<!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 Text Find Timing Test</title> <meta http-equiv="Content-Type" content="text/html; charset=us-ascii" /> </head> <body> <div id="page"> <h1>Tree-Based and Trie-Based Text <tt>find</tt> Find Timing Test</h1> <h2><a name="description" id="description">Description</a></h2> <p>This test inserts a number of values with keys from an arbitrary text ([<a href="references.html#wickland96thirty">wickland96thirty</a>]) into a container, then performs a series of finds using <tt>find</tt>. It measures the average time for <tt>find</tt> 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/text_find_timing.cc"><tt>text_find_timing_test</tt></a> thirty_years_among_the_dead_preproc.txt 200 200 2100)</p> <h2><a name="purpose" id="purpose">Purpose</a></h2> <p>The test checks the effect of different underlying data structures.</p> <h2><a name="results" id="results">Results</a></h2> <p>Figures <a href="#NTTG">NTTG</a>, <a href="#NTTM">NTTM</a>, and <a href="#NTTG">NTTL</a> show the results for the native, tree-based, and trie-based types in <a href="assoc_performance_tests.html#gcc"><u>g++</u></a>, <a href="assoc_performance_tests.html#local"><u>local</u></a>, and <a href="assoc_performance_tests.html#local"><u>local</u></a>, respectively.</p> <div id="NTTG_res_div"> <div id="NTTG_gcc"> <div id="NTTG_random_int_find_find_timing_test_tree"> <div id="NTTG_assoc"> <div id="NTTG_Native_456_tree-based_456_random_int_find_timing_test_using__tt_find_455tt_"><div style="border-style: dotted; border-width: 1px; border-color: lightgray"><h6 class="c1"><a name="NTTG" id="NTTG"><img src="random_int_find_find_timing_test_tree_gcc.png" alt="no image" /></a></h6>NTTG: Native, tree-based, random int find timing test using <tt>find</tt> - <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> splay_tree_map- <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="null_tree_node_update.html"><tt>null_tree_node_update</tt></a> </li> <li> ov_tree_map- <a href="tree.html"><tt>tree</tt></a> with <tt>Tag</tt> = <a href="ov_tree_tag.html"><tt>ov_tree_tag</tt></a> , and <tt>Node_Update</tt> = <a href="null_tree_node_update.html"><tt>null_tree_node_update</tt></a> </li> <li> n_map- <tt>std::map</tt></li> <li> rb_tree_map- <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="null_tree_node_update.html"><tt>null_tree_node_update</tt></a> </li> </ol> </div><div style="width: 100%; height: 20px"></div></div> </div> </div> <div id="NTTM_res_div"> <div id="NTTM_msvc"> <div id="NTTM_random_int_find_find_timing_test_tree"> <div id="NTTM_assoc"> <div id="NTTM_Native_456_tree-based_456_random_int_find_timing_test_using__tt_find_455tt_"><div style="border-style: dotted; border-width: 1px; border-color: lightgray"><h6 class="c1"><a name="NTTM" id="NTTM"><img src="random_int_find_find_timing_test_tree_msvc.png" alt="no image" /></a></h6>NTTM: Native, tree-based, random int find timing test using <tt>find</tt> - <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> splay_tree_map- <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="null_tree_node_update.html"><tt>null_tree_node_update</tt></a> </li> <li> ov_tree_map- <a href="tree.html"><tt>tree</tt></a> with <tt>Tag</tt> = <a href="ov_tree_tag.html"><tt>ov_tree_tag</tt></a> , and <tt>Node_Update</tt> = <a href="null_tree_node_update.html"><tt>null_tree_node_update</tt></a> </li> <li> n_map- <tt>std::map</tt></li> <li> rb_tree_map- <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="null_tree_node_update.html"><tt>null_tree_node_update</tt></a> </li> </ol> </div><div style="width: 100%; height: 20px"></div></div> </div> </div> <div id="NTTL_res_div"> <div id="NTTL_local"> <div id="NTTL_random_int_find_find_timing_test_tree"> <div id="NTTL_assoc"> <div id="NTTL_Native_456_tree-based_456_random_int_find_timing_test_using__tt_find_455tt_"><div style = "border-style: dotted; border-width: 1px; border-color: lightgray"><h6 class="c1"><a name="NTTL" id= "NTTL"><img src="random_int_find_find_timing_test_tree_local.png" alt="no image" /></a></h6>NTTL: Native, tree-based, random int find timing test using <tt>find</tt> - <a href = "assoc_performance_tests.html#local">local</a></div><div style = "width: 100%; height: 20px"></div></div> </div> </div> <h2><a name="observations" id="observations">Observations</a></h2> <p>For this setting, 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>) does not do well. This is possibly due to two reasons:</p> <ol> <li>A splay tree is not guaranteed to be balanced [<a href="references.html#motwani95random">motwani95random</a>]. If a splay tree contains <i>n</i> nodes, its average root-leaf path can be <i>m >> log(n)</i>.</li> <li>Assume a specific root-leaf search path has length <i>m</i>, and the search-target node has distance <i>m'</i> from the root. A red-black tree will require <i>m + 1</i> comparisons to find the required node; a splay tree will require <i>2 m'</i> comparisons. A splay tree, consequently, can perform many more comparisons than a red-black tree.</li> </ol> <p>An ordered-vector tree (<a href="tree.html"><tt>tree</tt></a> with <tt>Tag =</tt> <a href="ov_tree_tag.html"><tt>ov_tree_tag</tt></a>), a red-black tree (<a href="tree.html"><tt>tree</tt></a> with <tt>Tag =</tt> <a href="splay_tree_tag.html"><tt>rb_tree_tag</tt></a>), and the native red-black tree all share approximately the same performance.</p> <p>An ordered-vector tree is slightly slower than red-black trees, since it requires, in order to find a key, more math operations than they do. Conversely, an ordered-vector tree requires far lower space than the others. ([<a href="references.html#austern00noset">austern00noset</a>], however, seems to have an implementation that is also faster than a red-black tree).</p> <p>A PATRICIA trie (<a href="trie.html"><tt>trie</tt></a> with <tt>Tag =</tt> <a href="pat_trie_tag.html"><tt>pat_trie_tag</tt></a>) has good look-up performance, due to its large fan-out in this case. In this setting, a PATRICIA trie has lookup performance comparable to a hash table (see <a href="hash_text_find_find_timing_test.html">Hash-Based Text <tt>find</tt> Find Timing Test</a>), but it is order preserving. This is not that surprising, since a large fan-out PATRICIA trie works like a hash table with collisions resolved by a sub-trie. A large fan-out PATRICIA trie does not do well on modifications (see <a href="tree_text_insert_timing_test.html">Tree-Based and Trie-Based Text Insert Timing Test</a>). It is possibly beneficial to semi-static settings, therefore.</p> <p><a href="assoc_performance_tests.html#tree_like_based_types"> Observations::Tree-Like-Based Container Types</a> summarizes some observations on tree-based and trie-based containers.</p> </div> </div> </div> </div> </div> </div> </div> </body> </html>