chrome/test/data/dromaeo/tests/v8-deltablue.html

   1 <html>
   2 <head>
   3 <script src="../htmlrunner.js"></script>
   4 <script>
   5 // Copyright 2008 the V8 project authors. All rights reserved.
   6 // Copyright 1996 John Maloney and Mario Wolczko.
   7
   8 // This program is free software; you can redistribute it and/or modify
   9 // it under the terms of the GNU General Public License as published by
  10 // the Free Software Foundation; either version 2 of the License, or
  11 // (at your option) any later version.
  12 //
  13 // This program is distributed in the hope that it will be useful,
  14 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16 // GNU General Public License for more details.
  17 //
  18 // You should have received a copy of the GNU General Public License
  19 // along with this program; if not, write to the Free Software
  20 // Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  21
  22
  23 // This implementation of the DeltaBlue benchmark is derived
  24 // from the Smalltalk implementation by John Maloney and Mario
  25 // Wolczko. Some parts have been translated directly, whereas
  26 // others have been modified more aggresively to make it feel
  27 // more like a JavaScript program.
  28
  29
  30 /**
  31  * A JavaScript implementation of the DeltaBlue constrain-solving
  32  * algorithm, as described in:
  33  *
  34  * "The DeltaBlue Algorithm: An Incremental Constraint Hierarchy Solver"
  35  *   Bjorn N. Freeman-Benson and John Maloney
  36  *   January 1990 Communications of the ACM,
  37  *   also available as University of Washington TR 89-08-06.
  38  *
  39  * Beware: this benchmark is written in a grotesque style where
  40  * the constraint model is built by side-effects from constructors.
  41  * I've kept it this way to avoid deviating too much from the original
  42  * implementation.
  43  */
  44
  45
  46 /* --- O b j e c t   M o d e l --- */
  47
  48 function inherits(orig, shuper) {
  49   function Inheriter() { }
  50   Inheriter.prototype = shuper.prototype;
  51   orig.prototype = new Inheriter();
  52   orig.superConstructor = shuper;
  53 }
  54
  55 function OrderedCollection() {
  56   this.elms = new Array();
  57 }
  58
  59 OrderedCollection.prototype.add = function (elm) {
  60   this.elms.push(elm);
  61 }
  62
  63 OrderedCollection.prototype.at = function (index) {
  64   return this.elms[index];
  65 }
  66
  67 OrderedCollection.prototype.size = function () {
  68   return this.elms.length;
  69 }
  70
  71 OrderedCollection.prototype.removeFirst = function () {
  72   return this.elms.pop();
  73 }
  74
  75 OrderedCollection.prototype.remove = function (elm) {
  76   var index = 0, skipped = 0;
  77   for (var i = 0; i < this.elms.length; i++) {
  78     var value = this.elms[i];
  79     if (value != elm) {
  80       this.elms[index] = value;
  81       index++;
  82     } else {
  83       skipped++;
  84     }
  85   }
  86   for (var i = 0; i < skipped; i++)
  87     this.elms.pop();
  88 }
  89
  90 /* --- *
  91  * S t r e n g t h
  92  * --- */
  93
  94 /**
  95  * Strengths are used to measure the relative importance of constraints.
  96  * New strengths may be inserted in the strength hierarchy without
  97  * disrupting current constraints.  Strengths cannot be created outside
  98  * this class, so pointer comparison can be used for value comparison.
  99  */
 100 function Strength(strengthValue, name) {
 101   this.strengthValue = strengthValue;
 102   this.name = name;
 103 }
 104
 105 Strength.stronger = function (s1, s2) {
 106   return s1.strengthValue < s2.strengthValue;
 107 }
 108
 109 Strength.weaker = function (s1, s2) {
 110   return s1.strengthValue > s2.strengthValue;
 111 }
 112
 113 Strength.weakestOf = function (s1, s2) {
 114   return this.weaker(s1, s2) ? s1 : s2;
 115 }
 116
 117 Strength.strongest = function (s1, s2) {
 118   return this.stronger(s1, s2) ? s1 : s2;
 119 }
 120
 121 Strength.prototype.nextWeaker = function () {
 122   switch (this.strengthValue) {
 123     case 0: return Strength.WEAKEST;
 124     case 1: return Strength.WEAK_DEFAULT;
 125     case 2: return Strength.NORMAL;
 126     case 3: return Strength.STRONG_DEFAULT;
 127     case 4: return Strength.PREFERRED;
 128     case 5: return Strength.REQUIRED;
 129   }
 130 }
 131
 132 // Strength constants.
