Index: test/codegen/DeltaBlue.dart |
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-// Copyright 2011 Google Inc. All Rights Reserved. |
-// Copyright 1996 John Maloney and Mario Wolczko |
-// |
-// This file is part of GNU Smalltalk. |
-// |
-// GNU Smalltalk 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, or (at your option) any later version. |
-// |
-// GNU Smalltalk 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 |
-// GNU Smalltalk; see the file COPYING. If not, write to the Free Software |
-// Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. |
-// |
-// Translated first from Smalltalk to JavaScript, and finally to |
-// Dart by Google 2008-2010. |
- |
-/** |
- * A Dart implementation of the DeltaBlue constraint-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. |
- */ |
- |
-import "BenchmarkBase.dart"; |
- |
-main() { |
- new DeltaBlue().report(); |
-} |
- |
-/// Benchmark class required to report results. |
-class DeltaBlue extends BenchmarkBase { |
- const DeltaBlue() : super("DeltaBlue"); |
- |
- void run() { |
- chainTest(100); |
- projectionTest(100); |
- } |
-} |
- |
-/** |
- * 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 == can be used for value comparison. |
- */ |
-class Strength { |
- final int value; |
- final String name; |
- |
- const Strength(this.value, this.name); |
- |
- Strength nextWeaker() => const <Strength>[ |
- STRONG_PREFERRED, |
- PREFERRED, |
- STRONG_DEFAULT, |
- NORMAL, |
- WEAK_DEFAULT, |
- WEAKEST |
- ][value]; |
- |
- static bool stronger(Strength s1, Strength s2) { |
- return s1.value < s2.value; |
- } |
- |
- static bool weaker(Strength s1, Strength s2) { |
- return s1.value > s2.value; |
- } |
- |
- static Strength weakest(Strength s1, Strength s2) { |
- return weaker(s1, s2) ? s1 : s2; |
- } |
- |
- static Strength strongest(Strength s1, Strength s2) { |
- return stronger(s1, s2) ? s1 : s2; |
- } |
-} |
- |
-// Compile time computed constants. |
-const REQUIRED = const Strength(0, "required"); |
-const STRONG_PREFERRED = const Strength(1, "strongPreferred"); |
-const PREFERRED = const Strength(2, "preferred"); |
-const STRONG_DEFAULT = const Strength(3, "strongDefault"); |
-const NORMAL = const Strength(4, "normal"); |
-const WEAK_DEFAULT = const Strength(5, "weakDefault"); |
-const WEAKEST = const Strength(6, "weakest"); |
- |
-abstract class Constraint { |
- final Strength strength; |
- |
- const Constraint(this.strength); |
- |
- bool isSatisfied(); |
- void markUnsatisfied(); |
- void addToGraph(); |
- void removeFromGraph(); |
- void chooseMethod(int mark); |
- void markInputs(int mark); |
- bool inputsKnown(int mark); |
- Variable output(); |
- void execute(); |
- void recalculate(); |
- |
- /// Activate this constraint and attempt to satisfy it. |
- void addConstraint() { |
- 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 satisfy(mark) { |
- chooseMethod(mark); |
- if (!isSatisfied()) { |
- if (strength == REQUIRED) { |
- print("Could not satisfy a required constraint!"); |
- } |
- return null; |
- } |
- markInputs(mark); |
- Variable out = output(); |
- Constraint overridden = out.determinedBy; |
- if (overridden != null) overridden.markUnsatisfied(); |
- out.determinedBy = this; |
- if (!planner.addPropagate(this, mark)) print("Cycle encountered"); |
- out.mark = mark; |
- return overridden; |
- } |
- |
- void destroyConstraint() { |
- if (isSatisfied()) planner.incrementalRemove(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. |
- */ |
- bool isInput() => false; |
-} |
- |
-/** |
- * Abstract superclass for constraints having a single possible output variable. |
- */ |
-abstract class UnaryConstraint extends Constraint { |
- final Variable myOutput; |
- bool satisfied = false; |
- |
- UnaryConstraint(this.myOutput, Strength strength) : super(strength) { |
- addConstraint(); |
- } |
- |
- /// Adds this constraint to the constraint graph |
- void addToGraph() { |
- myOutput.addConstraint(this); |
- satisfied = false; |
- } |
- |
