michael@0: // Copyright 2008 the V8 project authors. All rights reserved.
michael@0: // Copyright 1996 John Maloney and Mario Wolczko.
michael@0: 
michael@0: // This program is free software; you can redistribute it and/or modify
michael@0: // it under the terms of the GNU General Public License as published by
michael@0: // the Free Software Foundation; either version 2 of the License, or
michael@0: // (at your option) any later version.
michael@0: //
michael@0: // This program is distributed in the hope that it will be useful,
michael@0: // but WITHOUT ANY WARRANTY; without even the implied warranty of
michael@0: // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
michael@0: // GNU General Public License for more details.
michael@0: //
michael@0: // You should have received a copy of the GNU General Public License
michael@0: // along with this program; if not, write to the Free Software
michael@0: // Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
michael@0: 
michael@0: 
michael@0: // This implementation of the DeltaBlue benchmark is derived
michael@0: // from the Smalltalk implementation by John Maloney and Mario
michael@0: // Wolczko. Some parts have been translated directly, whereas
michael@0: // others have been modified more aggresively to make it feel
michael@0: // more like a JavaScript program.
michael@0: 
michael@0: 
michael@0: var DeltaBlue = new BenchmarkSuite('DeltaBlue', 66118, [
michael@0:   new Benchmark('DeltaBlue', deltaBlue)
michael@0: ]);
michael@0: 
michael@0: 
michael@0: /**
michael@0:  * A JavaScript implementation of the DeltaBlue constraint-solving
michael@0:  * algorithm, as described in:
michael@0:  *
michael@0:  * "The DeltaBlue Algorithm: An Incremental Constraint Hierarchy Solver"
michael@0:  *   Bjorn N. Freeman-Benson and John Maloney
michael@0:  *   January 1990 Communications of the ACM,
michael@0:  *   also available as University of Washington TR 89-08-06.
michael@0:  *
michael@0:  * Beware: this benchmark is written in a grotesque style where
michael@0:  * the constraint model is built by side-effects from constructors.
michael@0:  * I've kept it this way to avoid deviating too much from the original
michael@0:  * implementation.
michael@0:  */
michael@0: 
michael@0: 
michael@0: /* --- O b j e c t   M o d e l --- */
michael@0: 
michael@0: Object.prototype.inheritsFrom = function (shuper) {
michael@0:   function Inheriter() { }
michael@0:   Inheriter.prototype = shuper.prototype;
michael@0:   this.prototype = new Inheriter();
michael@0:   this.superConstructor = shuper;
michael@0: }
michael@0: 
michael@0: function OrderedCollection() {
michael@0:   this.elms = new Array();
michael@0: }
michael@0: 
michael@0: OrderedCollection.prototype.add = function (elm) {
michael@0:   this.elms.push(elm);
michael@0: }
michael@0: 
michael@0: OrderedCollection.prototype.at = function (index) {
michael@0:   return this.elms[index];
michael@0: }
michael@0: 
michael@0: OrderedCollection.prototype.size = function () {
michael@0:   return this.elms.length;
michael@0: }
michael@0: 
michael@0: OrderedCollection.prototype.removeFirst = function () {
michael@0:   return this.elms.pop();
michael@0: }
michael@0: 
michael@0: OrderedCollection.prototype.remove = function (elm) {
michael@0:   var index = 0, skipped = 0;
michael@0:   for (var i = 0; i < this.elms.length; i++) {
michael@0:     var value = this.elms[i];
michael@0:     if (value != elm) {
michael@0:       this.elms[index] = value;
michael@0:       index++;
michael@0:     } else {
michael@0:       skipped++;
michael@0:     }
michael@0:   }
michael@0:   for (var i = 0; i < skipped; i++)
michael@0:     this.elms.pop();
michael@0: }
michael@0: 
michael@0: /* --- *
michael@0:  * S t r e n g t h
michael@0:  * --- */
michael@0: 
michael@0: /**
michael@0:  * Strengths are used to measure the relative importance of constraints.
michael@0:  * New strengths may be inserted in the strength hierarchy without
michael@0:  * disrupting current constraints.  Strengths cannot be created outside
michael@0:  * this class, so pointer comparison can be used for value comparison.
