lar::BulkAllocator< T > Class Template Reference

Aggressive allocator reserving a lot of memory in advance. More...

#include <BulkAllocator.h>

Inheritance diagram for lar::BulkAllocator< T >:

Classes
struct	rebind

Public Types
using	BaseAllocator_t = std::allocator< T >
typedef BaseAllocator_t::size_type	size_type
typedef BaseAllocator_t::difference_type	difference_type
typedef BaseAllocator_t::value_type	value_type
typedef BaseAllocator_t::pointer	pointer
typedef BaseAllocator_t::const_pointer	const_pointer
typedef BaseAllocator_t::reference	reference
typedef BaseAllocator_t::const_reference	const_reference

Public Member Functions
	BulkAllocator () noexcept
	Default constructor: uses the default chunk size. More...
	BulkAllocator (size_type ChunkSize, bool bPreallocate=false) noexcept
	Constructor: sets chunk size and optionally allocates the first chunk. More...
	BulkAllocator (const BulkAllocator &a) noexcept=default
	Copy constructor: default. More...
	BulkAllocator (BulkAllocator &&a) noexcept=default
	Move constructor: default. More...
template<class U >
	BulkAllocator (const BulkAllocator< U > &a) noexcept
	General copy constructor; currently, it does not preallocate. More...
BulkAllocator &	operator= (const BulkAllocator &a)=default
	Copy assignment: default. More...
BulkAllocator &	operator= (BulkAllocator &&a)=default
	Move assignment: default. More...
	~BulkAllocator ()
	Destructor; memory is freed only if no allocators are left around. More...
pointer	allocate (size_type n, const void *=0)
	Allocates memory for n elements. More...
void	deallocate (pointer p, size_type n)
	Frees n elements at p. More...

Static Public Member Functions
static void	Free ()
	Releases all the allocated memory: dangerous! More...
static size_type	GetChunkSize ()
	Returns the chunk size of the underlying global allocator. More...
static void	SetChunkSize (size_type ChunkSize)
	Sets chunk size of global allocator; only affects future allocations! More...

Private Types
typedef details::bulk_allocator::BulkAllocatorBase < T >	SharedAllocator_t
	shared allocator type More...

Private Member Functions
void	CreateGlobalAllocator (size_type ChunkSize, bool bPreallocate=false)
	Makes sure we have a valid "global allocator". More...

Static Private Attributes
static SharedAllocator_t	GlobalAllocator
	The allocator shared by all instances of this object. More...

Additional Inherited Members
Public Attributes inherited from std::allocator< T >
T	elements
	STL member. More...

Detailed Description

template<typename T>
class lar::BulkAllocator< T >

Aggressive allocator reserving a lot of memory in advance.

Parameters

T	type being allocated

This allocator appropriates memory in large chunks of GetChunkSize() elements of type T. The memory will never be deleted! (but read further)

Note

With C++17, an allocator called std::pmr::monotonic_buffer_resource is available that seems to have pretty much the same functionality as this one (but STL quality). When C++17 is adopted by LArSoft (and the supported compilers have a complete enough support for it), the users of BulkAllocator should migrate to that one. Note that the interface is different, and probably the way to use it is also different.

Deletion policy

This allocator does not release not reuse deallocated memory. This design choice is meant to reflect a specific use case where a large amount of elements is created and then used, and the created object is fairly static. Tracking freed memory fragments takes time and more memory, and reusing them too. Nevertheless, the allocator has a user count; when no user is present, all the memory is deallocated. This can be convenient, or disastrous: remember that the elements of a container can (or just might) not survive after the container is destroyed. Clearing the container will not trigger this self-distruction; if you are completely sure that no other container is currently using the same allocator, you can explicitly Free() its memory.

One allocator for them all

Since STL containers do not necessarely store their allocator but they may create it with a default constructor, allocators should be formally stateless, and every newly-created allocator should be equivalent (or else a copy of an allocator will not know what the original has allocated already).

This is implemented hiding a singleton in the allocator (as a static member). Each allocator type has its own singleton, i.e., a BulkAllocator<int> does not share memory with a BulkAllocator<double>, but all BulkAllocator<int> share.

Definition at line 92 of file BulkAllocator.h.

