1<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" 2 "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> 3 4<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> 5<head> 6<meta name="generator" content="HTML Tidy for Linux/x86 (vers 12 April 2005), see www.w3.org" /> 7<title>Priority Queue Text Modify (Up) Timing Test</title> 8<meta http-equiv="Content-Type" content="text/html; charset=us-ascii" /> 9</head> 10<body> 11<div id="page"> 12<h1>Priority Queue Text <tt>modify</tt> Timing Test - I</h1> 13<h2><a name="description" id="description">Description</a></h2> 14<p>This test inserts a number of values with keys from an 15 arbitrary text ([ <a href="references.html#wickland96thirty">wickland96thirty</a> ]) into 16 into a container then modifies each one "up" (<i>i.e.,</i> it 17 makes it larger). It uses <tt>modify</tt> for <tt>pb_ds</tt>'s 18 priority queues; for the STL's priority queues, it pops values 19 from a container until it reaches the value that should be 20 modified, then pushes values back in. It measures the average 21 time for <tt>modify</tt> as a function of the number of 22 values.</p> 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 thirty_years_among_the_dead_preproc.txt 200 200 2100 t)</p> 25<h2><a name="purpose" id="purpose">Purpose</a></h2> 26<p>The test checks the effect of different underlying 27 data structures (see <a href="pq_design.html#pq_imp">Design::Priority 28 Queues::Implementations</a>) for graph algorithms settings. 29 Note that making an arbitrary value larger (in the sense of the 30 priority queue's comparison functor) corresponds to 31 decrease-key in standard graph algorithms [<a href="references.html#clrs2001">clrs2001</a>].</p> 32<h2><a name="results" id="results">Results</a></h2> 33<p>Figures <a href="#NPG">NPG</a>, <a href="#NPM">NPM</a>, and 34 <a href="#NPL">NPL</a> show the results for the native priority 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 <a href="pq_performance_tests.html#local"><u>local</u></a>, 37 respectively; Figures <a href="#NRTG">NRTG</a>, <a href="#NRTM">NRTM</a>, and <a href="#NRTL">NRTL</a> show the results 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 <a href="pq_performance_tests.html#local"><u>local</u></a>, 40 respectively,</p> 41<div id="NPG_res_div"> 42<div id="NPG_gcc"> 43<div id="NPG_priority_queue_text_modify_up_timing_test"> 44<div id="NPG_pq"> 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> 46<ol> 47<li> 48n_pq_deque- 49<tt>std::priority_queue</tt> adapting <tt>std::deque</tt></li> 50<li> 51n_pq_vector- 52<tt>std::priority_queue</tt> adapting <tt>std::vector</tt></li> 53<li> 54binary_heap- 55<a href="priority_queue.html"><tt>priority_queue</tt></a> 56 with <tt>Tag</tt> = <a href="binary_heap_tag.html"><tt>binary_heap_tag</tt></a> 57</li> 58<li> 59rc_binomial_heap- 60<a href="priority_queue.html"><tt>priority_queue</tt></a> 61 with <tt>Tag</tt> = <a href="rc_binomial_heap_tag.html"><tt>rc_binomial_heap_tag</tt></a> 62</li> 63<li> 64pairing_heap- 65<a href="priority_queue.html"><tt>priority_queue</tt></a> 66 with <tt>Tag</tt> = <a href="pairing_heap_tag.html"><tt>pairing_heap_tag</tt></a> 67</li> 68<li> 69binomial_heap- 70<a href="priority_queue.html"><tt>priority_queue</tt></a> 71 with <tt>Tag</tt> = <a href="binomial_heap_tag.html"><tt>binomial_heap_tag</tt></a> 72</li> 73<li> 74thin_heap- 75<a href="priority_queue.html"><tt>priority_queue</tt></a> 76 with <tt>Tag</tt> = <a href="thin_heap_tag.html"><tt>thin_heap_tag</tt></a> 77</li> 78</ol> 79</div><div style="width: 100%; height: 20px"></div></div> 80</div> 81</div> 82</div> 83</div> 84<div id="NPM_res_div"> 85<div id="NPM_msvc"> 86<div id="NPM_priority_queue_text_modify_up_timing_test"> 87<div id="NPM_pq"> 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> 89<ol> 90<li> 91n_pq_deque- 92<tt>std::priority_queue</tt> adapting <tt>std::deque</tt></li> 93<li> 94n_pq_vector- 95<tt>std::priority_queue</tt> adapting <tt>std::vector</tt></li> 96<li> 97binary_heap- 98<a href="priority_queue.html"><tt>priority_queue</tt></a> 99 with <tt>Tag</tt> = <a href="binary_heap_tag.html"><tt>binary_heap_tag</tt></a> 100</li> 101<li> 102rc_binomial_heap- 103<a href="priority_queue.html"><tt>priority_queue</tt></a> 104 with <tt>Tag</tt> = <a href="rc_binomial_heap_tag.html"><tt>rc_binomial_heap_tag</tt></a> 105</li> 106<li> 107pairing_heap- 108<a href="priority_queue.html"><tt>priority_queue</tt></a> 109 with <tt>Tag</tt> = <a href="pairing_heap_tag.html"><tt>pairing_heap_tag</tt></a> 110</li> 