1 // Copyright 2008 the V8 project authors. All rights reserved.
2 // Copyright 1996 John Maloney and Mario Wolczko.
4 // This program is free software; you can redistribute it and/or modify
5 // it under the terms of the GNU General Public License as published by
6 // the Free Software Foundation; either version 2 of the License, or
7 // (at your option) any later version.
9 // This program is distributed in the hope that it will be useful,
10 // but WITHOUT ANY WARRANTY; without even the implied warranty of
11 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 // GNU General Public License for more details.
14 // You should have received a copy of the GNU General Public License
15 // along with this program; if not, write to the Free Software
16 // Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
19 // This implementation of the DeltaBlue benchmark is derived
20 // from the Smalltalk implementation by John Maloney and Mario
21 // Wolczko. Some parts have been translated directly, whereas
22 // others have been modified more aggresively to make it feel
23 // more like a JavaScript program.
26 var DeltaBlue = new BenchmarkSuite('DeltaBlue', 66118, [
27 new Benchmark('DeltaBlue', deltaBlue)
32 * A JavaScript implementation of the DeltaBlue constraint-solving
33 * algorithm, as described in:
35 * "The DeltaBlue Algorithm: An Incremental Constraint Hierarchy Solver"
36 * Bjorn N. Freeman-Benson and John Maloney
37 * January 1990 Communications of the ACM,
38 * also available as University of Washington TR 89-08-06.
40 * Beware: this benchmark is written in a grotesque style where
41 * the constraint model is built by side-effects from constructors.
42 * I've kept it this way to avoid deviating too much from the original
47 /* --- O b j e c t M o d e l --- */
49 Object.prototype.inheritsFrom = function (shuper) {
50 function Inheriter() { }
51 Inheriter.prototype = shuper.prototype;
52 this.prototype = new Inheriter();
53 this.superConstructor = shuper;
56 function OrderedCollection() {
57 this.elms = new Array();
60 OrderedCollection.prototype.add = function (elm) {
64 OrderedCollection.prototype.at = function (index) {
65 return this.elms[index];
68 OrderedCollection.prototype.size = function () {
69 return this.elms.length;
72 OrderedCollection.prototype.removeFirst = function () {
73 return this.elms.pop();
76 OrderedCollection.prototype.remove = function (elm) {
77 var index = 0, skipped = 0;
78 for (var i = 0; i < this.elms.length; i++) {
79 var value = this.elms[i];
81 this.elms[index] = value;
87 for (var i = 0; i < skipped; i++)
96 * Strengths are used to measure the relative importance of constraints.
97 * New strengths may be inserted in the strength hierarchy without
98 * disrupting current constraints. Strengths cannot be created outside
99 * this class, so pointer comparison can be used for value comparison.
101 function Strength(strengthValue, name) {
102 this.strengthValue = strengthValue;
106 Strength.stronger = function (s1, s2) {
107 return s1.strengthValue < s2.strengthValue;
110 Strength.weaker = function (s1, s2) {
111 return s1.strengthValue > s2.strengthValue;
114 Strength.weakestOf = function (s1, s2) {
115 return this.weaker(s1, s2) ? s1 : s2;
118 Strength.strongest = function (s1, s2) {
119 return this.stronger(s1, s2) ? s1 : s2;
122 Strength.prototype.nextWeaker = function () {
123 switch (this.strengthValue) {
124 case 0: return Strength.WEAKEST;
125 case 1: return Strength.WEAK_DEFAULT;
126 case 2: return Strength.NORMAL;
127 case 3: return Strength.STRONG_DEFAULT;
128 case 4: return Strength.PREFERRED;
129 case 5: return Strength.REQUIRED;
133 // Strength constants.
