libstdc++-v3/docs/html/ext/pb_ds/tree_text_find_find_timing_test.html

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  12 <h1>Tree-Based and Trie-Based Text <tt>find</tt> Find Timing
  13     Test</h1>
  14 <h2><a name="description" id="description">Description</a></h2>
  15 <p>This test inserts a number of values with keys from an
  16     arbitrary text ([<a href="references.html#wickland96thirty">wickland96thirty</a>]) into
  17     a container, then performs a series of finds using
  18     <tt>find</tt>. It measures the average time for <tt>find</tt>
  19     as a function of the number of values inserted.</p>
  20 <p>(The test was executed with <a href="../../../../testsuite/performance/ext/pb_ds/text_find_timing.cc"><tt>text_find_timing_test</tt></a>
  21     thirty_years_among_the_dead_preproc.txt 200 200 2100)</p>
  22 <h2><a name="purpose" id="purpose">Purpose</a></h2>
  23 <p>The test checks the effect of different underlying
  24     data structures.</p>
  25 <h2><a name="results" id="results">Results</a></h2>
  26 <p>Figures <a href="#NTTG">NTTG</a>, <a href="#NTTM">NTTM</a>,
  27     and <a href="#NTTG">NTTL</a> show the results for the native,
  28     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
  29     <a href="assoc_performance_tests.html#local"><u>local</u></a>,
  30     respectively.</p>
  31 <div id="NTTG_res_div">
  32 <div id="NTTG_gcc">
  33 <div id="NTTG_text_find_timing_test_tree_like">
  34 <div id="NTTG_assoc">
  35 <div id="NTTG_Native_456_tree-based_456_and_trie-based_456_text_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="text_find_timing_test_tree_like_gcc.png" alt="no image" /></a></h6>NTTG: Native, tree-based, and trie-based, text 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>
  36 <ol>
  37 <li>
  38 splay_tree_map-
  39 <a href="tree.html"><tt>tree</tt></a>
  40  with <tt>Tag</tt> = <a href="splay_tree_tag.html"><tt>splay_tree_tag</tt></a>
  41 , and <tt>Node_Update</tt> = <a href="null_tree_node_update.html"><tt>null_tree_node_update</tt></a>
  42 </li>
  43 <li>
  44 ov_tree_map-
  45 <a href="tree.html"><tt>tree</tt></a>
  46  with <tt>Tag</tt> = <a href="ov_tree_tag.html"><tt>ov_tree_tag</tt></a>
  47 , and <tt>Node_Update</tt> = <a href="null_tree_node_update.html"><tt>null_tree_node_update</tt></a>
  48 </li>
  49 <li>
  50 rb_tree_map-
  51 <a href="tree.html"><tt>tree</tt></a>
  52  with <tt>Tag</tt> = <a href="rb_tree_tag.html"><tt>rb_tree_tag</tt></a>
  53 , and <tt>Node_Update</tt> = <a href="null_tree_node_update.html"><tt>null_tree_node_update</tt></a>
  54 </li>
  55 <li>
  56 n_map-
  57 <tt>std::map</tt></li>
  58 <li>
  59 pat_trie_map-
  60 <a href="trie.html"><tt>trie</tt></a>
  61  with <tt>Tag</tt> = <a href="pat_trie_tag.html"><tt>pat_trie_tag</tt></a>
  62 , and <tt>Node_Update</tt> = <a href="null_trie_node_update.html"><tt>null_trie_node_update</tt></a>
  63 </li>
  64 </ol>
  65 </div><div style="width: 100%; height: 20px"></div></div>
  66 </div>
  67 </div>
  68 </div>
  69 </div>
  70 <div id="NTTM_res_div">
  71 <div id="NTTM_msvc">
  72 <div id="NTTM_text_find_timing_test_tree_like">
  73 <div id="NTTM_assoc">
  74 <div id="NTTM_Native_456_tree-based_456_and_trie-based_456_text_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="text_find_timing_test_tree_like_msvc.png" alt="no image" /></a></h6>NTTM: Native, tree-based, and trie-based, text 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>
  75 <ol>
  76 <li>
  77 splay_tree_map-
  78 <a href="tree.html"><tt>tree</tt></a>
  79  with <tt>Tag</tt> = <a href="splay_tree_tag.html"><tt>splay_tree_tag</tt></a>
  80 , and <tt>Node_Update</tt> = <a href="null_tree_node_update.html"><tt>null_tree_node_update</tt></a>
  81 </li>
  82 <li>
  83 ov_tree_map-
  84 <a href="tree.html"><tt>tree</tt></a>
  85  with <tt>Tag</tt> = <a href="ov_tree_tag.html"><tt>ov_tree_tag</tt></a>
  86 , and <tt>Node_Update</tt> = <a href="null_tree_node_update.html"><tt>null_tree_node_update</tt></a>
  87 </li>
  88 <li>
  89 rb_tree_map-
  90 <a href="tree.html"><tt>tree</tt></a>
