1<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" 2 "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> 3 4<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> 5<head> 6<meta name="generator" content="HTML Tidy for Linux/x86 (vers 12 April 2005), see www.w3.org" /> 7<title>Tree Text Locality of Reference Timing Test</title> 8<meta http-equiv="Content-Type" content="text/html; charset=us-ascii" /> 9</head> 10<body> 11<div id="page"> 12<h1>Hash-Based Erase Memory-Use Test</h1> 13<h2><a name="description" id="description">Description</a></h2> 14<p>This test inserts a number of uniform i.i.d. integer keys 15 into a container, then erases all keys except one. It measures 16 the final size of the container.</p> 17<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_random_int_erase_mem_usage.cc"><tt>hash_random_int_erase_mem_usage.cc</tt></a> 18 2000 2000 2100)</p> 19<h2><a name="purpose" id="purpose">Purpose</a></h2> 20<p>The test checks how containers adjust internally as their 21 logical size decreases (see <a href="motivation.html#assoc_ers_methods">Motivation::Associative 22 Containers::Slightly Different Methods::Methods Related to 23 Erase</a>).</p> 24<h2><a name="results" id="results">Results</a></h2> 25<p>Figures <a href="#NHG">NHG</a>, <a href="#NHM">NHM</a> and 26 <a href="#NHL">NHL</a> show the results for the native and 27 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 28 <a href="assoc_performance_tests.html#local"><u>local</u></a>, 29 respectively.</p> 30<div id="NHG_res_div"> 31<div id="NHG_gcc"> 32<div id="NHG_hash_random_int_erase_mem_usage_test"> 33<div id="NHG_assoc"> 34<div id="NHG_Native_456_collision-chaing_456_and_probing_456_hash_random_int_erase_test"><div style="border-style: dotted; border-width: 1px; border-color: lightgray"><h6 class="c1"><a name="NHG" id="NHG"><img src="hash_random_int_erase_mem_usage_test_gcc.png" alt="no image" /></a></h6>NHG: Native, collision-chaing, and probing, hash random int erase test - <a href="assoc_performance_tests.html#gcc">g++</a><p>In the above figure, the names in the legends have the following meaning:</p> 35<ol> 36<li> 37n_hash_set_ncah- 38<tt>std::tr1::unordered_set</tt> with <tt>cache_hash_code</tt> = <tt><b>false</b></tt></li> 39<li> 40gp_hash_mask_linp_exp_nea_lc_1div8_1div2_nsth_set- 41<a href="gp_hash_table.html"><tt>gp_hash_table</tt></a> 42 with <tt>Comb_Hash_Fn</tt> = <a href="direct_mask_range_hashing.html"><tt>direct_mask_range_hashing</tt></a> 43, <tt>Resize_Policy</tt> = <a href="hash_standard_resize_policy.html"><tt>hash_standard_resize_policy</tt></a> 44 with <tt>Size_Policy</tt> = <a href="hash_exponential_size_policy.html"><tt>hash_exponential_size_policy</tt></a> 45, and <tt>Trigger_Policy</tt> = <a href="hash_load_check_resize_trigger.html"><tt>hash_load_check_resize_trigger</tt></a> 46 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="linear_probe_fn.html"><tt>linear_probe_fn</tt></a> 47</li> 48<li> 49cc_hash_mod_prime_nea_lc_1div8_1div1_nsth_set- 50<a href="cc_hash_table.html"><tt>cc_hash_table</tt></a> 51with <tt>Comb_Hash_Fn</tt> = <a href="direct_mod_range_hashing.html"><tt>direct_mod_range_hashing</tt></a> 52, and <tt>Resize_Policy</tt> = <a href="hash_standard_resize_policy.html"><tt>hash_standard_resize_policy</tt></a> 53 with <tt>Size_Policy</tt> = <a href="hash_prime_size_policy.html"><tt>hash_prime_size_policy</tt></a> 54, and <tt>Trigger_Policy</tt> = <a href="hash_load_check_resize_trigger.html"><tt>hash_load_check_resize_trigger</tt></a> 55 with <i>α<sub>min</sub></i> = <i>1/8</i> and <i>α<sub>max</sub></i> = <i>1/1</i></li> 56<li> 57cc_hash_mask_exp_nea_lc_1div8_1div2_nsth_set- 58<a href="cc_hash_table.html"><tt>cc_hash_table</tt></a> 59with <tt>Comb_Hash_Fn</tt> = <a href="direct_mask_range_hashing.html"><tt>direct_mask_range_hashing</tt></a> 