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| 1 // Copyright 2011 Google Inc. All Rights Reserved. | |
| 2 // Copyright 1996 John Maloney and Mario Wolczko | |
| 3 // | |
| 4 // This file is part of GNU Smalltalk. | |
| 5 // | |
| 6 // GNU Smalltalk is free software; you can redistribute it and/or modify it | |
| 7 // under the terms of the GNU General Public License as published by the Free | |
| 8 // Software Foundation; either version 2, or (at your option) any later version. | |
| 9 // | |
| 10 // GNU Smalltalk is distributed in the hope that it will be useful, but WITHOUT | |
| 11 // ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS | |
| 12 // FOR A PARTICULAR PURPOSE. See the GNU General Public License for more | |
| 13 // details. | |
| 14 // | |
| 15 // You should have received a copy of the GNU General Public License along with | |
| 16 // GNU Smalltalk; see the file COPYING. If not, write to the Free Software | |
| 17 // Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. | |
| 18 // | |
| 19 // Translated first from Smalltalk to JavaScript, and finally to | |
| 20 // Dart by Google 2008-2010. | |
| 21 | |
| 22 /** | |
| 23 * A Dart implementation of the DeltaBlue constraint-solving | |
| 24 * algorithm, as described in: | |
| 25 * | |
| 26 * "The DeltaBlue Algorithm: An Incremental Constraint Hierarchy Solver" | |
| 27 * Bjorn N. Freeman-Benson and John Maloney | |
| 28 * January 1990 Communications of the ACM, | |
| 29 * also available as University of Washington TR 89-08-06. | |
| 30 * | |
| 31 * Beware: this benchmark is written in a grotesque style where | |
| 32 * the constraint model is built by side-effects from constructors. | |
| 33 * I've kept it this way to avoid deviating too much from the original | |
| 34 * implementation. | |
| 35 */ | |
| 36 | |
| 37 main() { | |
| 38 new DeltaBlue().run(); | |
| 39 } | |
| 40 | |
| 41 /// Benchmark class required to report results. | |
| 42 class DeltaBlue { | |
| 43 void run() { | |
| 44 chainTest(100); | |
| 45 projectionTest(100); | |
| 46 } | |
| 47 } | |
| 48 | |
| 49 /** | |
| 50 * Strengths are used to measure the relative importance of constraints. | |
| 51 * New strengths may be inserted in the strength hierarchy without | |
| 52 * disrupting current constraints. Strengths cannot be created outside | |
| 53 * this class, so == can be used for value comparison. | |
| 54 */ | |
| 55 class Strength { | |
| 56 final int value; | |
| 57 final String name; | |
| 58 | |
| 59 const Strength(this.value, this.name); | |
| 60 | |
| 61 Strength nextWeaker() => const <Strength>[ | |
| 62 STRONG_PREFERRED, | |
| 63 PREFERRED, | |
| 64 STRONG_DEFAULT, | |
| 65 NORMAL, | |
| 66 WEAK_DEFAULT, | |
| 67 WEAKEST | |
| 68 ][value]; | |
| 69 | |
| 70 static bool stronger(Strength s1, Strength s2) { | |
| 71 return s1.value < s2.value; | |
| 72 } | |
| 73 | |
| 74 static bool weaker(Strength s1, Strength s2) { | |
| 75 return s1.value > s2.value; | |
| 76 } | |
| 77 | |
| 78 static Strength weakest(Strength s1, Strength s2) { | |
| 79 return weaker(s1, s2) ? s1 : s2; | |
| 80 } | |
| 81 | |
| 82 static Strength strongest(Strength s1, Strength s2) { | |
| 83 return stronger(s1, s2) ? s1 : s2; | |
| 84 } | |
| 85 } | |
| 86 | |
| 87 // Compile time computed constants. | |
| 88 const REQUIRED = const Strength(0, "required"); | |
| 89 const STRONG_PREFERRED = const Strength(1, "strongPreferred"); | |
| 90 const PREFERRED = const Strength(2, "preferred"); | |
| 91 const STRONG_DEFAULT = const Strength(3, "strongDefault"); | |
| 92 const NORMAL = const Strength(4, "normal"); | |
| 93 const WEAK_DEFAULT = const Strength(5, "weakDefault"); | |
| 94 const WEAKEST = const Strength(6, "weakest"); | |
| 95 | |
| 96 abstract class Constraint { | |
| 97 final Strength strength; | |
| 98 | |
| 99 const Constraint(this.strength); | |
| 100 | |
| 101 bool isSatisfied(); | |
| 102 void markUnsatisfied(); | |
| 103 void addToGraph(); | |
| 104 void removeFromGraph(); | |
| 105 void chooseMethod(int mark); | |
| 106 void markInputs(int mark); | |
| 107 bool inputsKnown(int mark); | |
| 108 Variable output(); | |
| 109 void execute(); | |
| 110 void recalculate(); | |
| 111 | |
| 112 /// Activate this constraint and attempt to satisfy it. | |
| 113 void addConstraint() { | |
| 114 addToGraph(); | |
| 115 planner.incrementalAdd(this); | |
| 116 } | |
| 117 | |
| 118 /** | |
| 119 * Attempt to find a way to enforce this constraint. If successful, | |
| 120 * record the solution, perhaps modifying the current dataflow | |
