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  4. <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
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  6. <meta name="generator" content="HTML Tidy for Linux/x86 (vers 12 April 2005), see www.w3.org" />
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  7. <title>Tree Text Find Timing Test</title>
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  8. <meta http-equiv="Content-Type" content="text/html; charset=us-ascii" />
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  11. <div id="page">
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  12. <h1>Tree-Based and Trie-Based Text <tt>find</tt> Find Timing
    13. 

  13.     Test</h1>
    14. 

  14. <h2><a name="description" id="description">Description</a></h2>
    15. 

  15. <p>This test inserts a number of values with keys from an
    16. 

  16.     arbitrary text ([<a href="references.html#wickland96thirty">wickland96thirty</a>]) into
    17. 

  17.     a container, then performs a series of finds using
    18. 

  18.     <tt>find</tt>. It measures the average time for <tt>find</tt>
    19. 

  19.     as a function of the number of values inserted.</p>
    20. 

  20. <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>
    21. 

  21.     thirty_years_among_the_dead_preproc.txt 200 200 2100)</p>
    22. 

  22. <h2><a name="purpose" id="purpose">Purpose</a></h2>
    23. 

  23. <p>The test checks the effect of different underlying
    24. 

  24.     data structures.</p>
    25. 

  25. <h2><a name="results" id="results">Results</a></h2>
    26. 

  26. <p>Figures <a href="#NTTG">NTTG</a>, <a href="#NTTM">NTTM</a>,
    27. 

  27.     and <a href="#NTTG">NTTL</a> show the results for the native,
    28. 

  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. 

  29.     <a href="assoc_performance_tests.html#local"><u>local</u></a>,
    30. 

  30.     respectively.</p>
    31. 

  31. <div id="NTTG_res_div">
    32. 

  32. <div id="NTTG_gcc">
    33. 

  33. <div id="NTTG_text_find_timing_test_tree_like">
    34. 

  34. <div id="NTTG_assoc">
    35. 

  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. 

  36. <ol>
    37. 

  37. <li>
    38. 

  38. splay_tree_map-
    39. 

  39. <a href="tree.html"><tt>tree</tt></a>
    40. 

  40.  with <tt>Tag</tt> = <a href="splay_tree_tag.html"><tt>splay_tree_tag</tt></a>
    41. 

  41. , and <tt>Node_Update</tt> = <a href="null_tree_node_update.html"><tt>null_tree_node_update</tt></a>
    42. 

  42. </li>
    43. 

  43. <li>
    44. 

  44. ov_tree_map-
    45. 

  45. <a href="tree.html"><tt>tree</tt></a>
    46. 

  46.  with <tt>Tag</tt> = <a href="ov_tree_tag.html"><tt>ov_tree_tag</tt></a>
    47. 

  47. , and <tt>Node_Update</tt> = <a href="null_tree_node_update.html"><tt>null_tree_node_update</tt></a>
    48. 

  48. </li>
    49. 

  49. <li>
    50. 

  50. rb_tree_map-
    51. 

  51. <a href="tree.html"><tt>tree</tt></a>
    52. 

  52.  with <tt>Tag</tt> = <a href="rb_tree_tag.html"><tt>rb_tree_tag</tt></a>
    53. 

  53. , and <tt>Node_Update</tt> = <a href="null_tree_node_update.html"><tt>null_tree_node_update</tt></a>
    54. 

  54. </li>
    55. 

  55. <li>
    56. 

  56. n_map-
    57. 

  57. <tt>std::map</tt></li>
    58. 

  58. <li>
    59. 

  59. pat_trie_map-
    60. 

  60. <a href="trie.html"><tt>trie</tt></a>
    61. 

  61.  with <tt>Tag</tt> = <a href="pat_trie_tag.html"><tt>pat_trie_tag</tt></a>
    62. 

  62. , and <tt>Node_Update</tt> = <a href="null_trie_node_update.html"><tt>null_trie_node_update</tt></a>
    63. 

  63. </li>
    64. 

  64. </ol>
    65. 

  65. </div><div style="width: 100%; height: 20px"></div></div>
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  66. </div>
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  67. </div>
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  68. </div>
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  69. </div>
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  70. <div id="NTTM_res_div">
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  71. <div id="NTTM_msvc">
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  72. <div id="NTTM_text_find_timing_test_tree_like">
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  73. <div id="NTTM_assoc">
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  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>
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  75. <ol>
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  76. <li>
    77. 

  77. splay_tree_map-
    78. 

  78. <a href="tree.html"><tt>tree</tt></a>
    79. 

  79.  with <tt>Tag</tt> = <a href="splay_tree_tag.html"><tt>splay_tree_tag</tt></a>
    80. 

  80. , and <tt>Node_Update</tt> = <a href="null_tree_node_update.html"><tt>null_tree_node_update</tt></a>
    81. 

  81. </li>
    82. 

  82. <li>
    83. 

  83. ov_tree_map-
    84. 

  84. <a href="tree.html"><tt>tree</tt></a>
    85. 

  85.  with <tt>Tag</tt> = <a href="ov_tree_tag.html"><tt>ov_tree_tag</tt></a>
    86. 

  86. , and <tt>Node_Update</tt> = <a href="null_tree_node_update.html"><tt>null_tree_node_update</tt></a>
    87. 

  87. </li>
    88. 