michael@0:  */
michael@0: function Strength(strengthValue, name) {
michael@0:   this.strengthValue = strengthValue;
michael@0:   this.name = name;
michael@0: }
michael@0: 
michael@0: Strength.stronger = function (s1, s2) {
michael@0:   return s1.strengthValue < s2.strengthValue;
michael@0: }
michael@0: 
michael@0: Strength.weaker = function (s1, s2) {
michael@0:   return s1.strengthValue > s2.strengthValue;
michael@0: }
michael@0: 
michael@0: Strength.weakestOf = function (s1, s2) {
michael@0:   return this.weaker(s1, s2) ? s1 : s2;
michael@0: }
michael@0: 
michael@0: Strength.strongest = function (s1, s2) {
michael@0:   return this.stronger(s1, s2) ? s1 : s2;
michael@0: }
michael@0: 
michael@0: Strength.prototype.nextWeaker = function () {
michael@0:   switch (this.strengthValue) {
michael@0:     case 0: return Strength.WEAKEST;
michael@0:     case 1: return Strength.WEAK_DEFAULT;
michael@0:     case 2: return Strength.NORMAL;
michael@0:     case 3: return Strength.STRONG_DEFAULT;
michael@0:     case 4: return Strength.PREFERRED;
michael@0:     case 5: return Strength.REQUIRED;
michael@0:   }
michael@0: }
michael@0: 
michael@0: // Strength constants.
michael@0: Strength.REQUIRED        = new Strength(0, "required");
michael@0: Strength.STONG_PREFERRED = new Strength(1, "strongPreferred");
michael@0: Strength.PREFERRED       = new Strength(2, "preferred");
michael@0: Strength.STRONG_DEFAULT  = new Strength(3, "strongDefault");
michael@0: Strength.NORMAL          = new Strength(4, "normal");
michael@0: Strength.WEAK_DEFAULT    = new Strength(5, "weakDefault");
michael@0: Strength.WEAKEST         = new Strength(6, "weakest");
michael@0: 
michael@0: /* --- *
michael@0:  * C o n s t r a i n t
michael@0:  * --- */
michael@0: 
michael@0: /**
michael@0:  * An abstract class representing a system-maintainable relationship
michael@0:  * (or "constraint") between a set of variables. A constraint supplies
michael@0:  * a strength instance variable; concrete subclasses provide a means
michael@0:  * of storing the constrained variables and other information required
michael@0:  * to represent a constraint.
michael@0:  */
michael@0: function Constraint(strength) {
michael@0:   this.strength = strength;
michael@0: }
michael@0: 
michael@0: /**
michael@0:  * Activate this constraint and attempt to satisfy it.
michael@0:  */
michael@0: Constraint.prototype.addConstraint = function () {
michael@0:   this.addToGraph();
michael@0:   planner.incrementalAdd(this);
michael@0: }
michael@0: 
michael@0: /**
michael@0:  * Attempt to find a way to enforce this constraint. If successful,
michael@0:  * record the solution, perhaps modifying the current dataflow
michael@0:  * graph. Answer the constraint that this constraint overrides, if
michael@0:  * there is one, or nil, if there isn't.
michael@0:  * Assume: I am not already satisfied.
michael@0:  */
michael@0: Constraint.prototype.satisfy = function (mark) {
michael@0:   this.chooseMethod(mark);
michael@0:   if (!this.isSatisfied()) {
michael@0:     if (this.strength == Strength.REQUIRED)
michael@0:       alert("Could not satisfy a required constraint!");
michael@0:     return null;
michael@0:   }
michael@0:   this.markInputs(mark);
michael@0:   var out = this.output();
michael@0:   var overridden = out.determinedBy;
michael@0:   if (overridden != null) overridden.markUnsatisfied();
michael@0:   out.determinedBy = this;
michael@0:   if (!planner.addPropagate(this, mark))
michael@0:     alert("Cycle encountered");
michael@0:   out.mark = mark;
michael@0:   return overridden;
michael@0: }
michael@0: 
michael@0: Constraint.prototype.destroyConstraint = function () {
michael@0:   if (this.isSatisfied()) planner.incrementalRemove(this);
michael@0:   else this.removeFromGraph();
michael@0: }
michael@0: 
michael@0: /**
michael@0:  * Normal constraints are not input constraints.  An input constraint
michael@0:  * is one that depends on external state, such as the mouse, the
michael@0:  * keybord, a clock, or some arbitraty piece of imperative code.
michael@0:  */
michael@0: Constraint.prototype.isInput = function () {
michael@0:   return false;
michael@0: }
michael@0: 
michael@0: /* --- *
michael@0:  * U n a r y   C o n s t r a i n t
michael@0:  * --- */
michael@0: 
michael@0: /**
michael@0:  * Abstract superclass for constraints having a single possible output
michael@0:  * variable.
michael@0:  */
michael@0: function UnaryConstraint(v, strength) {
michael@0:   UnaryConstraint.superConstructor.call(this, strength);
michael@0:   this.myOutput = v;
michael@0:   this.satisfied = false;
michael@0:   this.addConstraint();
michael@0: }
michael@0: 
michael@0: UnaryConstraint.inheritsFrom(Constraint);
michael@0: 
michael@0: /**
michael@0:  * Adds this constraint to the constraint graph
michael@0:  */
michael@0: UnaryConstraint.prototype.addToGraph = function () {
michael@0:   this.myOutput.addConstraint(this);
michael@0:   this.satisfied = false;
michael@0: }
michael@0: 
michael@0: /**
michael@0:  * Decides if this constraint can be satisfied and records that
michael@0:  * decision.
