michael@0: // Copyright 2009 the V8 project authors. All rights reserved.
michael@0: // Redistribution and use in source and binary forms, with or without
michael@0: // modification, are permitted provided that the following conditions are
michael@0: // met:
michael@0: //
michael@0: //     * Redistributions of source code must retain the above copyright
michael@0: //       notice, this list of conditions and the following disclaimer.
michael@0: //     * Redistributions in binary form must reproduce the above
michael@0: //       copyright notice, this list of conditions and the following
michael@0: //       disclaimer in the documentation and/or other materials provided
michael@0: //       with the distribution.
michael@0: //     * Neither the name of Google Inc. nor the names of its
michael@0: //       contributors may be used to endorse or promote products derived
michael@0: //       from this software without specific prior written permission.
michael@0: //
michael@0: // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
michael@0: // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
michael@0: // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
michael@0: // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
michael@0: // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
michael@0: // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
michael@0: // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
michael@0: // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
michael@0: // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
michael@0: // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
michael@0: // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
michael@0: 
michael@0: // This benchmark is based on a JavaScript log processing module used
michael@0: // by the V8 profiler to generate execution time profiles for runs of
michael@0: // JavaScript applications, and it effectively measures how fast the
michael@0: // JavaScript engine is at allocating nodes and reclaiming the memory
michael@0: // used for old nodes. Because of the way splay trees work, the engine
michael@0: // also has to deal with a lot of changes to the large tree object
michael@0: // graph.
michael@0: 
michael@0: var Splay = new BenchmarkSuite('Splay', 81491, [
michael@0:   new Benchmark("Splay", SplayRun, SplaySetup, SplayTearDown)
michael@0: ]);
michael@0: 
michael@0: 
michael@0: // Configuration.
michael@0: var kSplayTreeSize = 8000;
michael@0: var kSplayTreeModifications = 80;
michael@0: var kSplayTreePayloadDepth = 5;
michael@0: 
michael@0: var splayTree = null;
michael@0: 
michael@0: 
michael@0: function GeneratePayloadTree(depth, tag) {
michael@0:   if (depth == 0) {
michael@0:     return {
michael@0:       array  : [ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 ],
michael@0:       string : 'String for key ' + tag + ' in leaf node'
michael@0:     };
michael@0:   } else {
michael@0:     return {
michael@0:       left:  GeneratePayloadTree(depth - 1, tag),
michael@0:       right: GeneratePayloadTree(depth - 1, tag)
michael@0:     };
michael@0:   }
michael@0: }
michael@0: 
michael@0: 
michael@0: function GenerateKey() {
michael@0:   // The benchmark framework guarantees that Math.random is
michael@0:   // deterministic; see base.js.
michael@0:   return Math.random();
michael@0: }
michael@0: 
michael@0: 
michael@0: function InsertNewNode() {
michael@0:   // Insert new node with a unique key.
michael@0:   var key;
michael@0:   do {
michael@0:     key = GenerateKey();
michael@0:   } while (splayTree.find(key) != null);
michael@0:   var payload = GeneratePayloadTree(kSplayTreePayloadDepth, String(key));
michael@0:   splayTree.insert(key, payload);
michael@0:   return key;
michael@0: }
michael@0: 
michael@0: 
michael@0: 
michael@0: function SplaySetup() {
michael@0:   splayTree = new SplayTree();
michael@0:   for (var i = 0; i < kSplayTreeSize; i++) InsertNewNode();
michael@0: }
michael@0: 
michael@0: 
michael@0: function SplayTearDown() {
michael@0:   // Allow the garbage collector to reclaim the memory
michael@0:   // used by the splay tree no matter how we exit the
michael@0:   // tear down function.
michael@0:   var keys = splayTree.exportKeys();
michael@0:   splayTree = null;
michael@0: 
michael@0:   // Verify that the splay tree has the right size.
michael@0:   var length = keys.length;
michael@0:   if (length != kSplayTreeSize) {
michael@0:     throw new Error("Splay tree has wrong size");
michael@0:   }
michael@0: 
michael@0:   // Verify that the splay tree has sorted, unique keys.
michael@0:   for (var i = 0; i < length - 1; i++) {
michael@0:     if (keys[i] >= keys[i + 1]) {
michael@0:       throw new Error("Splay tree not sorted");
michael@0:     }
michael@0:   }
michael@0: }
michael@0: 
michael@0: 
michael@0: function SplayRun() {
michael@0:   // Replace a few nodes in the splay tree.
michael@0:   for (var i = 0; i < kSplayTreeModifications; i++) {
michael@0:     var key = InsertNewNode();
michael@0:     var greatest = splayTree.findGreatestLessThan(key);
michael@0:     if (greatest == null) splayTree.remove(key);
michael@0:     else splayTree.remove(greatest.key);
michael@0:   }
michael@0: }
michael@0: 
michael@0: 
michael@0: /**
michael@0:  * Constructs a Splay tree.  A splay tree is a self-balancing binary
michael@0:  * search tree with the additional property that recently accessed
michael@0:  * elements are quick to access again. It performs basic operations
michael@0:  * such as insertion, look-up and removal in O(log(n)) amortized time.
