1 // Copyright 2009 the V8 project authors. All rights reserved. 2 // Redistribution and use in source and binary forms, with or without 3 // modification, are permitted provided that the following conditions are 4 // met: 5 // 6 // * Redistributions of source code must retain the above copyright 7 // notice, this list of conditions and the following disclaimer. 8 // * Redistributions in binary form must reproduce the above 9 // copyright notice, this list of conditions and the following 10 // disclaimer in the documentation and/or other materials provided 11 // with the distribution. 12 // * Neither the name of Google Inc. nor the names of its 13 // contributors may be used to endorse or promote products derived 14 // from this software without specific prior written permission. 15 // 16 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 17 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 18 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 19 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 20 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 21 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 22 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 23 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 24 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 25 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 26 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 27 28 // This benchmark is based on a JavaScript log processing module used 29 // by the V8 profiler to generate execution time profiles for runs of 30 // JavaScript applications, and it effectively measures how fast the 31 // JavaScript engine is at allocating nodes and reclaiming the memory 32 // used for old nodes. Because of the way splay trees work, the engine 33 // also has to deal with a lot of changes to the large tree object 34 // graph. 35 36 // Configuration. 37 var kSplayTreeSize = 8000; 38 var kSplayTreeModifications = 80; 39 var kSplayTreePayloadDepth = 5; 40 41 var splayTree = null; 42 43 44 function GeneratePayloadTree(depth, key) { 45 if (depth == 0) { 46 return { 47 array : [ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 ], 48 string : 'String for key ' + key + ' in leaf node' 49 }; 50 } else { 51 return { 52 left: GeneratePayloadTree(depth - 1, key), 53 right: GeneratePayloadTree(depth - 1, key) 54 }; 55 } 56 } 57 58 59 function GenerateKey() { 60 // The benchmark framework guarantees that Math.random is 61 // deterministic; see base.js. 62 return Math.random(); 63 } 64 65 66 function InsertNewNode() { 67 // Insert new node with a unique key. 68 var key; 69 do { 70 key = GenerateKey(); 71 } while (splayTree.find(key) != null); 72 splayTree.insert(key, GeneratePayloadTree(kSplayTreePayloadDepth, key)); 73 return key; 74 } 75 76 77 78 function SplaySetup() { 79 splayTree = new SplayTree(); 80 for (var i = 0; i < kSplayTreeSize; i++) InsertNewNode(); 81 } 82 83 84 function SplayTearDown() { 85 // Allow the garbage collector to reclaim the memory 86 // used by the splay tree no matter how we exit the 87 // tear down function. 88 var keys = splayTree.exportKeys(); 89 splayTree = null; 90 91 // Verify that the splay tree has the right size. 92 var length = keys.length; 93 if (length != kSplayTreeSize) { 94 throw new Error("Splay tree has wrong size"); 95 } 96 97 // Verify that the splay tree has sorted, unique keys. 98 for (var i = 0; i < length - 1; i++) { 99 if (keys[i] >= keys[i + 1]) { 100 throw new Error("Splay tree not sorted"); 101 } 102 } 103 } 104 105 106 function SplayRun() { 107 // Replace a few nodes in the splay tree. 108 for (var i = 0; i < kSplayTreeModifications; i++) { 109 var key = InsertNewNode(); 110 var greatest = splayTree.findGreatestLessThan(key); 111 if (greatest == null) splayTree.remove(key); 112 else splayTree.remove(greatest.key); 113 } 114 } 115 116 117 /** 118 * Constructs a Splay tree. A splay tree is a self-balancing binary 119 * search tree with the additional property that recently accessed 120 * elements are quick to access again. It performs basic operations 121 * such as insertion, look-up and removal in O(log(n)) amortized time. 122 * 123 * @constructor 124 */ 125 function SplayTree() { 126 }; 127 128 129 /** 130 * Pointer to the root node of the tree. 131 * 132 * @type {SplayTree.Node} 133 * @private 134 */ 135 SplayTree.prototype.root_ = null; 136 137 138 /** 139 * @return {boolean} Whether the tree is empty. 140 */ 141 SplayTree.prototype.isEmpty = function() { 142 return !this.root_; 143 }; 144 145 146 /** 147 * Inserts a node into the tree with the specified key and value if 148 * the tree does not already contain a node with the specified key. If 149 * the value is inserted, it becomes the root of the tree. 150 * 151 * @param {number} key Key to insert into the tree. 152 * @param {*} value Value to insert into the tree. 153 */ 154 SplayTree.prototype.insert = function(key, value) { 155 if (this.isEmpty()) { 156 this.root_ = new SplayTree.Node(key, value); 157 return; 158 } 159 // Splay on the key to move the last node on the search path for 160 // the key to the root of the tree. 161 this.splay_(key); 162 if (this.root_.key == key) { 163 return; 164 } 165 var node = new SplayTree.Node(key, value); 166 if (key > this.root_.key) { 167 node.left = this.root_; 168 node.right = this.root_.right; 169 this.root_.right = null; 170 } else { 171 node.right = this.root_; 172 node.left = this.root_.left; 173 this.root_.left = null; 174 } 175 this.root_ = node; 176 }; 177 178 179 /** 180 * Removes a node with the specified key from the tree if the tree 181 * contains a node with this key. The removed node is returned. If the 182 * key is not found, an exception is thrown. 