1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/js/src/v8/splay.js Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,394 @@
1.4 +// Copyright 2009 the V8 project authors. All rights reserved.
1.5 +// Redistribution and use in source and binary forms, with or without
1.6 +// modification, are permitted provided that the following conditions are
1.7 +// met:
1.8 +//
1.9 +// * Redistributions of source code must retain the above copyright
1.10 +// notice, this list of conditions and the following disclaimer.
1.11 +// * Redistributions in binary form must reproduce the above
1.12 +// copyright notice, this list of conditions and the following
1.13 +// disclaimer in the documentation and/or other materials provided
1.14 +// with the distribution.
1.15 +// * Neither the name of Google Inc. nor the names of its
1.16 +// contributors may be used to endorse or promote products derived
1.17 +// from this software without specific prior written permission.
1.18 +//
1.19 +// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
1.20 +// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
1.21 +// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
1.22 +// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
1.23 +// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
1.24 +// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
1.25 +// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
1.26 +// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
1.27 +// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
1.28 +// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
1.29 +// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
1.30 +
1.31 +// This benchmark is based on a JavaScript log processing module used
1.32 +// by the V8 profiler to generate execution time profiles for runs of
1.33 +// JavaScript applications, and it effectively measures how fast the
1.34 +// JavaScript engine is at allocating nodes and reclaiming the memory
1.35 +// used for old nodes. Because of the way splay trees work, the engine
1.36 +// also has to deal with a lot of changes to the large tree object
1.37 +// graph.
1.38 +
1.39 +var Splay = new BenchmarkSuite('Splay', 81491, [
1.40 + new Benchmark("Splay", SplayRun, SplaySetup, SplayTearDown)
1.41 +]);
1.42 +
1.43 +
1.44 +// Configuration.
1.45 +var kSplayTreeSize = 8000;
1.46 +var kSplayTreeModifications = 80;
1.47 +var kSplayTreePayloadDepth = 5;
1.48 +
1.49 +var splayTree = null;
1.50 +
1.51 +
1.52 +function GeneratePayloadTree(depth, tag) {
1.53 + if (depth == 0) {
1.54 + return {
1.55 + array : [ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 ],
1.56 + string : 'String for key ' + tag + ' in leaf node'
1.57 + };
1.58 + } else {
1.59 + return {
1.60 + left: GeneratePayloadTree(depth - 1, tag),
1.61 + right: GeneratePayloadTree(depth - 1, tag)
1.62 + };
1.63 + }
1.64 +}
1.65 +
1.66 +
1.67 +function GenerateKey() {
1.68 + // The benchmark framework guarantees that Math.random is
1.69 + // deterministic; see base.js.
1.70 + return Math.random();
1.71 +}
1.72 +
1.73 +
1.74 +function InsertNewNode() {
1.75 + // Insert new node with a unique key.
1.76 + var key;
1.77 + do {
1.78 + key = GenerateKey();
1.79 + } while (splayTree.find(key) != null);
1.80 + var payload = GeneratePayloadTree(kSplayTreePayloadDepth, String(key));
1.81 + splayTree.insert(key, payload);
1.82 + return key;
1.83 +}
1.84 +
1.85 +
1.86 +
1.87 +function SplaySetup() {
1.88 + splayTree = new SplayTree();
1.89 + for (var i = 0; i < kSplayTreeSize; i++) InsertNewNode();
1.90 +}
1.91 +
1.92 +
1.93 +function SplayTearDown() {
1.94 + // Allow the garbage collector to reclaim the memory
1.95 + // used by the splay tree no matter how we exit the
1.96 + // tear down function.
1.97 + var keys = splayTree.exportKeys();
1.98 + splayTree = null;
1.99 +
1.100 + // Verify that the splay tree has the right size.
1.101 + var length = keys.length;
1.102 + if (length != kSplayTreeSize) {
1.103 + throw new Error("Splay tree has wrong size");
1.104 + }
1.105 +
1.106 + // Verify that the splay tree has sorted, unique keys.
1.107 + for (var i = 0; i < length - 1; i++) {
1.108 + if (keys[i] >= keys[i + 1]) {
1.109 + throw new Error("Splay tree not sorted");
1.110 + }
1.111 + }
1.112 +}
1.113 +
1.114 +
1.115 +function SplayRun() {
1.116 + // Replace a few nodes in the splay tree.
1.117 + for (var i = 0; i < kSplayTreeModifications; i++) {
1.118 + var key = InsertNewNode();
1.119 + var greatest = splayTree.findGreatestLessThan(key);
1.120 + if (greatest == null) splayTree.remove(key);
1.121 + else splayTree.remove(greatest.key);
1.122 + }
1.123 +}
1.124 +
1.125 +
1.126 +/**
1.127 + * Constructs a Splay tree. A splay tree is a self-balancing binary
1.128 + * search tree with the additional property that recently accessed
1.129 + * elements are quick to access again. It performs basic operations
1.130 + * such as insertion, look-up and removal in O(log(n)) amortized time.
