1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
|
<!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">
<head>
<meta name="generator" content="HTML Tidy for Linux/x86 (vers 12 April 2005), see www.w3.org" />
<title>Hash Text Find Timing Test</title>
<meta http-equiv="Content-Type" content="text/html; charset=us-ascii" />
</head>
<body>
<div id="page">
<h1>Hash-Based Text <tt>find</tt> Find Timing Test</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
a container, then performs a series of finds using
<tt>find</tt> . It measures the average time for <tt>find</tt>
as a function of the number of values inserted.</p>
<p>(The test was executed with <a href="../../../../testsuite/performance/ext/pb_ds/text_find_timing.cc"><tt>text_find_timing_test</tt></a>
thirty_years_among_the_dead_preproc.txt 200 200 2100)</p>
<h2><a name="purpose" id="purpose">Purpose</a></h2>
<p>The test checks the effect of different range-hashing
functions, trigger policies, and cache-hashing policies (see
<a href="hash_based_containers.html#hash_policies">Design::Associative
Containers::Associative Containers::Hash-Based Containers::Hash
Policies</a> and <a href="hash_based_containers.html#resize_policies">Design::Associative
Containers::Hash-Based Containers::Resize Policies</a> ).</p>
<h2><a name="results" id="results">Results</a></h2>
<p>Figures <a href="#NCCG">NCCG</a>, <a href="#NCCM">NCCM</a>
and <a href="#NCCL">NCCL</a> show the results for the native
and collision-chaining types in <a href="assoc_performance_tests.html#gcc"><u>g++</u></a>, <a href="assoc_performance_tests.html#msvc"><u>msvc++</u></a>, and
<a href="assoc_performance_tests.html#local"><u>local</u></a>,
respetively.</p>
<div id="NCCG_res_div">
<div id="NCCG_gcc">
<div id="NCCG_text_find_timing_test_hash">
<div id="NCCG_assoc">
<div id="NCCG_Native_and_collision-chaining_hash_text_find_timing_test_using__tt_find_455tt_"><div style="border-style: dotted; border-width: 1px; border-color: lightgray"><h6 class="c1"><a name="NCCG" id="NCCG"><img src="text_find_timing_test_hash_gcc.png" alt="no image" /></a></h6>NCCG: Native and collision-chaining hash text find timing test using <tt>find</tt> - <a href="assoc_performance_tests.html#gcc">g++</a><p>In the above figure, the names in the legends have the following meaning:</p>
<ol>
<li>
n_hash_map_ncah-
<tt>std::tr1::unordered_map</tt> with <tt>cache_hash_code</tt> = <tt><b>false</b></tt></li>
<li>
cc_hash_mod_prime_nea_lc_1div8_1div1_nsth_map-
<a href="cc_hash_table.html"><tt>cc_hash_table</tt></a>
with <tt>Comb_Hash_Fn</tt> = <a href="direct_mod_range_hashing.html"><tt>direct_mod_range_hashing</tt></a>
, and <tt>Resize_Policy</tt> = <a href="hash_standard_resize_policy.html"><tt>hash_standard_resize_policy</tt></a>
with <tt>Size_Policy</tt> = <a href="hash_prime_size_policy.html"><tt>hash_prime_size_policy</tt></a>
, and <tt>Trigger_Policy</tt> = <a href="hash_load_check_resize_trigger.html"><tt>hash_load_check_resize_trigger</tt></a>
with <i>α<sub>min</sub></i> = <i>1/8</i> and <i>α<sub>max</sub></i> = <i>1/1</i></li>
<li>
cc_hash_mask_exp_nea_lc_1div8_1div2_sth_map-
<a href="cc_hash_table.html"><tt>cc_hash_table</tt></a>
with <tt>Comb_Hash_Fn</tt> = <a href="direct_mask_range_hashing.html"><tt>direct_mask_range_hashing</tt></a>
, and <tt>Resize_Policy</tt> = <a href="hash_standard_resize_policy.html"><tt>hash_standard_resize_policy</tt></a>
with <tt>Size_Policy</tt> = <a href="hash_exponential_size_policy.html"><tt>hash_exponential_size_policy</tt></a>
