mysql::containers::buffers::Grow_constraint Class Reference

Description of a heuristic to determine how much memory to allocate. More...

#include <grow_constraint.h>

Inheritance diagram for mysql::containers::buffers::Grow_constraint:

Public Types
using	Size_t = std::size_t
using	Result_t = std::pair< bool, Size_t >
	Return type for compute_new_size. More...

Public Member Functions
	Grow_constraint ()=default
	Grow_constraint (const Grow_constraint &other)=default
	Grow_constraint (Grow_constraint &&other)=default
Grow_constraint &	operator= (const Grow_constraint &other)=default
Grow_constraint &	operator= (Grow_constraint &&other)=default
virtual	~Grow_constraint ()=default
void	set_max_size (Size_t max_size)
	Set the maximum size. More...
Size_t	get_max_size () const
void	set_grow_factor (double grow_factor)
	Set the grow factor. More...
double	get_grow_factor () const
void	set_grow_increment (Size_t grow_increment)
	Set the grow increment. More...
Size_t	get_grow_increment () const
void	set_block_size (Size_t block_size)
	Set the block size. More...
Size_t	get_block_size () const
std::string	debug_string () const
	In debug mode, return a string that describes the internal structure of this object, to use for debugging. More...
template<class T >
T	combine_with (const T &other) const
	Combine the constraints of this object with another Grow_constraint or Grow_calculator object. More...

Static Public Attributes
static constexpr Size_t	machine_max_size = std::numeric_limits<Size_t>::max()
	Maximum allowed value for the application max size. More...

Private Attributes
Size_t	m_max_size {machine_max_size}
	Size must not exceed this number. More...
double	m_grow_factor {default_grow_factor}
Size_t	m_grow_increment {default_grow_increment}
Size_t	m_block_size {default_block_size}

Static Private Attributes
static constexpr double	default_grow_factor = 1.0
	By default, don't constrain the grow factor. More...
static constexpr Size_t	default_grow_increment = 0
	By default, don't constrain the grow increment. More...
static constexpr Size_t	default_block_size = 1
	By default, don't constrain the block size. More...

Detailed Description

Description of a heuristic to determine how much memory to allocate.

This may be used in diverse contexts such as growing a memory buffer, or growing a pool of objects.

This encapsulates several common heuristics for growth:

• The growth rate can be exponential. This is useful for cases such as contiguous memory buffers, where each size increment may copy all the existing data, e.g., using 'realloc'. Or, more generally, any data structure where size growth has a cost that is linear in the total size. In such cases an exponential growth rate ensures that execution time is not quadratic in the number of grow operations.
• The growth rate can be linear. This is useful for cases such as linked lists, where each size increment is linear in the increment size.
• There can be an upper bound on the size. This is useful e.g. when there are configurable memory limits.
• The size can be specified to be a multiple of a given number. This can potentially be useful if there is a way to align allocated objects to page sizes, or similar.

Member Typedef Documentation

Result_t

using mysql::containers::buffers::Grow_constraint::Result_t = std::pair<bool, Size_t>

Return type for compute_new_size.

Size_t

using mysql::containers::buffers::Grow_constraint::Size_t = std::size_t

Constructor & Destructor Documentation

Grow_constraint() [1/3]

mysql::containers::buffers::Grow_constraint::Grow_constraint ( )

default

Grow_constraint() [2/3]

mysql::containers::buffers::Grow_constraint::Grow_constraint ( const Grow_constraint &  other )

default

Grow_constraint() [3/3]

mysql::containers::buffers::Grow_constraint::Grow_constraint ( Grow_constraint &&  other )

default

~Grow_constraint()

virtual mysql::containers::buffers::Grow_constraint::~Grow_constraint ( )

virtualdefault

Member Function Documentation

combine_with()

template<class T >

T mysql::containers::buffers::Grow_constraint::combine_with ( const T &  other ) const

inline

Combine the constraints of this object with another Grow_constraint or Grow_calculator object.

This will return a new object of the same type as the argument. The returned object will have the smallest max_size among this and other, and the largest grow_factor, grow_increment, and block_size.

debug_string()

std::string mysql::containers::buffers::Grow_constraint::debug_string ( ) const

inline

In debug mode, return a string that describes the internal structure of this object, to use for debugging.

get_block_size()

Grow_constraint::Size_t mysql::containers::buffers::Grow_constraint::get_block_size

(

)

const

Returns

the block size.

get_grow_factor()

double mysql::containers::buffers::Grow_constraint::get_grow_factor

(

)

const

Returns

the grow factor.

get_grow_increment()

Grow_constraint::Size_t mysql::containers::buffers::Grow_constraint::get_grow_increment

(

)

const

Returns

the grow increment.

get_max_size()

Grow_constraint::Size_t mysql::containers::buffers::Grow_constraint::get_max_size

(

)

const

Returns

the maximum size.

operator=() [1/2]

Grow_constraint & mysql::containers::buffers::Grow_constraint::operator= ( const Grow_constraint &  other )

default

operator=() [2/2]

Grow_constraint & mysql::containers::buffers::Grow_constraint::operator= ( Grow_constraint &&  other )

default

set_block_size()

void mysql::containers::buffers::Grow_constraint::set_block_size

(

Size_t

block_size

)

Set the block size.

The size should be kept to a multiple of this number.

set_grow_factor()

void mysql::containers::buffers::Grow_constraint::set_grow_factor

(

double

grow_factor

)

Set the grow factor.

Whenever the size needs to increase, it should increase it by at least this factor.

Using a value > 1 ensures that successive calls to reserve() with sizes increasing up to N take amortized linear time in N; a value equal to 1 may result in execution time that is quadratic in N.

set_grow_increment()

void mysql::containers::buffers::Grow_constraint::set_grow_increment

(

Size_t

grow_increment

)

Set the grow increment.

Whenever the size needs to increase, it should increase by at least this amount.

set_max_size()

void mysql::containers::buffers::Grow_constraint::set_max_size

(

Size_t

max_size

)

Set the maximum size.

Whenever more than this is requested, the response should be to fail. This is an inclusive upper bound, so requests for exactly this size are allowed.

Member Data Documentation

default_block_size

constexpr Size_t mysql::containers::buffers::Grow_constraint::default_block_size = 1

staticconstexprprivate

By default, don't constrain the block size.

default_grow_factor

constexpr double mysql::containers::buffers::Grow_constraint::default_grow_factor = 1.0

staticconstexprprivate

By default, don't constrain the grow factor.

default_grow_increment

constexpr Size_t mysql::containers::buffers::Grow_constraint::default_grow_increment = 0

staticconstexprprivate

By default, don't constrain the grow increment.

m_block_size

Size_t mysql::containers::buffers::Grow_constraint::m_block_size {default_block_size}

private

m_grow_factor

double mysql::containers::buffers::Grow_constraint::m_grow_factor {default_grow_factor}

private

m_grow_increment

Size_t mysql::containers::buffers::Grow_constraint::m_grow_increment {default_grow_increment}

private

m_max_size

Size_t mysql::containers::buffers::Grow_constraint::m_max_size {machine_max_size}

private

Size must not exceed this number.

machine_max_size

constexpr Size_t mysql::containers::buffers::Grow_constraint::machine_max_size = std::numeric_limits<Size_t>::max()

staticconstexpr

Maximum allowed value for the application max size.

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The documentation for this class was generated from the following files:

• libs/mysql/containers/buffers/grow_constraint.h
• libs/mysql/containers/buffers/grow_constraint.cpp