#include <gromacs/utility/allocator.h>

Inherits AllocationPolicy.

Description

template<class T, typename AllocationPolicy>
class gmx::Allocator< T, AllocationPolicy >

Policy-based memory allocator.

Template Parameters

T	Type of objects to allocate
AllocationPolicy	Policy of (matching) allocation and deallocation functions.

This class can be used for the optional allocator template parameter in standard library containers. It must be configured with both the type of object to allocate, and an AllocationPolicy which effectively wraps a matching pair of malloc and free functions. This permits implementing a family of related allocators e.g. with SIMD alignment, GPU host-side page locking, or perhaps both, in a way that preserves a common programming interface and duplicates minimal code.

AllocationPolicy is used as a base class, so that if AllocationPolicy is stateless, then the empty base optimization will ensure that Allocation is also stateless, and objects made with the Allocator will incur no size penalty. (Embedding an AllocationPolicy object incurs a size penalty always, even if the object is empty.) Normally a stateless allocator will be used.

However, an AllocationPolicy with state might be desirable for simplifying writing code that needs to allocate suitably for a transfer to a GPU. That code needs to specify an Allocator that can do the right job, which can be stateless. However, if we have code that will not know until run time whether a GPU transfer will occur, then the allocator needs to be aware of the state. That will increase the size of a container that uses the stateful allocator.

Exceptions

std::bad_alloc Instead of a GROMACS exception object, we throw the standard one on allocation failures to make it as compatible as possible with the errors expected by code using the standard library containers.

Classes
struct	rebind
	Standard-required typedef to use allocator with different class. More...

Public Types
typedef T	value_type
	Type of allocated elements.

typedef T &	reference
	Reference to allocated elements.

typedef const T &	const_reference
	Constant reference to allocated elements.

typedef T *	pointer
	Pointer to allocated elements.

typedef const T *	const_pointer
	Constant pointer to allocated elements.

typedef std::size_t	size_type
	Integer type to use for size of objects.

typedef std::ptrdiff_t	difference_type
	Type to hold differences between pointers.

typedef AllocationPolicy	allocation_policy
	Type of the AllocationPolicy.

Public Member Functions
template<class U >
	Allocator (const Allocator< U, AllocationPolicy > &)
	Templated copy constructor. More...

	Allocator ()=default
	Constructor. More...

	Allocator (const AllocationPolicy &p)
	Constructor to accept an AllocationPolicy. More...

pointer	address (reference r) const
	Return address of an object. More...

const_pointer	address (const_reference r) const
	Return address of a const object. More...

pointer	allocate (std::size_t n, typename std::allocator< void >::const_pointer hint=nullptr)
	Do the actual memory allocation. More...

void	deallocate (pointer p, std::size_t n)
	Release memory. More...

AllocationPolicy	getPolicy () const
	Return the policy object for this allocator.

template<class... Args>
void	construct (pointer p, Args &&...args)
	Construct an object without allocating memory. More...

void	destroy (pointer p)
	Call the destructor of object without releasing memory. More...

std::size_t	max_size () const
	Return largest number of objects that can be allocated. More...

template<class T2 >
bool	operator== (const Allocator< T2, AllocationPolicy > &) const
	Return true if two allocators are identical. More...

bool	operator!= (const Allocator &rhs) const
	Return true if two allocators are different. More...

Constructor & Destructor Documentation

template<class T , typename AllocationPolicy >

template<class U >

gmx::Allocator< T, AllocationPolicy >::Allocator ( const Allocator< U, AllocationPolicy > & )

inlineexplicit

Templated copy constructor.

This template constructor cannot be auto-generated, and is normally unused, except e.g. MSVC2015 standard library uses it in debug mode, presumably to implement some checks.

template<class T , typename AllocationPolicy >

gmx::Allocator< T, AllocationPolicy >::Allocator ( )

default

Constructor.

No constructor can be auto-generated in the presence of any user-defined constructor, but we want the default constructor.

template<class T , typename AllocationPolicy >

gmx::Allocator< T, AllocationPolicy >::Allocator ( const AllocationPolicy & p )

inline

Constructor to accept an AllocationPolicy.

This is useful for AllocationPolicies with state.

Member Function Documentation

template<class T , typename AllocationPolicy >

pointer gmx::Allocator< T, AllocationPolicy >::address ( reference r ) const

inline

Return address of an object.

Parameters

r	Reference to object of type T

Returns: Pointer to T memory

template<class T , typename AllocationPolicy >

const_pointer gmx::Allocator< T, AllocationPolicy >::address ( const_reference r ) const

inline

Return address of a const object.

Parameters

r	Const reference to object of type T

Returns: Pointer to T memory

template<class T , typename AllocationPolicy >

pointer gmx::Allocator< T, AllocationPolicy >::allocate	(	std::size_t	n,
		typename std::allocator< void >::const_pointer	hint = `nullptr`
	)

inline

Do the actual memory allocation.

Parameters

n	Number of elements of type T to allocate. n can be 0 bytes, which will return a non-null properly aligned and padded pointer that should not be used.
hint	Optional value returned from previous call to allocate. For now this is not used.

Returns: Pointer to allocated memory

Exceptions

std::bad_alloc if the allocation fails.

template<class T , typename AllocationPolicy >

template<class... Args>

void gmx::Allocator< T, AllocationPolicy >::construct	(	pointer	p,
		Args &&...	args
	)

inline

Construct an object without allocating memory.

Template Parameters

Args	Variable-length list of types for constructor args

Parameters

p	Adress of memory where to construct object
args	Variable-length list of arguments to constructor

template<class T , typename AllocationPolicy >

void gmx::Allocator< T, AllocationPolicy >::deallocate	(	pointer	p,
		std::size_t	n
	)

inline

Release memory.

Parameters

p	Pointer to previously allocated memory returned from allocate()
n	number of objects previously passed to allocate()

template<class T , typename AllocationPolicy >

void gmx::Allocator< T, AllocationPolicy >::destroy ( pointer p )

inline

Call the destructor of object without releasing memory.

Parameters

p	Address of memory where to destroy object

template<class T , typename AllocationPolicy >

std::size_t gmx::Allocator< T, AllocationPolicy >::max_size ( ) const

inline

Return largest number of objects that can be allocated.

This will be set such that the number of objects T multiplied by the size of each object is the largest value that can be represented by size_type.

template<class T , typename AllocationPolicy >

bool gmx::Allocator< T, AllocationPolicy >::operator!= ( const Allocator< T, AllocationPolicy > & rhs ) const

inline

Return true if two allocators are different.

Parameters

rhs	Other allocator.

This is a member function of the left-hand-side allocator.

template<class T , typename AllocationPolicy >

template<class T2 >

bool gmx::Allocator< T, AllocationPolicy >::operator== ( const Allocator< T2, AllocationPolicy > & ) const

inline

Return true if two allocators are identical.

This is a member function of the left-hand-side allocator.

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

src/gromacs/utility/allocator.h

Description

template<class T, typename AllocationPolicy> class gmx::Allocator< T, AllocationPolicy >

Classes

Public Types

Public Member Functions

Constructor & Destructor Documentation

Member Function Documentation

template<class T, typename AllocationPolicy>
class gmx::Allocator< T, AllocationPolicy >