 133 Strength.REQUIRED        = new Strength(0, "required");
 134 Strength.STONG_PREFERRED = new Strength(1, "strongPreferred");
 135 Strength.PREFERRED       = new Strength(2, "preferred");
 136 Strength.STRONG_DEFAULT  = new Strength(3, "strongDefault");
 137 Strength.NORMAL          = new Strength(4, "normal");
 138 Strength.WEAK_DEFAULT    = new Strength(5, "weakDefault");
 139 Strength.WEAKEST         = new Strength(6, "weakest");
 140
 141 /* --- *
 142  * C o n s t r a i n t
 143  * --- */
 144
 145 /**
 146  * An abstract class representing a system-maintainable relationship
 147  * (or "constraint") between a set of variables. A constraint supplies
 148  * a strength instance variable; concrete subclasses provide a means
 149  * of storing the constrained variables and other information required
 150  * to represent a constraint.
 151  */
 152 function Constraint(strength) {
 153   this.strength = strength;
 154 }
 155
 156 /**
 157  * Activate this constraint and attempt to satisfy it.
 158  */
 159 Constraint.prototype.addConstraint = function () {
 160   this.addToGraph();
 161   planner.incrementalAdd(this);
 162 }
 163
 164 /**
 165  * Attempt to find a way to enforce this constraint. If successful,
 166  * record the solution, perhaps modifying the current dataflow
 167  * graph. Answer the constraint that this constraint overrides, if
 168  * there is one, or nil, if there isn't.
 169  * Assume: I am not already satisfied.
 170  */
 171 Constraint.prototype.satisfy = function (mark) {
 172   this.chooseMethod(mark);
 173   if (!this.isSatisfied()) {
 174     if (this.strength == Strength.REQUIRED)
 175       alert("Could not satisfy a required constraint!");
 176     return null;
 177   }
 178   this.markInputs(mark);
 179   var out = this.output();
 180   var overridden = out.determinedBy;
 181   if (overridden != null) overridden.markUnsatisfied();
 182   out.determinedBy = this;
 183   if (!planner.addPropagate(this, mark))
 184     alert("Cycle encountered");
 185   out.mark = mark;
 186   return overridden;
 187 }
 188
 189 Constraint.prototype.destroyConstraint = function () {
 190   if (this.isSatisfied()) planner.incrementalRemove(this);
 191   else this.removeFromGraph();
 192 }
 193
 194 /**
 195  * Normal constraints are not input constraints.  An input constraint
 196  * is one that depends on external state, such as the mouse, the
 197  * keybord, a clock, or some arbitraty piece of imperative code.
 198  */
 199 Constraint.prototype.isInput = function () {
 200   return false;
 201 }
 202
 203 /* --- *
 204  * U n a r y   C o n s t r a i n t
 205  * --- */
 206
 207 /**
 208  * Abstract superclass for constraints having a single possible output
 209  * variable.
 210  */
 211 function UnaryConstraint(v, strength) {
 212   UnaryConstraint.superConstructor.call(this, strength);
 213   this.myOutput = v;
 214   this.satisfied = false;
 215   this.addConstraint();
 216 }
 217
 218 inherits(UnaryConstraint,Constraint);
 219
 220 /**
 221  * Adds this constraint to the constraint graph
 222  */
 223 UnaryConstraint.prototype.addToGraph = function () {
 224   this.myOutput.addConstraint(this);
 225   this.satisfied = false;
 226 }
 227
 228 /**
 229  * Decides if this constraint can be satisfied and records that
 230  * decision.
