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// 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.
/**
* 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 --- */
function inherits(orig, shuper) {
function Inheriter() { }
Inheriter.prototype = shuper.prototype;
orig.prototype = new Inheriter();
orig.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();
}
inherits(UnaryConstraint,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);
}
inherits(StayConstraint,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);
}
inherits(EditConstraint,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();
}
inherits(BinaryConstraint,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);
this.direction = Direction.NONE;
}
/* --- *
* S c a l e C o n s t r a i n t
* --- */
/**
* Relates two variables by the linear scaling relationship: "v2 =
* (v1 * scale) + offset". Either v1 or v2 may be changed to maintain
* this relationship but the scale factor and offset are considered
* read-only.
*/
function ScaleConstraint(src, scale, offset, dest, strength) {
this.direction = Direction.NONE;
this.scale = scale;
this.offset = offset;
ScaleConstraint.superConstructor.call(this, src, dest, strength);
}
inherits(ScaleConstraint,BinaryConstraint);
/**
* Adds this constraint to the constraint graph.
*/
ScaleConstraint.prototype.addToGraph = function () {
ScaleConstraint.superConstructor.prototype.addToGraph.call(this);
this.scale.addConstraint(this);
this.offset.addConstraint(this);
}
ScaleConstraint.prototype.removeFromGraph = function () {
ScaleConstraint.superConstructor.prototype.removeFromGraph.call(this);
if (this.scale != null) this.scale.removeConstraint(this);
if (this.offset != null) this.offset.removeConstraint(this);
}
ScaleConstraint.prototype.markInputs = function (mark) {
ScaleConstraint.superConstructor.prototype.markInputs.call(this, mark);
this.scale.mark = this.offset.mark = mark;
}
/**
* Enforce this constraint. Assume that it is satisfied.
*/
ScaleConstraint.prototype.execute = function () {
if (this.direction == Direction.FORWARD) {
this.v2.value = this.v1.value * this.scale.value + this.offset.value;
} else {
this.v1.value = (this.v2.value - this.offset.value) / this.scale.value;
}
}
/**
* 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.
*/
ScaleConstraint.prototype.recalculate = function () {
var ihn = this.input(), out = this.output();
out.walkStrength = Strength.weakestOf(this.strength, ihn.walkStrength);
out.stay = ihn.stay && this.scale.stay && this.offset.stay;
if (out.stay) this.execute();
}
/* --- *
* E q u a l i t y C o n s t r a i n t
* --- */
/**
* Constrains two variables to have the same value.
*/
function EqualityConstraint(var1, var2, strength) {
EqualityConstraint.superConstructor.call(this, var1, var2, strength);
}
inherits(EqualityConstraint,BinaryConstraint);
/**
* Enforce this constraint. Assume that it is satisfied.
*/
EqualityConstraint.prototype.execute = function () {
this.output().value = this.input().value;
}
/* --- *
* V a r i a b l e
* --- */
/**
* A constrained variable. In addition to its value, it maintain the
* structure of the constraint graph, the current dataflow graph, and
* various parameters of interest to the DeltaBlue incremental
* constraint solver.
**/
function Variable(name, initialValue) {
this.value = initialValue || 0;
this.constraints = new OrderedCollection();
this.determinedBy = null;
this.mark = 0;
this.walkStrength = Strength.WEAKEST;
this.stay = true;
this.name = name;
}
/**
* Add the given constraint to the set of all constraints that refer
* this variable.
*/
Variable.prototype.addConstraint = function (c) {
this.constraints.add(c);
}
/**
* Removes all traces of c from this variable.
*/
Variable.prototype.removeConstraint = function (c) {
this.constraints.remove(c);
if (this.determinedBy == c) this.determinedBy = null;
}
/* --- *
* P l a n n e r
* --- */
/**
* The DeltaBlue planner
*/
function Planner() {
this.currentMark = 0;
}
/**
* Attempt to satisfy the given constraint and, if successful,
* incrementally update the dataflow graph. Details: If satifying
* the constraint is successful, it may override a weaker constraint
* on its output. The algorithm attempts to resatisfy that
* constraint using some other method. This process is repeated
* until either a) it reaches a variable that was not previously
* determined by any constraint or b) it reaches a constraint that
* is too weak to be satisfied using any of its methods. The
* variables of constraints that have been processed are marked with
* a unique mark value so that we know where we've been. This allows
* the algorithm to avoid getting into an infinite loop even if the
* constraint graph has an inadvertent cycle.
