gcc/libstdc++-v3/doc/html/ext/pb_ds/hash_zlob_random_int_find_find_timing_test.html - Issue 3050029: [gcc] GCC 4.5.0=>4.5.1

Unified Diff: gcc/libstdc++-v3/doc/html/ext/pb_ds/hash_zlob_random_int_find_find_timing_test.html

Issue 3050029: [gcc] GCC 4.5.0=>4.5.1 (Closed) Base URL: ssh://git@gitrw.chromium.org:9222/nacl-toolchain.git

Patch Set: Created 10 years, 5 months ago

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Index: gcc/libstdc++-v3/doc/html/ext/pb_ds/hash_zlob_random_int_find_find_timing_test.html

diff --git a/gcc/libstdc++-v3/doc/html/ext/pb_ds/hash_zlob_random_int_find_find_timing_test.html b/gcc/libstdc++-v3/doc/html/ext/pb_ds/hash_zlob_random_int_find_find_timing_test.html

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@@ -1,163 +0,0 @@

-<!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>Hash Skewed Distribution Memory Use Test</title>

-<meta http-equiv="Content-Type" content="text/html; charset=us-ascii" />

-</head>

-<body>

-<div id="page">

-<h1>Hash-Based Skewed-Distribution Random-Integer <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 a markedly

- non-uniform i.i.d. integer keys 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 in

- the containers. The keys are generated as follows. First, a

- uniform integer is created; it is then shifted left 8 bits.</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/hash_zlob_random_int_find_timing.cc"><tt>hash_zlob_random_int_find_timing_test</tt></a>

- 200 200 2100)</p>

-<h2><a name="purpose" id="purpose">Purpose</a></h2>

-<p>The test checks the effect of different range-hashing

- functions and trigger policies (see <a href="hash_based_containers.html#hash_policies">Design::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="#NHG">NHG</a>, <a href="#NHM">NHM</a>, and

- <a href="#NHL">NHL</a> show the results for various hash-based

- associative-containers 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>,

- respectively.</p>

-<div id="NHG_res_div">

-<div id="NHG_gcc">

-<div id="NHG_hash_zlob_random_int_find_timing_test">

-<div id="NHG_assoc">

-<div id="NHG_Skewed-distribution_random_int_find_timing_test_using__tt_find_455tt_"><div style="border-style: dotted; border-width: 1px; border-color: lightgray"><h6 class="c1"><a name="NHG" id="NHG"><img src="hash_zlob_random_int_find_timing_test_gcc.png" alt="no image" /></a></h6>NHG: Skewed-distribution random int 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>

-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>

-gp_hash_mod_quadp_prime_nea_lc_1div8_1div2_nsth_map-

-<a href="gp_hash_table.html"><tt>gp_hash_table</tt></a>

- with <tt>Comb_Hash_Fn</tt> = <a href="direct_mod_range_hashing.html"><tt>direct_mod_range_hashing</tt></a>

-, <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>1/2</i>, and <tt>Probe_Fn</tt> = <a href="quadratic_probe_fn.html"><tt>quadratic_probe_fn</tt></a>

-</li>

-<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>

-</ol>

-</div><div style="width: 100%; height: 20px"></div></div>

-</div>

-<div id="NHM_res_div">

-<div id="NHM_msvc">

-<div id="NHM_hash_zlob_random_int_find_timing_test">

-<div id="NHM_assoc">

-<div id="NHM_Skewed-distribution_random_int_find_timing_test_using__tt_find_455tt_"><div style="border-style: dotted; border-width: 1px; border-color: lightgray"><h6 class="c1"><a name="NHM" id="NHM"><img src="hash_zlob_random_int_find_timing_test_msvc.png" alt="no image" /></a></h6>NHM: Skewed-distribution random int 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_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>

-gp_hash_mod_quadp_prime_nea_lc_1div8_1div2_nsth_map-

-<a href="gp_hash_table.html"><tt>gp_hash_table</tt></a>

- with <tt>Comb_Hash_Fn</tt> = <a href="direct_mod_range_hashing.html"><tt>direct_mod_range_hashing</tt></a>

-, <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>1/2</i>, and <tt>Probe_Fn</tt> = <a href="quadratic_probe_fn.html"><tt>quadratic_probe_fn</tt></a>

-</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>

-</ol>

-</div><div style="width: 100%; height: 20px"></div></div>

-</div>

-<div id="NHL_res_div">

-<div id="NHL_local">

-<div id="NHL_hash_zlob_random_int_find_timing_test">

-<div id="NHL_assoc">

-<div id="NHL_Skewed-distribution_random_int_find_timing_test_using__tt_find_455tt_"><div style = "border-style: dotted; border-width: 1px; border-color: lightgray"><h6 class="c1"><a name="NHL" id= "NHL"><img src="hash_zlob_random_int_find_timing_test_local.png" alt="no image" /></a></h6>NHL: Skewed-distribution random int 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>

-<h2><a name="observations" id="observations">Observations</a></h2>

-<p>In this setting, the keys' distribution is so skewed that

- the unerlying hash-table type affects performance marginally.

- (This is in contrast with <a href="hash_text_find_find_timing_test.html">Hash-Based Text

- <tt>find</tt> Find Timing Test</a> , <a href="hash_random_int_find_find_timing_test.html">Hash-Based

- Random-Integer <tt>find</tt> Find Timing Test</a> , <a href="hash_random_int_subscript_find_timing_test.html">Hash-Based

- Random-Integer Subscript Find Timing Test</a> and <a href="hash_random_int_subscript_insert_timing_test.html">Hash-Based

- Random-Integer Subscript Insert Timing Test</a> .)</p>

-<p>The range-hashing scheme affects performance dramatically. A

- mask-based range-hashing scheme effectively maps all values

- into the same bucket. Access degenerates into a search within

- an unordered linked-list. In Figures <a href="#NHG">NHG</a> and

- <a href="#NHM">NHM</a> , it should be noted that

- <tt>std::tr1::unordered_map</tt> and <tt>stdext::hash_map</tt>

- are hard-wired currently to mod-based and mask-based schemes,

- respectively.</p>

-<p>When observing the settings of this test, it is apparent

- that the keys' distribution is far from natural. One might ask

- if the test is not contrived to show that, in some cases,

- mod-based range hashing does better than mask-based range

- hashing. This is, in fact just the case. We did not encounter a

- more natural case in which mod-based range hashing is better.

- In our opnion, real-life key distributions are handled better

- with an appropriate hash function and a mask-based

- range-hashing function. (<a href="http://gcc.gnu.org/viewcvs/*checkout*/trunk/libstdc%2B%2B-v3/testsuite/ext/pb_ds/example/hash_shift_mask.cc"><tt>shift_mask.cc</tt></a>

- shows an example of handling this a-priori known skewed

- distribution with a mask-based range-hashing function). If hash

- performance is bad, a <i>Χ<sup>2</sup></i> test can be used

- to check how to transform it into a more uniform

- distribution.</p>

-<p>For this reason, <tt>pb_ds</tt>'s default range-hashing

- function is mask-based.</p>

-<p><a href="assoc_performance_tests.html#hash_based_types">Observations::Hash-Based

- Container Types</a> summarizes some observations on hash-based

- containers; <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>