vnl_alloc.h File Reference

Default node allocator. More...

#include <cstddef>
#include "vnl/vnl_export.h"

Go to the source code of this file.

Classes
class	vnl_alloc
union	vnl_alloc::obj
class	vnl_alloc::lock

Variables
constexpr int	VNL_ALLOC_ALIGN = 8
constexpr std::size_t	VNL_ALLOC_MAX_BYTES = 256
constexpr std::size_t	VNL_ALLOC_NFREELISTS = VNL_ALLOC_MAX_BYTES/VNL_ALLOC_ALIGN

Detailed Description

Default node allocator.

Author

unknown

With a reasonable compiler, this should be roughly as fast as the original STL class-specific allocators, but with less fragmentation. Default_alloc_template parameters are experimental and MAY DISAPPEAR in the future. Clients should just use vcl_alloc for now.

Important implementation properties:

• If the client request an object of size > __MAX_BYTES, the resulting object will be obtained directly from malloc.
• In all other cases, we allocate an object of size exactly ROUND_UP(requested_size). Thus the client has enough size information that we can return the object to the proper free li*st without permanently losing part of the object.

The first template parameter specifies whether more than one thread may use this allocator. It is safe to allocate an object from one instance of a default_alloc and deallocate it with another one. This effectively transfers its ownership to the second one. This may have undesirable effects on reference locality. The second parameter is unreferenced and serves only to allow the creation of multiple default_alloc instances.

Note that containers built on different allocator instances have different types, limiting the utility of this approach.

Definition in file vnl_alloc.h.

Variable Documentation

VNL_ALLOC_ALIGN

constexpr int VNL_ALLOC_ALIGN = 8

Definition at line 40 of file vnl_alloc.h.

VNL_ALLOC_MAX_BYTES

constexpr std::size_t VNL_ALLOC_MAX_BYTES = 256

Definition at line 41 of file vnl_alloc.h.

VNL_ALLOC_NFREELISTS

constexpr std::size_t VNL_ALLOC_NFREELISTS = VNL_ALLOC_MAX_BYTES/VNL_ALLOC_ALIGN

Definition at line 42 of file vnl_alloc.h.