michael@0:  */
michael@0: UnaryConstraint.prototype.chooseMethod = function (mark) {
michael@0:   this.satisfied = (this.myOutput.mark != mark)
michael@0:     && Strength.stronger(this.strength, this.myOutput.walkStrength);
michael@0: }
michael@0: 
michael@0: /**
michael@0:  * Returns true if this constraint is satisfied in the current solution.
michael@0:  */
michael@0: UnaryConstraint.prototype.isSatisfied = function () {
michael@0:   return this.satisfied;
michael@0: }
michael@0: 
michael@0: UnaryConstraint.prototype.markInputs = function (mark) {
michael@0:   // has no inputs
michael@0: }
michael@0: 
michael@0: /**
michael@0:  * Returns the current output variable.
michael@0:  */
michael@0: UnaryConstraint.prototype.output = function () {
michael@0:   return this.myOutput;
michael@0: }
michael@0: 
michael@0: /**
michael@0:  * Calculate the walkabout strength, the stay flag, and, if it is
michael@0:  * 'stay', the value for the current output of this constraint. Assume
michael@0:  * this constraint is satisfied.
michael@0:  */
michael@0: UnaryConstraint.prototype.recalculate = function () {
michael@0:   this.myOutput.walkStrength = this.strength;
michael@0:   this.myOutput.stay = !this.isInput();
michael@0:   if (this.myOutput.stay) this.execute(); // Stay optimization
michael@0: }
michael@0: 
michael@0: /**
michael@0:  * Records that this constraint is unsatisfied
michael@0:  */
michael@0: UnaryConstraint.prototype.markUnsatisfied = function () {
michael@0:   this.satisfied = false;
michael@0: }
michael@0: 
michael@0: UnaryConstraint.prototype.inputsKnown = function () {
michael@0:   return true;
michael@0: }
michael@0: 
michael@0: UnaryConstraint.prototype.removeFromGraph = function () {
michael@0:   if (this.myOutput != null) this.myOutput.removeConstraint(this);
michael@0:   this.satisfied = false;
michael@0: }
michael@0: 
michael@0: /* --- *
michael@0:  * S t a y   C o n s t r a i n t
michael@0:  * --- */
michael@0: 
michael@0: /**
michael@0:  * Variables that should, with some level of preference, stay the same.
michael@0:  * Planners may exploit the fact that instances, if satisfied, will not
michael@0:  * change their output during plan execution.  This is called "stay
michael@0:  * optimization".
michael@0:  */
michael@0: function StayConstraint(v, str) {
michael@0:   StayConstraint.superConstructor.call(this, v, str);
michael@0: }
michael@0: 
michael@0: StayConstraint.inheritsFrom(UnaryConstraint);
michael@0: 
michael@0: StayConstraint.prototype.execute = function () {
michael@0:   // Stay constraints do nothing
michael@0: }
michael@0: 
michael@0: /* --- *
michael@0:  * E d i t   C o n s t r a i n t
michael@0:  * --- */
michael@0: 
michael@0: /**
michael@0:  * A unary input constraint used to mark a variable that the client
michael@0:  * wishes to change.
michael@0:  */
michael@0: function EditConstraint(v, str) {
michael@0:   EditConstraint.superConstructor.call(this, v, str);
michael@0: }
michael@0: 
michael@0: EditConstraint.inheritsFrom(UnaryConstraint);
michael@0: 
michael@0: /**
michael@0:  * Edits indicate that a variable is to be changed by imperative code.
michael@0:  */
michael@0: EditConstraint.prototype.isInput = function () {
michael@0:   return true;
michael@0: }
michael@0: 
michael@0: EditConstraint.prototype.execute = function () {
michael@0:   // Edit constraints do nothing
michael@0: }
michael@0: 
michael@0: /* --- *
michael@0:  * B i n a r y   C o n s t r a i n t
michael@0:  * --- */
michael@0: 
michael@0: var Direction = new Object();
michael@0: Direction.NONE     = 0;
michael@0: Direction.FORWARD  = 1;
michael@0: Direction.BACKWARD = -1;
michael@0: 
michael@0: /**
michael@0:  * Abstract superclass for constraints having two possible output
michael@0:  * variables.