  91  with <tt>Tag</tt> = <a href="rb_tree_tag.html"><tt>rb_tree_tag</tt></a>
  92 , and <tt>Node_Update</tt> = <a href="null_tree_node_update.html"><tt>null_tree_node_update</tt></a>
  93 </li>
  94 <li>
  95 n_map-
  96 <tt>std::map</tt></li>
  97 <li>
  98 pat_trie_map-
  99 <a href="trie.html"><tt>trie</tt></a>
 100  with <tt>Tag</tt> = <a href="pat_trie_tag.html"><tt>pat_trie_tag</tt></a>
 101 , and <tt>Node_Update</tt> = <a href="null_trie_node_update.html"><tt>null_trie_node_update</tt></a>
 102 </li>
 103 </ol>
 104 </div><div style="width: 100%; height: 20px"></div></div>
 105 </div>
 106 </div>
 107 </div>
 108 </div>
 109 <div id="NTTL_res_div">
 110 <div id="NTTL_local">
 111 <div id="NTTL_text_find_timing_test_tree_like">
 112 <div id="NTTL_assoc">
 113 <div id="NTTL_Native_456_tree-based_456_and_trie-based_456_text_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="text_find_timing_test_tree_like_local.png" alt="no image" /></a></h6>NTTL: Native, tree-based, and trie-based, text 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>
 114 </div>
 115 </div>
 116 </div>
 117 </div>
 118 <h2><a name="observations" id="observations">Observations</a></h2>
 119 <p>For this setting, a splay tree (<a href="tree.html"><tt>tree</tt></a>
 120     with <tt>Tag =</tt> <a href="splay_tree_tag.html"><tt>splay_tree_tag</tt></a>) does
 121     not do well. This is possibly due to two reasons:</p>
 122 <ol>
 123 <li>A splay tree is not guaranteed to be balanced [<a href="references.html#motwani95random">motwani95random</a>]. If a
 124       splay tree contains <i>n</i> nodes, its average root-leaf
 125       path can be <i>m &gt;&gt; log(n)</i>.</li>
 126 <li>Assume a specific root-leaf search path has length
 127       <i>m</i>, and the search-target node has distance <i>m'</i>
 128       from the root. A red-black tree will require <i>m + 1</i>
 129       comparisons to find the required node; a splay tree will
 130       require <i>2 m'</i> comparisons. A splay tree, consequently,
 131       can perform many more comparisons than a red-black tree.</li>
 132 </ol>
 133 <p>An ordered-vector tree (<a href="tree.html"><tt>tree</tt></a>
 134     with <tt>Tag =</tt> <a href="ov_tree_tag.html"><tt>ov_tree_tag</tt></a>), a red-black
 135     tree (<a href="tree.html"><tt>tree</tt></a>
 136     with <tt>Tag =</tt> <a href="splay_tree_tag.html"><tt>rb_tree_tag</tt></a>), and the
 137     native red-black tree all share approximately the same
 138     performance.</p>
 139 <p>An ordered-vector tree is slightly slower than red-black
 140     trees, since it requires, in order to find a key, more math
 141     operations than they do. Conversely, an ordered-vector tree
 142     requires far lower space than the others. ([<a href="references.html#austern00noset">austern00noset</a>], however,
 143     seems to have an implementation that is also faster than a
 144     red-black tree).</p>
 145 <p>A PATRICIA trie (<a href="trie.html"><tt>trie</tt></a>
 146     with <tt>Tag =</tt> <a href="pat_trie_tag.html"><tt>pat_trie_tag</tt></a>) has good
 147     look-up performance, due to its large fan-out in this case. In
 148     this setting, a PATRICIA trie has look-up performance comparable
 149     to a hash table (see <a href="hash_text_find_find_timing_test.html">Hash-Based Text
 150     <tt>find</tt> Find Timing Test</a>), but it is order
 151     preserving. This is not that surprising, since a large-fan-out
 152     PATRICIA trie works like a hash table with collisions resolved
 153     by a sub-trie. A large-fan-out PATRICIA trie does not do well on
 154     modifications (see <a href="tree_text_insert_timing_test.html">Tree-Based and Trie-Based
 155     Text Insert Timing Test</a>). It is possibly beneficial to
 156     semi-static settings, therefore.</p>
 157 <p><a href="assoc_performance_tests.html#tree_like_based_types">Observations::Tree-Like-Based
 158     Container Types</a> summarizes some observations on tree-based
 159     and trie-based containers.</p>
 160 </div>
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