134 Strength.REQUIRED = new Strength(0, "required");
135 Strength.STONG_PREFERRED = new Strength(1, "strongPreferred");
136 Strength.PREFERRED = new Strength(2, "preferred");
137 Strength.STRONG_DEFAULT = new Strength(3, "strongDefault");
138 Strength.NORMAL = new Strength(4, "normal");
139 Strength.WEAK_DEFAULT = new Strength(5, "weakDefault");
140 Strength.WEAKEST = new Strength(6, "weakest");
143 * C o n s t r a i n t
147 * An abstract class representing a system-maintainable relationship
148 * (or "constraint") between a set of variables. A constraint supplies
149 * a strength instance variable; concrete subclasses provide a means
150 * of storing the constrained variables and other information required
151 * to represent a constraint.
153 function Constraint(strength) {
154 this.strength = strength;
158 * Activate this constraint and attempt to satisfy it.
160 Constraint.prototype.addConstraint = function () {
162 planner.incrementalAdd(this);
166 * Attempt to find a way to enforce this constraint. If successful,
167 * record the solution, perhaps modifying the current dataflow
168 * graph. Answer the constraint that this constraint overrides, if
169 * there is one, or nil, if there isn't.
170 * Assume: I am not already satisfied.
172 Constraint.prototype.satisfy = function (mark) {
173 this.chooseMethod(mark);
174 if (!this.isSatisfied()) {
175 if (this.strength == Strength.REQUIRED)
176 alert("Could not satisfy a required constraint!");
179 this.markInputs(mark);
180 var out = this.output();
181 var overridden = out.determinedBy;
182 if (overridden != null) overridden.markUnsatisfied();
183 out.determinedBy = this;
184 if (!planner.addPropagate(this, mark))
185 alert("Cycle encountered");
190 Constraint.prototype.destroyConstraint = function () {
191 if (this.isSatisfied()) planner.incrementalRemove(this);
192 else this.removeFromGraph();
196 * Normal constraints are not input constraints. An input constraint
197 * is one that depends on external state, such as the mouse, the
198 * keybord, a clock, or some arbitraty piece of imperative code.
200 Constraint.prototype.isInput = function () {
205 * U n a r y C o n s t r a i n t
209 * Abstract superclass for constraints having a single possible output
212 function UnaryConstraint(v, strength) {
213 UnaryConstraint.superConstructor.call(this, strength);
215 this.satisfied = false;
216 this.addConstraint();
219 UnaryConstraint.inheritsFrom(Constraint);
222 * Adds this constraint to the constraint graph
224 UnaryConstraint.prototype.addToGraph = function () {
225 this.myOutput.addConstraint(this);
226 this.satisfied = false;
230 * Decides if this constraint can be satisfied and records that
233 UnaryConstraint.prototype.chooseMethod = function (mark) {
234 this.satisfied = (this.myOutput.mark != mark)
235 && Strength.stronger(this.strength, this.myOutput.walkStrength);
239 * Returns true if this constraint is satisfied in the current solution.
241 UnaryConstraint.prototype.isSatisfied = function () {
242 return this.satisfied;
245 UnaryConstraint.prototype.markInputs = function (mark) {
250 * Returns the current output variable.
252 UnaryConstraint.prototype.output = function () {
253 return this.myOutput;
257 * Calculate the walkabout strength, the stay flag, and, if it is
258 * 'stay', the value for the current output of this constraint. Assume
259 * this constraint is satisfied.
261 UnaryConstraint.prototype.recalculate = function () {
262 this.myOutput.walkStrength = this.strength;
263 this.myOutput.stay = !this.isInput();
264 if (this.myOutput.stay) this.execute(); // Stay optimization
268 * Records that this constraint is unsatisfied
270 UnaryConstraint.prototype.markUnsatisfied = function () {
271 this.satisfied = false;
274 UnaryConstraint.prototype.inputsKnown = function () {
278 UnaryConstraint.prototype.removeFromGraph = function () {
279 if (this.myOutput != null) this.myOutput.removeConstraint(this);
280 this.satisfied = false;
284 * S t a y C o n s t r a i n t
288 * Variables that should, with some level of preference, stay the same.
