residing in device memory whose bits will be counted
[in]	indices	A vector of indices used to specify ranges to count the number of unset bits

Returns

std::vector<size_type> A vector storing the number of zero bits in the specified ranges

set_null_mask()

void cudf::set_null_mask	(	bitmask_type *	bitmask,
		size_type	begin_bit,
		size_type	end_bit,
		bool	valid
	)

Sets a pre-allocated bitmask buffer to a given state in the range [begin_bit, end_bit)

Sets [begin_bit, end_bit) bits of bitmask to valid if valid==true or null otherwise.

Parameters

bitmask	Pointer to bitmask (e.g. returned by column_view.null_mask())
begin_bit	Index of the first bit to set (inclusive)
end_bit	Index of the last bit to set (exclusive)
valid	If true set all entries to valid; otherwise, set all to null.

state_null_count()

size_type cudf::state_null_count	(	mask_state	state,
		size_type	size
	)

Returns the null count for a null mask of the specified state representing size elements.

Parameters

state	The state of the null mask
size	The number of elements represented by the mask

Returns

size_type The count of null elements