 231  */
 232 UnaryConstraint.prototype.chooseMethod = function (mark) {
 233   this.satisfied = (this.myOutput.mark != mark)
 234     && Strength.stronger(this.strength, this.myOutput.walkStrength);
 235 }
 236
 237 /**
 238  * Returns true if this constraint is satisfied in the current solution.
 239  */
 240 UnaryConstraint.prototype.isSatisfied = function () {
 241   return this.satisfied;
 242 }
 243
 244 UnaryConstraint.prototype.markInputs = function (mark) {
 245   // has no inputs
 246 }
 247
 248 /**
 249  * Returns the current output variable.
 250  */
 251 UnaryConstraint.prototype.output = function () {
 252   return this.myOutput;
 253 }
 254
 255 /**
 256  * Calculate the walkabout strength, the stay flag, and, if it is
 257  * 'stay', the value for the current output of this constraint. Assume
 258  * this constraint is satisfied.
 259  */
 260 UnaryConstraint.prototype.recalculate = function () {
 261   this.myOutput.walkStrength = this.strength;
 262   this.myOutput.stay = !this.isInput();
 263   if (this.myOutput.stay) this.execute(); // Stay optimization
 264 }
 265
 266 /**
 267  * Records that this constraint is unsatisfied
 268  */
 269 UnaryConstraint.prototype.markUnsatisfied = function () {
 270   this.satisfied = false;
 271 }
 272
 273 UnaryConstraint.prototype.inputsKnown = function () {
 274   return true;
 275 }
 276
 277 UnaryConstraint.prototype.removeFromGraph = function () {
 278   if (this.myOutput != null) this.myOutput.removeConstraint(this);
 279   this.satisfied = false;
 280 }
 281
 282 /* --- *
 283  * S t a y   C o n s t r a i n t
 284  * --- */
 285
 286 /**
 287  * Variables that should, with some level of preference, stay the same.
 288  * Planners may exploit the fact that instances, if satisfied, will not
 289  * change their output during plan execution.  This is called "stay
 290  * optimization".
 291  */
 292 function StayConstraint(v, str) {
 293   StayConstraint.superConstructor.call(this, v, str);
 294 }
 295
 296 inherits(StayConstraint,UnaryConstraint);
 297
 298 StayConstraint.prototype.execute = function () {
 299   // Stay constraints do nothing
 300 }
 301
 302 /* --- *
 303  * E d i t   C o n s t r a i n t
 304  * --- */
 305
 306 /**
 307  * A unary input constraint used to mark a variable that the client
 308  * wishes to change.
 309  */
 310 function EditConstraint(v, str) {
 311   EditConstraint.superConstructor.call(this, v, str);
 312 }
 313
 314 inherits(EditConstraint,UnaryConstraint);
 315
 316 /**
 317  * Edits indicate that a variable is to be changed by imperative code.
 318  */
 319 EditConstraint.prototype.isInput = function () {
 320   return true;
 321 }
 322
 323 EditConstraint.prototype.execute = function () {
 324   // Edit constraints do nothing
 325 }
 326
 327 /* --- *
 328  * B i n a r y   C o n s t r a i n t
 329  * --- */
 330
 331 var Direction = new Object();
 332 Direction.NONE     = 0;
 333 Direction.FORWARD  = 1;
 334 Direction.BACKWARD = -1;
 335
 336 /**
 337  * Abstract superclass for constraints having two possible output
 338  * variables.
 339  */
 340 function BinaryConstraint(var1, var2, strength) {
 341   BinaryConstraint.superConstructor.call(this, strength);
 342   this.v1 = var1;
 343   this.v2 = var2;
 344   this.direction = Direction.NONE;
 345   this.addConstraint();
 346 }
 347
 348 inherits(BinaryConstraint,Constraint);
 349
 350 /**
 351  * Decides if this constratint can be satisfied and which way it
 352  * should flow based on the relative strength of the variables related,
 353  * and record that decision.