289 * Planners may exploit the fact that instances, if satisfied, will not
290 * change their output during plan execution. This is called "stay
293 function StayConstraint(v, str) {
294 StayConstraint.superConstructor.call(this, v, str);
297 StayConstraint.inheritsFrom(UnaryConstraint);
299 StayConstraint.prototype.execute = function () {
300 // Stay constraints do nothing
304 * E d i t C o n s t r a i n t
308 * A unary input constraint used to mark a variable that the client
311 function EditConstraint(v, str) {
312 EditConstraint.superConstructor.call(this, v, str);
315 EditConstraint.inheritsFrom(UnaryConstraint);
318 * Edits indicate that a variable is to be changed by imperative code.
320 EditConstraint.prototype.isInput = function () {
324 EditConstraint.prototype.execute = function () {
325 // Edit constraints do nothing
329 * B i n a r y C o n s t r a i n t
332 var Direction = new Object();
334 Direction.FORWARD = 1;
335 Direction.BACKWARD = -1;
338 * Abstract superclass for constraints having two possible output
341 function BinaryConstraint(var1, var2, strength) {
342 BinaryConstraint.superConstructor.call(this, strength);
345 this.direction = Direction.NONE;
346 this.addConstraint();
349 BinaryConstraint.inheritsFrom(Constraint);
352 * Decides if this constraint can be satisfied and which way it
353 * should flow based on the relative strength of the variables related,
354 * and record that decision.
356 BinaryConstraint.prototype.chooseMethod = function (mark) {
357 if (this.v1.mark == mark) {
358 this.direction = (this.v2.mark != mark && Strength.stronger(this.strength, this.v2.walkStrength))
362 if (this.v2.mark == mark) {
363 this.direction = (this.v1.mark != mark && Strength.stronger(this.strength, this.v1.walkStrength))
367 if (Strength.weaker(this.v1.walkStrength, this.v2.walkStrength)) {
368 this.direction = Strength.stronger(this.strength, this.v1.walkStrength)
372 this.direction = Strength.stronger(this.strength, this.v2.walkStrength)
379 * Add this constraint to the constraint graph
381 BinaryConstraint.prototype.addToGraph = function () {
382 this.v1.addConstraint(this);
383 this.v2.addConstraint(this);
384 this.direction = Direction.NONE;
388 * Answer true if this constraint is satisfied in the current solution.
390 BinaryConstraint.prototype.isSatisfied = function () {
391 return this.direction != Direction.NONE;
395 * Mark the input variable with the given mark.
397 BinaryConstraint.prototype.markInputs = function (mark) {
398 this.input().mark = mark;
402 * Returns the current input variable
404 BinaryConstraint.prototype.input = function () {
405 return (this.direction == Direction.FORWARD) ? this.v1 : this.v2;
409 * Returns the current output variable
411 BinaryConstraint.prototype.output = function () {
412 return (this.direction == Direction.FORWARD) ? this.v2 : this.v1;
416 * Calculate the walkabout strength, the stay flag, and, if it is
417 * 'stay', the value for the current output of this
418 * constraint. Assume this constraint is satisfied.
420 BinaryConstraint.prototype.recalculate = function () {
421 var ihn = this.input(), out = this.output();
422 out.walkStrength = Strength.weakestOf(this.strength, ihn.walkStrength);
424 if (out.stay) this.execute();
428 * Record the fact that this constraint is unsatisfied.
430 BinaryConstraint.prototype.markUnsatisfied = function () {
431 this.direction = Direction.NONE;
434 BinaryConstraint.prototype.inputsKnown = function (mark) {
435 var i = this.input();
436 return i.mark == mark || i.stay || i.determinedBy == null;
439 BinaryConstraint.prototype.removeFromGraph = function () {
440 if (this.v1 != null) this.v1.removeConstraint(this);
441 if (this.v2 != null) this.v2.removeConstraint(this);
442 this.direction = Direction.NONE;
446 * S c a l e C o n s t r a i n t
450 * Relates two variables by the linear scaling relationship: "v2 =
451 * (v1 * scale) + offset". Either v1 or v2 may be changed to maintain
452 * this relationship but the scale factor and offset are considered
455 function ScaleConstraint(src, scale, offset, dest, strength) {
456 this.direction = Direction.NONE;
458 this.offset = offset;
459 ScaleConstraint.superConstructor.call(this, src, dest, strength);
462 ScaleConstraint.inheritsFrom(BinaryConstraint);
465 * Adds this constraint to the constraint graph.