, and <tt>Trigger_Policy</tt> = <a href="hash_load_check_resize_trigger.html"><tt>hash_load_check_resize_trigger</tt></a>
with <i>α<sub>min</sub></i> = <i>1/8</i> and <i>α<sub>max</sub></i> = <i>1/2</i></li>
<li>
cc_hash_mask_exp_nea_lc_1div8_1div1_nsth_map-
<a href="cc_hash_table.html"><tt>cc_hash_table</tt></a>
with <tt>Comb_Hash_Fn</tt> = <a href="direct_mask_range_hashing.html"><tt>direct_mask_range_hashing</tt></a>
, and <tt>Resize_Policy</tt> = <a href="hash_standard_resize_policy.html"><tt>hash_standard_resize_policy</tt></a>
with <tt>Size_Policy</tt> = <a href="hash_exponential_size_policy.html"><tt>hash_exponential_size_policy</tt></a>
, and <tt>Trigger_Policy</tt> = <a href="hash_load_check_resize_trigger.html"><tt>hash_load_check_resize_trigger</tt></a>
with <i>α<sub>min</sub></i> = <i>1/8</i> and <i>α<sub>max</sub></i> = <i>1/1</i></li>
<li>
cc_hash_mask_exp_nea_lc_1div8_1div2_nsth_map-
<a href="cc_hash_table.html"><tt>cc_hash_table</tt></a>
with <tt>Comb_Hash_Fn</tt> = <a href="direct_mask_range_hashing.html"><tt>direct_mask_range_hashing</tt></a>
, and <tt>Resize_Policy</tt> = <a href="hash_standard_resize_policy.html"><tt>hash_standard_resize_policy</tt></a>
with <tt>Size_Policy</tt> = <a href="hash_exponential_size_policy.html"><tt>hash_exponential_size_policy</tt></a>
, and <tt>Trigger_Policy</tt> = <a href="hash_load_check_resize_trigger.html"><tt>hash_load_check_resize_trigger</tt></a>
with <i>α<sub>min</sub></i> = <i>1/8</i> and <i>α<sub>max</sub></i> = <i>1/2</i></li>
</ol>
</div><div style="width: 100%; height: 20px"></div></div>
</div>
</div>
</div>
</div>
<div id="NCCM_res_div">
<div id="NCCM_msvc">
<div id="NCCM_text_find_timing_test_hash">
<div id="NCCM_assoc">
<div id="NCCM_Native_and_collision-chaining_hash_text_find_timing_test_using__tt_find_455tt_"><div style="border-style: dotted; border-width: 1px; border-color: lightgray"><h6 class="c1"><a name="NCCM" id="NCCM"><img src="text_find_timing_test_hash_msvc.png" alt="no image" /></a></h6>NCCM: Native and collision-chaining hash text find timing test using <tt>find</tt> - <a href="assoc_performance_tests.html#msvc">msvc++</a><p>In the above figure, the names in the legends have the following meaning:</p>
<ol>
<li>
n_hash_map_ncah-
<tt>stdext::hash_map</tt></li>
<li>
cc_hash_mod_prime_nea_lc_1div8_1div1_nsth_map-
<a href="cc_hash_table.html"><tt>cc_hash_table</tt></a>
with <tt>Comb_Hash_Fn</tt> = <a href="direct_mod_range_hashing.html"><tt>direct_mod_range_hashing</tt></a>
, and <tt>Resize_Policy</tt> = <a href="hash_standard_resize_policy.html"><tt>hash_standard_resize_policy</tt></a>
with <tt>Size_Policy</tt> = <a href="hash_prime_size_policy.html"><tt>hash_prime_size_policy</tt></a>
, and <tt>Trigger_Policy</tt> = <a href="hash_load_check_resize_trigger.html"><tt>hash_load_check_resize_trigger</tt></a>
with <i>α<sub>min</sub></i> = <i>1/8</i> and <i>α<sub>max</sub></i> = <i>1/1</i></li>
<li>
cc_hash_mask_exp_nea_lc_1div8_1div1_nsth_map-
<a href="cc_hash_table.html"><tt>cc_hash_table</tt></a>
with <tt>Comb_Hash_Fn</tt> = <a href="direct_mask_range_hashing.html"><tt>direct_mask_range_hashing</tt></a>
, and <tt>Resize_Policy</tt> = <a href="hash_standard_resize_policy.html"><tt>hash_standard_resize_policy</tt></a>
with <tt>Size_Policy</tt> = <a href="hash_exponential_size_policy.html"><tt>hash_exponential_size_policy</tt></a>
, and <tt>Trigger_Policy</tt> = <a href="hash_load_check_resize_trigger.html"><tt>hash_load_check_resize_trigger</tt></a>