 354  */
 355 BinaryConstraint.prototype.chooseMethod = function (mark) {
 356   if (this.v1.mark == mark) {
 357     this.direction = (this.v1.mark != mark && Strength.stronger(this.strength, this.v2.walkStrength))
 358       ? Direction.FORWARD
 359       : Direction.NONE;
 360   }
 361   if (this.v2.mark == mark) {
 362     this.direction = (this.v1.mark != mark && Strength.stronger(this.strength, this.v1.walkStrength))
 363       ? Direction.BACKWARD
 364       : Direction.NONE;
 365   }
 366   if (Strength.weaker(this.v1.walkStrength, this.v2.walkStrength)) {
 367     this.direction = Strength.stronger(this.strength, this.v1.walkStrength)
 368       ? Direction.BACKWARD
 369       : Direction.NONE;
 370   } else {
 371     this.direction = Strength.stronger(this.strength, this.v2.walkStrength)
 372       ? Direction.FORWARD
 373       : Direction.BACKWARD
 374   }
 375 }
 376
 377 /**
 378  * Add this constraint to the constraint graph
 379  */
 380 BinaryConstraint.prototype.addToGraph = function () {
 381   this.v1.addConstraint(this);
 382   this.v2.addConstraint(this);
 383   this.direction = Direction.NONE;
 384 }
 385
 386 /**
 387  * Answer true if this constraint is satisfied in the current solution.
 388  */
 389 BinaryConstraint.prototype.isSatisfied = function () {
 390   return this.direction != Direction.NONE;
 391 }
 392
 393 /**
 394  * Mark the input variable with the given mark.
 395  */
 396 BinaryConstraint.prototype.markInputs = function (mark) {
 397   this.input().mark = mark;
 398 }
 399
 400 /**
 401  * Returns the current input variable
 402  */
 403 BinaryConstraint.prototype.input = function () {
 404   return (this.direction == Direction.FORWARD) ? this.v1 : this.v2;
 405 }
 406
 407 /**
 408  * Returns the current output variable
 409  */
 410 BinaryConstraint.prototype.output = function () {
 411   return (this.direction == Direction.FORWARD) ? this.v2 : this.v1;
 412 }
 413
 414 /**
 415  * Calculate the walkabout strength, the stay flag, and, if it is
 416  * 'stay', the value for the current output of this
 417  * constraint. Assume this constraint is satisfied.
 418  */
 419 BinaryConstraint.prototype.recalculate = function () {
 420   var ihn = this.input(), out = this.output();
 421   out.walkStrength = Strength.weakestOf(this.strength, ihn.walkStrength);
 422   out.stay = ihn.stay;
 423   if (out.stay) this.execute();
 424 }
 425
 426 /**
 427  * Record the fact that this constraint is unsatisfied.
 428  */
 429 BinaryConstraint.prototype.markUnsatisfied = function () {
 430   this.direction = Direction.NONE;
 431 }
 432
 433 BinaryConstraint.prototype.inputsKnown = function (mark) {
 434   var i = this.input();
 435   return i.mark == mark || i.stay || i.determinedBy == null;
 436 }
 437
 438 BinaryConstraint.prototype.removeFromGraph = function () {
 439   if (this.v1 != null) this.v1.removeConstraint(this);
 440   if (this.v2 != null) this.v2.removeConstraint(this);
 441   this.direction = Direction.NONE;
 442 }
 443
 444 /* --- *
 445  * S c a l e   C o n s t r a i n t
 446  * --- */
 447
 448 /**
 449  * Relates two variables by the linear scaling relationship: "v2 =
 450  * (v1 * scale) + offset". Either v1 or v2 may be changed to maintain
 451  * this relationship but the scale factor and offset are considered
 452  * read-only.
