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# tbb::concurrent_vector< T, A > Class Template Reference
[Containers]

Concurrent vector container. More...

`#include <concurrent_vector.h>`

List of all members.

## Public Types
typedef internal::concurrent_vector_base_v3::size_type | size_type
typedef internal::allocator_base< T, A >::allocator_type | allocator_type
typedef T | value_type
typedef ptrdiff_t | difference_type
typedef T & | reference
typedef const T & | const_reference
typedef T * | pointer
typedef const T * | const_pointer
typedef internal::vector_iterator< concurrent_vector, T > | iterator
typedef internal::vector_iterator< concurrent_vector, const T > | const_iterator
typedef std::reverse_iterator< iterator > | reverse_iterator
typedef std::reverse_iterator< const_iterator > | const_reverse_iterator
typedef std::reverse_iterator< iterator, T, T &, T * > | reverse_iterator
typedef std::reverse_iterator< const_iterator, T, const T &, const T * > | const_reverse_iterator
typedef generic_range_type< iterator > | range_type
typedef generic_range_type< const_iterator > | const_range_type
## Public Member Functions
| concurrent_vector (const allocator_type &a=allocator_type())
| Construct empty vector.
| concurrent_vector (const concurrent_vector &vector, const allocator_type &a=allocator_type())
| Copying constructor.
template<class M>
| concurrent_vector (const concurrent_vector< T, M > &vector, const allocator_type &a=allocator_type())
| Copying constructor for vector with different allocator type.
| concurrent_vector (size_type n)
| Construction with initial size specified by argument n.
| concurrent_vector (size_type n, const_reference t, const allocator_type &a=allocator_type())
| Construction with initial size specified by argument n, initialization by copying of t, and given allocator instance.
template<class I>
| concurrent_vector (I first, I last, const allocator_type &a=allocator_type())
| Construction with copying iteration range and given allocator instance.
concurrent_vector & | operator= (const concurrent_vector &vector)
| Assignment.
template<class M>
concurrent_vector & | operator= (const concurrent_vector< T, M > &vector)
| Assignment for vector with different allocator type.
size_type | grow_by (size_type delta)
| Grow by "delta" elements.
iterator | grow_by (size_type delta)
size_type | grow_by (size_type delta, const_reference t)
| Grow by "delta" elements using copying constuctor.
iterator | grow_by (size_type delta, const_reference t)
void | grow_to_at_least (size_type n)
| Append minimal sequence of elements such that size()>=n.
iterator | grow_to_at_least (size_type n)
size_type | push_back (const_reference item) iterator push_back(const _reference item)
| Push item.
reference | operator[] (size_type index)
| Get reference to element at given index.
const_reference | operator[] (size_type index) const
| Get const reference to element at given index.
reference | at (size_type index)
| Get reference to element at given index. Throws exceptions on errors.
const_reference | at (size_type index) const
| Get const reference to element at given index. Throws exceptions on errors.
range_type | range (size_t grainsize=1)
| Get range for iterating with parallel algorithms.
const_range_type | range (size_t grainsize=1) const
| Get const range for iterating with parallel algorithms.
size_type | size () const
| Return size of vector. It may include elements under construction.
bool | empty () const
| Return true if vector is not empty or has elements under construction at least.
size_type | capacity () const
| Maximum size to which array can grow without allocating more memory. Concurrent allocations are not included in the value.
void | reserve (size_type n)
| Allocate enough space to grow to size n without having to allocate more memory later.
void | resize (size_type n)
| Resize the vector. Not thread-safe.
void | resize (size_type n, const_reference t)
| Resize the vector, copy t for new elements. Not thread-safe.
void | compact ()
| An alias for shrink_to_fit().
void | shrink_to_fit ()
| Optimize memory usage and fragmentation.
size_type | max_size () const
| Upper bound on argument to reserve.
iterator | begin ()
| start iterator
iterator | end ()
| end iterator
const_iterator | begin () const
| start const iterator
const_iterator | end () const
| end const iterator
const_iterator | cbegin () const
| start const iterator
const_iterator | cend () const
| end const iterator
reverse_iterator | rbegin ()
| reverse start iterator
reverse_iterator | rend ()
| reverse end iterator
const_reverse_iterator | rbegin () const
| reverse start const iterator
const_reverse_iterator | rend () const
| reverse end const iterator
const_reverse_iterator | crbegin () const
| reverse start const iterator
const_reverse_iterator | crend () const
| reverse end const iterator
reference | front ()
| the first item
const_reference | front () const
| the first item const
reference | back ()
| the last item
const_reference | back () const
| the last item const
allocator_type | get_allocator () const
| return allocator object
void | assign (size_type n, const_reference t)
| assign n items by copying t item
template<class I>
void | assign (I first, I last)
| assign range [first, last)
void | swap (concurrent_vector &vector)
| swap two instances
void | clear ()
| Clear container while keeping memory allocated.
| ~concurrent_vector ()
| Clear and destroy vector.
const internal::concurrent_vector_base_v3 & | internal_vector_base () const
## Friends
class | internal::vector_iterator
## Classes
class | generic_range_type
class | internal_loop_guide
| Exception-aware helper class for filling a segment by exception-danger operators of user class.

## Detailed Description

### template<typename T, class A>
class tbb::concurrent_vector< T, A >

Concurrent vector container.

concurrent_vector is a container having the following main properties:

- It provides random indexed access to its elements. The index of the first element is 0.
- It ensures safe concurrent growing its size (different threads can safely append new elements).
- Adding new elements does not invalidate existing iterators and does not change indices of existing items.

