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7<title>Priority Queue Text Modify (Down) Timing Test</title>
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12<h1>Priority Queue Text <tt>modify</tt> Timing Test - II</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 "down" (<i>i.e.,</i> it
17    makes it smaller). 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_down_timing_test</tt></a>
24    thirty_years_among_the_dead_preproc.txt 200 200 2100 f)</p>
25<h2><a name="purpose" id="purpose">Purpose</a></h2>
26<p>The main purpose of this test is to contrast <a href="priority_queue_text_modify_up_timing_test.html">Priority Queue
27    Text <tt>modify</tt> Timing Test - I</a>.</p>
28<h2><a name="results" id="results">Results</a></h2>
29<p>Figures <a href="#NPG">NPG</a>, <a href="#NPM">NPM</a>, and
30    <a href="#NPL">NPL</a> show the results for the native priority
31    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
32    <a href="pq_performance_tests.html#local"><u>local</u></a>,
33    respectively; Figures <a href="#NRTG">NRTG</a>, <a href="#NRTM">NRTM</a>, and <a href="#NRTL">NRTL</a> show the results
34    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
35    <a href="pq_performance_tests.html#local"><u>local</u></a>,
36    respectively,</p>
37<div id="NPG_res_div">
38<div id="NPG_gcc">
39<div id="NPG_priority_queue_text_modify_down_timing_test">
40<div id="NPG_pq">
41<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_down_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>
42<ol>
43<li>
44n_pq_deque-
45<tt>std::priority_queue</tt> adapting <tt>std::deque</tt></li>
46<li>
47n_pq_vector-
48<tt>std::priority_queue</tt> adapting <tt>std::vector</tt></li>
49<li>
50binary_heap-
51<a href="priority_queue.html"><tt>priority_queue</tt></a>
52 with <tt>Tag</tt> = <a href="binary_heap_tag.html"><tt>binary_heap_tag</tt></a>
53</li>
54<li>
55thin_heap-
56<a href="priority_queue.html"><tt>priority_queue</tt></a>
57 with <tt>Tag</tt> = <a href="thin_heap_tag.html"><tt>thin_heap_tag</tt></a>
58</li>
59<li>
60rc_binomial_heap-
61<a href="priority_queue.html"><tt>priority_queue</tt></a>
62 with <tt>Tag</tt> = <a href="rc_binomial_heap_tag.html"><tt>rc_binomial_heap_tag</tt></a>
63</li>
64<li>
65binomial_heap-
66<a href="priority_queue.html"><tt>priority_queue</tt></a>
67 with <tt>Tag</tt> = <a href="binomial_heap_tag.html"><tt>binomial_heap_tag</tt></a>
68</li>
69<li>
70pairing_heap-
71<a href="priority_queue.html"><tt>priority_queue</tt></a>
72 with <tt>Tag</tt> = <a href="pairing_heap_tag.html"><tt>pairing_heap_tag</tt></a>
73</li>
74</ol>
75</div><div style="width: 100%; height: 20px"></div></div>
76</div>
77</div>
78</div>
79</div>
80<div id="NPM_res_div">
81<div id="NPM_msvc">
82<div id="NPM_priority_queue_text_modify_down_timing_test">
83<div id="NPM_pq">
84<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_down_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>
85<ol>
86<li>
87n_pq_deque-
88<tt>std::priority_queue</tt> adapting <tt>std::deque</tt></li>
89<li>
90n_pq_vector-
91<tt>std::priority_queue</tt> adapting <tt>std::vector</tt></li>
92<li>
93binary_heap-
94<a href="priority_queue.html"><tt>priority_queue</tt></a>
95 with <tt>Tag</tt> = <a href="binary_heap_tag.html"><tt>binary_heap_tag</tt></a>
96</li>
97<li>
98thin_heap-
99<a href="priority_queue.html"><tt>priority_queue</tt></a>
100 with <tt>Tag</tt> = <a href="thin_heap_tag.html"><tt>thin_heap_tag</tt></a>
101</li>
102<li>
103rc_binomial_heap-
104<a href="priority_queue.html"><tt>priority_queue</tt></a>
105 with <tt>Tag</tt> = <a href="rc_binomial_heap_tag.html"><tt>rc_binomial_heap_tag</tt></a>
106</li>
107<li>
108binomial_heap-
109<a href="priority_queue.html"><tt>priority_queue</tt></a>