- /// Decides if this constraint can be satisfied and records that decision. |
- void chooseMethod(int mark) { |
- satisfied = (myOutput.mark != mark) && |
- Strength.stronger(strength, myOutput.walkStrength); |
- } |
- |
- /// Returns true if this constraint is satisfied in the current solution. |
- bool isSatisfied() => satisfied; |
- |
- void markInputs(int mark) { |
- // has no inputs. |
- } |
- |
- /// Returns the current output variable. |
- Variable output() => 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. |
- */ |
- void recalculate() { |
- myOutput.walkStrength = strength; |
- myOutput.stay = !isInput(); |
- if (myOutput.stay) execute(); // Stay optimization. |
- } |
- |
- /// Records that this constraint is unsatisfied. |
- void markUnsatisfied() { |
- satisfied = false; |
- } |
- |
- bool inputsKnown(int mark) => true; |
- |
- void removeFromGraph() { |
- if (myOutput != null) myOutput.removeConstraint(this); |
- satisfied = false; |
- } |
-} |
- |
-/** |
- * 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". |
- */ |
-class StayConstraint extends UnaryConstraint { |
- StayConstraint(Variable v, Strength str) : super(v, str); |
- |
- void execute() { |
- // Stay constraints do nothing. |
- } |
-} |
- |
-/** |
- * A unary input constraint used to mark a variable that the client |
- * wishes to change. |
- */ |
-class EditConstraint extends UnaryConstraint { |
- EditConstraint(Variable v, Strength str) : super(v, str); |
- |
- /// Edits indicate that a variable is to be changed by imperative code. |
- bool isInput() => true; |
- |
- void execute() { |
- // Edit constraints do nothing. |
- } |
-} |
- |
-// Directions. |
-const int NONE = 1; |
-const int FORWARD = 2; |
-const int BACKWARD = 0; |
- |
-/** |
- * Abstract superclass for constraints having two possible output |
- * variables. |
- */ |
-abstract class BinaryConstraint extends Constraint { |
- Variable v1; |
- Variable v2; |
- int direction = NONE; |
- |
- BinaryConstraint(this.v1, this.v2, Strength strength) : super(strength) { |
- addConstraint(); |
- } |
- |
- /** |
- * Decides if this constraint can be satisfied and which way it |
- * should flow based on the relative strength of the variables related, |
- * and record that decision. |
- */ |
- void chooseMethod(int mark) { |
- if (v1.mark == mark) { |
- direction = (v2.mark != mark && |
- Strength.stronger(strength, v2.walkStrength)) ? FORWARD : NONE; |
- } |
- if (v2.mark == mark) { |
- direction = (v1.mark != mark && |
- Strength.stronger(strength, v1.walkStrength)) ? BACKWARD : NONE; |
- } |
- if (Strength.weaker(v1.walkStrength, v2.walkStrength)) { |
- direction = |
- Strength.stronger(strength, v1.walkStrength) ? BACKWARD : NONE; |
- } else { |
- direction = |
- Strength.stronger(strength, v2.walkStrength) ? FORWARD : BACKWARD; |
- } |
- } |
- |
- /// Add this constraint to the constraint graph. |
- void addToGraph() { |
- v1.addConstraint(this); |
- v2.addConstraint(this); |
- direction = NONE; |
- } |
- |
- /// Answer true if this constraint is satisfied in the current solution. |
- bool isSatisfied() => direction != NONE; |
- |
- /// Mark the input variable with the given mark. |
- void markInputs(int mark) { |
- input().mark = mark; |
- } |
- |
- /// Returns the current input variable |
- Variable input() => direction == FORWARD ? v1 : v2; |
- |
- /// Returns the current output variable. |
- Variable output() => direction == FORWARD ? v2 : 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. |
- */ |
- void recalculate() { |
- Variable ihn = input(), |
- out = output(); |
- out.walkStrength = Strength.weakest(strength, ihn.walkStrength); |
- out.stay = ihn.stay; |
- if (out.stay) execute(); |
- } |
- |
- /// Record the fact that this constraint is unsatisfied. |
- void markUnsatisfied() { |
- direction = NONE; |
- } |
- |
- bool inputsKnown(int mark) { |
- Variable i = input(); |
- return i.mark == mark || i.stay || i.determinedBy == null; |
- } |
- |
- void removeFromGraph() { |