  88. <li>
    89. 

  89. rb_tree_map-
    90. 

  90. <a href="tree.html"><tt>tree</tt></a>
    91. 

  91.  with <tt>Tag</tt> = <a href="rb_tree_tag.html"><tt>rb_tree_tag</tt></a>
    92. 

  92. , and <tt>Node_Update</tt> = <a href="null_tree_node_update.html"><tt>null_tree_node_update</tt></a>
    93. 

  93. </li>
    94. 

  94. <li>
    95. 

  95. n_map-
    96. 

  96. <tt>std::map</tt></li>
    97. 

  97. <li>
    98. 

  98. pat_trie_map-
    99. 

  99. <a href="trie.html"><tt>trie</tt></a>
    100. 

  100.  with <tt>Tag</tt> = <a href="pat_trie_tag.html"><tt>pat_trie_tag</tt></a>
    101. 

  101. , and <tt>Node_Update</tt> = <a href="null_trie_node_update.html"><tt>null_trie_node_update</tt></a>
    102. 

  102. </li>
    103. 

  103. </ol>
    104. 

  104. </div><div style="width: 100%; height: 20px"></div></div>
    105. 

  105. </div>
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  106. </div>
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  107. </div>
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  108. </div>
    109. 

  109. <div id="NTTL_res_div">
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  110. <div id="NTTL_local">
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  111. <div id="NTTL_text_find_timing_test_tree_like">
    112. 

  112. <div id="NTTL_assoc">
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  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. 

  114. </div>
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  115. </div>
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  116. </div>
    117. 

  117. </div>
    118. 

  118. <h2><a name="observations" id="observations">Observations</a></h2>
    119. 

  119. <p>For this setting, a splay tree (<a href="tree.html"><tt>tree</tt></a>
    120. 

  120.     with <tt>Tag =</tt> <a href="splay_tree_tag.html"><tt>splay_tree_tag</tt></a>) does
    121. 

  121.     not do well. This is possibly due to two reasons:</p>
    122. 

  122. <ol>
    123. 

  123. <li>A splay tree is not guaranteed to be balanced [<a href="references.html#motwani95random">motwani95random</a>]. If a
    124. 

  124.       splay tree contains <i>n</i> nodes, its average root-leaf
    125. 

  125.       path can be <i>m &gt;&gt; log(n)</i>.</li>
    126. 

  126. <li>Assume a specific root-leaf search path has length
    127. 

  127.       <i>m</i>, and the search-target node has distance <i>m'</i>
    128. 

  128.       from the root. A red-black tree will require <i>m + 1</i>
    129. 

  129.       comparisons to find the required node; a splay tree will
    130. 

  130.       require <i>2 m'</i> comparisons. A splay tree, consequently,
    131. 

  131.       can perform many more comparisons than a red-black tree.</li>
    132. 

  132. </ol>
    133. 

  133. <p>An ordered-vector tree (<a href="tree.html"><tt>tree</tt></a>
    134. 

  134.     with <tt>Tag =</tt> <a href="ov_tree_tag.html"><tt>ov_tree_tag</tt></a>), a red-black
    135. 

  135.     tree (<a href="tree.html"><tt>tree</tt></a>
    136. 

  136.     with <tt>Tag =</tt> <a href="splay_tree_tag.html"><tt>rb_tree_tag</tt></a>), and the
    137. 

  137.     native red-black tree all share approximately the same
    138. 

  138.     performance.</p>
    139. 

  139. <p>An ordered-vector tree is slightly slower than red-black
    140. 

  140.     trees, since it requires, in order to find a key, more math
    141. 

  141.     operations than they do. Conversely, an ordered-vector tree
    142. 

  142.     requires far lower space than the others. ([<a href="references.html#austern00noset">austern00noset</a>], however,
    143. 

  143.     seems to have an implementation that is also faster than a
    144. 

  144.     red-black tree).</p>
    145. 

  145. <p>A PATRICIA trie (<a href="trie.html"><tt>trie</tt></a>
    146. 

  146.     with <tt>Tag =</tt> <a href="pat_trie_tag.html"><tt>pat_trie_tag</tt></a>) has good
    147. 

  147.     look-up performance, due to its large fan-out in this case. In
    148. 

  148.     this setting, a PATRICIA trie has look-up performance comparable
    149. 

  149.     to a hash table (see <a href="hash_text_find_find_timing_test.html">Hash-Based Text
    150. 

  150.     <tt>find</tt> Find Timing Test</a>), but it is order
    151. 

  151.     preserving. This is not that surprising, since a large-fan-out
    152. 

  152.     PATRICIA trie works like a hash table with collisions resolved
    153. 

  153.     by a sub-trie. A large-fan-out PATRICIA trie does not do well on
    154. 

  154.     modifications (see <a href="tree_text_insert_timing_test.html">Tree-Based and Trie-Based
    155. 

  155.     Text Insert Timing Test</a>). It is possibly beneficial to
    156. 

  156.     semi-static settings, therefore.</p>
    157. 

  157. <p><a href="assoc_performance_tests.html#tree_like_based_types">Observations::Tree-Like-Based
    158. 

  158.     Container Types</a> summarizes some observations on tree-based
    159. 

  159.     and trie-based containers.</p>
    160. 

  160. </div>
    161. 

  161. </body>
    162. 

  162. </html>
    163. 

  163.