michael@0:  *
michael@0:  * @constructor
michael@0:  */
michael@0: function SplayTree() {
michael@0: };
michael@0: 
michael@0: 
michael@0: /**
michael@0:  * Pointer to the root node of the tree.
michael@0:  *
michael@0:  * @type {SplayTree.Node}
michael@0:  * @private
michael@0:  */
michael@0: SplayTree.prototype.root_ = null;
michael@0: 
michael@0: 
michael@0: /**
michael@0:  * @return {boolean} Whether the tree is empty.
michael@0:  */
michael@0: SplayTree.prototype.isEmpty = function() {
michael@0:   return !this.root_;
michael@0: };
michael@0: 
michael@0: 
michael@0: /**
michael@0:  * Inserts a node into the tree with the specified key and value if
michael@0:  * the tree does not already contain a node with the specified key. If
michael@0:  * the value is inserted, it becomes the root of the tree.
michael@0:  *
michael@0:  * @param {number} key Key to insert into the tree.
michael@0:  * @param {*} value Value to insert into the tree.
michael@0:  */
michael@0: SplayTree.prototype.insert = function(key, value) {
michael@0:   if (this.isEmpty()) {
michael@0:     this.root_ = new SplayTree.Node(key, value);
michael@0:     return;
michael@0:   }
michael@0:   // Splay on the key to move the last node on the search path for
michael@0:   // the key to the root of the tree.
michael@0:   this.splay_(key);
michael@0:   if (this.root_.key == key) {
michael@0:     return;
michael@0:   }
michael@0:   var node = new SplayTree.Node(key, value);
michael@0:   if (key > this.root_.key) {
michael@0:     node.left = this.root_;
michael@0:     node.right = this.root_.right;
michael@0:     this.root_.right = null;
michael@0:   } else {
michael@0:     node.right = this.root_;
michael@0:     node.left = this.root_.left;
michael@0:     this.root_.left = null;
michael@0:   }
michael@0:   this.root_ = node;
michael@0: };
michael@0: 
michael@0: 
michael@0: /**
michael@0:  * Removes a node with the specified key from the tree if the tree
michael@0:  * contains a node with this key. The removed node is returned. If the
michael@0:  * key is not found, an exception is thrown.
michael@0:  *
michael@0:  * @param {number} key Key to find and remove from the tree.
michael@0:  * @return {SplayTree.Node} The removed node.
michael@0:  */
michael@0: SplayTree.prototype.remove = function(key) {
michael@0:   if (this.isEmpty()) {
michael@0:     throw Error('Key not found: ' + key);
michael@0:   }
michael@0:   this.splay_(key);
michael@0:   if (this.root_.key != key) {
michael@0:     throw Error('Key not found: ' + key);
michael@0:   }
michael@0:   var removed = this.root_;
michael@0:   if (!this.root_.left) {
michael@0:     this.root_ = this.root_.right;
michael@0:   } else {
michael@0:     var right = this.root_.right;
michael@0:     this.root_ = this.root_.left;
michael@0:     // Splay to make sure that the new root has an empty right child.
michael@0:     this.splay_(key);
michael@0:     // Insert the original right child as the right child of the new
michael@0:     // root.
michael@0:     this.root_.right = right;
michael@0:   }
michael@0:   return removed;
michael@0: };
michael@0: 
michael@0: 
michael@0: /**
michael@0:  * Returns the node having the specified key or null if the tree doesn't contain
michael@0:  * a node with the specified key.
michael@0:  *
michael@0:  * @param {number} key Key to find in the tree.
michael@0:  * @return {SplayTree.Node} Node having the specified key.
michael@0:  */
michael@0: SplayTree.prototype.find = function(key) {
michael@0:   if (this.isEmpty()) {
michael@0:     return null;
michael@0:   }
michael@0:   this.splay_(key);
michael@0:   return this.root_.key == key ? this.root_ : null;
michael@0: };
michael@0: 
michael@0: 
michael@0: /**
michael@0:  * @return {SplayTree.Node} Node having the maximum key value.
michael@0:  */
michael@0: SplayTree.prototype.findMax = function(opt_startNode) {
michael@0:   if (this.isEmpty()) {
michael@0:     return null;
michael@0:   }
michael@0:   var current = opt_startNode || this.root_;
michael@0:   while (current.right) {
michael@0:     current = current.right;
michael@0:   }
michael@0:   return current;
michael@0: };
michael@0: 
michael@0: 
michael@0: /**
michael@0:  * @return {SplayTree.Node} Node having the maximum key value that
michael@0:  *     is less than the specified key value.
michael@0:  */
michael@0: SplayTree.prototype.findGreatestLessThan = function(key) {
michael@0:   if (this.isEmpty()) {
michael@0:     return null;
michael@0:   }
michael@0:   // Splay on the key to move the node with the given key or the last
michael@0:   // node on the search path to the top of the tree.
