<!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>Priority Queue Text Modify (Up) Timing Test</title> <meta http-equiv="Content-Type" content="text/html; charset=us-ascii" /> </head> <body> <div id="page"> <h1>Priority Queue Text <tt>modify</tt> Timing Test - I</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 into a container then modifies each one "up" (<i>i.e.,</i> it makes it larger). It uses <tt>modify</tt> for <tt>pb_ds</tt>'s priority queues; for the STL's priority queues, it pops values from a container until it reaches the value that should be modified, then pushes values back in. It measures the average time for <tt>modify</tt> as a function of the number of values.</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/priority_queue_text_modify_timing.cc"><tt>priority_queue_text_modify_up_timing_test</tt></a> thirty_years_among_the_dead_preproc.txt 200 200 2100 t)</p> <h2><a name="purpose" id="purpose">Purpose</a></h2> <p>The test checks the effect of different underlying data structures (see <a href="pq_design.html#pq_imp">Design::Priority Queues::Implementations</a>) for graph algorithms settings. Note that making an arbitrary value larger (in the sense of the priority queue's comparison functor) corresponds to decrease-key in standard graph algorithms [<a href="references.html#clrs2001">clrs2001</a>].</p> <h2><a name="results" id="results">Results</a></h2> <p>Figures <a href="#NPG">NPG</a>, <a href="#NPM">NPM</a>, and <a href="#NPL">NPL</a> show the results for the native priority 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 <a href="pq_performance_tests.html#local"><u>local</u></a>, respectively; Figures <a href="#NRTG">NRTG</a>, <a href="#NRTM">NRTM</a>, and <a href="#NRTL">NRTL</a> show the results 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 <a href="pq_performance_tests.html#local"><u>local</u></a>, respectively,</p> <div id="NPG_res_div"> <div id="NPG_gcc"> <div id="NPG_priority_queue_text_modify_up_timing_test"> <div id="NPG_pq"> <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> <ol> <li> n_pq_deque- <tt>std::priority_queue</tt> adapting <tt>std::deque</tt></li> <li> n_pq_vector- <tt>std::priority_queue</tt> adapting <tt>std::vector</tt></li> <li> binary_heap- <a href="priority_queue.html"><tt>priority_queue</tt></a> with <tt>Tag</tt> = <a href="binary_heap_tag.html"><tt>binary_heap_tag</tt></a> </li> <li> rc_binomial_heap- <a href="priority_queue.html"><tt>priority_queue</tt></a> with <tt>Tag</tt> = <a href="rc_binomial_heap_tag.html"><tt>rc_binomial_heap_tag</tt></a> </li> <li> pairing_heap- <a href="priority_queue.html"><tt>priority_queue</tt></a> with <tt>Tag</tt> = <a href="pairing_heap_tag.html"><tt>pairing_heap_tag</tt></a> </li> <li> binomial_heap- <a href="priority_queue.html"><tt>priority_queue</tt></a> with <tt>Tag</tt> = <a href="binomial_heap_tag.html"><tt>binomial_heap_tag</tt></a> </li> <li> thin_heap- <a href="priority_queue.html"><tt>priority_queue</tt></a> with <tt>Tag</tt> = <a href="thin_heap_tag.html"><tt>thin_heap_tag</tt></a> </li> </ol> </div><div style="width: 100%; height: 20px"></div></div> </div> </div> </div> </div> <div id="NPM_res_div"> <div id="NPM_msvc"> <div id="NPM_priority_queue_text_modify_up_timing_test"> <div id="NPM_pq"> <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> <ol> <li> n_pq_deque- <tt>std::priority_queue</tt> adapting <tt>std::deque</tt></li> <li> n_pq_vector- <tt>std::priority_queue</tt> adapting <tt>std::vector</tt></li> <li> binary_heap- <a href="priority_queue.html"><tt>priority_queue</tt></a> with <tt>Tag</tt> = <a href="binary_heap_tag.html"><tt>binary_heap_tag</tt></a> </li> <li> rc_binomial_heap- <a href="priority_queue.html"><tt>priority_queue</tt></a> with <tt>Tag</tt> = <a href="rc_binomial_heap_tag.html"><tt>rc_binomial_heap_tag</tt></a> </li> <li> pairing_heap- <a href="priority_queue.html"><tt>priority_queue</tt></a> with <tt>Tag</tt> = <a href="pairing_heap_tag.html"><tt>pairing_heap_tag</tt></a> </li> <li> binomial_heap- <a href="priority_queue.html"><tt>priority_queue</tt></a> with <tt>Tag</tt> = <a href="binomial_heap_tag.html"><tt>binomial_heap_tag</tt></a> </li> <li> thin_heap- <a href="priority_queue.html"><tt>priority_queue</tt></a> with <tt>Tag</tt> = <a href="thin_heap_tag.html"><tt>thin_heap_tag</tt></a> </li> </ol> </div><div style="width: 100%; height: 20px"></div></div> </div> </div> </div> </div> <div id="NPL_res_div"> <div id="NPL_local"> <div id="NPL_priority_queue_text_modify_up_timing_test"> <div id="NPL_pq"> <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> </div> </div> </div> </div> <div id="NRTG_res_div"> <div id="NRTG_gcc"> <div id="NRTG_priority_queue_text_modify_up_timing_test_pairing_thin"> <div id="NRTG_pq"> <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> <ol> <li> pairing_heap- <a href="priority_queue.html"><tt>priority_queue</tt></a> with <tt>Tag</tt> = <a href="pairing_heap_tag.html"><tt>pairing_heap_tag</tt></a> </li> <li> thin_heap- <a href="priority_queue.html"><tt>priority_queue</tt></a> with <tt>Tag</tt> = <a href="thin_heap_tag.html"><tt>thin_heap_tag</tt></a> </li> </ol> </div><div style="width: 100%; height: 20px"></div></div> </div> </div> </div> </div> <div id="NRTM_res_div"> <div id="NRTM_msvc"> <div id="NRTM_priority_queue_text_modify_up_timing_test_pairing_thin"> <div id="NRTM_pq"> <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> <ol> <li> pairing_heap- <a href="priority_queue.html"><tt>priority_queue</tt></a> with <tt>Tag</tt> = <a href="pairing_heap_tag.html"><tt>pairing_heap_tag</tt></a> </li> <li> thin_heap- <a href="priority_queue.html"><tt>priority_queue</tt></a> with <tt>Tag</tt> = <a href="thin_heap_tag.html"><tt>thin_heap_tag</tt></a> </li> </ol> </div><div style="width: 100%; height: 20px"></div></div> </div> </div> </div> </div> <div id="NRTL_res_div"> <div id="NRTL_local"> <div id="NRTL_priority_queue_text_modify_up_timing_test_pairing_thin"> <div id="NRTL_pq"> <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> </div> </div> </div> </div> <h2><a name="observations" id="observations">Observations</a></h2> <p>As noted above, increasing an arbitrary value (in the sense of the priority queue's comparison functor) is very common in graph-related algorithms. In this case, a thin heap (<a href="priority_queue.html"><tt>priority_queue</tt></a> with <tt>Tag</tt> = <a href="thin_heap_tag.html"><tt>thin_heap_tag</tt></a>) outperforms a pairing heap (<a href="priority_queue.html"><tt>priority_queue</tt></a> with <tt>Tag</tt> = <a href="pairing_heap_tag.html"><tt>pairing_heap_tag</tt></a>). Conversely, <a href="priority_queue_text_push_timing_test.html">Priority Queue Text <tt>push</tt> Timing Test</a>, <a href="priority_queue_text_push_pop_timing_test.html">Priority Queue Text <tt>push</tt> and <tt>pop</tt> Timing Test</a>, <a href="priority_queue_random_int_push_timing_test.html">Priority Queue Random Integer <tt>push</tt> Timing Test</a>, and <a href="priority_queue_random_int_push_pop_timing_test.html">Priority Queue Random Integer <tt>push</tt> and <tt>pop</tt> Timing Test</a> show that the situation is reversed for other operations. It is not clear when to prefer one of these two different types.</p> <p>In this test <tt>pb_ds</tt>'s binary heaps effectively perform modify in linear time. As explained in <a href="pq_design.html#pq_traits">Priority Queue Design::Traits</a>, given a valid point-type iterator, a binary heap can perform <tt>modify</tt> logarithmically. The problem is that binary heaps invalidate their find iterators with each modifying operation, and so the only way to obtain a valid point-type iterator is to iterate using a range-type iterator until finding the appropriate value, then use the range-type iterator for the <tt>modify</tt> operation.</p> <p>The explanation for the STL's priority queues' performance is similar to that in <a href="priority_queue_text_join_timing_test.html">Priority Queue Text <tt>join</tt> Timing Test</a>.</p> <p><a href="pq_performance_tests.html#pq_observations">Priority-Queue Performance Tests::Observations</a> discusses this further and summarizes.</p> </div> </body> </html>