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diff --git a/gcc-4.4.3/libstdc++-v3/doc/html/ext/pb_ds/hash_zlob_random_int_find_find_timing_test.html b/gcc-4.4.3/libstdc++-v3/doc/html/ext/pb_ds/hash_zlob_random_int_find_find_timing_test.html new file mode 100644 index 000000000..bfbb3b086 --- /dev/null +++ b/gcc-4.4.3/libstdc++-v3/doc/html/ext/pb_ds/hash_zlob_random_int_find_find_timing_test.html @@ -0,0 +1,163 @@ +<!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> +</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> +</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> +</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> |