michael@0:   this.splay_(key);
michael@0:   // Now the result is either the root node or the greatest node in
michael@0:   // the left subtree.
michael@0:   if (this.root_.key < key) {
michael@0:     return this.root_;
michael@0:   } else if (this.root_.left) {
michael@0:     return this.findMax(this.root_.left);
michael@0:   } else {
michael@0:     return null;
michael@0:   }
michael@0: };
michael@0: 
michael@0: 
michael@0: /**
michael@0:  * @return {Array<*>} An array containing all the keys of tree's nodes.
michael@0:  */
michael@0: SplayTree.prototype.exportKeys = function() {
michael@0:   var result = [];
michael@0:   if (!this.isEmpty()) {
michael@0:     this.root_.traverse_(function(node) { result.push(node.key); });
michael@0:   }
michael@0:   return result;
michael@0: };
michael@0: 
michael@0: 
michael@0: /**
michael@0:  * Perform the splay operation for the given key. Moves the node with
michael@0:  * the given key to the top of the tree.  If no node has the given
michael@0:  * key, the last node on the search path is moved to the top of the
michael@0:  * tree. This is the simplified top-down splaying algorithm from:
michael@0:  * "Self-adjusting Binary Search Trees" by Sleator and Tarjan
michael@0:  *
michael@0:  * @param {number} key Key to splay the tree on.
michael@0:  * @private
michael@0:  */
michael@0: SplayTree.prototype.splay_ = function(key) {
michael@0:   if (this.isEmpty()) {
michael@0:     return;
michael@0:   }
michael@0:   // Create a dummy node.  The use of the dummy node is a bit
michael@0:   // counter-intuitive: The right child of the dummy node will hold
michael@0:   // the L tree of the algorithm.  The left child of the dummy node
michael@0:   // will hold the R tree of the algorithm.  Using a dummy node, left
michael@0:   // and right will always be nodes and we avoid special cases.
michael@0:   var dummy, left, right;
michael@0:   dummy = left = right = new SplayTree.Node(null, null);
michael@0:   var current = this.root_;
michael@0:   while (true) {
michael@0:     if (key < current.key) {
michael@0:       if (!current.left) {
michael@0:         break;
michael@0:       }
michael@0:       if (key < current.left.key) {
michael@0:         // Rotate right.
michael@0:         var tmp = current.left;
michael@0:         current.left = tmp.right;
michael@0:         tmp.right = current;
michael@0:         current = tmp;
michael@0:         if (!current.left) {
michael@0:           break;
michael@0:         }
michael@0:       }
michael@0:       // Link right.
michael@0:       right.left = current;
michael@0:       right = current;
michael@0:       current = current.left;
michael@0:     } else if (key > current.key) {
michael@0:       if (!current.right) {
michael@0:         break;
michael@0:       }
michael@0:       if (key > current.right.key) {
michael@0:         // Rotate left.
michael@0:         var tmp = current.right;
michael@0:         current.right = tmp.left;
michael@0:         tmp.left = current;
michael@0:         current = tmp;
michael@0:         if (!current.right) {
michael@0:           break;
michael@0:         }
michael@0:       }
michael@0:       // Link left.
michael@0:       left.right = current;
michael@0:       left = current;
michael@0:       current = current.right;
michael@0:     } else {
michael@0:       break;
michael@0:     }
michael@0:   }
michael@0:   // Assemble.
michael@0:   left.right = current.left;
michael@0:   right.left = current.right;
michael@0:   current.left = dummy.right;
michael@0:   current.right = dummy.left;
michael@0:   this.root_ = current;
michael@0: };
michael@0: 
michael@0: 
michael@0: /**
michael@0:  * Constructs a Splay tree node.
michael@0:  *
michael@0:  * @param {number} key Key.
michael@0:  * @param {*} value Value.
michael@0:  */
michael@0: SplayTree.Node = function(key, value) {
michael@0:   this.key = key;
michael@0:   this.value = value;
michael@0: };
michael@0: 
michael@0: 
michael@0: /**
michael@0:  * @type {SplayTree.Node}
michael@0:  */
michael@0: SplayTree.Node.prototype.left = null;
michael@0: 
michael@0: 
michael@0: /**
michael@0:  * @type {SplayTree.Node}
michael@0:  */
michael@0: SplayTree.Node.prototype.right = null;
michael@0: 
michael@0: 
michael@0: /**
michael@0:  * Performs an ordered traversal of the subtree starting at
michael@0:  * this SplayTree.Node.
michael@0:  *
michael@0:  * @param {function(SplayTree.Node)} f Visitor function.
michael@0:  * @private
michael@0:  */
michael@0: SplayTree.Node.prototype.traverse_ = function(f) {
michael@0:   var current = this;
michael@0:   while (current) {
michael@0:     var left = current.left;
michael@0:     if (left) left.traverse_(f);
michael@0:     f(current);
michael@0:     current = current.right;
michael@0:   }
michael@0: };