deltablue.js.svn-base

Google浏览器V8内核代码

// Copyright 2008 the V8 project authors. All rights reserved.
// Copyright 1996 John Maloney and Mario Wolczko.

// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 2 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA


// This implementation of the DeltaBlue benchmark is derived 
// from the Smalltalk implementation by John Maloney and Mario 
// Wolczko. Some parts have been translated directly, whereas 
// others have been modified more aggresively to make it feel 
// more like a JavaScript program.


var DeltaBlue = new BenchmarkSuite('DeltaBlue', 71104, [
  new Benchmark('DeltaBlue', deltaBlue)
]);


/**
 * A JavaScript implementation of the DeltaBlue constrain-solving
 * algorithm, as described in:
 *
 * "The DeltaBlue Algorithm: An Incremental Constraint Hierarchy Solver"
 *   Bjorn N. Freeman-Benson and John Maloney
 *   January 1990 Communications of the ACM,
 *   also available as University of Washington TR 89-08-06.
 *
 * Beware: this benchmark is written in a grotesque style where
 * the constraint model is built by side-effects from constructors.
 * I've kept it this way to avoid deviating too much from the original
 * implementation.
 */


/* --- O b j e c t   M o d e l --- */

Object.prototype.inherits = function (shuper) {
  function Inheriter() { }
  Inheriter.prototype = shuper.prototype;
  this.prototype = new Inheriter();
  this.superConstructor = shuper;
}

function OrderedCollection() {
  this.elms = new Array();
}

OrderedCollection.prototype.add = function (elm) {
  this.elms.push(elm);
}

OrderedCollection.prototype.at = function (index) {
  return this.elms[index];
}

OrderedCollection.prototype.size = function () {
  return this.elms.length;
}

OrderedCollection.prototype.removeFirst = function () {
  return this.elms.pop();
}

OrderedCollection.prototype.remove = function (elm) {
  var index = 0, skipped = 0;
  for (var i = 0; i < this.elms.length; i++) {
    var value = this.elms[i];
    if (value != elm) {
      this.elms[index] = value;
      index++;
    } else {
      skipped++;
    }
  }
  for (var i = 0; i < skipped; i++)
    this.elms.pop();
}

/* --- *
 * S t r e n g t h
 * --- */

/**
 * Strengths are used to measure the relative importance of constraints.
 * New strengths may be inserted in the strength hierarchy without
 * disrupting current constraints.  Strengths cannot be created outside
 * this class, so pointer comparison can be used for value comparison.
 */
function Strength(strengthValue, name) {
  this.strengthValue = strengthValue;
  this.name = name;
}

Strength.stronger = function (s1, s2) {
  return s1.strengthValue < s2.strengthValue;
}

Strength.weaker = function (s1, s2) {
  return s1.strengthValue > s2.strengthValue;
}

Strength.weakestOf = function (s1, s2) {
  return this.weaker(s1, s2) ? s1 : s2;
}

Strength.strongest = function (s1, s2) {
  return this.stronger(s1, s2) ? s1 : s2;
}

Strength.prototype.nextWeaker = function () {
  switch (this.strengthValue) {
    case 0: return Strength.WEAKEST;
    case 1: return Strength.WEAK_DEFAULT;
    case 2: return Strength.NORMAL;
    case 3: return Strength.STRONG_DEFAULT;
    case 4: return Strength.PREFERRED;
    case 5: return Strength.REQUIRED;
  }
}

// Strength constants.
Strength.REQUIRED        = new Strength(0, "required");
Strength.STONG_PREFERRED = new Strength(1, "strongPreferred");
Strength.PREFERRED       = new Strength(2, "preferred");
Strength.STRONG_DEFAULT  = new Strength(3, "strongDefault");
Strength.NORMAL          = new Strength(4, "normal");
Strength.WEAK_DEFAULT    = new Strength(5, "weakDefault");
Strength.WEAKEST         = new Strength(6, "weakest");

