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| <div class="titlepage"><div><div><h2 class="title" style="clear: both"> |
| <a name="intrusive.splay_set_multiset"></a><a class="link" href="splay_set_multiset.html" title="Intrusive splay tree based associative containers: splay_set, splay_multiset and , splay_tree">Intrusive splay tree based |
| associative containers: splay_set, splay_multiset and , splay_tree</a> |
| </h2></div></div></div> |
| <div class="toc"><dl class="toc"> |
| <dt><span class="section"><a href="splay_set_multiset.html#intrusive.splay_set_multiset.splay_set_multiset_disadvantages">Advantages |
| and disadvantages of splay tree based containers</a></span></dt> |
| <dt><span class="section"><a href="splay_set_multiset.html#intrusive.splay_set_multiset.set_multiset_containers">splay_set, |
| splay_multiset and splaytree containers</a></span></dt> |
| <dt><span class="section"><a href="splay_set_multiset.html#intrusive.splay_set_multiset.splay_set_multiset_example">Example</a></span></dt> |
| </dl></div> |
| <p> |
| C++ associative containers are usually based on red-black tree implementations |
| (e.g.: STL, Boost.Intrusive associative containers). However, there are other |
| interesting data structures that offer some advantages (and also disadvantages). |
| </p> |
| <p> |
| Splay trees are self-adjusting binary search trees used typically in caches, |
| memory allocators and other applications, because splay trees have a "caching |
| effect": recently accessed elements have better access times than elements |
| accessed less frequently. For more information on splay trees see <a href="http://en.wikipedia.org/wiki/Splay_tree" target="_top">the |
| corresponding Wikipedia entry</a>. |
| </p> |
| <p> |
| <span class="bold"><strong>Boost.Intrusive</strong></span> offers 3 containers based |
| on splay trees: <code class="computeroutput"><a class="link" href="../boost/intrusive/splay_set.html" title="Class template splay_set">splay_set</a></code>, |
| <code class="computeroutput"><a class="link" href="../boost/intrusive/splay_multiset.html" title="Class template splay_multiset">splay_multiset</a></code> |
| and <code class="computeroutput"><a class="link" href="../boost/intrusive/splaytree.html" title="Class template splaytree">splaytree</a></code>. The |
| first two are similar to <code class="computeroutput"><a class="link" href="../boost/intrusive/set.html" title="Class template set">set</a></code> |
| or <code class="computeroutput"><a class="link" href="../boost/intrusive/multiset.html" title="Class template multiset">multiset</a></code> and the |
| latter is a generalization that offers functions both to insert unique and |
| multiple keys. |
| </p> |
| <p> |
| The memory overhead of these containers with Boost.Intrusive hooks is usually |
| 3 pointers. An empty, non constant-time size splay container has also a size |
| of 3 pointers. |
| </p> |
| <div class="section"> |
| <div class="titlepage"><div><div><h3 class="title"> |
| <a name="intrusive.splay_set_multiset.splay_set_multiset_disadvantages"></a><a class="link" href="splay_set_multiset.html#intrusive.splay_set_multiset.splay_set_multiset_disadvantages" title="Advantages and disadvantages of splay tree based containers">Advantages |
| and disadvantages of splay tree based containers</a> |
| </h3></div></div></div> |
| <p> |
| Splay tree based intrusive containers have logarithmic complexity in many |
| operations like searches, insertions, erasures, etc., but if some elements |
| are more frequently accessed than others, splay trees perform faster searches |
| than equivalent balanced binary trees (such as red-black trees). |
| </p> |
| <p> |
| The caching effect offered by splay trees comes with a cost: the tree must |
| be rebalanced when an element is searched. To maintain const-correctness |
| and thread-safety guarantees, this caching effect is not updated when const |
| versions of search functions like <code class="computeroutput"><span class="identifier">find</span><span class="special">()</span></code>, <code class="computeroutput"><span class="identifier">lower_bound</span><span class="special">()</span></code>, <code class="computeroutput"><span class="identifier">upper_bound</span><span class="special">()</span></code>, <code class="computeroutput"><span class="identifier">equal_range</span><span class="special">()</span></code>, <code class="computeroutput"><span class="identifier">count</span><span class="special">()</span></code>... are called. This means that using splay-tree |
| based associative containers as drop-in replacements of <code class="computeroutput"><a class="link" href="../boost/intrusive/set.html" title="Class template set">set</a></code>/ |
