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<h1 class="topictitle1">Containers</h1>
<div>
<p>Intel® Threading Building Blocks (Intel® TBB) provides highly concurrent
container classes. These containers can be used with raw Windows* OS or Linux*
OS threads, or in conjunction with task-based programming.
</p>
<p>A concurrent container allows multiple threads to concurrently access
and update items in the container. Typical C++ STL containers do not permit
concurrent update; attempts to modify them concurrently often result in
corrupting the container. STL containers can be wrapped in a mutex to make them
safe for concurrent access, by letting only one thread operate on the container
at a time, but that approach eliminates concurrency, thus restricting parallel
speedup.
</p>
<p>Containers provided by Intel® TBB offer a much higher level of
concurrency, via one or both of the following methods:
</p>
<ul type="disc">
<li>
<p><strong>Fine-grained locking:</strong> Multiple threads operate on the
container by locking only those portions they really need to lock. As long as
different threads access different portions, they can proceed concurrently.
</p>
</li>
<li>
<p><strong>Lock-free techniques:</strong> Different threads account and correct
for the effects of other interfering threads.
</p>
</li>
</ul>
<p>Notice that highly-concurrent containers come at a cost. They
typically have higher overheads than regular STL containers. Operations on
highly-concurrent containers may take longer than for STL containers.
Therefore, use highly-concurrent containers when the speedup from the
additional concurrency that they enable outweighs their slower sequential
performance.
</p>
<div class="Note"><h3 class="NoteTipHead">
Caution</h3>
<p>As with most objects in C++, the constructor or destructor of a
container object must not be invoked concurrently with another operation on the
same object. Otherwise the resulting race may cause the operation to be
executed on an undefined object.
</p>
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<li class="ulchildlink"><a href="../tbb_userguide/concurrent_hash_map.htm">concurrent_hash_map</a><br>
</li>
<li class="ulchildlink"><a href="../tbb_userguide/concurrent_vector.htm">concurrent_vector</a><br>
</li>
<li class="ulchildlink"><a href="../tbb_userguide/Concurrent_Queue_Classes.htm">Concurrent Queue Classes</a><br>
</li>
<li class="ulchildlink"><a href="../tbb_userguide/Summary_of_Containers.htm">Summary of Containers</a><br>
</li>
</ul>
<h2>See Also</h2>
<div class="linklist">
<div><a href="Task-Based_Programming.htm">Task Based Programming
</a></div></div>
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