michael@0:  */
michael@0: function BinaryConstraint(var1, var2, strength) {
michael@0:   BinaryConstraint.superConstructor.call(this, strength);
michael@0:   this.v1 = var1;
michael@0:   this.v2 = var2;
michael@0:   this.direction = Direction.NONE;
michael@0:   this.addConstraint();
michael@0: }
michael@0: 
michael@0: BinaryConstraint.inheritsFrom(Constraint);
michael@0: 
michael@0: /**
michael@0:  * Decides if this constraint can be satisfied and which way it
michael@0:  * should flow based on the relative strength of the variables related,
michael@0:  * and record that decision.
michael@0:  */
michael@0: BinaryConstraint.prototype.chooseMethod = function (mark) {
michael@0:   if (this.v1.mark == mark) {
michael@0:     this.direction = (this.v2.mark != mark && Strength.stronger(this.strength, this.v2.walkStrength))
michael@0:       ? Direction.FORWARD
michael@0:       : Direction.NONE;
michael@0:   }
michael@0:   if (this.v2.mark == mark) {
michael@0:     this.direction = (this.v1.mark != mark && Strength.stronger(this.strength, this.v1.walkStrength))
michael@0:       ? Direction.BACKWARD
michael@0:       : Direction.NONE;
michael@0:   }
michael@0:   if (Strength.weaker(this.v1.walkStrength, this.v2.walkStrength)) {
michael@0:     this.direction = Strength.stronger(this.strength, this.v1.walkStrength)
michael@0:       ? Direction.BACKWARD
michael@0:       : Direction.NONE;
michael@0:   } else {
michael@0:     this.direction = Strength.stronger(this.strength, this.v2.walkStrength)
michael@0:       ? Direction.FORWARD
michael@0:       : Direction.BACKWARD
michael@0:   }
michael@0: }
michael@0: 
michael@0: /**
michael@0:  * Add this constraint to the constraint graph
michael@0:  */
michael@0: BinaryConstraint.prototype.addToGraph = function () {
michael@0:   this.v1.addConstraint(this);
michael@0:   this.v2.addConstraint(this);
michael@0:   this.direction = Direction.NONE;
michael@0: }
michael@0: 
michael@0: /**
michael@0:  * Answer true if this constraint is satisfied in the current solution.
michael@0:  */
michael@0: BinaryConstraint.prototype.isSatisfied = function () {
michael@0:   return this.direction != Direction.NONE;
michael@0: }
michael@0: 
michael@0: /**
michael@0:  * Mark the input variable with the given mark.
michael@0:  */
michael@0: BinaryConstraint.prototype.markInputs = function (mark) {
michael@0:   this.input().mark = mark;
michael@0: }
michael@0: 
michael@0: /**
michael@0:  * Returns the current input variable
michael@0:  */
michael@0: BinaryConstraint.prototype.input = function () {
michael@0:   return (this.direction == Direction.FORWARD) ? this.v1 : this.v2;
michael@0: }
michael@0: 
michael@0: /**
michael@0:  * Returns the current output variable
michael@0:  */
michael@0: BinaryConstraint.prototype.output = function () {
michael@0:   return (this.direction == Direction.FORWARD) ? this.v2 : this.v1;
michael@0: }
michael@0: 
michael@0: /**
michael@0:  * Calculate the walkabout strength, the stay flag, and, if it is
michael@0:  * 'stay', the value for the current output of this
michael@0:  * constraint. Assume this constraint is satisfied.
michael@0:  */
michael@0: BinaryConstraint.prototype.recalculate = function () {
michael@0:   var ihn = this.input(), out = this.output();
michael@0:   out.walkStrength = Strength.weakestOf(this.strength, ihn.walkStrength);
michael@0:   out.stay = ihn.stay;
michael@0:   if (out.stay) this.execute();
michael@0: }
michael@0: 
michael@0: /**
michael@0:  * Record the fact that this constraint is unsatisfied.
michael@0:  */
michael@0: BinaryConstraint.prototype.markUnsatisfied = function () {
michael@0:   this.direction = Direction.NONE;
michael@0: }
michael@0: 
michael@0: BinaryConstraint.prototype.inputsKnown = function (mark) {
michael@0:   var i = this.input();
michael@0:   return i.mark == mark || i.stay || i.determinedBy == null;
michael@0: }
michael@0: 
michael@0: BinaryConstraint.prototype.removeFromGraph = function () {
michael@0:   if (this.v1 != null) this.v1.removeConstraint(this);
michael@0:   if (this.v2 != null) this.v2.removeConstraint(this);
michael@0:   this.direction = Direction.NONE;
michael@0: }
michael@0: 
michael@0: /* --- *
michael@0:  * S c a l e   C o n s t r a i n t
michael@0:  * --- */
michael@0: 
michael@0: /**
michael@0:  * Relates two variables by the linear scaling relationship: "v2 =
michael@0:  * (v1 * scale) + offset". Either v1 or v2 may be changed to maintain
michael@0:  * this relationship but the scale factor and offset are considered
michael@0:  * read-only.