| <code class="computeroutput"><a class="link" href="../boost/intrusive/multiset.html" title="Class template multiset">multiset</a></code>, specially |
| for const search functions, might not result in desired performance improvements. |
| </p> |
| <p> |
| If element searches are randomized, the tree will be continuously srebalanced |
| without taking advantage of the cache effect, so splay trees can offer worse |
| performance than other balanced trees for several search patterns. |
| </p> |
| <p> |
| <span class="bold"><strong>Boost.Intrusive</strong></span> splay associative containers |
| don't use their own hook types but plain Binary search tree hooks. See <a class="link" href="bst_hooks.html" title="Binary search tree hooks: bs_set_base_hook and bs_set_member_hook">Binary search tree hooks: bs_set_base_hook |
| and bs_set_member_hook</a> section for more information about these hooks. |
| </p> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h3 class="title"> |
| <a name="intrusive.splay_set_multiset.set_multiset_containers"></a><a class="link" href="splay_set_multiset.html#intrusive.splay_set_multiset.set_multiset_containers" title="splay_set, splay_multiset and splaytree containers">splay_set, |
| splay_multiset and splaytree containers</a> |
| </h3></div></div></div> |
| <pre class="programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">,</span> <span class="keyword">class</span> <span class="special">...</span><span class="identifier">Options</span><span class="special">></span> |
| <span class="keyword">class</span> <span class="identifier">splay_set</span><span class="special">;</span> |
| |
| <span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">,</span> <span class="keyword">class</span> <span class="special">...</span><span class="identifier">Options</span><span class="special">></span> |
| <span class="keyword">class</span> <span class="identifier">splay_multiset</span><span class="special">;</span> |
| |
| <span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">,</span> <span class="keyword">class</span> <span class="special">...</span><span class="identifier">Options</span><span class="special">></span> |
| <span class="keyword">class</span> <span class="identifier">splaytree</span><span class="special">;</span> |
| </pre> |
| <p> |
| These containers receive the same options explained in the section <a class="link" href="usage.html" title="How to use Boost.Intrusive">How to use Boost.Intrusive</a>: |
| </p> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| <span class="bold"><strong><code class="computeroutput"><span class="identifier">base_hook</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">Hook</span><span class="special">></span></code></strong></span> |
| / <span class="bold"><strong><code class="computeroutput"><span class="identifier">member_hook</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Hook</span><span class="special">,</span> <span class="identifier">Hook</span> <span class="identifier">T</span><span class="special">::*</span> <span class="identifier">PtrToMember</span><span class="special">></span></code></strong></span> |
| / <span class="bold"><strong><code class="computeroutput"><span class="identifier">value_traits</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">ValueTraits</span><span class="special">></span></code></strong></span>: |
| To specify the hook type or value traits used to configure the container. |
| (To learn about value traits go to the section <a class="link" href="value_traits.html" title="Containers with custom ValueTraits">Containers |
| with custom ValueTraits</a>.) |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong><code class="computeroutput"><span class="identifier">constant_time_size</span><span class="special"><</span><span class="keyword">bool</span> <span class="identifier">Enabled</span><span class="special">></span></code></strong></span>: |
| To activate the constant-time <code class="computeroutput"><span class="identifier">size</span><span class="special">()</span></code> operation. Default: <code class="computeroutput"><span class="identifier">constant_time_size</span><span class="special"><</span><span class="keyword">true</span><span class="special">></span></code> |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong><code class="computeroutput"><span class="identifier">size_type</span><span class="special"><</span><span class="keyword">bool</span> <span class="identifier">Enabled</span><span class="special">></span></code></strong></span>: |