- if (v1 != null) v1.removeConstraint(this); |
- if (v2 != null) v2.removeConstraint(this); |
- direction = NONE; |
- } |
-} |
- |
-/** |
- * 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. |
- */ |
- |
-class ScaleConstraint extends BinaryConstraint { |
- final Variable scale; |
- final Variable offset; |
- |
- ScaleConstraint( |
- Variable src, this.scale, this.offset, Variable dest, Strength strength) |
- : super(src, dest, strength); |
- |
- /// Adds this constraint to the constraint graph. |
- void addToGraph() { |
- super.addToGraph(); |
- scale.addConstraint(this); |
- offset.addConstraint(this); |
- } |
- |
- void removeFromGraph() { |
- super.removeFromGraph(); |
- if (scale != null) scale.removeConstraint(this); |
- if (offset != null) offset.removeConstraint(this); |
- } |
- |
- void markInputs(int mark) { |
- super.markInputs(mark); |
- scale.mark = offset.mark = mark; |
- } |
- |
- /// Enforce this constraint. Assume that it is satisfied. |
- void execute() { |
- if (direction == FORWARD) { |
- v2.value = v1.value * scale.value + offset.value; |
- } else { |
- v1.value = (v2.value - offset.value) ~/ 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. |
- */ |
- void recalculate() { |
- Variable ihn = input(), |
- out = output(); |
- out.walkStrength = Strength.weakest(strength, ihn.walkStrength); |
- out.stay = ihn.stay && scale.stay && offset.stay; |
- if (out.stay) execute(); |
- } |
-} |
- |
-/** |
- * Constrains two variables to have the same value. |
- */ |
-class EqualityConstraint extends BinaryConstraint { |
- EqualityConstraint(Variable v1, Variable v2, Strength strength) |
- : super(v1, v2, strength); |
- |
- /// Enforce this constraint. Assume that it is satisfied. |
- void execute() { |
- output().value = input().value; |
- } |
-} |
- |
-/** |
- * 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. |
- **/ |
-class Variable { |
- List<Constraint> constraints = <Constraint>[]; |
- Constraint determinedBy; |
- int mark = 0; |
- Strength walkStrength = WEAKEST; |
- bool stay = true; |
- int value; |
- final String name; |
- |
- Variable(this.name, this.value); |
- |
- /** |
- * Add the given constraint to the set of all constraints that refer |
- * this variable. |
- */ |
- void addConstraint(Constraint c) { |
- constraints.add(c); |
- } |
- |
- /// Removes all traces of c from this variable. |
- void removeConstraint(Constraint c) { |
- constraints.remove(c); |
- if (determinedBy == c) determinedBy = null; |
- } |
-} |
- |
-class Planner { |
- int 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. |
- */ |
- void incrementalAdd(Constraint c) { |
- int mark = newMark(); |
- for (Constraint overridden = c.satisfy(mark); |
- 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. |
- */ |
- void incrementalRemove(Constraint c) { |
- Variable out = c.output(); |
- c.markUnsatisfied(); |
- c.removeFromGraph(); |
- List<Constraint> unsatisfied = removePropagateFrom(out); |
- Strength strength = REQUIRED; |
- do { |
- for (int i = 0; i < unsatisfied.length; i++) { |
- Constraint u = unsatisfied[i]; |
- if (u.strength == strength) incrementalAdd(u); |
- } |
- strength = strength.nextWeaker(); |
- } while (strength != WEAKEST); |
- } |
- |
- /// Select a previously unused mark value. |
- int newMark() => ++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. |
- */ |
- Plan makePlan(List<Constraint> sources) { |
- int mark = newMark(); |
- Plan plan = new Plan(); |
- List<Constraint> todo = sources; |
- while (todo.length > 0) { |
- Constraint c = todo.removeLast(); |
- if (c.output().mark != mark && c.inputsKnown(mark)) { |
- plan.addConstraint(c); |
- c.output().mark = mark; |
- 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. |
- */ |
- Plan extractPlanFromConstraints(List<Constraint> constraints) { |
- List<Constraint> sources = <Constraint>[]; |
- for (int i = 0; i < constraints.length; i++) { |
- Constraint c = constraints[i]; |
- // if not in plan already and eligible for inclusion. |