183 * 184 * @param {number} key Key to find and remove from the tree. 185 * @return {SplayTree.Node} The removed node. 186 */ 187 SplayTree.prototype.remove = function(key) { 188 if (this.isEmpty()) { 189 throw Error('Key not found: ' + key); 190 } 191 this.splay_(key); 192 if (this.root_.key != key) { 193 throw Error('Key not found: ' + key); 194 } 195 var removed = this.root_; 196 if (!this.root_.left) { 197 this.root_ = this.root_.right; 198 } else { 199 var right = this.root_.right; 200 this.root_ = this.root_.left; 201 // Splay to make sure that the new root has an empty right child. 202 this.splay_(key); 203 // Insert the original right child as the right child of the new 204 // root. 205 this.root_.right = right; 206 } 207 return removed; 208 }; 209 210 211 /** 212 * Returns the node having the specified key or null if the tree doesn't contain 213 * a node with the specified key. 214 * 215 * @param {number} key Key to find in the tree. 216 * @return {SplayTree.Node} Node having the specified key. 217 */ 218 SplayTree.prototype.find = function(key) { 219 if (this.isEmpty()) { 220 return null; 221 } 222 this.splay_(key); 223 return this.root_.key == key ? this.root_ : null; 224 }; 225 226 227 /** 228 * @return {SplayTree.Node} Node having the maximum key value that 229 * is less or equal to the specified key value. 230 */ 231 SplayTree.prototype.findGreatestLessThan = function(key) { 232 if (this.isEmpty()) { 233 return null; 234 } 235 // Splay on the key to move the node with the given key or the last 236 // node on the search path to the top of the tree. 237 this.splay_(key); 238 // Now the result is either the root node or the greatest node in 239 // the left subtree. 240 if (this.root_.key <= key) { 241 return this.root_; 242 } else if (this.root_.left) { 243 return this.findMax(this.root_.left); 244 } else { 245 return null; 246 } 247 }; 248 249 250 /** 251 * @return {Array<*>} An array containing all the keys of tree's nodes. 252 */ 253 SplayTree.prototype.exportKeys = function() { 254 var result = []; 255 if (!this.isEmpty()) { 256 this.root_.traverse_(function(node) { result.push(node.key); }); 257 } 258 return result; 259 }; 260 261 262 /** 263 * Perform the splay operation for the given key. Moves the node with 264 * the given key to the top of the tree. If no node has the given 265 * key, the last node on the search path is moved to the top of the 266 * tree. This is the simplified top-down splaying algorithm from: 267 * "Self-adjusting Binary Search Trees" by Sleator and Tarjan 268 * 269 * @param {number} key Key to splay the tree on. 270 * @private 271 */ 272 SplayTree.prototype.splay_ = function(key) { 273 if (this.isEmpty()) { 274 return; 275 } 276 // Create a dummy node. The use of the dummy node is a bit 277 // counter-intuitive: The right child of the dummy node will hold 278 // the L tree of the algorithm. The left child of the dummy node 279 // will hold the R tree of the algorithm. Using a dummy node, left 280 // and right will always be nodes and we avoid special cases. 281 var dummy, left, right; 282 dummy = left = right = new SplayTree.Node(null, null); 283 var current = this.root_; 284 while (true) { 285 if (key < current.key) { 286 if (!current.left) { 287 break; 288 } 289 if (key < current.left.key) { 290 // Rotate right. 291 var tmp = current.left; 292 current.left = tmp.right; 293 tmp.right = current; 294 current = tmp; 295 if (!current.left) { 296 break; 297 } 298 } 299 // Link right. 300 right.left = current; 301 right = current; 302 current = current.left; 303 } else if (key > current.key) { 304 if (!current.right) { 305 break; 306 } 307 if (key > current.right.key) { 308 // Rotate left. 309 var tmp = current.right; 310 current.right = tmp.left; 311 tmp.left = current; 312 current = tmp; 313 if (!current.right) { 314 break; 315 } 316 } 317 // Link left. 318 left.right = current; 319 left = current; 320 current = current.right; 321 } else { 322 break; 323 } 324 } 325 // Assemble. 326 left.right = current.left; 327 right.left = current.right; 328 current.left = dummy.right; 329 current.right = dummy.left; 330 this.root_ = current; 331 }; 332 333 334 /** 335 * Constructs a Splay tree node. 336 * 337 * @param {number} key Key. 338 * @param {*} value Value. 339 */ 340 SplayTree.Node = function(key, value) { 341 this.key = key; 342 this.value = value; 343 }; 344 345 346 /** 347 * @type {SplayTree.Node} 348 */ 349 SplayTree.Node.prototype.left = null; 350 351 352 /** 353 * @type {SplayTree.Node} 354 */ 355 SplayTree.Node.prototype.right = null; 356 357 358 /** 359 * Performs an ordered traversal of the subtree starting at 360 * this SplayTree.Node. 361 * 362 * @param {function(SplayTree.Node)} f Visitor function. 363 * @private 364 */ 365 SplayTree.Node.prototype.traverse_ = function(f) { 366 var current = this; 367 while (current) { 368 var left = current.left; 369 if (left) left.traverse_(f); 370 f(current); 371 current = current.right; 372 } 373 }; 374 375 SplaySetup(); 376 SplayRun(); 377 SplayTearDown(); 378