| To specify the type that will be used to store the size of the container. |
| Default: <code class="computeroutput"><span class="identifier">size_type</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span><span class="special">></span></code> |
| </li> |
| </ul></div> |
| <p> |
| And they also can receive an additional option: |
| </p> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> |
| <span class="bold"><strong><code class="computeroutput"><span class="identifier">compare</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">Compare</span><span class="special">></span></code></strong></span>: |
| Comparison function for the objects to be inserted in containers. The |
| comparison functor must induce a strict weak ordering. Default: <code class="computeroutput"><span class="identifier">compare</span><span class="special"><</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">less</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="special">></span></code> |
| </li></ul></div> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h3 class="title"> |
| <a name="intrusive.splay_set_multiset.splay_set_multiset_example"></a><a class="link" href="splay_set_multiset.html#intrusive.splay_set_multiset.splay_set_multiset_example" title="Example">Example</a> |
| </h3></div></div></div> |
| <p> |
| Now let's see a small example using <code class="computeroutput"><a class="link" href="../boost/intrusive/splay_set.html" title="Class template splay_set">splay_set</a></code>/ |
| <code class="computeroutput"><a class="link" href="../boost/intrusive/splay_multiset.html" title="Class template splay_multiset">splay_multiset</a></code> |
| containers: |
| </p> |
| <p> |
| </p> |
| <pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">intrusive</span><span class="special">/</span><span class="identifier">splay_set</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> |
| <span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">vector</span><span class="special">></span> |
| <span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">functional</span><span class="special">></span> |
| |
| <span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">intrusive</span><span class="special">;</span> |
| |
| <span class="keyword">class</span> <span class="identifier">mytag</span><span class="special">;</span> |
| |
| <span class="keyword">class</span> <span class="identifier">MyClass</span> |
| <span class="special">:</span> <span class="keyword">public</span> <span class="identifier">bs_set_base_hook</span><span class="special"><></span> |
| <span class="special">{</span> |
| <span class="keyword">int</span> <span class="identifier">int_</span><span class="special">;</span> |
| |
| <span class="keyword">public</span><span class="special">:</span> |
| <span class="comment">//This is a member hook</span> |
| <span class="identifier">bs_set_member_hook</span><span class="special"><></span> <span class="identifier">member_hook_</span><span class="special">;</span> |
| |
| <span class="identifier">MyClass</span><span class="special">(</span><span class="keyword">int</span> <span class="identifier">i</span><span class="special">)</span> |
| <span class="special">:</span> <span class="identifier">int_</span><span class="special">(</span><span class="identifier">i</span><span class="special">)</span> |
| <span class="special">{}</span> |
| <span class="keyword">friend</span> <span class="keyword">bool</span> <span class="keyword">operator</span><span class="special"><</span> <span class="special">(</span><span class="keyword">const</span> <span class="identifier">MyClass</span> <span class="special">&</span><span class="identifier">a</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">MyClass</span> <span class="special">&</span><span class="identifier">b</span><span class="special">)</span> |
| <span class="special">{</span> <span class="keyword">return</span> <span class="identifier">a</span><span class="special">.</span><span class="identifier">int_</span> <span class="special"><</span> <span class="identifier">b</span><span class="special">.</span><span class="identifier">int_</span><span class="special">;</span> <span class="special">}</span> |
| <span class="keyword">friend</span> <span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">></span> <span class="special">(</span><span class="keyword">const</span> <span class="identifier">MyClass</span> <span class="special">&</span><span class="identifier">a</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">MyClass</span> <span class="special">&</span><span class="identifier">b</span><span class="special">)</span> |