Compatibility
  The class meets all Container Requirements and Reversible Container Requirements from C++ Standard (See ISO/IEC 14882:2003(E), clause 23.1). But it doesn't meet Sequence Requirements due to absence of insert() and erase() methods.

Exception Safety
  Methods working with memory allocation and/or new elements construction can throw an exception if allocator fails to allocate memory or element's default constructor throws one. Concurrent vector's element of type T must conform to the following requirements:
  - Throwing an exception is forbidden for destructor of T.
  - Default constructor of T must not throw an exception OR its non-virtual destructor must safely work when its object memory is zero-initialized.
  Otherwise, the program's behavior is undefined.

  If an exception happens inside growth or assignment operation, an instance of the vector becomes invalid unless it is stated otherwise in the method documentation. Invalid state means:
  - There are no guaranties that all items were initialized by a constructor. The rest of items is zero-filled, including item where exception happens.
  - An invalid vector instance cannot be repaired; it is unable to grow anymore.
  - Size and capacity reported by the vector are incorrect, and calculated as if the failed operation were successful.
  - Attempt to access not allocated elements using operator[] or iterators results in access violation or segmentation fault exception, and in case of using at() method a C++ exception is thrown.
  If a concurrent grow operation successfully completes, all the elements it has added to the vector will remain valid and accessible even if one of subsequent grow operations fails.

Fragmentation
  Unlike an STL vector, a concurrent_vector does not move existing elements if it needs to allocate more memory. The container is divided into a series of contiguous arrays of elements. The first reservation, growth, or assignment operation determines the size of the first array. Using small number of elements as initial size incurs fragmentation that may increase element access time. Internal layout can be optimized by method compact() that merges several smaller arrays into one solid.

Changes since TBB 2.1
  - Fixed guarantees of concurrent_vector::size() and grow_to_at_least() methods to assure elements are allocated.
  - Methods end()/rbegin()/back() are partly thread-safe since they use size() to get the end of vector
  - Added resize() methods (not thread-safe)
  - Added cbegin/cend/crbegin/crend methods
  - Changed return type of methods grow* and push_back to iterator

Changes since TBB 2.0
  - Implemented exception-safety guaranties
  - Added template argument for allocator
  - Added allocator argument in constructors
  - Faster index calculation
  - First growth call specifies a number of segments to be merged in the first allocation.
  - Fixed memory blow up for swarm of vector's instances of small size
  - Added grow_by(size_type n, const_reference t) growth using copying constructor to init new items.
  - Added STL-like constructors.
  - Added operators ==, < and derivatives
  - Added at() method, approved for using after an exception was thrown inside the vector
  - Added get_allocator() method.
  - Added assign() methods
  - Added compact() method to defragment first segments
  - Added swap() method
  - range() defaults on grainsize = 1 supporting auto grainsize algorithms.

## Member Function Documentation

template<typename T, class A>

void tbb::concurrent_vector< T, A >::clear | ( |  | ) | `[inline]`

Clear container while keeping memory allocated.

To free up the memory, use in conjunction with method compact(). Not thread safe

template<typename T, class A>

iterator tbb::concurrent_vector< T, A >::grow_by | ( | size_type | delta,
|  | const_reference | t |
| ) |  |  | `[inline]`

Returns iterator pointing to the first new element.

template<typename T, class A>

size_type tbb::concurrent_vector< T, A >::grow_by | ( | size_type | delta,
|  | const_reference | t |
| ) |  |  | `[inline]`

Grow by "delta" elements using copying constuctor.

Returns old size.

template<typename T, class A>

iterator tbb::concurrent_vector< T, A >::grow_by | ( | size_type | delta | ) | `[inline]`

Returns iterator pointing to the first new element.

template<typename T, class A>

size_type tbb::concurrent_vector< T, A >::grow_by | ( | size_type | delta | ) | `[inline]`

Grow by "delta" elements.

Returns old size.

template<typename T, class A>

iterator tbb::concurrent_vector< T, A >::grow_to_at_least | ( | size_type | n | ) | `[inline]`

The new elements are default constructed. Blocks until all elements in range [0..n) are allocated. May return while other elements are being constructed by other threads. Returns iterator that points to beginning of appended sequence. If no elements were appended, returns iterator pointing to nth element.

template<typename T, class A>

void tbb::concurrent_vector< T, A >::grow_to_at_least | ( | size_type | n | ) | `[inline]`

Append minimal sequence of elements such that size()>=n.

The new elements are default constructed. Blocks until all elements in range [0..n) are allocated. May return while other elements are being constructed by other threads.

template<typename T, class A>

reference tbb::concurrent_vector< T, A >::operator[] | ( | size_type | index | ) | `[inline]`

Get reference to element at given index.

This method is thread-safe for concurrent reads, and also while growing the vector, as long as the calling thread has checked that index<size().

template<typename T, class A>

size_type tbb::concurrent_vector< T, A >::push_back | ( | const_reference | item | ) | const`[inline]`

Push item.

Returns iterator pointing to the new element.

template<typename T, class A>

void tbb::concurrent_vector< T, A >::reserve | ( | size_type | n | ) | `[inline]`

Allocate enough space to grow to size n without having to allocate more memory later.

Like most of the methods provided for STL compatibility, this method is *not* thread safe. The capacity afterwards may be bigger than the requested reservation.

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

- concurrent_vector.h

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