with <i>α<sub>min</sub></i> = <i>1/8</i> and <i>α<sub>max</sub></i> = <i>1/1</i></li>
<li>
cc_hash_mask_exp_nea_lc_1div8_1div2_nsth_map-
<a href="cc_hash_table.html"><tt>cc_hash_table</tt></a>
with <tt>Comb_Hash_Fn</tt> = <a href="direct_mask_range_hashing.html"><tt>direct_mask_range_hashing</tt></a>
, and <tt>Resize_Policy</tt> = <a href="hash_standard_resize_policy.html"><tt>hash_standard_resize_policy</tt></a>
with <tt>Size_Policy</tt> = <a href="hash_exponential_size_policy.html"><tt>hash_exponential_size_policy</tt></a>
, and <tt>Trigger_Policy</tt> = <a href="hash_load_check_resize_trigger.html"><tt>hash_load_check_resize_trigger</tt></a>
with <i>α<sub>min</sub></i> = <i>1/8</i> and <i>α<sub>max</sub></i> = <i>1/2</i></li>
<li>
cc_hash_mask_exp_nea_lc_1div8_1div2_sth_map-
<a href="cc_hash_table.html"><tt>cc_hash_table</tt></a>
with <tt>Comb_Hash_Fn</tt> = <a href="direct_mask_range_hashing.html"><tt>direct_mask_range_hashing</tt></a>
, and <tt>Resize_Policy</tt> = <a href="hash_standard_resize_policy.html"><tt>hash_standard_resize_policy</tt></a>
with <tt>Size_Policy</tt> = <a href="hash_exponential_size_policy.html"><tt>hash_exponential_size_policy</tt></a>
, and <tt>Trigger_Policy</tt> = <a href="hash_load_check_resize_trigger.html"><tt>hash_load_check_resize_trigger</tt></a>
with <i>α<sub>min</sub></i> = <i>1/8</i> and <i>α<sub>max</sub></i> = <i>1/2</i></li>
</ol>
</div><div style="width: 100%; height: 20px"></div></div>
</div>
</div>
</div>
</div>
<div id="NCCL_res_div">
<div id="NCCL_local">
<div id="NCCL_text_find_timing_test_hash">
<div id="NCCL_assoc">
<div id="NCCL_Native_and_collision-chaining_hash_text_find_timing_test_using__tt_find_455tt_"><div style = "border-style: dotted; border-width: 1px; border-color: lightgray"><h6 class="c1"><a name="NCCL" id= "NCCL"><img src="text_find_timing_test_hash_local.png" alt="no image" /></a></h6>NCCL: Native and collision-chaining hash text find timing test using <tt>find</tt> - <a href = "assoc_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>In this setting, the range-hashing scheme (See <a href="hash_based_containers.html#hash_policies">Design::Associative
Containers::Hash-Based Containers::Hash Policies</a> ) affects
performance more than other policies. As Figure <a href="#NCCG">NCCG</a> shows, containers using mod-based
range-hashing (including the native hash-based container, which
is currently hard-wired to this scheme) have lower performance
than those using mask-based range-hashing. A modulo-based
range-hashing scheme's main benefit is that it takes into
account all hash-value bits. Standard string hash-functions are
designed to create hash values that are nearly-uniform as is [
<a href="references.html#knuth98sorting">knuth98sorting</a>
].</p>
<p>Trigger policies (see <a href="hash_based_containers.html#resize_policies">Design::Associative
Containers::Hash-Based Containers::Resize Policies</a> ),
<i>i.e.</i> the load-checks constants, affect performance to a
lesser extent.</p>
<p>Perhaps surprisingly, storing the hash value alongside each
entry affects performance only marginally, at least in
<tt>pb_ds</tt> 's implementation. (Unfortunately, it was not
possible to run the tests with <tt>std::tr1::unordered_map</tt>
's <tt>cache_hash_code = <b>true</b></tt> , as it appeared to
malfuntion.)</p>
<p><a href="assoc_performance_tests.html#hash_based_policies">Observations::Hash-Based
Containers' Policies</a> summarizes some observations on
hash-based containers' policies.</p>
</div>
</body>
</html>
|
