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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>Priority Queue Text Modify (Up) Timing Test</title>
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  11. <div id="page">
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  12. <h1>Priority Queue Text <tt>modify</tt> Timing Test - I</h1>
    13. 

  13. <h2><a name="description" id="description">Description</a></h2>
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  14. <p>This test inserts a number of values with keys from an
    15. 

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

  16.     into a container then modifies each one "up" (<i>i.e.,</i> it
    17. 

  17.     makes it larger). It uses <tt>modify</tt> for <tt>pb_ds</tt>'s
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  18.     priority queues; for the STL's priority queues, it pops values
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  19.     from a container until it reaches the value that should be
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  20.     modified, then pushes values back in. It measures the average
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  21.     time for <tt>modify</tt> as a function of the number of
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  22.     values.</p>
    23. 

  23. <p>(The test was executed with <a href="http://gcc.gnu.org/viewcvs/*checkout*/trunk/libstdc%2B%2B-v3/testsuite/performance/ext/pb_ds/priority_queue_text_modify_timing.cc"><tt>priority_queue_text_modify_up_timing_test</tt></a>
    24. 

  24.     thirty_years_among_the_dead_preproc.txt 200 200 2100 t)</p>
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  25. <h2><a name="purpose" id="purpose">Purpose</a></h2>
    26. 

  26. <p>The test checks the effect of different underlying
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  27.     data structures (see <a href="pq_design.html#pq_imp">Design::Priority
    28. 

  28.     Queues::Implementations</a>) for graph algorithms settings.
    29. 

  29.     Note that making an arbitrary value larger (in the sense of the
    30. 

  30.     priority queue's comparison functor) corresponds to
    31. 

  31.     decrease-key in standard graph algorithms [<a href="references.html#clrs2001">clrs2001</a>].</p>
    32. 

  32. <h2><a name="results" id="results">Results</a></h2>
    33. 

  33. <p>Figures <a href="#NPG">NPG</a>, <a href="#NPM">NPM</a>, and
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  34.     <a href="#NPL">NPL</a> show the results for the native priority
    35. 

  35.     queues and <tt>pb_ds</tt> 's priority queues in <a href="pq_performance_tests.html#gcc"><u>g++</u></a>, <a href="pq_performance_tests.html#msvc"><u>msvc++</u></a>, and
    36. 

  36.     <a href="pq_performance_tests.html#local"><u>local</u></a>,
    37. 

  37.     respectively; Figures <a href="#NRTG">NRTG</a>, <a href="#NRTM">NRTM</a>, and <a href="#NRTL">NRTL</a> show the results
    38. 

  38.     for the pairing heap and thin heaps in <a href="pq_performance_tests.html#gcc"><u>g++</u></a>, <a href="pq_performance_tests.html#msvc"><u>msvc++</u></a>, and
    39. 

  39.     <a href="pq_performance_tests.html#local"><u>local</u></a>,
    40. 

  40.     respectively,</p>
    41. 

  41. <div id="NPG_res_div">
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  42. <div id="NPG_gcc">
    43. 

  43. <div id="NPG_priority_queue_text_modify_up_timing_test">
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  44. <div id="NPG_pq">
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  45. <div id="NPG_Native_and__tt_pb_ds_455tt__priority_queue__tt_modify_455tt__timing_test"><div style="border-style: dotted; border-width: 1px; border-color: lightgray"><h6 class="c1"><a name="NPG" id="NPG"><img src="priority_queue_text_modify_up_timing_test_gcc.png" alt="no image" /></a></h6>NPG: Native and <tt>pb ds</tt> priority queue <tt>modify</tt> timing test - <a href="pq_performance_tests.html#gcc">g++</a><p>In the above figure, the names in the legends have the following meaning:</p>
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  46. <ol>
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  47. <li>
    48. 

  48. n_pq_deque-
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  49. <tt>std::priority_queue</tt> adapting <tt>std::deque</tt></li>
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  50. <li>
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  51. n_pq_vector-
    52. 