 453  */
 454 function ScaleConstraint(src, scale, offset, dest, strength) {
 455   this.direction = Direction.NONE;
 456   this.scale = scale;
 457   this.offset = offset;
 458   ScaleConstraint.superConstructor.call(this, src, dest, strength);
 459 }
 460
 461 inherits(ScaleConstraint,BinaryConstraint);
 462
 463 /**
 464  * Adds this constraint to the constraint graph.
 465  */
 466 ScaleConstraint.prototype.addToGraph = function () {
 467   ScaleConstraint.superConstructor.prototype.addToGraph.call(this);
 468   this.scale.addConstraint(this);
 469   this.offset.addConstraint(this);
 470 }
 471
 472 ScaleConstraint.prototype.removeFromGraph = function () {
 473   ScaleConstraint.superConstructor.prototype.removeFromGraph.call(this);
 474   if (this.scale != null) this.scale.removeConstraint(this);
 475   if (this.offset != null) this.offset.removeConstraint(this);
 476 }
 477
 478 ScaleConstraint.prototype.markInputs = function (mark) {
 479   ScaleConstraint.superConstructor.prototype.markInputs.call(this, mark);
 480   this.scale.mark = this.offset.mark = mark;
 481 }
 482
 483 /**
 484  * Enforce this constraint. Assume that it is satisfied.
 485  */
 486 ScaleConstraint.prototype.execute = function () {
 487   if (this.direction == Direction.FORWARD) {
 488     this.v2.value = this.v1.value * this.scale.value + this.offset.value;
 489   } else {
 490     this.v1.value = (this.v2.value - this.offset.value) / this.scale.value;
 491   }
 492 }
 493
 494 /**
 495  * Calculate the walkabout strength, the stay flag, and, if it is
 496  * 'stay', the value for the current output of this constraint. Assume
 497  * this constraint is satisfied.
 498  */
 499 ScaleConstraint.prototype.recalculate = function () {
 500   var ihn = this.input(), out = this.output();
 501   out.walkStrength = Strength.weakestOf(this.strength, ihn.walkStrength);
 502   out.stay = ihn.stay && this.scale.stay && this.offset.stay;
 503   if (out.stay) this.execute();
 504 }
 505
 506 /* --- *
 507  * E q u a l i t  y   C o n s t r a i n t
 508  * --- */
 509
 510 /**
 511  * Constrains two variables to have the same value.
 512  */
 513 function EqualityConstraint(var1, var2, strength) {
 514   EqualityConstraint.superConstructor.call(this, var1, var2, strength);
 515 }
 516
 517 inherits(EqualityConstraint,BinaryConstraint);
 518
 519 /**
 520  * Enforce this constraint. Assume that it is satisfied.
 521  */
 522 EqualityConstraint.prototype.execute = function () {
 523   this.output().value = this.input().value;
 524 }
 525
 526 /* --- *
 527  * V a r i a b l e
 528  * --- */
 529
 530 /**
 531  * A constrained variable. In addition to its value, it maintain the
 532  * structure of the constraint graph, the current dataflow graph, and
 533  * various parameters of interest to the DeltaBlue incremental
 534  * constraint solver.
 535  **/
 536 function Variable(name, initialValue) {
 537   this.value = initialValue || 0;
 538   this.constraints = new OrderedCollection();
 539   this.determinedBy = null;
 540   this.mark = 0;
 541   this.walkStrength = Strength.WEAKEST;
 542   this.stay = true;
 543   this.name = name;
 544 }
 545
 546 /**
 547  * Add the given constraint to the set of all constraints that refer
 548  * this variable.
 549  */
 550 Variable.prototype.addConstraint = function (c) {
 551   this.constraints.add(c);
 552 }
 553
 554 /**
 555  * Removes all traces of c from this variable.