110 with <tt>Tag</tt> = <a href="binomial_heap_tag.html"><tt>binomial_heap_tag</tt></a>
111</li>
112<li>
113pairing_heap-
114<a href="priority_queue.html"><tt>priority_queue</tt></a>
115 with <tt>Tag</tt> = <a href="pairing_heap_tag.html"><tt>pairing_heap_tag</tt></a>
116</li>
117</ol>
118</div><div style="width: 100%; height: 20px"></div></div>
119</div>
120</div>
121</div>
122</div>
123<div id="NPL_res_div">
124<div id="NPL_local">
125<div id="NPL_priority_queue_text_modify_down_timing_test">
126<div id="NPL_pq">
127<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_down_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>
128</div>
129</div>
130</div>
131</div>
132<div id="NRTG_res_div">
133<div id="NRTG_gcc">
134<div id="NRTG_priority_queue_text_modify_down_timing_test_pairing_thin">
135<div id="NRTG_pq">
136<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_down_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>
137<ol>
138<li>
139thin_heap-
140<a href="priority_queue.html"><tt>priority_queue</tt></a>
141 with <tt>Tag</tt> = <a href="thin_heap_tag.html"><tt>thin_heap_tag</tt></a>
142</li>
143<li>
144pairing_heap-
145<a href="priority_queue.html"><tt>priority_queue</tt></a>
146 with <tt>Tag</tt> = <a href="pairing_heap_tag.html"><tt>pairing_heap_tag</tt></a>
147</li>
148</ol>
149</div><div style="width: 100%; height: 20px"></div></div>
150</div>
151</div>
152</div>
153</div>
154<div id="NRTM_res_div">
155<div id="NRTM_msvc">
156<div id="NRTM_priority_queue_text_modify_down_timing_test_pairing_thin">
157<div id="NRTM_pq">
158<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_down_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>
159<ol>
160<li>
161thin_heap-
162<a href="priority_queue.html"><tt>priority_queue</tt></a>
163 with <tt>Tag</tt> = <a href="thin_heap_tag.html"><tt>thin_heap_tag</tt></a>
164</li>
165<li>
166pairing_heap-
167<a href="priority_queue.html"><tt>priority_queue</tt></a>
168 with <tt>Tag</tt> = <a href="pairing_heap_tag.html"><tt>pairing_heap_tag</tt></a>
169</li>
170</ol>
171</div><div style="width: 100%; height: 20px"></div></div>
172</div>
173</div>
174</div>
175</div>
176<div id="NRTL_res_div">
177<div id="NRTL_local">
178<div id="NRTL_priority_queue_text_modify_down_timing_test_pairing_thin">
179<div id="NRTL_pq">
180<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_down_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>
181</div>
182</div>
183</div>
184</div>
185<h2><a name="observations" id="observations">Observations</a></h2>
186<p>Most points in these results are similar to <a href="priority_queue_text_modify_up_timing_test.html">Priority Queue
187    Text <tt>modify</tt> Timing Test - I</a>.</p>
188<p>It is interesting to note, however, that as opposed to that
189    test, a thin heap (<a href="priority_queue.html"><tt>priority_queue</tt></a> with
190    <tt>Tag</tt> = <a href="thin_heap_tag.html"><tt>thin_heap_tag</tt></a>) is
191    outperformed by a pairing heap (<a href="priority_queue.html"><tt>priority_queue</tt></a> with
192    <tt>Tag</tt> = <a href="pairing_heap_tag.html"><tt>pairing_heap_tag</tt></a>).
193    In this case, both heaps essentially perform an <tt>erase</tt>
194    operation followed by a <tt>push</tt> operation. As the other
195    tests show, a pairing heap is usually far more efficient than a
196    thin heap, so this is not surprising.</p>
197<p>Most algorithms that involve priority queues increase values
198    (in the sense of the priority queue's comparison functor), and
199    so <a href="priority_queue_text_modify_up_timing_test.html">Priority Queue
200    Text <tt>modify</tt> Timing Test - I</a> is more interesting
201    than this test.</p>
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