*/
Planner.prototype.incrementalAdd = function (c) {
var mark = this.newMark();
var overridden = c.satisfy(mark);
while (overridden != null)
overridden = overridden.satisfy(mark);
}
/**
* Entry point for retracting a constraint. Remove the given
* constraint and incrementally update the dataflow graph.
* Details: Retracting the given constraint may allow some currently
* unsatisfiable downstream constraint to be satisfied. We therefore collect
* a list of unsatisfied downstream constraints and attempt to
* satisfy each one in turn. This list is traversed by constraint
* strength, strongest first, as a heuristic for avoiding
* unnecessarily adding and then overriding weak constraints.
* Assume: c is satisfied.
*/
Planner.prototype.incrementalRemove = function (c) {
var out = c.output();
c.markUnsatisfied();
c.removeFromGraph();
var unsatisfied = this.removePropagateFrom(out);
var strength = Strength.REQUIRED;
do {
for (var i = 0; i < unsatisfied.size(); i++) {
var u = unsatisfied.at(i);
if (u.strength == strength)
this.incrementalAdd(u);
}
strength = strength.nextWeaker();
} while (strength != Strength.WEAKEST);
}
/**
* Select a previously unused mark value.
*/
Planner.prototype.newMark = function () {
return ++this.currentMark;
}
/**
* Extract a plan for resatisfaction starting from the given source
* constraints, usually a set of input constraints. This method
* assumes that stay optimization is desired; the plan will contain
* only constraints whose output variables are not stay. Constraints
* that do no computation, such as stay and edit constraints, are
* not included in the plan.
* Details: The outputs of a constraint are marked when it is added
* to the plan under construction. A constraint may be appended to
* the plan when all its input variables are known. A variable is
* known if either a) the variable is marked (indicating that has
* been computed by a constraint appearing earlier in the plan), b)
* the variable is 'stay' (i.e. it is a constant at plan execution
* time), or c) the variable is not determined by any
* constraint. The last provision is for past states of history
* variables, which are not stay but which are also not computed by
* any constraint.
* Assume: sources are all satisfied.
*/
Planner.prototype.makePlan = function (sources) {
var mark = this.newMark();
var plan = new Plan();
var todo = sources;
while (todo.size() > 0) {
var c = todo.removeFirst();
if (c.output().mark != mark && c.inputsKnown(mark)) {
plan.addConstraint(c);
c.output().mark = mark;
this.addConstraintsConsumingTo(c.output(), todo);
}
}
return plan;
}
/**
* Extract a plan for resatisfying starting from the output of the
* given constraints, usually a set of input constraints.
*/
Planner.prototype.extractPlanFromConstraints = function (constraints) {
var sources = new OrderedCollection();
for (var i = 0; i < constraints.size(); i++) {
var c = constraints.at(i);
if (c.isInput() && c.isSatisfied())
// not in plan already and eligible for inclusion
sources.add(c);
}
return this.makePlan(sources);
}
/**
* Recompute the walkabout strengths and stay flags of all variables
* downstream of the given constraint and recompute the actual
* values of all variables whose stay flag is true. If a cycle is
* detected, remove the given constraint and answer
* false. Otherwise, answer true.
* Details: Cycles are detected when a marked variable is
* encountered downstream of the given constraint. The sender is
* assumed to have marked the inputs of the given constraint with
* the given mark. Thus, encountering a marked node downstream of
* the output constraint means that there is a path from the
* constraint's output to one of its inputs.
*/
Planner.prototype.addPropagate = function (c, mark) {
var todo = new OrderedCollection();
todo.add(c);
while (todo.size() > 0) {
var d = todo.removeFirst();
if (d.output().mark == mark) {
this.incrementalRemove(c);
return false;
}
d.recalculate();
this.addConstraintsConsumingTo(d.output(), todo);
}
return true;
}
/**
* Update the walkabout strengths and stay flags of all variables
* downstream of the given constraint. Answer a collection of
* unsatisfied constraints sorted in order of decreasing strength.