  52. <tt>std::priority_queue</tt> adapting <tt>std::vector</tt></li>
    53. 

  53. <li>
    54. 

  54. binary_heap-
    55. 

  55. <a href="priority_queue.html"><tt>priority_queue</tt></a>
    56. 

  56.  with <tt>Tag</tt> = <a href="binary_heap_tag.html"><tt>binary_heap_tag</tt></a>
    57. 

  57. </li>
    58. 

  58. <li>
    59. 

  59. rc_binomial_heap-
    60. 

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

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

  62. </li>
    63. 

  63. <li>
    64. 

  64. pairing_heap-
    65. 

  65. <a href="priority_queue.html"><tt>priority_queue</tt></a>
    66. 

  66.  with <tt>Tag</tt> = <a href="pairing_heap_tag.html"><tt>pairing_heap_tag</tt></a>
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  67. </li>
    68. 

  68. <li>
    69. 

  69. binomial_heap-
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  70. <a href="priority_queue.html"><tt>priority_queue</tt></a>
    71. 

  71.  with <tt>Tag</tt> = <a href="binomial_heap_tag.html"><tt>binomial_heap_tag</tt></a>
    72. 

  72. </li>
    73. 

  73. <li>
    74. 

  74. thin_heap-
    75. 

  75. <a href="priority_queue.html"><tt>priority_queue</tt></a>
    76. 

  76.  with <tt>Tag</tt> = <a href="thin_heap_tag.html"><tt>thin_heap_tag</tt></a>
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  77. </li>
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  78. </ol>
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  79. </div><div style="width: 100%; height: 20px"></div></div>
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  80. </div>
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  81. </div>
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  82. </div>
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  83. </div>
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  84. <div id="NPM_res_div">
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  85. <div id="NPM_msvc">
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  86. <div id="NPM_priority_queue_text_modify_up_timing_test">
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  87. <div id="NPM_pq">
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  88. <div id="NPM_Native_and__tt_pb_ds_455tt__priority_queue__tt_modify_455tt__timing_test"><div style="border-style: dotted; border-width: 1px; border-color: lightgray"><h6 class="c1"><a name="NPM" id="NPM"><img src="priority_queue_text_modify_up_timing_test_msvc.png" alt="no image" /></a></h6>NPM: Native and <tt>pb ds</tt> priority queue <tt>modify</tt> timing test - <a href="pq_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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  89. <ol>
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  90. <li>
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  91. n_pq_deque-
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  92. <tt>std::priority_queue</tt> adapting <tt>std::deque</tt></li>
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  93. <li>
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  94. n_pq_vector-
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  95. <tt>std::priority_queue</tt> adapting <tt>std::vector</tt></li>
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  96. <li>
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  97. binary_heap-
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  98. <a href="priority_queue.html"><tt>priority_queue</tt></a>
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  99.  with <tt>Tag</tt> = <a href="binary_heap_tag.html"><tt>binary_heap_tag</tt></a>
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  100. </li>
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  101. <li>
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  102. rc_binomial_heap-
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  103. <a href="priority_queue.html"><tt>priority_queue</tt></a>
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  104.  with <tt>Tag</tt> = <a href="rc_binomial_heap_tag.html"><tt>rc_binomial_heap_tag</tt></a>
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  105. </li>
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  106. <li>
    107. 

  107. pairing_heap-
    108. 