 556  */
 557 Variable.prototype.removeConstraint = function (c) {
 558   this.constraints.remove(c);
 559   if (this.determinedBy == c) this.determinedBy = null;
 560 }
 561
 562 /* --- *
 563  * P l a n n e r
 564  * --- */
 565
 566 /**
 567  * The DeltaBlue planner
 568  */
 569 function Planner() {
 570   this.currentMark = 0;
 571 }
 572
 573 /**
 574  * Attempt to satisfy the given constraint and, if successful,
 575  * incrementally update the dataflow graph.  Details: If satifying
 576  * the constraint is successful, it may override a weaker constraint
 577  * on its output. The algorithm attempts to resatisfy that
 578  * constraint using some other method. This process is repeated
 579  * until either a) it reaches a variable that was not previously
 580  * determined by any constraint or b) it reaches a constraint that
 581  * is too weak to be satisfied using any of its methods. The
 582  * variables of constraints that have been processed are marked with
 583  * a unique mark value so that we know where we've been. This allows
 584  * the algorithm to avoid getting into an infinite loop even if the
 585  * constraint graph has an inadvertent cycle.
 586  */
 587 Planner.prototype.incrementalAdd = function (c) {
 588   var mark = this.newMark();
 589   var overridden = c.satisfy(mark);
 590   while (overridden != null)
 591     overridden = overridden.satisfy(mark);
 592 }
 593
 594 /**
 595  * Entry point for retracting a constraint. Remove the given
 596  * constraint and incrementally update the dataflow graph.
 597  * Details: Retracting the given constraint may allow some currently
 598  * unsatisfiable downstream constraint to be satisfied. We therefore collect
 599  * a list of unsatisfied downstream constraints and attempt to
 600  * satisfy each one in turn. This list is traversed by constraint
 601  * strength, strongest first, as a heuristic for avoiding
 602  * unnecessarily adding and then overriding weak constraints.
 603  * Assume: c is satisfied.
 604  */
 605 Planner.prototype.incrementalRemove = function (c) {
 606   var out = c.output();
 607   c.markUnsatisfied();
 608   c.removeFromGraph();
 609   var unsatisfied = this.removePropagateFrom(out);
 610   var strength = Strength.REQUIRED;
 611   do {
 612     for (var i = 0; i < unsatisfied.size(); i++) {
 613       var u = unsatisfied.at(i);
 614       if (u.strength == strength)
 615         this.incrementalAdd(u);
 616     }
 617     strength = strength.nextWeaker();
 618   } while (strength != Strength.WEAKEST);
 619 }
 620
 621 /**
 622  * Select a previously unused mark value.
 623  */
 624 Planner.prototype.newMark = function () {
 625   return ++this.currentMark;
 626 }
 627
 628 /**
 629  * Extract a plan for resatisfaction starting from the given source
 630  * constraints, usually a set of input constraints. This method
 631  * assumes that stay optimization is desired; the plan will contain
 632  * only constraints whose output variables are not stay. Constraints
 633  * that do no computation, such as stay and edit constraints, are
 634  * not included in the plan.
 635  * Details: The outputs of a constraint are marked when it is added
 636  * to the plan under construction. A constraint may be appended to
 637  * the plan when all its input variables are known. A variable is
 638  * known if either a) the variable is marked (indicating that has
 639  * been computed by a constraint appearing earlier in the plan), b)
 640  * the variable is 'stay' (i.e. it is a constant at plan execution
 641  * time), or c) the variable is not determined by any
 642  * constraint. The last provision is for past states of history
 643  * variables, which are not stay but which are also not computed by
 644  * any constraint.
 645  * Assume: sources are all satisfied.
 646  */
 647 Planner.prototype.makePlan = function (sources) {
 648   var mark = this.newMark();
 649   var plan = new Plan();
 650   var todo = sources;
 651   while (todo.size() > 0) {
 652     var c = todo.removeFirst();
 653     if (c.output().mark != mark && c.inputsKnown(mark)) {
 654       plan.addConstraint(c);
 655       c.output().mark = mark;
 656       this.addConstraintsConsumingTo(c.output(), todo);
 657     }
 658   }
 659   return plan;
 660 }
 661
 662 /**
 663  * Extract a plan for resatisfying starting from the output of the
 664  * given constraints, usually a set of input constraints.