| <span class="special">{</span> <span class="keyword">return</span> <span class="identifier">a</span><span class="special">.</span><span class="identifier">int_</span> <span class="special">></span> <span class="identifier">b</span><span class="special">.</span><span class="identifier">int_</span><span class="special">;</span> <span class="special">}</span> |
| <span class="keyword">friend</span> <span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">==</span> <span class="special">(</span><span class="keyword">const</span> <span class="identifier">MyClass</span> <span class="special">&</span><span class="identifier">a</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">MyClass</span> <span class="special">&</span><span class="identifier">b</span><span class="special">)</span> |
| <span class="special">{</span> <span class="keyword">return</span> <span class="identifier">a</span><span class="special">.</span><span class="identifier">int_</span> <span class="special">==</span> <span class="identifier">b</span><span class="special">.</span><span class="identifier">int_</span><span class="special">;</span> <span class="special">}</span> |
| <span class="special">};</span> |
| |
| <span class="comment">//Define a set using the base hook that will store values in reverse order</span> |
| <span class="keyword">typedef</span> <span class="identifier">splay_set</span><span class="special"><</span> <span class="identifier">MyClass</span><span class="special">,</span> <span class="identifier">compare</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">greater</span><span class="special"><</span><span class="identifier">MyClass</span><span class="special">></span> <span class="special">></span> <span class="special">></span> <span class="identifier">BaseSplaySet</span><span class="special">;</span> |
| |
| <span class="comment">//Define an multiset using the member hook</span> |
| <span class="keyword">typedef</span> <span class="identifier">member_hook</span><span class="special"><</span><span class="identifier">MyClass</span><span class="special">,</span> <span class="identifier">bs_set_member_hook</span><span class="special"><>,</span> <span class="special">&</span><span class="identifier">MyClass</span><span class="special">::</span><span class="identifier">member_hook_</span><span class="special">></span> <span class="identifier">MemberOption</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="identifier">splay_multiset</span><span class="special"><</span> <span class="identifier">MyClass</span><span class="special">,</span> <span class="identifier">MemberOption</span><span class="special">></span> <span class="identifier">MemberSplayMultiset</span><span class="special">;</span> |
| |
| <span class="keyword">int</span> <span class="identifier">main</span><span class="special">()</span> |
| <span class="special">{</span> |
| <span class="keyword">typedef</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">vector</span><span class="special"><</span><span class="identifier">MyClass</span><span class="special">>::</span><span class="identifier">iterator</span> <span class="identifier">VectIt</span><span class="special">;</span> |
| |
| <span class="comment">//Create several MyClass objects, each one with a different value</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">vector</span><span class="special"><</span><span class="identifier">MyClass</span><span class="special">></span> <span class="identifier">values</span><span class="special">;</span> |
| <span class="keyword">for</span><span class="special">(</span><span class="keyword">int</span> <span class="identifier">i</span> <span class="special">=</span> <span class="number">0</span><span class="special">;</span> <span class="identifier">i</span> <span class="special"><</span> <span class="number">100</span><span class="special">;</span> <span class="special">++</span><span class="identifier">i</span><span class="special">)</span> <span class="identifier">values</span><span class="special">.</span><span class="identifier">push_back</span><span class="special">(</span><span class="identifier">MyClass</span><span class="special">(</span><span class="identifier">i</span><span class="special">));</span> |
| |
| <span class="identifier">BaseSplaySet</span> <span class="identifier">baseset</span><span class="special">;</span> |
| <span class="identifier">MemberSplayMultiset</span> <span class="identifier">membermultiset</span><span class="special">;</span> |
| |
| |
| <span class="comment">//Insert values in the container</span> |
