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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
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<title>Tree Order Statistics Timing Test</title>
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<h1>Tree Order-Statistics Timing Test</h1>
<h2><a name="description" id="description">Description</a></h2>
<p>This test creates a container, inserts random integers into
the the container, and then checks the order-statistics of the
container's values. (If the container is one of <tt>pb_ds</tt>
's trees, it does this with the <tt>order_of_key</tt> method of
<a href="tree_order_statistics_node_update.html"><tt>tree_order_statistics_node_update</tt></a>
; otherwise, it uses the <tt>find</tt> method and
<tt>std::distance</tt> .) It measures the average time for such
queries as a function of the number of values inserted.</p>
<p>(The test was executed with <a href="http://gcc.gnu.org/viewcvs/*checkout*/trunk/libstdc%2B%2B-v3/testsuite/performance/ext/pb_ds/tree_order_statistics_timing.cc"><tt>tree_order_statistics_timing_test</tt></a>
200 200 2100)</p>
<h2><a name="purpose" id="purpose">Purpose</a></h2>
<p>The test checks the performance difference of policies based
on node-invariant as opposed to a external functions. (see
<a href="tree_based_containers.html#invariants">Design::Associative
Containers::Tree-Based Containers::Node Invariants</a> .)</p>
<h2><a name="results" id="results">Results</a></h2>
<p>Figures <a href="#NTG">NTG</a>, <a href="#NTM">NTM</a>, and
<a href="#NTL">NTL</a> show the results for the native and
tree-based containers in <a href="assoc_performance_tests.html#gcc"><u>g++</u></a>, <a href="assoc_performance_tests.html#msvc"><u>msvc++</u></a>, and
<a href="assoc_performance_tests.html#local"><u>local</u></a>,
respectively.</p>
<div id="NTG_res_div">
<div id="NTG_gcc">
<div id="NTG_tree_order_statistics_timing_test">
<div id="NTG_assoc">
<div id="NTG_Native_and_tree-based_container_order-statistics_queries"><div style="border-style: dotted; border-width: 1px; border-color: lightgray"><h6 class="c1"><a name="NTG" id="NTG"><img src="tree_order_statistics_timing_test_gcc.png" alt="no image" /></a></h6>NTG: Native and tree-based container order-statistics queries - <a href="assoc_performance_tests.html#gcc">g++</a><p>In the above figure, the names in the legends have the following meaning:</p>
<ol>
<li>
n_set-
<tt>std::set</tt></li>
<li>
splay_tree_ost_set-
<a href="tree.html"><tt>tree</tt></a>
with <tt>Tag</tt> = <a href="splay_tree_tag.html"><tt>splay_tree_tag</tt></a>
, and <tt>Node_Update</tt> = <a href="tree_order_statistics_node_update.html"><tt>tree_order_statistics_node_update</tt></a>
</li>
<li>
rb_tree_ost_set-
<a href="tree.html"><tt>tree</tt></a>
with <tt>Tag</tt> = <a href="rb_tree_tag.html"><tt>rb_tree_tag</tt></a>
, and <tt>Node_Update</tt> = <a href="tree_order_statistics_node_update.html"><tt>tree_order_statistics_node_update</tt></a>
</li>
</ol>
</div><div style="width: 100%; height: 20px"></div></div>
</div>
</div>
</div>
</div>
<div id="NTM_res_div">
<div id="NTM_msvc">
<div id="NTM_tree_order_statistics_timing_test">
<div id="NTM_assoc">
<div id="NTM_Native_and_tree-based_container_order-statistics_queries"><div style="border-style: dotted; border-width: 1px; border-color: lightgray"><h6 class="c1"><a name="NTM" id="NTM"><img src="tree_order_statistics_timing_test_msvc.png" alt="no image" /></a></h6>NTM: Native and tree-based container order-statistics queries - <a href="assoc_performance_tests.html#msvc">msvc++</a><p>In the above figure, the names in the legends have the following meaning:</p>
<ol>
<li>
n_set-
<tt>std::set</tt></li>
<li>
splay_tree_ost_set-
<a href="tree.html"><tt>tree</tt></a>
with <tt>Tag</tt> = <a href="splay_tree_tag.html"><tt>splay_tree_tag</tt></a>
, and <tt>Node_Update</tt> = <a href="tree_order_statistics_node_update.html"><tt>tree_order_statistics_node_update</tt></a>
</li>
<li>
rb_tree_ost_set-
<a href="tree.html"><tt>tree</tt></a>
with <tt>Tag</tt> = <a href="rb_tree_tag.html"><tt>rb_tree_tag</tt></a>
, and <tt>Node_Update</tt> = <a href="tree_order_statistics_node_update.html"><tt>tree_order_statistics_node_update</tt></a>
</li>
</ol>
</div><div style="width: 100%; height: 20px"></div></div>
</div>
</div>
</div>
</div>
<div id="NTL_res_div">
<div id="NTL_local">
<div id="NTL_tree_order_statistics_timing_test">
<div id="NTL_assoc">
<div id="NTL_Native_and_tree-based_container_order-statistics_queries"><div style = "border-style: dotted; border-width: 1px; border-color: lightgray"><h6 class="c1"><a name="NTL" id= "NTL"><img src="tree_order_statistics_timing_test_local.png" alt="no image" /></a></h6>NTL: Native and tree-based container order-statistics queries - <a href = "assoc_performance_tests.html#local">local</a></div><div style = "width: 100%; height: 20px"></div></div>
</div>
</div>
</div>
</div>
<h2><a name="observations" id="observations">Observations</a></h2>
<p>In this test, the native red-black tree can support
order-statistics queries only externally, by performing a
<tt>find</tt> (alternatively, <tt>lower_bound</tt> or
<tt>upper_bound</tt> ) and then using <tt>std::distance</tt> .
This is clearly linear, and it is not that surprising that the
cost is high.</p>
<p><tt>pb_ds</tt> 's tree-based containers use in this test the
<tt>order_of_key</tt> method of <a href="tree_order_statistics_node_update.html"><tt>tree_order_statistics_node_update</tt></a>.
This method has only linear complexity in the length of the
root-node path. Unfortunately, the average path of a splay tree
(<a href="tree.html"><tt>tree</tt></a>
with <tt>Tag =</tt> <a href="splay_tree_tag.html"><tt>splay_tree_tag</tt></a> ) can
be higher than logarithmic; the longest path of a red-black
tree (<a href="tree.html"><tt>tree</tt></a>
with <tt>Tag =</tt> <a href="rb_tree_tag.html"><tt>rb_tree_tag</tt></a> ) is
logarithmic in the number of elements. Consequently, the splay
tree has worse performance than the red-black tree.</p>
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