boost-react-native-bundle

<html> <head> <meta http-equiv="Content-Type" content="text/html; charset=US-ASCII"> <title>Intrusive splay tree based associative containers: splay_set, splay_multiset and , splay_tree</title> <link rel="stylesheet" href="../../../doc/src/boostbook.css" type="text/css"> <meta name="generator" content="DocBook XSL Stylesheets V1.78.1"> <link rel="home" href="../index.html" title="The Boost C++ Libraries BoostBook Documentation Subset"> <link rel="up" href="../intrusive.html" title="Chapter 15. Boost.Intrusive"> <link rel="prev" href="avl_set_multiset.html" title="Intrusive avl tree based associative containers: avl_set, avl_multiset and avltree"> <link rel="next" href="sg_set_multiset.html" title="Intrusive scapegoat tree based associative containers: sg_set, sg_multiset and sgtree"> </head> <body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> <table cellpadding="2" width="100%"><tr> <td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../boost.png"></td> <td align="center"><a href="../../../index.html">Home</a></td> <td align="center"><a href="../../../libs/libraries.htm">Libraries</a></td> <td align="center"><a href="http://www.boost.org/users/people.html">People</a></td> <td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td> <td align="center"><a href="../../../more/index.htm">More</a></td> </tr></table> <hr> <div class="spirit-nav"> <a accesskey="p" href="avl_set_multiset.html"><img src="../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../intrusive.html"><img src="../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="sg_set_multiset.html"><img src="../../../doc/src/images/next.png" alt="Next"></a> </div> <div class="section"> <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><a href="splay_set_multiset.html#intrusive.splay_set_multiset.splay_set_multiset_disadvantages">Advantages and disadvantages of splay tree based containers</a></dt> <dt><a href="splay_set_multiset.html#intrusive.splay_set_multiset.set_multiset_containers">splay_set, splay_multiset and splaytree containers</a></dt> <dt><a href="splay_set_multiset.html#intrusive.splay_set_multiset.splay_set_multiset_example">Example</a></dt> </dl></div> 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). 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>. Boost.Intrusive 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. 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. <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> 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). 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">find()</code>, <code class="computeroutput">lower_bound()</code>, <code class="computeroutput">upper_bound()</code>, <code class="computeroutput">equal_range()</code>, <code class="computeroutput">count()</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. 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. Boost.Intrusive 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. </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">template <class T, class ...Options> class splay_set; template <class T, class ...Options> class splay_multiset; template <class T, class ...Options> class splaytree; </pre> 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>: <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <code class="computeroutput">base_hook<class Hook></code> / <code class="computeroutput">member_hook<class T, class Hook, Hook T::* PtrToMember></code> / <code class="computeroutput">value_traits<class ValueTraits></code>: 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"> <code class="computeroutput">constant_time_size<bool Enabled></code>: To activate the constant-time <code class="computeroutput">size()</code> operation. Default: <code class="computeroutput">constant_time_size<true></code> </li> <li class="listitem"> <code class="computeroutput">size_type<bool Enabled></code>: To specify the type that will be used to store the size of the container. Default: <code class="computeroutput">size_type<std::size_t></code> </li> </ul></div> And they also can receive an additional option: <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> <code class="computeroutput">compare<class Compare></code>: Comparison function for the objects to be inserted in containers. The comparison functor must induce a strict weak ordering. Default: <code class="computeroutput">compare< std::less<T> ></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> 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: <pre class="programlisting">#include <boost/intrusive/splay_set.hpp> #include <vector> #include <algorithm> using namespace boost::intrusive; class mytag; class MyClass : public bs_set_base_hook<> { int int_; public: //This is a member hook bs_set_member_hook<> member_hook_; MyClass(int i) : int_(i) {} friend bool operator< (const MyClass &a, const MyClass &b) { return a.int_ < b.int_; } friend bool operator> (const MyClass &a, const MyClass &b) { return a.int_ > b.int_; } friend bool operator== (const MyClass &a, const MyClass &b) { return a.int_ == b.int_; } }; //Define a set using the base hook that will store values in reverse order typedef splay_set< MyClass, compare<std::greater<MyClass> > > BaseSplaySet; //Define an multiset using the member hook typedef member_hook<MyClass, bs_set_member_hook<>, &MyClass::member_hook_> MemberOption; typedef splay_multiset< MyClass, MemberOption> MemberSplayMultiset; int main() { typedef std::vector<MyClass>::iterator VectIt; //Create several MyClass objects, each one with a different value std::vector<MyClass> values; for(int i = 0; i < 100; ++i) values.push_back(MyClass(i)); BaseSplaySet baseset; MemberSplayMultiset membermultiset; //Insert values in the container for(VectIt it(values.begin()), itend(values.end()); it != itend; ++it){ baseset.insert(*it); membermultiset.insert(*it); } //Now test sets { BaseSplaySet::reverse_iterator rbit(baseset.rbegin()); MemberSplayMultiset::iterator mit(membermultiset.begin()); VectIt it(values.begin()), itend(values.end()); //Test the objects inserted in the base hook set for(; it != itend; ++it, ++rbit){ if(&*rbit != &*it) return 1; } //Test the objects inserted in member and binary search hook sets for(it = values.begin(); it != itend; ++it, ++mit){ if(&*mit != &*it) return 1; } } return 0; } </pre> </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 Copyright © 2006-2013 Ion Gaztanaga Distributed under the Boost Software License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>) </div></td> </tr></table> <hr> <div class="spirit-nav"> <a accesskey="p" href="avl_set_multiset.html"><img src="../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../intrusive.html"><img src="../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="sg_set_multiset.html"><img src="../../../doc/src/images/next.png" alt="Next"></a> </div> </body> </html>