llvm-gcc-4.2/libstdc++-v3/docs/html/ext/pb_ds/priority_queue_text_modify_up_timing_test.html - llvm-archive - Git at Google

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 <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="../../../../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>
	<!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="../../../../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>