  108. <a href="priority_queue.html"><tt>priority_queue</tt></a>
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  109.  with <tt>Tag</tt> = <a href="pairing_heap_tag.html"><tt>pairing_heap_tag</tt></a>
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  110. </li>
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  111. <li>
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  112. binomial_heap-
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  113. <a href="priority_queue.html"><tt>priority_queue</tt></a>
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  114.  with <tt>Tag</tt> = <a href="binomial_heap_tag.html"><tt>binomial_heap_tag</tt></a>
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  115. </li>
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  116. <li>
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  117. thin_heap-
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  118. <a href="priority_queue.html"><tt>priority_queue</tt></a>
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  119.  with <tt>Tag</tt> = <a href="thin_heap_tag.html"><tt>thin_heap_tag</tt></a>
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  120. </li>
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  121. </ol>
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  122. </div><div style="width: 100%; height: 20px"></div></div>
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  123. </div>
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  124. </div>
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  125. </div>
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  126. </div>
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  127. <div id="NPL_res_div">
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  128. <div id="NPL_local">
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  129. <div id="NPL_priority_queue_text_modify_up_timing_test">
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  130. <div id="NPL_pq">
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  131. <div id="NPL_Native_and__tt_pb_ds_455tt__priority_queue__tt_modify_455tt__timing_test"><div style = "border-style: dotted; border-width: 1px; border-color: lightgray"><h6 class="c1"><a name="NPL" id= "NPL"><img src="priority_queue_text_modify_up_timing_test_local.png" alt="no image" /></a></h6>NPL: Native and <tt>pb ds</tt> priority queue <tt>modify</tt> timing test - <a href = "pq_performance_tests.html#local">local</a></div><div style = "width: 100%; height: 20px"></div></div>
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  132. </div>
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  133. </div>
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  134. </div>
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  135. </div>
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  136. <div id="NRTG_res_div">
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  137. <div id="NRTG_gcc">
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  138. <div id="NRTG_priority_queue_text_modify_up_timing_test_pairing_thin">
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  139. <div id="NRTG_pq">
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  140. <div id="NRTG_Pairing_and_thin__priority_queue__tt_modify_455tt__timing_test"><div style="border-style: dotted; border-width: 1px; border-color: lightgray"><h6 class="c1"><a name="NRTG" id="NRTG"><img src="priority_queue_text_modify_up_timing_test_pairing_thin_gcc.png" alt="no image" /></a></h6>NRTG: Pairing and thin  priority queue <tt>modify</tt> timing test - <a href="pq_performance_tests.html#gcc">g++</a><p>In the above figure, the names in the legends have the following meaning:</p>
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  141. <ol>
    142. 

  142. <li>
    143. 

  143. pairing_heap-
    144. 

  144. <a href="priority_queue.html"><tt>priority_queue</tt></a>
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  145.  with <tt>Tag</tt> = <a href="pairing_heap_tag.html"><tt>pairing_heap_tag</tt></a>
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  146. </li>
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  147. <li>
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  148. thin_heap-
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  149. <a href="priority_queue.html"><tt>priority_queue</tt></a>
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  150.  with <tt>Tag</tt> = <a href="thin_heap_tag.html"><tt>thin_heap_tag</tt></a>
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  151. </li>
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  152. </ol>
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  153. </div><div style="width: 100%; height: 20px"></div></div>
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  154. </div>
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  155. </div>
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  156. </div>
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  157. </div>
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  158. <div id="NRTM_res_div">
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  159. <div id="NRTM_msvc">
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  160. <div id="NRTM_priority_queue_text_modify_up_timing_test_pairing_thin">
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  161. <div id="NRTM_pq">
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  162. <div id="NRTM_Pairing_and_thin__priority_queue__tt_modify_455tt__timing_test"><div style="border-style: dotted; border-width: 1px; border-color: lightgray"><h6 class="c1"><a name="NRTM" id="NRTM"><img src="priority_queue_text_modify_up_timing_test_pairing_thin_msvc.png" alt="no image" /></a></h6>NRTM: Pairing and thin  priority queue <tt>modify</tt> timing test - <a href="pq_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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  163. <ol>
    164. 

  164. <li>
    165. 

  165. pairing_heap-
    166. 

  166. <a href="priority_queue.html"><tt>priority_queue</tt></a>
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  167.  with <tt>Tag</tt> = <a href="pairing_heap_tag.html"><tt>pairing_heap_tag</tt></a>
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  168. </li>
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  169. <li>
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  170. thin_heap-
    171. 

  171. <a href="priority_queue.html"><tt>priority_queue</tt></a>
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  172.  with <tt>Tag</tt> = <a href="thin_heap_tag.html"><tt>thin_heap_tag</tt></a>
    173. 