- if (c.isInput() && c.isSatisfied()) sources.add(c); |
- } |
- return 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. |
- */ |
- bool addPropagate(Constraint c, int mark) { |
- List<Constraint> todo = <Constraint>[c]; |
- while (todo.length > 0) { |
- Constraint d = todo.removeLast(); |
- if (d.output().mark == mark) { |
- incrementalRemove(c); |
- return false; |
- } |
- d.recalculate(); |
- 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. |
- */ |
- List<Constraint> removePropagateFrom(Variable out) { |
- out.determinedBy = null; |
- out.walkStrength = WEAKEST; |
- out.stay = true; |
- List<Constraint> unsatisfied = <Constraint>[]; |
- List<Variable> todo = <Variable>[out]; |
- while (todo.length > 0) { |
- Variable v = todo.removeLast(); |
- for (int i = 0; i < v.constraints.length; i++) { |
- Constraint c = v.constraints[i]; |
- if (!c.isSatisfied()) unsatisfied.add(c); |
- } |
- Constraint determining = v.determinedBy; |
- for (int i = 0; i < v.constraints.length; i++) { |
- Constraint next = v.constraints[i]; |
- if (next != determining && next.isSatisfied()) { |
- next.recalculate(); |
- todo.add(next.output()); |
- } |
- } |
- } |
- return unsatisfied; |
- } |
- |
- void addConstraintsConsumingTo(Variable v, List<Constraint> coll) { |
- Constraint determining = v.determinedBy; |
- for (int i = 0; i < v.constraints.length; i++) { |
- Constraint c = v.constraints[i]; |
- if (c != determining && c.isSatisfied()) coll.add(c); |
- } |
- } |
-} |
- |
-/** |
- * 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. |
- */ |
-class Plan { |
- List<Constraint> list = <Constraint>[]; |
- |
- void addConstraint(Constraint c) { |
- list.add(c); |
- } |
- |
- int size() => list.length; |
- |
- void execute() { |
- for (int i = 0; i < list.length; i++) { |
- list[i].execute(); |
- } |
- } |
-} |
- |
-/** |
- * 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. |
- */ |
-void chainTest(int n) { |
- planner = new Planner(); |
- Variable prev = null, |
- first = null, |
- last = null; |
- // Build chain of n equality constraints. |
- for (int i = 0; i <= n; i++) { |
- Variable v = new Variable("v", 0); |
- if (prev != null) new EqualityConstraint(prev, v, REQUIRED); |
- if (i == 0) first = v; |
- if (i == n) last = v; |
- prev = v; |
- } |
- new StayConstraint(last, STRONG_DEFAULT); |
- EditConstraint edit = new EditConstraint(first, PREFERRED); |
- Plan plan = planner.extractPlanFromConstraints(<Constraint>[edit]); |
- for (int i = 0; i < 100; i++) { |
- first.value = i; |
- plan.execute(); |
- if (last.value != i) { |
- print("Chain test failed:"); |
- print("Expected last value to be $i but it was ${last.value}."); |
- } |
- } |
-} |
- |
-/** |
- * 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. |
- */ |
-void projectionTest(int n) { |
- planner = new Planner(); |
- Variable scale = new Variable("scale", 10); |
- Variable offset = new Variable("offset", 1000); |
- Variable src = null, |
- dst = null; |
- |
- List<Variable> dests = <Variable>[]; |
- for (int i = 0; i < n; i++) { |
- src = new Variable("src", i); |
- dst = new Variable("dst", i); |
- dests.add(dst); |
- new StayConstraint(src, NORMAL); |
- new ScaleConstraint(src, scale, offset, dst, REQUIRED); |
- } |
- change(src, 17); |
- if (dst.value != 1170) print("Projection 1 failed"); |
- change(dst, 1050); |
- if (src.value != 5) print("Projection 2 failed"); |
- change(scale, 5); |
- for (int i = 0; i < n - 1; i++) { |
- if (dests[i].value != i * 5 + 1000) print("Projection 3 failed"); |
- } |
- change(offset, 2000); |
- for (int i = 0; i < n - 1; i++) { |
- if (dests[i].value != i * 5 + 2000) print("Projection 4 failed"); |
- } |
-} |
- |
-void change(Variable v, int newValue) { |
- EditConstraint edit = new EditConstraint(v, PREFERRED); |
- Plan plan = planner.extractPlanFromConstraints(<EditConstraint>[edit]); |
- for (int i = 0; i < 10; i++) { |
- v.value = newValue; |
- plan.execute(); |
- } |
- edit.destroyConstraint(); |
-} |
- |
-Planner planner; |