michael@0:  */
michael@0: function ScaleConstraint(src, scale, offset, dest, strength) {
michael@0:   this.direction = Direction.NONE;
michael@0:   this.scale = scale;
michael@0:   this.offset = offset;
michael@0:   ScaleConstraint.superConstructor.call(this, src, dest, strength);
michael@0: }
michael@0: 
michael@0: ScaleConstraint.inheritsFrom(BinaryConstraint);
michael@0: 
michael@0: /**
michael@0:  * Adds this constraint to the constraint graph.
michael@0:  */
michael@0: ScaleConstraint.prototype.addToGraph = function () {
michael@0:   ScaleConstraint.superConstructor.prototype.addToGraph.call(this);
michael@0:   this.scale.addConstraint(this);
michael@0:   this.offset.addConstraint(this);
michael@0: }
michael@0: 
michael@0: ScaleConstraint.prototype.removeFromGraph = function () {
michael@0:   ScaleConstraint.superConstructor.prototype.removeFromGraph.call(this);
michael@0:   if (this.scale != null) this.scale.removeConstraint(this);
michael@0:   if (this.offset != null) this.offset.removeConstraint(this);
michael@0: }
michael@0: 
michael@0: ScaleConstraint.prototype.markInputs = function (mark) {
michael@0:   ScaleConstraint.superConstructor.prototype.markInputs.call(this, mark);
michael@0:   this.scale.mark = this.offset.mark = mark;
michael@0: }
michael@0: 
michael@0: /**
michael@0:  * Enforce this constraint. Assume that it is satisfied.
michael@0:  */
michael@0: ScaleConstraint.prototype.execute = function () {
michael@0:   if (this.direction == Direction.FORWARD) {
michael@0:     this.v2.value = this.v1.value * this.scale.value + this.offset.value;
michael@0:   } else {
michael@0:     this.v1.value = (this.v2.value - this.offset.value) / this.scale.value;
michael@0:   }
michael@0: }
michael@0: 
michael@0: /**
michael@0:  * Calculate the walkabout strength, the stay flag, and, if it is
michael@0:  * 'stay', the value for the current output of this constraint. Assume
michael@0:  * this constraint is satisfied.
michael@0:  */
michael@0: ScaleConstraint.prototype.recalculate = function () {
michael@0:   var ihn = this.input(), out = this.output();
michael@0:   out.walkStrength = Strength.weakestOf(this.strength, ihn.walkStrength);
michael@0:   out.stay = ihn.stay && this.scale.stay && this.offset.stay;
michael@0:   if (out.stay) this.execute();
michael@0: }
michael@0: 
michael@0: /* --- *
michael@0:  * E q u a l i t  y   C o n s t r a i n t
michael@0:  * --- */
michael@0: 
michael@0: /**
michael@0:  * Constrains two variables to have the same value.
michael@0:  */
michael@0: function EqualityConstraint(var1, var2, strength) {
michael@0:   EqualityConstraint.superConstructor.call(this, var1, var2, strength);
michael@0: }
michael@0: 
michael@0: EqualityConstraint.inheritsFrom(BinaryConstraint);
michael@0: 
michael@0: /**
michael@0:  * Enforce this constraint. Assume that it is satisfied.
michael@0:  */
michael@0: EqualityConstraint.prototype.execute = function () {
michael@0:   this.output().value = this.input().value;
michael@0: }
michael@0: 
michael@0: /* --- *
michael@0:  * V a r i a b l e
michael@0:  * --- */
michael@0: 
michael@0: /**
michael@0:  * A constrained variable. In addition to its value, it maintain the
michael@0:  * structure of the constraint graph, the current dataflow graph, and
michael@0:  * various parameters of interest to the DeltaBlue incremental
michael@0:  * constraint solver.
michael@0:  **/
michael@0: function Variable(name, initialValue) {
michael@0:   this.value = initialValue || 0;
michael@0:   this.constraints = new OrderedCollection();
michael@0:   this.determinedBy = null;
michael@0:   this.mark = 0;
michael@0:   this.walkStrength = Strength.WEAKEST;
michael@0:   this.stay = true;
michael@0:   this.name = name;
michael@0: }
michael@0: 
michael@0: /**
michael@0:  * Add the given constraint to the set of all constraints that refer
michael@0:  * this variable.
michael@0:  */
michael@0: Variable.prototype.addConstraint = function (c) {
michael@0:   this.constraints.add(c);
michael@0: }
michael@0: 
michael@0: /**
michael@0:  * Removes all traces of c from this variable.