60, and <tt>Resize_Policy</tt> = <a href="hash_standard_resize_policy.html"><tt>hash_standard_resize_policy</tt></a> 61 with <tt>Size_Policy</tt> = <a href="hash_exponential_size_policy.html"><tt>hash_exponential_size_policy</tt></a> 62, and <tt>Trigger_Policy</tt> = <a href="hash_load_check_resize_trigger.html"><tt>hash_load_check_resize_trigger</tt></a> 63 with <i>α<sub>min</sub></i> = <i>1/8</i> and <i>α<sub>max</sub></i> = <i>1/2</i></li> 64</ol> 65</div><div style="width: 100%; height: 20px"></div></div> 66</div> 67</div> 68</div> 69</div> 70<div id="NHM_res_div"> 71<div id="NHM_msvc"> 72<div id="NHM_hash_random_int_erase_mem_usage_test"> 73<div id="NHM_assoc"> 74<div id="NHM_Native_456_collision-chaing_456_and_probing_456_hash_random_int_erase_test"><div style="border-style: dotted; border-width: 1px; border-color: lightgray"><h6 class="c1"><a name="NHM" id="NHM"><img src="hash_random_int_erase_mem_usage_test_msvc.png" alt="no image" /></a></h6>NHM: Native, collision-chaing, and probing, hash random int erase test - <a href="assoc_performance_tests.html#msvc">msvc++</a><p>In the above figure, the names in the legends have the following meaning:</p> 75<ol> 76<li> 77n_hash_set_ncah- 78<tt>stdext::hash_set</tt></li> 79<li> 80gp_hash_mask_linp_exp_nea_lc_1div8_1div2_nsth_set- 81<a href="gp_hash_table.html"><tt>gp_hash_table</tt></a> 82 with <tt>Comb_Hash_Fn</tt> = <a href="direct_mask_range_hashing.html"><tt>direct_mask_range_hashing</tt></a> 83, <tt>Resize_Policy</tt> = <a href="hash_standard_resize_policy.html"><tt>hash_standard_resize_policy</tt></a> 84 with <tt>Size_Policy</tt> = <a href="hash_exponential_size_policy.html"><tt>hash_exponential_size_policy</tt></a> 85, and <tt>Trigger_Policy</tt> = <a href="hash_load_check_resize_trigger.html"><tt>hash_load_check_resize_trigger</tt></a> 86 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="linear_probe_fn.html"><tt>linear_probe_fn</tt></a> 87</li> 88<li> 89cc_hash_mod_prime_nea_lc_1div8_1div1_nsth_set- 90<a href="cc_hash_table.html"><tt>cc_hash_table</tt></a> 91with <tt>Comb_Hash_Fn</tt> = <a href="direct_mod_range_hashing.html"><tt>direct_mod_range_hashing</tt></a> 92, and <tt>Resize_Policy</tt> = <a href="hash_standard_resize_policy.html"><tt>hash_standard_resize_policy</tt></a> 93 with <tt>Size_Policy</tt> = <a href="hash_prime_size_policy.html"><tt>hash_prime_size_policy</tt></a> 94, and <tt>Trigger_Policy</tt> = <a href="hash_load_check_resize_trigger.html"><tt>hash_load_check_resize_trigger</tt></a> 95 with <i>α<sub>min</sub></i> = <i>1/8</i> and <i>α<sub>max</sub></i> = <i>1/1</i></li> 96<li> 97cc_hash_mask_exp_nea_lc_1div8_1div2_nsth_set- 98<a href="cc_hash_table.html"><tt>cc_hash_table</tt></a> 99with <tt>Comb_Hash_Fn</tt> = <a href="direct_mask_range_hashing.html"><tt>direct_mask_range_hashing</tt></a> 100, and <tt>Resize_Policy</tt> = <a href="hash_standard_resize_policy.html"><tt>hash_standard_resize_policy</tt></a> 101 with <tt>Size_Policy</tt> = <a href="hash_exponential_size_policy.html"><tt>hash_exponential_size_policy</tt></a> 102, and <tt>Trigger_Policy</tt> = <a href="hash_load_check_resize_trigger.html"><tt>hash_load_check_resize_trigger</tt></a> 103 with <i>α<sub>min</sub></i> = <i>1/8</i> and <i>α<sub>max</sub></i> = <i>1/2</i></li> 104</ol> 105</div><div style="width: 100%; height: 20px"></div></div> 106</div> 107</div> 108</div> 109</div> 110<div id="NHM_res_div"> 111<div id="NHM_msvc"> 112<div id="NHM_hash_random_int_erase_mem_usage_test"> 113<div id="NHM_assoc"> 114<div id="NHM_Native_456_collision-chaing_456_and_probing_456_hash_random_int_erase_test"><div style="border-style: dotted; border-width: 1px; border-color: lightgray"><h6 class="c1"><a name="NHM" id="NHM"><img src="hash_random_int_erase_mem_usage_test_msvc.png" alt="no image" /></a></h6>NHM: Native, collision-chaing, and