467 ScaleConstraint.prototype.addToGraph = function () {
468 ScaleConstraint.superConstructor.prototype.addToGraph.call(this);
469 this.scale.addConstraint(this);
470 this.offset.addConstraint(this);
473 ScaleConstraint.prototype.removeFromGraph = function () {
474 ScaleConstraint.superConstructor.prototype.removeFromGraph.call(this);
475 if (this.scale != null) this.scale.removeConstraint(this);
476 if (this.offset != null) this.offset.removeConstraint(this);
479 ScaleConstraint.prototype.markInputs = function (mark) {
480 ScaleConstraint.superConstructor.prototype.markInputs.call(this, mark);
481 this.scale.mark = this.offset.mark = mark;
485 * Enforce this constraint. Assume that it is satisfied.
487 ScaleConstraint.prototype.execute = function () {
488 if (this.direction == Direction.FORWARD) {
489 this.v2.value = this.v1.value * this.scale.value + this.offset.value;
491 this.v1.value = (this.v2.value - this.offset.value) / this.scale.value;
496 * Calculate the walkabout strength, the stay flag, and, if it is
497 * 'stay', the value for the current output of this constraint. Assume
498 * this constraint is satisfied.
500 ScaleConstraint.prototype.recalculate = function () {
501 var ihn = this.input(), out = this.output();
502 out.walkStrength = Strength.weakestOf(this.strength, ihn.walkStrength);
503 out.stay = ihn.stay && this.scale.stay && this.offset.stay;
504 if (out.stay) this.execute();
508 * E q u a l i t y C o n s t r a i n t
512 * Constrains two variables to have the same value.
514 function EqualityConstraint(var1, var2, strength) {
515 EqualityConstraint.superConstructor.call(this, var1, var2, strength);
518 EqualityConstraint.inheritsFrom(BinaryConstraint);
521 * Enforce this constraint. Assume that it is satisfied.
523 EqualityConstraint.prototype.execute = function () {
524 this.output().value = this.input().value;
532 * A constrained variable. In addition to its value, it maintain the
533 * structure of the constraint graph, the current dataflow graph, and
534 * various parameters of interest to the DeltaBlue incremental
537 function Variable(name, initialValue) {
538 this.value = initialValue || 0;
539 this.constraints = new OrderedCollection();
540 this.determinedBy = null;
542 this.walkStrength = Strength.WEAKEST;
548 * Add the given constraint to the set of all constraints that refer
551 Variable.prototype.addConstraint = function (c) {
552 this.constraints.add(c);
556 * Removes all traces of c from this variable.
558 Variable.prototype.removeConstraint = function (c) {
559 this.constraints.remove(c);
560 if (this.determinedBy == c) this.determinedBy = null;
568 * The DeltaBlue planner
571 this.currentMark = 0;
575 * Attempt to satisfy the given constraint and, if successful,
576 * incrementally update the dataflow graph. Details: If satifying
577 * the constraint is successful, it may override a weaker constraint
578 * on its output. The algorithm attempts to resatisfy that
579 * constraint using some other method. This process is repeated
580 * until either a) it reaches a variable that was not previously
581 * determined by any constraint or b) it reaches a constraint that
582 * is too weak to be satisfied using any of its methods. The
583 * variables of constraints that have been processed are marked with
584 * a unique mark value so that we know where we've been. This allows
585 * the algorithm to avoid getting into an infinite loop even if the
586 * constraint graph has an inadvertent cycle.
588 Planner.prototype.incrementalAdd = function (c) {
589 var mark = this.newMark();
590 var overridden = c.satisfy(mark);
591 while (overridden != null)
592 overridden = overridden.satisfy(mark);
596 * Entry point for retracting a constraint. Remove the given
597 * constraint and incrementally update the dataflow graph.