 665  */
 666 Planner.prototype.extractPlanFromConstraints = function (constraints) {
 667   var sources = new OrderedCollection();
 668   for (var i = 0; i < constraints.size(); i++) {
 669     var c = constraints.at(i);
 670     if (c.isInput() && c.isSatisfied())
 671       // not in plan already and eligible for inclusion
 672       sources.add(c);
 673   }
 674   return this.makePlan(sources);
 675 }
 676
 677 /**
 678  * Recompute the walkabout strengths and stay flags of all variables
 679  * downstream of the given constraint and recompute the actual
 680  * values of all variables whose stay flag is true. If a cycle is
 681  * detected, remove the given constraint and answer
 682  * false. Otherwise, answer true.
 683  * Details: Cycles are detected when a marked variable is
 684  * encountered downstream of the given constraint. The sender is
 685  * assumed to have marked the inputs of the given constraint with
 686  * the given mark. Thus, encountering a marked node downstream of
 687  * the output constraint means that there is a path from the
 688  * constraint's output to one of its inputs.
 689  */
 690 Planner.prototype.addPropagate = function (c, mark) {
 691   var todo = new OrderedCollection();
 692   todo.add(c);
 693   while (todo.size() > 0) {
 694     var d = todo.removeFirst();
 695     if (d.output().mark == mark) {
 696       this.incrementalRemove(c);
 697       return false;
 698     }
 699     d.recalculate();
 700     this.addConstraintsConsumingTo(d.output(), todo);
 701   }
 702   return true;
 703 }
 704
 705
 706 /**
 707  * Update the walkabout strengths and stay flags of all variables
 708  * downstream of the given constraint. Answer a collection of
 709  * unsatisfied constraints sorted in order of decreasing strength.
 710  */
 711 Planner.prototype.removePropagateFrom = function (out) {
 712   out.determinedBy = null;
 713   out.walkStrength = Strength.WEAKEST;
 714   out.stay = true;
 715   var unsatisfied = new OrderedCollection();
 716   var todo = new OrderedCollection();
 717   todo.add(out);
 718   while (todo.size() > 0) {
 719     var v = todo.removeFirst();
 720     for (var i = 0; i < v.constraints.size(); i++) {
 721       var c = v.constraints.at(i);
 722       if (!c.isSatisfied())
 723         unsatisfied.add(c);
 724     }
 725     var determining = v.determinedBy;
 726     for (var i = 0; i < v.constraints.size(); i++) {
 727       var next = v.constraints.at(i);
 728       if (next != determining && next.isSatisfied()) {
 729         next.recalculate();
 730         todo.add(next.output());
 731       }
 732     }
 733   }
 734   return unsatisfied;
 735 }
 736
 737 Planner.prototype.addConstraintsConsumingTo = function (v, coll) {
 738   var determining = v.determinedBy;
 739   var cc = v.constraints;
 740   for (var i = 0; i < cc.size(); i++) {
 741     var c = cc.at(i);
 742     if (c != determining && c.isSatisfied())
 743       coll.add(c);
 744   }
 745 }
 746
 747 /* --- *
 748  * P l a n
 749  * --- */
 750
 751 /**
 752  * A Plan is an ordered list of constraints to be executed in sequence
 753  * to resatisfy all currently satisfiable constraints in the face of
 754  * one or more changing inputs.
 755  */
 756 function Plan() {
 757   this.v = new OrderedCollection();
 758 }
 759
 760 Plan.prototype.addConstraint = function (c) {
 761   this.v.add(c);
 762 }
 763
 764 Plan.prototype.size = function () {
 765   return this.v.size();
 766 }
 767
 768 Plan.prototype.constraintAt = function (index) {
 769   return this.v.at(index);
 770 }
 771
 772 Plan.prototype.execute = function () {
 773   for (var i = 0; i < this.size(); i++) {
 774     var c = this.constraintAt(i);
 775     c.execute();
 776   }
 777 }
 778
 779 /* --- *
 780  * M a i n
 781  * --- */
 782
 783 /**
 784  * This is the standard DeltaBlue benchmark. A long chain of equality
 785  * constraints is constructed with a stay constraint on one end. An
 786  * edit constraint is then added to the opposite end and the time is
 787  * measured for adding and removing this constraint, and extracting
 788  * and executing a constraint satisfaction plan. There are two cases.