michael@0:  */
michael@0: Variable.prototype.removeConstraint = function (c) {
michael@0:   this.constraints.remove(c);
michael@0:   if (this.determinedBy == c) this.determinedBy = null;
michael@0: }
michael@0: 
michael@0: /* --- *
michael@0:  * P l a n n e r
michael@0:  * --- */
michael@0: 
michael@0: /**
michael@0:  * The DeltaBlue planner
michael@0:  */
michael@0: function Planner() {
michael@0:   this.currentMark = 0;
michael@0: }
michael@0: 
michael@0: /**
michael@0:  * Attempt to satisfy the given constraint and, if successful,
michael@0:  * incrementally update the dataflow graph.  Details: If satifying
michael@0:  * the constraint is successful, it may override a weaker constraint
michael@0:  * on its output. The algorithm attempts to resatisfy that
michael@0:  * constraint using some other method. This process is repeated
michael@0:  * until either a) it reaches a variable that was not previously
michael@0:  * determined by any constraint or b) it reaches a constraint that
michael@0:  * is too weak to be satisfied using any of its methods. The
michael@0:  * variables of constraints that have been processed are marked with
michael@0:  * a unique mark value so that we know where we've been. This allows
michael@0:  * the algorithm to avoid getting into an infinite loop even if the
michael@0:  * constraint graph has an inadvertent cycle.
michael@0:  */
michael@0: Planner.prototype.incrementalAdd = function (c) {
michael@0:   var mark = this.newMark();
michael@0:   var overridden = c.satisfy(mark);
michael@0:   while (overridden != null)
michael@0:     overridden = overridden.satisfy(mark);
michael@0: }
michael@0: 
michael@0: /**
michael@0:  * Entry point for retracting a constraint. Remove the given
michael@0:  * constraint and incrementally update the dataflow graph.
michael@0:  * Details: Retracting the given constraint may allow some currently
michael@0:  * unsatisfiable downstream constraint to be satisfied. We therefore collect
michael@0:  * a list of unsatisfied downstream constraints and attempt to
michael@0:  * satisfy each one in turn. This list is traversed by constraint
michael@0:  * strength, strongest first, as a heuristic for avoiding
michael@0:  * unnecessarily adding and then overriding weak constraints.
michael@0:  * Assume: c is satisfied.
michael@0:  */
michael@0: Planner.prototype.incrementalRemove = function (c) {
michael@0:   var out = c.output();
michael@0:   c.markUnsatisfied();
michael@0:   c.removeFromGraph();
michael@0:   var unsatisfied = this.removePropagateFrom(out);
michael@0:   var strength = Strength.REQUIRED;
michael@0:   do {
michael@0:     for (var i = 0; i < unsatisfied.size(); i++) {
michael@0:       var u = unsatisfied.at(i);
michael@0:       if (u.strength == strength)
michael@0:         this.incrementalAdd(u);
michael@0:     }
michael@0:     strength = strength.nextWeaker();
michael@0:   } while (strength != Strength.WEAKEST);
michael@0: }
michael@0: 
michael@0: /**
michael@0:  * Select a previously unused mark value.
michael@0:  */
michael@0: Planner.prototype.newMark = function () {
michael@0:   return ++this.currentMark;
michael@0: }
michael@0: 
michael@0: /**
michael@0:  * Extract a plan for resatisfaction starting from the given source
michael@0:  * constraints, usually a set of input constraints. This method
michael@0:  * assumes that stay optimization is desired; the plan will contain
michael@0:  * only constraints whose output variables are not stay. Constraints
michael@0:  * that do no computation, such as stay and edit constraints, are
michael@0:  * not included in the plan.
michael@0:  * Details: The outputs of a constraint are marked when it is added
michael@0:  * to the plan under construction. A constraint may be appended to
michael@0:  * the plan when all its input variables are known. A variable is
michael@0:  * known if either a) the variable is marked (indicating that has
michael@0:  * been computed by a constraint appearing earlier in the plan), b)
michael@0:  * the variable is 'stay' (i.e. it is a constant at plan execution
michael@0:  * time), or c) the variable is not determined by any
michael@0:  * constraint. The last provision is for past states of history
michael@0:  * variables, which are not stay but which are also not computed by
michael@0:  * any constraint.
michael@0:  * Assume: sources are all satisfied.
michael@0:  */
michael@0: Planner.prototype.makePlan = function (sources) {
michael@0:   var mark = this.newMark();
michael@0:   var plan = new Plan();
michael@0:   var todo = sources;
michael@0:   while (todo.size() > 0) {
michael@0:     var c = todo.removeFirst();
michael@0:     if (c.output().mark != mark && c.inputsKnown(mark)) {
michael@0:       plan.addConstraint(c);
michael@0:       c.output().mark = mark;
michael@0:       this.addConstraintsConsumingTo(c.output(), todo);
michael@0:     }
michael@0:   }
michael@0:   return plan;
michael@0: }
michael@0: 
michael@0: /**
michael@0:  * Extract a plan for resatisfying starting from the output of the
michael@0:  * given constraints, usually a set of input constraints.