598 * Details: Retracting the given constraint may allow some currently
599 * unsatisfiable downstream constraint to be satisfied. We therefore collect
600 * a list of unsatisfied downstream constraints and attempt to
601 * satisfy each one in turn. This list is traversed by constraint
602 * strength, strongest first, as a heuristic for avoiding
603 * unnecessarily adding and then overriding weak constraints.
604 * Assume: c is satisfied.
606 Planner.prototype.incrementalRemove = function (c) {
607 var out = c.output();
610 var unsatisfied = this.removePropagateFrom(out);
611 var strength = Strength.REQUIRED;
613 for (var i = 0; i < unsatisfied.size(); i++) {
614 var u = unsatisfied.at(i);
615 if (u.strength == strength)
616 this.incrementalAdd(u);
618 strength = strength.nextWeaker();
619 } while (strength != Strength.WEAKEST);
623 * Select a previously unused mark value.
625 Planner.prototype.newMark = function () {
626 return ++this.currentMark;
630 * Extract a plan for resatisfaction starting from the given source
631 * constraints, usually a set of input constraints. This method
632 * assumes that stay optimization is desired; the plan will contain
633 * only constraints whose output variables are not stay. Constraints
634 * that do no computation, such as stay and edit constraints, are
635 * not included in the plan.
636 * Details: The outputs of a constraint are marked when it is added
637 * to the plan under construction. A constraint may be appended to
638 * the plan when all its input variables are known. A variable is
639 * known if either a) the variable is marked (indicating that has
640 * been computed by a constraint appearing earlier in the plan), b)
641 * the variable is 'stay' (i.e. it is a constant at plan execution
642 * time), or c) the variable is not determined by any
643 * constraint. The last provision is for past states of history
644 * variables, which are not stay but which are also not computed by
646 * Assume: sources are all satisfied.
648 Planner.prototype.makePlan = function (sources) {
649 var mark = this.newMark();
650 var plan = new Plan();
652 while (todo.size() > 0) {
653 var c = todo.removeFirst();
654 if (c.output().mark != mark && c.inputsKnown(mark)) {
655 plan.addConstraint(c);
656 c.output().mark = mark;
657 this.addConstraintsConsumingTo(c.output(), todo);
664 * Extract a plan for resatisfying starting from the output of the
665 * given constraints, usually a set of input constraints.
667 Planner.prototype.extractPlanFromConstraints = function (constraints) {
668 var sources = new OrderedCollection();
669 for (var i = 0; i < constraints.size(); i++) {
670 var c = constraints.at(i);
671 if (c.isInput() && c.isSatisfied())
672 // not in plan already and eligible for inclusion
675 return this.makePlan(sources);
679 * Recompute the walkabout strengths and stay flags of all variables
680 * downstream of the given constraint and recompute the actual
681 * values of all variables whose stay flag is true. If a cycle is
682 * detected, remove the given constraint and answer
683 * false. Otherwise, answer true.
684 * Details: Cycles are detected when a marked variable is
685 * encountered downstream of the given constraint. The sender is
686 * assumed to have marked the inputs of the given constraint with
687 * the given mark. Thus, encountering a marked node downstream of
688 * the output constraint means that there is a path from the
689 * constraint's output to one of its inputs.
691 Planner.prototype.addPropagate = function (c, mark) {
692 var todo = new OrderedCollection();
694 while (todo.size() > 0) {
695 var d = todo.removeFirst();
696 if (d.output().mark == mark) {
697 this.incrementalRemove(c);
701 this.addConstraintsConsumingTo(d.output(), todo);
708 * Update the walkabout strengths and stay flags of all variables
709 * downstream of the given constraint. Answer a collection of
710 * unsatisfied constraints sorted in order of decreasing strength.