| <span class="keyword">for</span><span class="special">(</span><span class="identifier">VectIt</span> <span class="identifier">it</span><span class="special">(</span><span class="identifier">values</span><span class="special">.</span><span class="identifier">begin</span><span class="special">()),</span> <span class="identifier">itend</span><span class="special">(</span><span class="identifier">values</span><span class="special">.</span><span class="identifier">end</span><span class="special">());</span> <span class="identifier">it</span> <span class="special">!=</span> <span class="identifier">itend</span><span class="special">;</span> <span class="special">++</span><span class="identifier">it</span><span class="special">){</span> |
| <span class="identifier">baseset</span><span class="special">.</span><span class="identifier">insert</span><span class="special">(*</span><span class="identifier">it</span><span class="special">);</span> |
| <span class="identifier">membermultiset</span><span class="special">.</span><span class="identifier">insert</span><span class="special">(*</span><span class="identifier">it</span><span class="special">);</span> |
| <span class="special">}</span> |
| |
| <span class="comment">//Now test sets</span> |
| <span class="special">{</span> |
| <span class="identifier">BaseSplaySet</span><span class="special">::</span><span class="identifier">reverse_iterator</span> <span class="identifier">rbit</span><span class="special">(</span><span class="identifier">baseset</span><span class="special">.</span><span class="identifier">rbegin</span><span class="special">());</span> |
| <span class="identifier">MemberSplayMultiset</span><span class="special">::</span><span class="identifier">iterator</span> <span class="identifier">mit</span><span class="special">(</span><span class="identifier">membermultiset</span><span class="special">.</span><span class="identifier">begin</span><span class="special">());</span> |
| <span class="identifier">VectIt</span> <span class="identifier">it</span><span class="special">(</span><span class="identifier">values</span><span class="special">.</span><span class="identifier">begin</span><span class="special">()),</span> <span class="identifier">itend</span><span class="special">(</span><span class="identifier">values</span><span class="special">.</span><span class="identifier">end</span><span class="special">());</span> |
| |
| <span class="comment">//Test the objects inserted in the base hook set</span> |
| <span class="keyword">for</span><span class="special">(;</span> <span class="identifier">it</span> <span class="special">!=</span> <span class="identifier">itend</span><span class="special">;</span> <span class="special">++</span><span class="identifier">it</span><span class="special">,</span> <span class="special">++</span><span class="identifier">rbit</span><span class="special">){</span> |
| <span class="keyword">if</span><span class="special">(&*</span><span class="identifier">rbit</span> <span class="special">!=</span> <span class="special">&*</span><span class="identifier">it</span><span class="special">)</span> <span class="keyword">return</span> <span class="number">1</span><span class="special">;</span> |
| <span class="special">}</span> |
| |
| <span class="comment">//Test the objects inserted in member and binary search hook sets</span> |
| <span class="keyword">for</span><span class="special">(</span><span class="identifier">it</span> <span class="special">=</span> <span class="identifier">values</span><span class="special">.</span><span class="identifier">begin</span><span class="special">();</span> <span class="identifier">it</span> <span class="special">!=</span> <span class="identifier">itend</span><span class="special">;</span> <span class="special">++</span><span class="identifier">it</span><span class="special">,</span> <span class="special">++</span><span class="identifier">mit</span><span class="special">){</span> |
| <span class="keyword">if</span><span class="special">(&*</span><span class="identifier">mit</span> <span class="special">!=</span> <span class="special">&*</span><span class="identifier">it</span><span class="special">)</span> <span class="keyword">return</span> <span class="number">1</span><span class="special">;</span> |
| <span class="special">}</span> |
| <span class="special">}</span> |
| <span class="keyword">return</span> <span class="number">0</span><span class="special">;</span> |
| <span class="special">}</span> |
| </pre> |
| <p> |
| </p> |
| </div> |
| </div> |
| <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> |
| <td align="left"></td> |
| <td align="right"><div class="copyright-footer">Copyright © 2005 Olaf Krzikalla<br>Copyright © 2006-2013 Ion Gaztanaga<p> |
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