l4/pkg/libstdc++-v3/contrib/libstdc++-v3-4.3.3/doc/html/ext/pb_ds/tree_order_statistics_timing_test.html

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   7 <title>Tree Order Statistics Timing Test</title>
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  12 <h1>Tree Order-Statistics Timing Test</h1>
  13 <h2><a name="description" id="description">Description</a></h2>
  14 <p>This test creates a container, inserts random integers into
  15     the the container, and then checks the order-statistics of the
  16     container's values. (If the container is one of <tt>pb_ds</tt>
  17     's trees, it does this with the <tt>order_of_key</tt> method of
  18     <a href="tree_order_statistics_node_update.html"><tt>tree_order_statistics_node_update</tt></a>
  19     ; otherwise, it uses the <tt>find</tt> method and
  20     <tt>std::distance</tt> .) It measures the average time for such
  21     queries as a function of the number of values inserted.</p>
  22 <p>(The test was executed with <a href="../../../../testsuite/performance/ext/pb_ds/tree_order_statistics_timing.cc"><tt>tree_order_statistics_timing_test</tt></a>
  23     200 200 2100)</p>
  24 <h2><a name="purpose" id="purpose">Purpose</a></h2>
  25 <p>The test checks the performance difference of policies based
  26     on node-invariant as opposed to a external functions. (see
  27     <a href="tree_based_containers.html#invariants">Design::Associative
  28     Containers::Tree-Based Containers::Node Invariants</a> .)</p>
  29 <h2><a name="results" id="results">Results</a></h2>
  30 <p>Figures <a href="#NTG">NTG</a>, <a href="#NTM">NTM</a>, and
  31     <a href="#NTL">NTL</a> show the results for the native and
  32     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
  33     <a href="assoc_performance_tests.html#local"><u>local</u></a>,
  34     respectively.</p>
  35 <div id="NTG_res_div">
  36 <div id="NTG_gcc">
  37 <div id="NTG_tree_order_statistics_timing_test">
  38 <div id="NTG_assoc">
  39 <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>
  40 <ol>
  41 <li>
  42 n_set-
  43 <tt>std::set</tt></li>
  44 <li>
  45 splay_tree_ost_set-
  46 <a href="tree.html"><tt>tree</tt></a>
  47  with <tt>Tag</tt> = <a href="splay_tree_tag.html"><tt>splay_tree_tag</tt></a>
  48 , and <tt>Node_Update</tt> = <a href="tree_order_statistics_node_update.html"><tt>tree_order_statistics_node_update</tt></a>
  49 </li>
  50 <li>
  51 rb_tree_ost_set-
  52 <a href="tree.html"><tt>tree</tt></a>
  53  with <tt>Tag</tt> = <a href="rb_tree_tag.html"><tt>rb_tree_tag</tt></a>
  54 , and <tt>Node_Update</tt> = <a href="tree_order_statistics_node_update.html"><tt>tree_order_statistics_node_update</tt></a>
  55 </li>
  56 </ol>
  57 </div><div style="width: 100%; height: 20px"></div></div>
  58 </div>
  59 </div>
  60 </div>
  61 </div>
  62 <div id="NTM_res_div">
  63 <div id="NTM_msvc">
  64 <div id="NTM_tree_order_statistics_timing_test">
  65 <div id="NTM_assoc">
  66 <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>
  67 <ol>
  68 <li>
  69 n_set-
  70 <tt>std::set</tt></li>
  71 <li>
  72 splay_tree_ost_set-
  73 <a href="tree.html"><tt>tree</tt></a>
  74  with <tt>Tag</tt> = <a href="splay_tree_tag.html"><tt>splay_tree_tag</tt></a>
  75 , and <tt>Node_Update</tt> = <a href="tree_order_statistics_node_update.html"><tt>tree_order_statistics_node_update</tt></a>
  76 </li>
  77 <li>
  78 rb_tree_ost_set-
  79 <a href="tree.html"><tt>tree</tt></a>
  80  with <tt>Tag</tt> = <a href="rb_tree_tag.html"><tt>rb_tree_tag</tt></a>
  81 , and <tt>Node_Update</tt> = <a href="tree_order_statistics_node_update.html"><tt>tree_order_statistics_node_update</tt></a>
  82 </li>
  83 </ol>
  84 </div><div style="width: 100%; height: 20px"></div></div>
  85 </div>
  86 </div>
  87 </div>
  88 </div>
  89 <div id="NTL_res_div">
  90 <div id="NTL_local">
  91 <div id="NTL_tree_order_statistics_timing_test">
  92 <div id="NTL_assoc">
  93 <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>
  94 </div>
  95 </div>
  96 </div>
  97 </div>
  98 <h2><a name="observations" id="observations">Observations</a></h2>
  99 <p>In this test, the native red-black tree can support
 100     order-statistics queries only externally, by performing a
 101     <tt>find</tt> (alternatively, <tt>lower_bound</tt> or
 102     <tt>upper_bound</tt> ) and then using <tt>std::distance</tt> .
 103     This is clearly linear, and it is not that surprising that the
 104     cost is high.</p>
 105 <p><tt>pb_ds</tt> 's tree-based containers use in this test the
 106     <tt>order_of_key</tt> method of <a href="tree_order_statistics_node_update.html"><tt>tree_order_statistics_node_update</tt></a>.
 107     This method has only linear complexity in the length of the
 108     root-node path. Unfortunately, the average path of a splay tree
 109     (<a href="tree.html"><tt>tree</tt></a>
 110     with <tt>Tag =</tt> <a href="splay_tree_tag.html"><tt>splay_tree_tag</tt></a> ) can
 111     be higher than logarithmic; the longest path of a red-black
 112     tree (<a href="tree.html"><tt>tree</tt></a>
 113     with <tt>Tag =</tt> <a href="rb_tree_tag.html"><tt>rb_tree_tag</tt></a> ) is
 114     logarithmic in the number of elements. Consequently, the splay
 115     tree has worse performance than the red-black tree.</p>
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