712 Planner.prototype.removePropagateFrom = function (out) {
713 out.determinedBy = null;
714 out.walkStrength = Strength.WEAKEST;
716 var unsatisfied = new OrderedCollection();
717 var todo = new OrderedCollection();
719 while (todo.size() > 0) {
720 var v = todo.removeFirst();
721 for (var i = 0; i < v.constraints.size(); i++) {
722 var c = v.constraints.at(i);
723 if (!c.isSatisfied())
726 var determining = v.determinedBy;
727 for (var i = 0; i < v.constraints.size(); i++) {
728 var next = v.constraints.at(i);
729 if (next != determining && next.isSatisfied()) {
731 todo.add(next.output());
738 Planner.prototype.addConstraintsConsumingTo = function (v, coll) {
739 var determining = v.determinedBy;
740 var cc = v.constraints;
741 for (var i = 0; i < cc.size(); i++) {
743 if (c != determining && c.isSatisfied())
753 * A Plan is an ordered list of constraints to be executed in sequence
754 * to resatisfy all currently satisfiable constraints in the face of
755 * one or more changing inputs.
758 this.v = new OrderedCollection();
761 Plan.prototype.addConstraint = function (c) {
765 Plan.prototype.size = function () {
766 return this.v.size();
769 Plan.prototype.constraintAt = function (index) {
770 return this.v.at(index);
773 Plan.prototype.execute = function () {
774 for (var i = 0; i < this.size(); i++) {
775 var c = this.constraintAt(i);
785 * This is the standard DeltaBlue benchmark. A long chain of equality
786 * constraints is constructed with a stay constraint on one end. An
787 * edit constraint is then added to the opposite end and the time is
788 * measured for adding and removing this constraint, and extracting
789 * and executing a constraint satisfaction plan. There are two cases.
790 * In case 1, the added constraint is stronger than the stay
791 * constraint and values must propagate down the entire length of the
792 * chain. In case 2, the added constraint is weaker than the stay
793 * constraint so it cannot be accomodated. The cost in this case is,
794 * of course, very low. Typical situations lie somewhere between these
797 function chainTest(n) {
798 planner = new Planner();
799 var prev = null, first = null, last = null;
801 // Build chain of n equality constraints
802 for (var i = 0; i <= n; i++) {
804 var v = new Variable(name);
806 new EqualityConstraint(prev, v, Strength.REQUIRED);
807 if (i == 0) first = v;
808 if (i == n) last = v;
812 new StayConstraint(last, Strength.STRONG_DEFAULT);
813 var edit = new EditConstraint(first, Strength.PREFERRED);
814 var edits = new OrderedCollection();
816 var plan = planner.extractPlanFromConstraints(edits);
817 for (var i = 0; i < 100; i++) {
821 alert("Chain test failed.");
826 * This test constructs a two sets of variables related to each
827 * other by a simple linear transformation (scale and offset). The
828 * time is measured to change a variable on either side of the
829 * mapping and to change the scale and offset factors.
831 function projectionTest(n) {
832 planner = new Planner();
833 var scale = new Variable("scale", 10);
834 var offset = new Variable("offset", 1000);
835 var src = null, dst = null;
837 var dests = new OrderedCollection();
838 for (var i = 0; i < n; i++) {
839 src = new Variable("src" + i, i);
840 dst = new Variable("dst" + i, i);
842 new StayConstraint(src, Strength.NORMAL);
843 new ScaleConstraint(src, scale, offset, dst, Strength.REQUIRED);
847 if (dst.value != 1170) alert("Projection 1 failed");
849 if (src.value != 5) alert("Projection 2 failed");
851 for (var i = 0; i < n - 1; i++) {
852 if (dests.at(i).value != i * 5 + 1000)
853 alert("Projection 3 failed");
855 change(offset, 2000);
856 for (var i = 0; i < n - 1; i++) {
857 if (dests.at(i).value != i * 5 + 2000)
858 alert("Projection 4 failed");
862 function change(v, newValue) {
863 var edit = new EditConstraint(v, Strength.PREFERRED);
864 var edits = new OrderedCollection();
866 var plan = planner.extractPlanFromConstraints(edits);
867 for (var i = 0; i < 10; i++) {
871 edit.destroyConstraint();
874 // Global variable holding the current planner.
877 function deltaBlue() {