michael@0:  */
michael@0: Planner.prototype.extractPlanFromConstraints = function (constraints) {
michael@0:   var sources = new OrderedCollection();
michael@0:   for (var i = 0; i < constraints.size(); i++) {
michael@0:     var c = constraints.at(i);
michael@0:     if (c.isInput() && c.isSatisfied())
michael@0:       // not in plan already and eligible for inclusion
michael@0:       sources.add(c);
michael@0:   }
michael@0:   return this.makePlan(sources);
michael@0: }
michael@0: 
michael@0: /**
michael@0:  * Recompute the walkabout strengths and stay flags of all variables
michael@0:  * downstream of the given constraint and recompute the actual
michael@0:  * values of all variables whose stay flag is true. If a cycle is
michael@0:  * detected, remove the given constraint and answer
michael@0:  * false. Otherwise, answer true.
michael@0:  * Details: Cycles are detected when a marked variable is
michael@0:  * encountered downstream of the given constraint. The sender is
michael@0:  * assumed to have marked the inputs of the given constraint with
michael@0:  * the given mark. Thus, encountering a marked node downstream of
michael@0:  * the output constraint means that there is a path from the
michael@0:  * constraint's output to one of its inputs.
michael@0:  */
michael@0: Planner.prototype.addPropagate = function (c, mark) {
michael@0:   var todo = new OrderedCollection();
michael@0:   todo.add(c);
michael@0:   while (todo.size() > 0) {
michael@0:     var d = todo.removeFirst();
michael@0:     if (d.output().mark == mark) {
michael@0:       this.incrementalRemove(c);
michael@0:       return false;
michael@0:     }
michael@0:     d.recalculate();
michael@0:     this.addConstraintsConsumingTo(d.output(), todo);
michael@0:   }
michael@0:   return true;
michael@0: }
michael@0: 
michael@0: 
michael@0: /**
michael@0:  * Update the walkabout strengths and stay flags of all variables
michael@0:  * downstream of the given constraint. Answer a collection of
michael@0:  * unsatisfied constraints sorted in order of decreasing strength.
michael@0:  */
michael@0: Planner.prototype.removePropagateFrom = function (out) {
michael@0:   out.determinedBy = null;
michael@0:   out.walkStrength = Strength.WEAKEST;
michael@0:   out.stay = true;
michael@0:   var unsatisfied = new OrderedCollection();
michael@0:   var todo = new OrderedCollection();
michael@0:   todo.add(out);
michael@0:   while (todo.size() > 0) {
michael@0:     var v = todo.removeFirst();
michael@0:     for (var i = 0; i < v.constraints.size(); i++) {
michael@0:       var c = v.constraints.at(i);
michael@0:       if (!c.isSatisfied())
michael@0:         unsatisfied.add(c);
michael@0:     }
michael@0:     var determining = v.determinedBy;
michael@0:     for (var i = 0; i < v.constraints.size(); i++) {
michael@0:       var next = v.constraints.at(i);
michael@0:       if (next != determining && next.isSatisfied()) {
michael@0:         next.recalculate();
michael@0:         todo.add(next.output());
michael@0:       }
michael@0:     }
michael@0:   }
michael@0:   return unsatisfied;
michael@0: }
michael@0: 
michael@0: Planner.prototype.addConstraintsConsumingTo = function (v, coll) {
michael@0:   var determining = v.determinedBy;
michael@0:   var cc = v.constraints;
michael@0:   for (var i = 0; i < cc.size(); i++) {
michael@0:     var c = cc.at(i);
michael@0:     if (c != determining && c.isSatisfied())
michael@0:       coll.add(c);
michael@0:   }
michael@0: }
michael@0: 
michael@0: /* --- *
michael@0:  * P l a n
michael@0:  * --- */
michael@0: 
michael@0: /**
michael@0:  * A Plan is an ordered list of constraints to be executed in sequence
michael@0:  * to resatisfy all currently satisfiable constraints in the face of
michael@0:  * one or more changing inputs.