  173. </li>
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  174. </ol>
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  175. </div><div style="width: 100%; height: 20px"></div></div>
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  176. </div>
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  177. </div>
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  178. </div>
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  179. </div>
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  180. <div id="NRTL_res_div">
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  181. <div id="NRTL_local">
    182. 

  182. <div id="NRTL_priority_queue_text_modify_up_timing_test_pairing_thin">
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  183. <div id="NRTL_pq">
    184. 

  184. <div id="NRTL_Pairing_and_thin__priority_queue__tt_modify_455tt__timing_test"><div style = "border-style: dotted; border-width: 1px; border-color: lightgray"><h6 class="c1"><a name="NRTL" id= "NRTL"><img src="priority_queue_text_modify_up_timing_test_pairing_thin_local.png" alt="no image" /></a></h6>NRTL: Pairing and thin  priority queue <tt>modify</tt> timing test - <a href = "pq_performance_tests.html#local">local</a></div><div style = "width: 100%; height: 20px"></div></div>
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  185. </div>
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  186. </div>
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  187. </div>
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  188. </div>
    189. 

  189. <h2><a name="observations" id="observations">Observations</a></h2>
    190. 

  190. <p>As noted above, increasing an arbitrary value (in the sense
    191. 

  191.     of the priority queue's comparison functor) is very common in
    192. 

  192.     graph-related algorithms. In this case, a thin heap (<a href="priority_queue.html"><tt>priority_queue</tt></a> with
    193. 

  193.     <tt>Tag</tt> = <a href="thin_heap_tag.html"><tt>thin_heap_tag</tt></a>)
    194. 

  194.     outperforms a pairing heap (<a href="priority_queue.html"><tt>priority_queue</tt></a> with
    195. 

  195.     <tt>Tag</tt> = <a href="pairing_heap_tag.html"><tt>pairing_heap_tag</tt></a>).
    196. 

  196.     Conversely, <a href="priority_queue_text_push_timing_test.html">Priority Queue Text
    197. 

  197.     <tt>push</tt> Timing Test</a>, <a href="priority_queue_text_push_pop_timing_test.html">Priority Queue
    198. 

  198.     Text <tt>push</tt> and <tt>pop</tt> Timing Test</a>, <a href="priority_queue_random_int_push_timing_test.html">Priority
    199. 

  199.     Queue Random Integer <tt>push</tt> Timing Test</a>, and
    200. 

  200.     <a href="priority_queue_random_int_push_pop_timing_test.html">Priority
    201. 

  201.     Queue Random Integer <tt>push</tt> and <tt>pop</tt> Timing
    202. 

  202.     Test</a> show that the situation is reversed for other
    203. 

  203.     operations. It is not clear when to prefer one of these two
    204. 

  204.     different types.</p>
    205. 

  205. <p>In this test <tt>pb_ds</tt>'s binary heaps effectively
    206. 

  206.     perform modify in linear time. As explained in <a href="pq_design.html#pq_traits">Priority Queue Design::Traits</a>,
    207. 

  207.     given a valid point-type iterator, a binary heap can perform
    208. 

  208.     <tt>modify</tt> logarithmically. The problem is that binary
    209. 

  209.     heaps invalidate their find iterators with each modifying
    210. 

  210.     operation, and so the only way to obtain a valid point-type
    211. 

  211.     iterator is to iterate using a range-type iterator until
    212. 

  212.     finding the appropriate value, then use the range-type iterator
    213. 

  213.     for the <tt>modify</tt> operation.</p>
    214. 

  214. <p>The explanation for the STL's priority queues' performance
    215. 

  215.     is similar to that in <a href="priority_queue_text_join_timing_test.html">Priority Queue Text
    216. 

  216.     <tt>join</tt> Timing Test</a>.</p>
    217. 

  217. <p><a href="pq_performance_tests.html#pq_observations">Priority-Queue
    218. 

  218.     Performance Tests::Observations</a> discusses this further and
    219. 

  219.     summarizes.</p>
    220. 

  220. </div>
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  221. </body>
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  222. </html>
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  223.