1.131 + *
1.132 + * @constructor
1.133 + */
1.134 +function SplayTree() {
1.135 +};
1.136 +
1.137 +
1.138 +/**
1.139 + * Pointer to the root node of the tree.
1.140 + *
1.141 + * @type {SplayTree.Node}
1.142 + * @private
1.143 + */
1.144 +SplayTree.prototype.root_ = null;
1.145 +
1.146 +
1.147 +/**
1.148 + * @return {boolean} Whether the tree is empty.
1.149 + */
1.150 +SplayTree.prototype.isEmpty = function() {
1.151 + return !this.root_;
1.152 +};
1.153 +
1.154 +
1.155 +/**
1.156 + * Inserts a node into the tree with the specified key and value if
1.157 + * the tree does not already contain a node with the specified key. If
1.158 + * the value is inserted, it becomes the root of the tree.
1.159 + *
1.160 + * @param {number} key Key to insert into the tree.
1.161 + * @param {*} value Value to insert into the tree.
1.162 + */
1.163 +SplayTree.prototype.insert = function(key, value) {
1.164 + if (this.isEmpty()) {
1.165 + this.root_ = new SplayTree.Node(key, value);
1.166 + return;
1.167 + }
1.168 + // Splay on the key to move the last node on the search path for
1.169 + // the key to the root of the tree.
1.170 + this.splay_(key);
1.171 + if (this.root_.key == key) {
1.172 + return;
1.173 + }
1.174 + var node = new SplayTree.Node(key, value);
1.175 + if (key > this.root_.key) {
1.176 + node.left = this.root_;
1.177 + node.right = this.root_.right;
1.178 + this.root_.right = null;
1.179 + } else {
1.180 + node.right = this.root_;
1.181 + node.left = this.root_.left;
1.182 + this.root_.left = null;
1.183 + }
1.184 + this.root_ = node;
1.185 +};
1.186 +
1.187 +
1.188 +/**
1.189 + * Removes a node with the specified key from the tree if the tree
1.190 + * contains a node with this key. The removed node is returned. If the
1.191 + * key is not found, an exception is thrown.
1.192 + *
1.193 + * @param {number} key Key to find and remove from the tree.
1.194 + * @return {SplayTree.Node} The removed node.
1.195 + */
1.196 +SplayTree.prototype.remove = function(key) {
1.197 + if (this.isEmpty()) {
1.198 + throw Error('Key not found: ' + key);
1.199 + }
1.200 + this.splay_(key);
1.201 + if (this.root_.key != key) {
1.202 + throw Error('Key not found: ' + key);
1.203 + }
1.204 + var removed = this.root_;
1.205 + if (!this.root_.left) {
1.206 + this.root_ = this.root_.right;
1.207 + } else {
1.208 + var right = this.root_.right;
1.209 + this.root_ = this.root_.left;
1.210 + // Splay to make sure that the new root has an empty right child.
1.211 + this.splay_(key);
1.212 + // Insert the original right child as the right child of the new
1.213 + // root.
1.214 + this.root_.right = right;
1.215 + }
1.216 + return removed;
1.217 +};
1.218 +
1.219 +
1.220 +/**
1.221 + * Returns the node having the specified key or null if the tree doesn't contain
1.222 + * a node with the specified key.
1.223 + *
1.224 + * @param {number} key Key to find in the tree.
1.225 + * @return {SplayTree.Node} Node having the specified key.
1.226 + */
1.227 +SplayTree.prototype.find = function(key) {
1.228 + if (this.isEmpty()) {
1.229 + return null;
1.230 + }
1.231 + this.splay_(key);
1.232 + return this.root_.key == key ? this.root_ : null;
1.233 +};
1.234 +
1.235 +
1.236 +/**
1.237 + * @return {SplayTree.Node} Node having the maximum key value.
1.238 + */
1.239 +SplayTree.prototype.findMax = function(opt_startNode) {
1.240 + if (this.isEmpty()) {
1.241 + return null;
1.242 + }
1.243 + var current = opt_startNode || this.root_;
1.244 + while (current.right) {
1.245 + current = current.right;
1.246 + }
1.247 + return current;
1.248 +};
1.249 +
1.250 +
1.251 +/**
1.252 + * @return {SplayTree.Node} Node having the maximum key value that
1.253 + * is less than the specified key value.
1.254 + */
1.255 +SplayTree.prototype.findGreatestLessThan = function(key) {
1.256 + if (this.isEmpty()) {
1.257 + return null;
1.258 + }
1.259 + // Splay on the key to move the node with the given key or the last
1.260 + // node on the search path to the top of the tree.