michael@0:  */
michael@0: function Plan() {
michael@0:   this.v = new OrderedCollection();
michael@0: }
michael@0: 
michael@0: Plan.prototype.addConstraint = function (c) {
michael@0:   this.v.add(c);
michael@0: }
michael@0: 
michael@0: Plan.prototype.size = function () {
michael@0:   return this.v.size();
michael@0: }
michael@0: 
michael@0: Plan.prototype.constraintAt = function (index) {
michael@0:   return this.v.at(index);
michael@0: }
michael@0: 
michael@0: Plan.prototype.execute = function () {
michael@0:   for (var i = 0; i < this.size(); i++) {
michael@0:     var c = this.constraintAt(i);
michael@0:     c.execute();
michael@0:   }
michael@0: }
michael@0: 
michael@0: /* --- *
michael@0:  * M a i n
michael@0:  * --- */
michael@0: 
michael@0: /**
michael@0:  * This is the standard DeltaBlue benchmark. A long chain of equality
michael@0:  * constraints is constructed with a stay constraint on one end. An
michael@0:  * edit constraint is then added to the opposite end and the time is
michael@0:  * measured for adding and removing this constraint, and extracting
michael@0:  * and executing a constraint satisfaction plan. There are two cases.
michael@0:  * In case 1, the added constraint is stronger than the stay
michael@0:  * constraint and values must propagate down the entire length of the
michael@0:  * chain. In case 2, the added constraint is weaker than the stay
michael@0:  * constraint so it cannot be accomodated. The cost in this case is,
michael@0:  * of course, very low. Typical situations lie somewhere between these
michael@0:  * two extremes.
michael@0:  */
michael@0: function chainTest(n) {
michael@0:   planner = new Planner();
michael@0:   var prev = null, first = null, last = null;
michael@0: 
michael@0:   // Build chain of n equality constraints
michael@0:   for (var i = 0; i <= n; i++) {
michael@0:     var name = "v" + i;
michael@0:     var v = new Variable(name);
michael@0:     if (prev != null)
michael@0:       new EqualityConstraint(prev, v, Strength.REQUIRED);
michael@0:     if (i == 0) first = v;
michael@0:     if (i == n) last = v;
michael@0:     prev = v;
michael@0:   }
michael@0: 
michael@0:   new StayConstraint(last, Strength.STRONG_DEFAULT);
michael@0:   var edit = new EditConstraint(first, Strength.PREFERRED);
michael@0:   var edits = new OrderedCollection();
michael@0:   edits.add(edit);
michael@0:   var plan = planner.extractPlanFromConstraints(edits);
michael@0:   for (var i = 0; i < 100; i++) {
michael@0:     first.value = i;
michael@0:     plan.execute();
michael@0:     if (last.value != i)
michael@0:       alert("Chain test failed.");
michael@0:   }
michael@0: }
michael@0: 
michael@0: /**
michael@0:  * This test constructs a two sets of variables related to each
michael@0:  * other by a simple linear transformation (scale and offset). The
michael@0:  * time is measured to change a variable on either side of the
michael@0:  * mapping and to change the scale and offset factors.
michael@0:  */
michael@0: function projectionTest(n) {
michael@0:   planner = new Planner();
michael@0:   var scale = new Variable("scale", 10);
michael@0:   var offset = new Variable("offset", 1000);
michael@0:   var src = null, dst = null;
michael@0: 
michael@0:   var dests = new OrderedCollection();
michael@0:   for (var i = 0; i < n; i++) {
michael@0:     src = new Variable("src" + i, i);
michael@0:     dst = new Variable("dst" + i, i);
michael@0:     dests.add(dst);
michael@0:     new StayConstraint(src, Strength.NORMAL);
michael@0:     new ScaleConstraint(src, scale, offset, dst, Strength.REQUIRED);
michael@0:   }
michael@0: 
michael@0:   change(src, 17);
michael@0:   if (dst.value != 1170) alert("Projection 1 failed");
michael@0:   change(dst, 1050);
michael@0:   if (src.value != 5) alert("Projection 2 failed");
michael@0:   change(scale, 5);
michael@0:   for (var i = 0; i < n - 1; i++) {
michael@0:     if (dests.at(i).value != i * 5 + 1000)
michael@0:       alert("Projection 3 failed");
michael@0:   }
michael@0:   change(offset, 2000);
michael@0:   for (var i = 0; i < n - 1; i++) {
michael@0:     if (dests.at(i).value != i * 5 + 2000)
michael@0:       alert("Projection 4 failed");
michael@0:   }
michael@0: }
michael@0: 
michael@0: function change(v, newValue) {
michael@0:   var edit = new EditConstraint(v, Strength.PREFERRED);
michael@0:   var edits = new OrderedCollection();
michael@0:   edits.add(edit);
michael@0:   var plan = planner.extractPlanFromConstraints(edits);
michael@0:   for (var i = 0; i < 10; i++) {
michael@0:     v.value = newValue;
michael@0:     plan.execute();
michael@0:   }
michael@0:   edit.destroyConstraint();
michael@0: }
michael@0: 
michael@0: // Global variable holding the current planner.
michael@0: var planner = null;
michael@0: 
michael@0: function deltaBlue() {
michael@0:   chainTest(100);
michael@0:   projectionTest(100);
michael@0: }