 789  * In case 1, the added constraint is stronger than the stay
 790  * constraint and values must propagate down the entire length of the
 791  * chain. In case 2, the added constraint is weaker than the stay
 792  * constraint so it cannot be accomodated. The cost in this case is,
 793  * of course, very low. Typical situations lie somewhere between these
 794  * two extremes.
 795  */
 796 function chainTest(n) {
 797   planner = new Planner();
 798   var prev = null, first = null, last = null;
 799
 800   // Build chain of n equality constraints
 801   for (var i = 0; i <= n; i++) {
 802     var name = "v" + i;
 803     var v = new Variable(name);
 804     if (prev != null)
 805       new EqualityConstraint(prev, v, Strength.REQUIRED);
 806     if (i == 0) first = v;
 807     if (i == n) last = v;
 808     prev = v;
 809   }
 810
 811   new StayConstraint(last, Strength.STRONG_DEFAULT);
 812   var edit = new EditConstraint(first, Strength.PREFERRED);
 813   var edits = new OrderedCollection();
 814   edits.add(edit);
 815   var plan = planner.extractPlanFromConstraints(edits);
 816   for (var i = 0; i < 100; i++) {
 817     first.value = i;
 818     plan.execute();
 819     if (last.value != i)
 820       alert("Chain test failed.");
 821   }
 822 }
 823
 824 /**
 825  * This test constructs a two sets of variables related to each
 826  * other by a simple linear transformation (scale and offset). The
 827  * time is measured to change a variable on either side of the
 828  * mapping and to change the scale and offset factors.
 829  */
 830 function projectionTest(n) {
 831   planner = new Planner();
 832   var scale = new Variable("scale", 10);
 833   var offset = new Variable("offset", 1000);
 834   var src = null, dst = null;
 835
 836   var dests = new OrderedCollection();
 837   for (var i = 0; i < n; i++) {
 838     src = new Variable("src" + i, i);
 839     dst = new Variable("dst" + i, i);
 840     dests.add(dst);
 841     new StayConstraint(src, Strength.NORMAL);
 842     new ScaleConstraint(src, scale, offset, dst, Strength.REQUIRED);
 843   }
 844
 845   change(src, 17);
 846   if (dst.value != 1170) alert("Projection 1 failed");
 847   change(dst, 1050);
 848   if (src.value != 5) alert("Projection 2 failed");
 849   change(scale, 5);
 850   for (var i = 0; i < n - 1; i++) {
 851     if (dests.at(i).value != i * 5 + 1000)
 852       alert("Projection 3 failed");
 853   }
 854   change(offset, 2000);
 855   for (var i = 0; i < n - 1; i++) {
 856     if (dests.at(i).value != i * 5 + 2000)
 857       alert("Projection 4 failed");
 858   }
 859 }
 860
 861 function change(v, newValue) {
 862   var edit = new EditConstraint(v, Strength.PREFERRED);
 863   var edits = new OrderedCollection();
 864   edits.add(edit);
 865   var plan = planner.extractPlanFromConstraints(edits);
 866   for (var i = 0; i < 10; i++) {
 867     v.value = newValue;
 868     plan.execute();
 869   }
 870   edit.destroyConstraint();
 871 }
 872
 873 // Global variable holding the current planner.
 874 var planner = null;
 875
 876 window.onload = function(){ startTest("v8-deltablue", 'b95228dc');
 877
 878 test("Constraint Solving", function deltaBlue() {
 879   chainTest(100);
 880   projectionTest(100);
 881 });
 882
 883 endTest(); };
 884 </script>
 885 </head>
 886 <body></body>
 887 </html>