/* --- *
 * C o n s t r a i n t
 * --- */

/**
 * An abstract class representing a system-maintainable relationship
 * (or "constraint") between a set of variables. A constraint supplies
 * a strength instance variable; concrete subclasses provide a means
 * of storing the constrained variables and other information required
 * to represent a constraint.
 */
function Constraint(strength) {
  this.strength = strength;
}

/**
 * Activate this constraint and attempt to satisfy it.
 */
Constraint.prototype.addConstraint = function () {
  this.addToGraph();
  planner.incrementalAdd(this);
}

/**
 * Attempt to find a way to enforce this constraint. If successful,
 * record the solution, perhaps modifying the current dataflow
 * graph. Answer the constraint that this constraint overrides, if
 * there is one, or nil, if there isn't.
 * Assume: I am not already satisfied.
 */
Constraint.prototype.satisfy = function (mark) {
  this.chooseMethod(mark);
  if (!this.isSatisfied()) {
    if (this.strength == Strength.REQUIRED)
      alert("Could not satisfy a required constraint!");
    return null;
  }
  this.markInputs(mark);
  var out = this.output();
  var overridden = out.determinedBy;
  if (overridden != null) overridden.markUnsatisfied();
  out.determinedBy = this;
  if (!planner.addPropagate(this, mark))
    alert("Cycle encountered");
  out.mark = mark;
  return overridden;
}

Constraint.prototype.destroyConstraint = function () {
  if (this.isSatisfied()) planner.incrementalRemove(this);
  else this.removeFromGraph();
}

/**
 * Normal constraints are not input constraints.  An input constraint
 * is one that depends on external state, such as the mouse, the
 * keybord, a clock, or some arbitraty piece of imperative code.
 */
Constraint.prototype.isInput = function () {
  return false;
}

/* --- *
 * U n a r y   C o n s t r a i n t
 * --- */

/**
 * Abstract superclass for constraints having a single possible output
 * variable.
 */
function UnaryConstraint(v, strength) {
  UnaryConstraint.superConstructor.call(this, strength);
  this.myOutput = v;
  this.satisfied = false;
  this.addConstraint();
}

UnaryConstraint.inherits(Constraint);

/**
 * Adds this constraint to the constraint graph
 */
UnaryConstraint.prototype.addToGraph = function () {
  this.myOutput.addConstraint(this);
  this.satisfied = false;
}

/**
 * Decides if this constraint can be satisfied and records that
 * decision.
 */
UnaryConstraint.prototype.chooseMethod = function (mark) {
  this.satisfied = (this.myOutput.mark != mark)
    && Strength.stronger(this.strength, this.myOutput.walkStrength);
}

/**
 * Returns true if this constraint is satisfied in the current solution.
 */
UnaryConstraint.prototype.isSatisfied = function () {
  return this.satisfied;
}

UnaryConstraint.prototype.markInputs = function (mark) {
  // has no inputs
}

/**
 * Returns the current output variable.
 */
UnaryConstraint.prototype.output = function () {
  return this.myOutput;
}

/**
 * Calculate the walkabout strength, the stay flag, and, if it is
 * 'stay', the value for the current output of this constraint. Assume
 * this constraint is satisfied.
 */
UnaryConstraint.prototype.recalculate = function () {
  this.myOutput.walkStrength = this.strength;
  this.myOutput.stay = !this.isInput();
  if (this.myOutput.stay) this.execute(); // Stay optimization
}

/**
 * Records that this constraint is unsatisfied
 */
UnaryConstraint.prototype.markUnsatisfied = function () {
  this.satisfied = false;
}

UnaryConstraint.prototype.inputsKnown = function () {
  return true;
}

UnaryConstraint.prototype.removeFromGraph = function () {
  if (this.myOutput != null) this.myOutput.removeConstraint(this);
  this.satisfied = false;
}

/* --- *
 * S t a y   C o n s t r a i n t
 * --- */

/**
 * Variables that should, with some level of preference, stay the same.
 * Planners may exploit the fact that instances, if satisfied, will not
 * change their output during plan execution.  This is called "stay
 * optimization".
 */
function StayConstraint(v, str) {
  StayConstraint.superConstructor.call(this, v, str);
}

StayConstraint.inherits(UnaryConstraint);