probing, hash random int erase test - <a href="assoc_performance_tests.html#msvc">msvc++</a><p>In the above figure, the names in the legends have the following meaning:</p> 115<ol> 116<li> 117n_hash_set_ncah- 118<tt>stdext::hash_set</tt></li> 119<li> 120gp_hash_mask_linp_exp_nea_lc_1div8_1div2_nsth_set- 121<a href="gp_hash_table.html"><tt>gp_hash_table</tt></a> 122 with <tt>Comb_Hash_Fn</tt> = <a href="direct_mask_range_hashing.html"><tt>direct_mask_range_hashing</tt></a> 123, <tt>Resize_Policy</tt> = <a href="hash_standard_resize_policy.html"><tt>hash_standard_resize_policy</tt></a> 124 with <tt>Size_Policy</tt> = <a href="hash_exponential_size_policy.html"><tt>hash_exponential_size_policy</tt></a> 125, and <tt>Trigger_Policy</tt> = <a href="hash_load_check_resize_trigger.html"><tt>hash_load_check_resize_trigger</tt></a> 126 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="linear_probe_fn.html"><tt>linear_probe_fn</tt></a> 127</li> 128<li> 129cc_hash_mod_prime_nea_lc_1div8_1div1_nsth_set- 130<a href="cc_hash_table.html"><tt>cc_hash_table</tt></a> 131with <tt>Comb_Hash_Fn</tt> = <a href="direct_mod_range_hashing.html"><tt>direct_mod_range_hashing</tt></a> 132, and <tt>Resize_Policy</tt> = <a href="hash_standard_resize_policy.html"><tt>hash_standard_resize_policy</tt></a> 133 with <tt>Size_Policy</tt> = <a href="hash_prime_size_policy.html"><tt>hash_prime_size_policy</tt></a> 134, and <tt>Trigger_Policy</tt> = <a href="hash_load_check_resize_trigger.html"><tt>hash_load_check_resize_trigger</tt></a> 135 with <i>α<sub>min</sub></i> = <i>1/8</i> and <i>α<sub>max</sub></i> = <i>1/1</i></li> 136<li> 137cc_hash_mask_exp_nea_lc_1div8_1div2_nsth_set- 138<a href="cc_hash_table.html"><tt>cc_hash_table</tt></a> 139with <tt>Comb_Hash_Fn</tt> = <a href="direct_mask_range_hashing.html"><tt>direct_mask_range_hashing</tt></a> 140, and <tt>Resize_Policy</tt> = <a href="hash_standard_resize_policy.html"><tt>hash_standard_resize_policy</tt></a> 141 with <tt>Size_Policy</tt> = <a href="hash_exponential_size_policy.html"><tt>hash_exponential_size_policy</tt></a> 142, and <tt>Trigger_Policy</tt> = <a href="hash_load_check_resize_trigger.html"><tt>hash_load_check_resize_trigger</tt></a> 143 with <i>α<sub>min</sub></i> = <i>1/8</i> and <i>α<sub>max</sub></i> = <i>1/2</i></li> 144</ol> 145</div><div style="width: 100%; height: 20px"></div></div> 146</div> 147</div> 148</div> 149</div> 150<div id="NHL_res_div"> 151<div id="NHL_local"> 152<div id="NHL_hash_random_int_erase_mem_usage_test"> 153<div id="NHL_assoc"> 154<div id="NHL_Native_456_collision-chaing_456_and_probing_456_hash_random_int_erase_test"><div style = "border-style: dotted; border-width: 1px; border-color: lightgray"><h6 class="c1"><a name="NHL" id= "NHL"><img src="hash_random_int_erase_mem_usage_test_local.png" alt="no image" /></a></h6>NHL: Native, collision-chaing, and probing, hash random int erase test - <a href = "assoc_performance_tests.html#local">local</a></div><div style = "width: 100%; height: 20px"></div></div> 155</div> 156</div> 157</div> 158</div> 159<h2><a name="observations" id="observations">Observations</a></h2> 160<p>STL hash-based containers act very differently than trees in 161 this respect. When erasing numerous keys from an STL 162 associative-container, the resulting memory user varies greatly 163 depending on whether the container is tree-based or hash-based. 164 As noted in <a href="motivation.html#assoc_methods">Motivation::Choice of 165 Methods</a> , this is a fundamental consequence of the STL's 166 associative containers' interface, it is not due to a specific 167 implementation.</p> 168<p>(See <a href="priority_queue_text_pop_mem_usage_test.html">Priority Queue 169 Text <tt>pop</tt> Memory Use Test</a> for a similar phenomenon 170 regarding priority queues.)</p> 171</div> 172</body> 173</html> 174