1.261 + this.splay_(key);
1.262 + // Now the result is either the root node or the greatest node in
1.263 + // the left subtree.
1.264 + if (this.root_.key < key) {
1.265 + return this.root_;
1.266 + } else if (this.root_.left) {
1.267 + return this.findMax(this.root_.left);
1.268 + } else {
1.269 + return null;
1.270 + }
1.271 +};
1.272 +
1.273 +
1.274 +/**
1.275 + * @return {Array<*>} An array containing all the keys of tree's nodes.
1.276 + */
1.277 +SplayTree.prototype.exportKeys = function() {
1.278 + var result = [];
1.279 + if (!this.isEmpty()) {
1.280 + this.root_.traverse_(function(node) { result.push(node.key); });
1.281 + }
1.282 + return result;
1.283 +};
1.284 +
1.285 +
1.286 +/**
1.287 + * Perform the splay operation for the given key. Moves the node with
1.288 + * the given key to the top of the tree. If no node has the given
1.289 + * key, the last node on the search path is moved to the top of the
1.290 + * tree. This is the simplified top-down splaying algorithm from:
1.291 + * "Self-adjusting Binary Search Trees" by Sleator and Tarjan
1.292 + *
1.293 + * @param {number} key Key to splay the tree on.
1.294 + * @private
1.295 + */
1.296 +SplayTree.prototype.splay_ = function(key) {
1.297 + if (this.isEmpty()) {
1.298 + return;
1.299 + }
1.300 + // Create a dummy node. The use of the dummy node is a bit
1.301 + // counter-intuitive: The right child of the dummy node will hold
1.302 + // the L tree of the algorithm. The left child of the dummy node
1.303 + // will hold the R tree of the algorithm. Using a dummy node, left
1.304 + // and right will always be nodes and we avoid special cases.
1.305 + var dummy, left, right;
1.306 + dummy = left = right = new SplayTree.Node(null, null);
1.307 + var current = this.root_;
1.308 + while (true) {
1.309 + if (key < current.key) {
1.310 + if (!current.left) {
1.311 + break;
1.312 + }
1.313 + if (key < current.left.key) {
1.314 + // Rotate right.
1.315 + var tmp = current.left;
1.316 + current.left = tmp.right;
1.317 + tmp.right = current;
1.318 + current = tmp;
1.319 + if (!current.left) {
1.320 + break;
1.321 + }
1.322 + }
1.323 + // Link right.
1.324 + right.left = current;
1.325 + right = current;
1.326 + current = current.left;
1.327 + } else if (key > current.key) {
1.328 + if (!current.right) {
1.329 + break;
1.330 + }
1.331 + if (key > current.right.key) {
1.332 + // Rotate left.
1.333 + var tmp = current.right;
1.334 + current.right = tmp.left;
1.335 + tmp.left = current;
1.336 + current = tmp;
1.337 + if (!current.right) {
1.338 + break;
1.339 + }
1.340 + }
1.341 + // Link left.
1.342 + left.right = current;
1.343 + left = current;
1.344 + current = current.right;
1.345 + } else {
1.346 + break;
1.347 + }
1.348 + }
1.349 + // Assemble.
1.350 + left.right = current.left;
1.351 + right.left = current.right;
1.352 + current.left = dummy.right;
1.353 + current.right = dummy.left;
1.354 + this.root_ = current;
1.355 +};
1.356 +
1.357 +
1.358 +/**
1.359 + * Constructs a Splay tree node.
1.360 + *
1.361 + * @param {number} key Key.
1.362 + * @param {*} value Value.
1.363 + */
1.364 +SplayTree.Node = function(key, value) {
1.365 + this.key = key;
1.366 + this.value = value;
1.367 +};
1.368 +
1.369 +
1.370 +/**
1.371 + * @type {SplayTree.Node}
1.372 + */
1.373 +SplayTree.Node.prototype.left = null;
1.374 +
1.375 +
1.376 +/**
1.377 + * @type {SplayTree.Node}
1.378 + */
1.379 +SplayTree.Node.prototype.right = null;
1.380 +
1.381 +
1.382 +/**
1.383 + * Performs an ordered traversal of the subtree starting at
1.384 + * this SplayTree.Node.
1.385 + *
1.386 + * @param {function(SplayTree.Node)} f Visitor function.
1.387 + * @private
1.388 + */
1.389 +SplayTree.Node.prototype.traverse_ = function(f) {
1.390 + var current = this;
1.391 + while (current) {
1.392 + var left = current.left;
1.393 + if (left) left.traverse_(f);
1.394 + f(current);
1.395 + current = current.right;
1.396 + }
1.397 +};