111<li> 112binomial_heap- 113<a href="priority_queue.html"><tt>priority_queue</tt></a> 114 with <tt>Tag</tt> = <a href="binomial_heap_tag.html"><tt>binomial_heap_tag</tt></a> 115</li> 116<li> 117thin_heap- 118<a href="priority_queue.html"><tt>priority_queue</tt></a> 119 with <tt>Tag</tt> = <a href="thin_heap_tag.html"><tt>thin_heap_tag</tt></a> 120</li> 121</ol> 122</div><div style="width: 100%; height: 20px"></div></div> 123</div> 124</div> 125</div> 126</div> 127<div id="NPL_res_div"> 128<div id="NPL_local"> 129<div id="NPL_priority_queue_text_modify_up_timing_test"> 130<div id="NPL_pq"> 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> 132</div> 133</div> 134</div> 135</div> 136<div id="NRTG_res_div"> 137<div id="NRTG_gcc"> 138<div id="NRTG_priority_queue_text_modify_up_timing_test_pairing_thin"> 139<div id="NRTG_pq"> 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> 141<ol> 142<li> 143pairing_heap- 144<a href="priority_queue.html"><tt>priority_queue</tt></a> 145 with <tt>Tag</tt> = <a href="pairing_heap_tag.html"><tt>pairing_heap_tag</tt></a> 146</li> 147<li> 148thin_heap- 149<a href="priority_queue.html"><tt>priority_queue</tt></a> 150 with <tt>Tag</tt> = <a href="thin_heap_tag.html"><tt>thin_heap_tag</tt></a> 151</li> 152</ol> 153</div><div style="width: 100%; height: 20px"></div></div> 154</div> 155</div> 156</div> 157</div> 158<div id="NRTM_res_div"> 159<div id="NRTM_msvc"> 160<div id="NRTM_priority_queue_text_modify_up_timing_test_pairing_thin"> 161<div id="NRTM_pq"> 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> 163<ol> 164<li> 165pairing_heap- 166<a href="priority_queue.html"><tt>priority_queue</tt></a> 167 with <tt>Tag</tt> = <a href="pairing_heap_tag.html"><tt>pairing_heap_tag</tt></a> 168</li> 169<li> 170thin_heap- 171<a href="priority_queue.html"><tt>priority_queue</tt></a> 172 with <tt>Tag</tt> = <a href="thin_heap_tag.html"><tt>thin_heap_tag</tt></a> 173</li> 174</ol> 175</div><div style="width: 100%; height: 20px"></div></div> 176</div> 177</div> 178</div> 179</div> 180<div id="NRTL_res_div"> 181<div id="NRTL_local"> 182<div id="NRTL_priority_queue_text_modify_up_timing_test_pairing_thin"> 183<div id="NRTL_pq"> 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> 185</div> 186</div> 187</div> 188</div> 189<h2><a name="observations" id="observations">Observations</a></h2> 190<p>As noted above, increasing an arbitrary value (in the sense 191 of the priority queue's comparison functor) is very common in 192 graph-related algorithms. In this case, a thin heap (<a href="priority_queue.html"><tt>priority_queue</tt></a> with 193 <tt>Tag</tt> = <a href="thin_heap_tag.html"><tt>thin_heap_tag</tt></a>) 194 outperforms a pairing heap (<a href="priority_queue.html"><tt>priority_queue</tt></a> with 195 <tt>Tag</tt> = <a href="pairing_heap_tag.html"><tt>pairing_heap_tag</tt></a>). 196 Conversely, <a href="priority_queue_text_push_timing_test.html">Priority Queue Text 197 <tt>push</tt> Timing Test</a>, <a href="priority_queue_text_push_pop_timing_test.html">Priority Queue 198 Text <tt>push</tt> and <tt>pop</tt> Timing Test</a>, <a href="priority_queue_random_int_push_timing_test.html">Priority 199 Queue Random Integer <tt>push</tt> Timing Test</a>, and 200 <a href="priority_queue_random_int_push_pop_timing_test.html">Priority 201 Queue Random Integer <tt>push</tt> and <tt>pop</tt> Timing 202 Test</a> show that the situation is reversed for other 203 operations. It is not clear when to prefer one of these two 204 different types.</p> 205<p>In this test <tt>pb_ds</tt>'s binary heaps effectively 206 perform modify in linear time. As explained in <a href="pq_design.html#pq_traits">Priority Queue Design::Traits</a>, 207 given a valid point-type iterator, a binary heap can perform 208 <tt>modify</tt> logarithmically. The problem is that binary 209 heaps invalidate their find iterators with each modifying 210 operation, and so the only way to obtain a valid point-type 211 iterator is to iterate using a range-type iterator until 212 finding the appropriate value, then use the range-type iterator 213 for the <tt>modify</tt> operation.</p> 214<p>The explanation for the STL's priority queues' performance 215 is similar to that in <a href="priority_queue_text_join_timing_test.html">Priority Queue Text 216 <tt>join</tt> Timing Test</a>.</p> 217<p><a href="pq_performance_tests.html#pq_observations">Priority-Queue 218 Performance Tests::Observations</a> discusses this further and 219 summarizes.</p> 220</div> 221</body> 222</html> 223