Member Typedef Documentation

template<typename T>

using lar::BulkAllocator< T >::BaseAllocator_t = std::allocator<T>

Definition at line 94 of file BulkAllocator.h.

template<typename T>

typedef BaseAllocator_t::const_pointer lar::BulkAllocator< T >::const_pointer

Definition at line 103 of file BulkAllocator.h.

template<typename T>

typedef BaseAllocator_t::const_reference lar::BulkAllocator< T >::const_reference

Definition at line 106 of file BulkAllocator.h.

template<typename T>

typedef BaseAllocator_t::difference_type lar::BulkAllocator< T >::difference_type

Definition at line 98 of file BulkAllocator.h.

template<typename T>

typedef BaseAllocator_t::pointer lar::BulkAllocator< T >::pointer

Definition at line 102 of file BulkAllocator.h.

template<typename T>

typedef BaseAllocator_t::reference lar::BulkAllocator< T >::reference

Definition at line 105 of file BulkAllocator.h.

template<typename T>

typedef details::bulk_allocator::BulkAllocatorBase<T> lar::BulkAllocator< T >::SharedAllocator_t

private

shared allocator type

Definition at line 158 of file BulkAllocator.h.

template<typename T>

typedef BaseAllocator_t::size_type lar::BulkAllocator< T >::size_type

Definition at line 97 of file BulkAllocator.h.

template<typename T>

typedef BaseAllocator_t::value_type lar::BulkAllocator< T >::value_type

Definition at line 100 of file BulkAllocator.h.

Constructor & Destructor Documentation

template<typename T>

lar::BulkAllocator< T >::BulkAllocator ( )

inlinenoexcept

Default constructor: uses the default chunk size.

Definition at line 114 of file BulkAllocator.h.

: BulkAllocator(GetChunkSize(), false) {}

template<typename T>

lar::BulkAllocator< T >::BulkAllocator ( size_type  ChunkSize, bool  bPreallocate = false  )

inlinenoexcept

Constructor: sets chunk size and optionally allocates the first chunk.

Definition at line 117 of file BulkAllocator.h.

      { CreateGlobalAllocator(ChunkSize, bPreallocate); }

template<typename T>

lar::BulkAllocator< T >::BulkAllocator ( const BulkAllocator< T > &  a )

defaultnoexcept

Copy constructor: default.

template<typename T>

lar::BulkAllocator< T >::BulkAllocator ( BulkAllocator< T > &&  a )

defaultnoexcept

Move constructor: default.

template<typename T>

template<class U >

lar::BulkAllocator< T >::BulkAllocator ( const BulkAllocator< U > &  a )

inlinenoexcept

General copy constructor; currently, it does not preallocate.

Definition at line 128 of file BulkAllocator.h.

                                                     :
      BaseAllocator_t(a) { SetChunkSize(a.GetChunkSize()); }

template<typename T>

lar::BulkAllocator< T >::~BulkAllocator ( )

inline

Destructor; memory is freed only if no allocators are left around.

Definition at line 138 of file BulkAllocator.h.

{ GlobalAllocator.RemoveUser(); }

Member Function Documentation

template<typename T >

BulkAllocator< T >::pointer lar::BulkAllocator< T >::allocate ( size_type  n, const void *  = 0  )

inline

Allocates memory for n elements.

Definition at line 562 of file BulkAllocator.h.

    { return GlobalAllocator.Get(n); }

template<typename T >

void lar::BulkAllocator< T >::CreateGlobalAllocator ( size_type  ChunkSize, bool  bPreallocate = false  )

private

Makes sure we have a valid "global allocator".

Definition at line 555 of file BulkAllocator.h.

  {
    GlobalAllocator.AddUser(ChunkSize, bPreallocate);
  } // BulkAllocator<T>::CreateGlobalAllocator()

template<typename T >

void lar::BulkAllocator< T >::deallocate ( pointer  p, size_type  n  )

inline

Frees n elements at p.

Definition at line 566 of file BulkAllocator.h.

                                                                 {
    return GlobalAllocator.Release(p);
  } // BulkAllocator<T>::deallocate()

template<typename T>

static void lar::BulkAllocator< T >::Free ( )

inlinestatic

Releases all the allocated memory: dangerous!

Definition at line 147 of file BulkAllocator.h.

{ GlobalAllocator.Free(); }

template<typename T>

static size_type lar::BulkAllocator< T >::GetChunkSize ( )

inlinestatic

Returns the chunk size of the underlying global allocator.

Definition at line 150 of file BulkAllocator.h.

{ return GlobalAllocator.GetChunkSize(); }

template<typename T>

BulkAllocator& lar::BulkAllocator< T >::operator= ( const BulkAllocator< T > &  a )

default

Copy assignment: default.

template<typename T>

BulkAllocator& lar::BulkAllocator< T >::operator= ( BulkAllocator< T > &&  a )

default

Move assignment: default.

template<typename T>

static void lar::BulkAllocator< T >::SetChunkSize ( size_type  ChunkSize )

inlinestatic

Sets chunk size of global allocator; only affects future allocations!

Definition at line 153 of file BulkAllocator.h.

      { GlobalAllocator.SetChunkSize(ChunkSize); }

Member Data Documentation

template<typename T>

BulkAllocator< T >::SharedAllocator_t lar::BulkAllocator< T >::GlobalAllocator

staticprivate

The allocator shared by all instances of this object.

Definition at line 164 of file BulkAllocator.h.

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

• BulkAllocator.h