StayConstraint.prototype.execute = function () {
  // Stay constraints do nothing
}

/* --- *
 * E d i t   C o n s t r a i n t
 * --- */

/**
 * A unary input constraint used to mark a variable that the client
 * wishes to change.
 */
function EditConstraint(v, str) {
  EditConstraint.superConstructor.call(this, v, str);
}

EditConstraint.inherits(UnaryConstraint);

/**
 * Edits indicate that a variable is to be changed by imperative code.
 */
EditConstraint.prototype.isInput = function () {
  return true;
}

EditConstraint.prototype.execute = function () {
  // Edit constraints do nothing
}

/* --- *
 * B i n a r y   C o n s t r a i n t
 * --- */

var Direction = new Object();
Direction.NONE     = 0;
Direction.FORWARD  = 1;
Direction.BACKWARD = -1;

/**
 * Abstract superclass for constraints having two possible output
 * variables.
 */
function BinaryConstraint(var1, var2, strength) {
  BinaryConstraint.superConstructor.call(this, strength);
  this.v1 = var1;
  this.v2 = var2;
  this.direction = Direction.NONE;
  this.addConstraint();
}

BinaryConstraint.inherits(Constraint);

/**
 * Decides if this constratint can be satisfied and which way it
 * should flow based on the relative strength of the variables related,
 * and record that decision.
 */
BinaryConstraint.prototype.chooseMethod = function (mark) {
  if (this.v1.mark == mark) {
    this.direction = (this.v1.mark != mark && Strength.stronger(this.strength, this.v2.walkStrength))
      ? Direction.FORWARD
      : Direction.NONE;
  }
  if (this.v2.mark == mark) {
    this.direction = (this.v1.mark != mark && Strength.stronger(this.strength, this.v1.walkStrength))
      ? Direction.BACKWARD
      : Direction.NONE;
  }
  if (Strength.weaker(this.v1.walkStrength, this.v2.walkStrength)) {
    this.direction = Strength.stronger(this.strength, this.v1.walkStrength)
      ? Direction.BACKWARD
      : Direction.NONE;
  } else {
    this.direction = Strength.stronger(this.strength, this.v2.walkStrength)
      ? Direction.FORWARD
      : Direction.BACKWARD
  }
}

/**
 * Add this constraint to the constraint graph
 */
BinaryConstraint.prototype.addToGraph = function () {
  this.v1.addConstraint(this);
  this.v2.addConstraint(this);
  this.direction = Direction.NONE;
}

/**
 * Answer true if this constraint is satisfied in the current solution.
 */
BinaryConstraint.prototype.isSatisfied = function () {
  return this.direction != Direction.NONE;
}

/**
 * Mark the input variable with the given mark.
 */
BinaryConstraint.prototype.markInputs = function (mark) {
  this.input().mark = mark;
}

/**
 * Returns the current input variable
 */
BinaryConstraint.prototype.input = function () {
  return (this.direction == Direction.FORWARD) ? this.v1 : this.v2;
}

/**
 * Returns the current output variable
 */
BinaryConstraint.prototype.output = function () {
  return (this.direction == Direction.FORWARD) ? this.v2 : this.v1;
}

/**
 * Calculate the walkabout strength, the stay flag, and, if it is
 * 'stay', the value for the current output of this
 * constraint. Assume this constraint is satisfied.
 */
BinaryConstraint.prototype.recalculate = function () {
  var ihn = this.input(), out = this.output();
  out.walkStrength = Strength.weakestOf(this.strength, ihn.walkStrength);
  out.stay = ihn.stay;
  if (out.stay) this.execute();
}

/**
 * Record the fact that this constraint is unsatisfied.
 */
BinaryConstraint.prototype.markUnsatisfied = function () {
  this.direction = Direction.NONE;
}

BinaryConstraint.prototype.inputsKnown = function (mark) {
  var i = this.input();
  return i.mark == mark || i.stay || i.determinedBy == null;
}

BinaryConstraint.prototype.removeFromGraph = function () {
  if (this.v1 != null) this.v1.removeConstraint(this);
  if (this.v2 != null) this.v2.removeConstraint(this);