*/
Planner.prototype.removePropagateFrom = function (out) {
out.determinedBy = null;
out.walkStrength = Strength.WEAKEST;
out.stay = true;
var unsatisfied = new OrderedCollection();
var todo = new OrderedCollection();
todo.add(out);
while (todo.size() > 0) {
var v = todo.removeFirst();
for (var i = 0; i < v.constraints.size(); i++) {
var c = v.constraints.at(i);
if (!c.isSatisfied())
unsatisfied.add(c);
}
var determining = v.determinedBy;
for (var i = 0; i < v.constraints.size(); i++) {
var next = v.constraints.at(i);
if (next != determining && next.isSatisfied()) {
next.recalculate();
todo.add(next.output());
}
}
}
return unsatisfied;
}
Planner.prototype.addConstraintsConsumingTo = function (v, coll) {
var determining = v.determinedBy;
var cc = v.constraints;
for (var i = 0; i < cc.size(); i++) {
var c = cc.at(i);
if (c != determining && c.isSatisfied())
coll.add(c);
}
}
/* --- *
* P l a n
* --- */
/**
* A Plan is an ordered list of constraints to be executed in sequence
* to resatisfy all currently satisfiable constraints in the face of
* one or more changing inputs.
*/
function Plan() {
this.v = new OrderedCollection();
}
Plan.prototype.addConstraint = function (c) {
this.v.add(c);
}
Plan.prototype.size = function () {
return this.v.size();
}
Plan.prototype.constraintAt = function (index) {
return this.v.at(index);
}
Plan.prototype.execute = function () {
for (var i = 0; i < this.size(); i++) {
var c = this.constraintAt(i);
c.execute();
}
}
/* --- *
* M a i n
* --- */
/**
* This is the standard DeltaBlue benchmark. A long chain of equality
* constraints is constructed with a stay constraint on one end. An
* edit constraint is then added to the opposite end and the time is
* measured for adding and removing this constraint, and extracting
* and executing a constraint satisfaction plan. There are two cases.
* In case 1, the added constraint is stronger than the stay
* constraint and values must propagate down the entire length of the
* chain. In case 2, the added constraint is weaker than the stay
* constraint so it cannot be accomodated. The cost in this case is,
* of course, very low. Typical situations lie somewhere between these
* two extremes.
*/
function chainTest(n) {
planner = new Planner();
var prev = null, first = null, last = null;
// Build chain of n equality constraints
for (var i = 0; i <= n; i++) {
var name = "v" + i;
var v = new Variable(name);
if (prev != null)
new EqualityConstraint(prev, v, Strength.REQUIRED);
if (i == 0) first = v;
if (i == n) last = v;
prev = v;
}
new StayConstraint(last, Strength.STRONG_DEFAULT);
var edit = new EditConstraint(first, Strength.PREFERRED);
var edits = new OrderedCollection();
edits.add(edit);
var plan = planner.extractPlanFromConstraints(edits);
for (var i = 0; i < 100; i++) {
first.value = i;
plan.execute();
if (last.value != i)
alert("Chain test failed.");
}
}
/**
* This test constructs a two sets of variables related to each
* other by a simple linear transformation (scale and offset). The
* time is measured to change a variable on either side of the
* mapping and to change the scale and offset factors.
*/
function projectionTest(n) {
planner = new Planner();
var scale = new Variable("scale", 10);
var offset = new Variable("offset", 1000);
var src = null, dst = null;
var dests = new OrderedCollection();
for (var i = 0; i < n; i++) {
src = new Variable("src" + i, i);
dst = new Variable("dst" + i, i);
dests.add(dst);
new StayConstraint(src, Strength.NORMAL);
new ScaleConstraint(src, scale, offset, dst, Strength.REQUIRED);
}
change(src, 17);
if (dst.value != 1170) alert("Projection 1 failed");
change(dst, 1050);
if (src.value != 5) alert("Projection 2 failed");
change(scale, 5);
for (var i = 0; i < n - 1; i++) {
if (dests.at(i).value != i * 5 + 1000)
alert("Projection 3 failed");
}
change(offset, 2000);
for (var i = 0; i < n - 1; i++) {
if (dests.at(i).value != i * 5 + 2000)
alert("Projection 4 failed");
}
}
function change(v, newValue) {
var edit = new EditConstraint(v, Strength.PREFERRED);
var edits = new OrderedCollection();
edits.add(edit);
var plan = planner.extractPlanFromConstraints(edits);
for (var i = 0; i < 10; i++) {
v.value = newValue;
plan.execute();
}
edit.destroyConstraint();
}
// Global variable holding the current planner.
var planner = null;
window.onload = function(){ startTest("v8-deltablue", 'b95228dc');
test("Constraint Solving", function deltaBlue() {
chainTest(100);
projectionTest(100);
});
endTest(); };
</script>
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