<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> <head> <meta name="generator" content="HTML Tidy for Linux/x86 (vers 12 April 2005), see www.w3.org" /> <title>Tree Order Statistics Timing Test</title> <meta http-equiv="Content-Type" content="text/html; charset=us-ascii" /> </head> <body> <div id="page"> <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> </div> </body> </html>