ext/pb_ds/tree_random_int_find_find_timing_test.html

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<h1>Tree-Based and Trie-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="http://gcc.gnu.org/viewcvs/*checkout*/trunk/libstdc%2B%2B-v3/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 underlying
    data structures.</p>
<h2><a name="results" id="results">Results</a></h2>
<p>Figures <a href="#NTTG">NTTG</a>, <a href="#NTTM">NTTM</a>,
    and <a href="#NTTG">NTTL</a> show the results for the native,
    tree-based, and trie-based types in <a href="assoc_performance_tests.html#gcc"><u>g++</u></a>, <a href="assoc_performance_tests.html#local"><u>local</u></a>, and
    <a href="assoc_performance_tests.html#local"><u>local</u></a>,
    respectively.</p>
<div id="NTTG_res_div">
<div id="NTTG_gcc">
<div id="NTTG_random_int_find_find_timing_test_tree">
<div id="NTTG_assoc">
<div id="NTTG_Native_456_tree-based_456_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="NTTG" id="NTTG"><img src="random_int_find_find_timing_test_tree_gcc.png" alt="no image" /></a></h6>NTTG: Native, tree-based, 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>
splay_tree_map-
<a href="tree.html"><tt>tree</tt></a>
 with <tt>Tag</tt> = <a href="splay_tree_tag.html"><tt>splay_tree_tag</tt></a>
, and <tt>Node_Update</tt> = <a href="null_tree_node_update.html"><tt>null_tree_node_update</tt></a>
</li>
<li>
ov_tree_map-
<a href="tree.html"><tt>tree</tt></a>
 with <tt>Tag</tt> = <a href="ov_tree_tag.html"><tt>ov_tree_tag</tt></a>
, and <tt>Node_Update</tt> = <a href="null_tree_node_update.html"><tt>null_tree_node_update</tt></a>
</li>
<li>
n_map-
<tt>std::map</tt></li>
<li>
rb_tree_map-
<a href="tree.html"><tt>tree</tt></a>
 with <tt>Tag</tt> = <a href="rb_tree_tag.html"><tt>rb_tree_tag</tt></a>
, and <tt>Node_Update</tt> = <a href="null_tree_node_update.html"><tt>null_tree_node_update</tt></a>
</li>
</ol>
</div><div style="width: 100%; height: 20px"></div></div>
</div>
</div>
<div id="NTTM_res_div">
<div id="NTTM_msvc">
<div id="NTTM_random_int_find_find_timing_test_tree">
<div id="NTTM_assoc">
<div id="NTTM_Native_456_tree-based_456_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="NTTM" id="NTTM"><img src="random_int_find_find_timing_test_tree_msvc.png" alt="no image" /></a></h6>NTTM: Native, tree-based, 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>
splay_tree_map-
<a href="tree.html"><tt>tree</tt></a>
 with <tt>Tag</tt> = <a href="splay_tree_tag.html"><tt>splay_tree_tag</tt></a>
, and <tt>Node_Update</tt> = <a href="null_tree_node_update.html"><tt>null_tree_node_update</tt></a>
</li>
<li>
ov_tree_map-
<a href="tree.html"><tt>tree</tt></a>
 with <tt>Tag</tt> = <a href="ov_tree_tag.html"><tt>ov_tree_tag</tt></a>
, and <tt>Node_Update</tt> = <a href="null_tree_node_update.html"><tt>null_tree_node_update</tt></a>
</li>
<li>
n_map-
<tt>std::map</tt></li>
<li>
rb_tree_map-
<a href="tree.html"><tt>tree</tt></a>
 with <tt>Tag</tt> = <a href="rb_tree_tag.html"><tt>rb_tree_tag</tt></a>
, and <tt>Node_Update</tt> = <a href="null_tree_node_update.html"><tt>null_tree_node_update</tt></a>
</li>
</ol>
</div><div style="width: 100%; height: 20px"></div></div>
</div>
</div>
<div id="NTTL_res_div">
<div id="NTTL_local">
<div id="NTTL_random_int_find_find_timing_test_tree">
<div id="NTTL_assoc">
<div id="NTTL_Native_456_tree-based_456_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="NTTL" id= "NTTL"><img src="random_int_find_find_timing_test_tree_local.png" alt="no image" /></a></h6>NTTL: Native, tree-based, 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>
<h2><a name="observations" id="observations">Observations</a></h2>
<p>For this setting, a splay tree (<a href="tree.html"><tt>tree</tt></a>
                with <tt>Tag =</tt> <a href="splay_tree_tag.html"><tt>splay_tree_tag</tt></a>)
                does not do well. This is possibly due to two
                reasons:</p>
<ol>
<li>A splay tree is not guaranteed to be balanced
                  [<a href="references.html#motwani95random">motwani95random</a>].
                  If a splay tree contains <i>n</i> nodes, its
                  average root-leaf path can be <i>m &gt;&gt;
                  log(n)</i>.</li>
<li>Assume a specific root-leaf search path has
                  length <i>m</i>, and the search-target node has
                  distance <i>m'</i> from the root. A red-black
                  tree will require <i>m + 1</i> comparisons to
                  find the required node; a splay tree will require
                  <i>2 m'</i> comparisons. A splay tree,
                  consequently, can perform many more comparisons
                  than a red-black tree.</li>
</ol>
<p>An ordered-vector tree (<a href="tree.html"><tt>tree</tt></a>
                with <tt>Tag =</tt> <a href="ov_tree_tag.html"><tt>ov_tree_tag</tt></a>),
                a red-black tree (<a href="tree.html"><tt>tree</tt></a>
                with <tt>Tag =</tt> <a href="splay_tree_tag.html"><tt>rb_tree_tag</tt></a>),
                and the native red-black tree all share
                approximately the same performance.</p>
<p>An ordered-vector tree is slightly slower than
                red-black trees, since it requires, in order to
                find a key, more math operations than they do.
                Conversely, an ordered-vector tree requires far
                lower space than the others. ([<a href="references.html#austern00noset">austern00noset</a>],
                however, seems to have an implementation that is
                also faster than a red-black tree).</p>
<p>A PATRICIA trie (<a href="trie.html"><tt>trie</tt></a>
                with <tt>Tag =</tt> <a href="pat_trie_tag.html"><tt>pat_trie_tag</tt></a>)
                has good look-up performance, due to its large
                fan-out in this case. In this setting, a PATRICIA
                trie has lookup performance comparable to a hash
                table (see <a href="hash_text_find_find_timing_test.html">Hash-Based
                Text <tt>find</tt> Find Timing Test</a>), but it is
                order preserving. This is not that surprising,
                since a large fan-out PATRICIA trie works like a
                hash table with collisions resolved by a sub-trie.
                A large fan-out PATRICIA trie does not do well on
                modifications (see <a href="tree_text_insert_timing_test.html">Tree-Based and
                Trie-Based Text Insert Timing Test</a>). It is
                possibly beneficial to semi-static settings,
                therefore.</p>
<p><a href="assoc_performance_tests.html#tree_like_based_types">
                Observations::Tree-Like-Based Container Types</a>
                summarizes some observations on tree-based and
                trie-based containers.</p>
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