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| <title>Tree Split Join Timing Test</title> |
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| <h1>Tree Split-Join Timing Test</h1> |
| <h2><a name="description" id="description">Description</a></h2> |
| <p>This test a container, inserts into a number of values, |
| splits the container at the median, and joins the two |
| containers. (If the containers are one of <tt>pb_ds</tt> 's |
| trees, it splits and joins with the <tt>split</tt> and |
| <tt>join</tt> method; otherwise, it uses the <tt>erase</tt> and |
| <tt>insert</tt> methods.) It measures the time for splitting |
| and joining the containers as a function of the number of |
| values inserted.</p> |
| <p>(The test was executed with <a href="../../../../testsuite/performance/ext/pb_ds/tree_split_join_timing.cc"><tt>tree_split_join_timing_test</tt></a> |
| 200 200 2100)</p> |
| <h2><a name="purpose" id="purpose">Purpose</a></h2> |
| <p>The test checks the performance difference of <tt>join</tt> |
| as opposed to a sequence of <tt>insert</tt> operations; by |
| implication, this test checks the most efficient way to erase a |
| sub-sequence from a tree-like-based container, since this can |
| always be performed by a small sequence of splits and joins |
| (see <a href="motivation.html#assoc_split_join_methods">Motivation::Associative |
| Containers::Slightly Different Methods::Methods Related to |
| Split and Join</a> and <a href="tree_based_containers.html#add_methods">Design::Associative |
| Containers::Tree-Based Containers::Additional Methods</a> |
| .)</p> |
| <h2><a name="results" id="results">Results</a></h2> |
| <p>Figures <a href="#NTG">NTG</a>, <a href="#NTM">NTM</a>, and |
| <a href="#NTL">NTL</a> show the results for the native and |
| tree-based 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="NTG_res_div"> |
| <div id="NTG_gcc"> |
| <div id="NTG_tree_split_join_timing_test"> |
| <div id="NTG_assoc"> |
| <div id="NTG_Native_and_tree-based_container_splits_and_joins"><div style="border-style: dotted; border-width: 1px; border-color: lightgray"><h6 class="c1"><a name="NTG" id="NTG"><img src="tree_split_join_timing_test_gcc.png" alt="no image" /></a></h6>NTG: Native and tree-based container splits and joins - <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_set- |
| <tt>std::set</tt></li> |
| <li> |
| splay_tree_set- |
| <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> |
| rb_tree_set- |
| <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> |
| <li> |
| ov_tree_set- |
| <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> |
| </ol> |
| </div><div style="width: 100%; height: 20px"></div></div> |
| </div> |
| </div> |
| </div> |
| </div> |
| <div id="NTM_res_div"> |
| <div id="NTM_msvc"> |
| <div id="NTM_tree_split_join_timing_test"> |
| <div id="NTM_assoc"> |
| <div id="NTM_Native_and_tree-based_container_splits_and_joins"><div style="border-style: dotted; border-width: 1px; border-color: lightgray"><h6 class="c1"><a name="NTM" id="NTM"><img src="tree_split_join_timing_test_msvc.png" alt="no image" /></a></h6>NTM: Native and tree-based container splits and joins - <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_set- |
| <tt>std::set</tt></li> |
| <li> |
| splay_tree_set- |
| <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> |
| rb_tree_set- |
| <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> |
| <li> |
| ov_tree_set- |
| <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> |
| </ol> |
| </div><div style="width: 100%; height: 20px"></div></div> |
| </div> |
| </div> |
| </div> |
| </div> |
| <div id="NTL_res_div"> |
| <div id="NTL_local"> |
| <div id="NTL_tree_split_join_timing_test"> |
| <div id="NTL_assoc"> |
| <div id="NTL_Native_and_tree-based_container_splits_and_joins"><div style = "border-style: dotted; border-width: 1px; border-color: lightgray"><h6 class="c1"><a name="NTL" id= "NTL"><img src="tree_split_join_timing_test_local.png" alt="no image" /></a></h6>NTL: Native and tree-based container splits and joins - <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 test, the native red-black trees must be split and |
| joined externally, through a sequence of <tt>erase</tt> and |
| <tt>insert</tt> operations. This is clearly super-linear, and |
| it is not that surprising that the cost is high.</p> |
| <p><tt>pb_ds</tt> 's tree-based containers use in this test the |
| <tt>split</tt> and <tt>join</tt> methods, which have lower |
| complexity: the <tt>join</tt> method of 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> ) is |
| quadratic in the length of the longest root-leaf path, and |
| linear in the total number of elements; the <tt>join</tt> |
| method of a red-black tree ( <a href="tree.html"><tt>tree</tt></a> |
| with <tt>Tag =</tt> <a href="rb_tree_tag.html"><tt>rb_tree_tag</tt></a> ) or 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> ) is linear |
| in the number of elements.</p> |
| <p>Asides from orders of growth, <tt>pb_ds</tt> 's trees access |
| their allocator very little in these operations, and some of |
| them do not access it at all. This leads to lower constants in |
| their complexity, and, for some containers, to exception-free |
| splits and joins (which can be determined via <a href="assoc_container_traits.html"><tt>container_traits</tt></a>).</p> |
| <p>It is important to note that <tt>split</tt> and |
| <tt>join</tt> are not esoteric methods - they are the most |
| efficient means of erasing a contiguous range of values from a |
| tree based container.</p> |
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