| 121 * graph. Answer the constraint that this constraint overrides, if | |
| 122 * there is one, or nil, if there isn't. | |
| 123 * Assume: I am not already satisfied. | |
| 124 */ | |
| 125 Constraint satisfy(mark) { | |
| 126 chooseMethod(mark); | |
| 127 if (!isSatisfied()) { | |
| 128 if (strength == REQUIRED) { | |
| 129 print("Could not satisfy a required constraint!"); | |
| 130 } | |
| 131 return null; | |
| 132 } | |
| 133 markInputs(mark); | |
| 134 Variable out = output(); | |
| 135 Constraint overridden = out.determinedBy; | |
| 136 if (overridden != null) overridden.markUnsatisfied(); | |
| 137 out.determinedBy = this; | |
| 138 if (!planner.addPropagate(this, mark)) print("Cycle encountered"); | |
| 139 out.mark = mark; | |
| 140 return overridden; | |
| 141 } | |
| 142 | |
| 143 void destroyConstraint() { | |
| 144 if (isSatisfied()) planner.incrementalRemove(this); | |
| 145 removeFromGraph(); | |
| 146 } | |
| 147 | |
| 148 /** | |
| 149 * Normal constraints are not input constraints. An input constraint | |
| 150 * is one that depends on external state, such as the mouse, the | |
| 151 * keybord, a clock, or some arbitraty piece of imperative code. | |
| 152 */ | |
| 153 bool isInput() => false; | |
| 154 } | |
| 155 | |
| 156 /** | |
| 157 * Abstract superclass for constraints having a single possible output variable. | |
| 158 */ | |
| 159 abstract class UnaryConstraint extends Constraint { | |
| 160 final Variable myOutput; | |
| 161 bool satisfied = false; | |
| 162 | |
| 163 UnaryConstraint(this.myOutput, Strength strength) : super(strength) { | |
| 164 addConstraint(); | |
| 165 } | |
| 166 | |
| 167 /// Adds this constraint to the constraint graph | |
| 168 void addToGraph() { | |
| 169 myOutput.addConstraint(this); | |
| 170 satisfied = false; | |
| 171 } | |
| 172 | |
| 173 /// Decides if this constraint can be satisfied and records that decision. | |
| 174 void chooseMethod(int mark) { | |
| 175 satisfied = (myOutput.mark != mark) && | |
| 176 Strength.stronger(strength, myOutput.walkStrength); | |
| 177 } | |
| 178 | |
| 179 /// Returns true if this constraint is satisfied in the current solution. | |
| 180 bool isSatisfied() => satisfied; | |
| 181 | |
| 182 void markInputs(int mark) { | |
| 183 // has no inputs. | |
| 184 } | |
| 185 | |
| 186 /// Returns the current output variable. | |
| 187 Variable output() => myOutput; | |
| 188 | |
| 189 /** | |
| 190 * Calculate the walkabout strength, the stay flag, and, if it is | |
| 191 * 'stay', the value for the current output of this constraint. Assume | |
| 192 * this constraint is satisfied. | |
| 193 */ | |
| 194 void recalculate() { | |
| 195 myOutput.walkStrength = strength; | |
| 196 myOutput.stay = !isInput(); | |
| 197 if (myOutput.stay) execute(); // Stay optimization. | |
| 198 } | |
| 199 | |
| 200 /// Records that this constraint is unsatisfied. | |
| 201 void markUnsatisfied() { | |
| 202 satisfied = false; | |
| 203 } | |
| 204 | |
| 205 bool inputsKnown(int mark) => true; | |
| 206 | |
| 207 void removeFromGraph() { | |
| 208 if (myOutput != null) myOutput.removeConstraint(this); | |
| 209 satisfied = false; | |
| 210 } | |
| 211 } | |
| 212 | |
| 213 /** | |
| 214 * Variables that should, with some level of preference, stay the same. | |
| 215 * Planners may exploit the fact that instances, if satisfied, will not | |
| 216 * change their output during plan execution. This is called "stay | |
| 217 * optimization". | |
| 218 */ | |
| 219 class StayConstraint extends UnaryConstraint { | |
| 220 StayConstraint(Variable v, Strength str) : super(v, str); | |
| 221 | |
| 222 void execute() { | |
| 223 // Stay constraints do nothing. | |
| 224 } | |
| 225 } | |
| 226 | |
| 227 /** | |
| 228 * A unary input constraint used to mark a variable that the client | |
| 229 * wishes to change. | |
| 230 */ | |
| 231 class EditConstraint extends UnaryConstraint { | |
| 232 EditConstraint(Variable v, Strength str) : super(v, str); | |
| 233 | |
| 234 /// Edits indicate that a variable is to be changed by imperative code. | |
| 235 bool isInput() => true; | |
| 236 | |
| 237 void execute() { | |
| 238 // Edit constraints do nothing. | |
| 239 } | |
| 240 } | |
| 241 | |
| 242 // Directions. | |
| 243 const int NONE = 1; | |
| 244 const int FORWARD = 2; | |
| 245 const int BACKWARD = 0; | |
| 246 | |
| 247 /** | |
| 248 * Abstract superclass for constraints having two possible output | |
| 249 * variables. | |
| 250 */ | |
| 251 abstract class BinaryConstraint extends Constraint { | |
| 252 Variable v1; | |
| 253 Variable v2; | |
| 254 int direction = NONE; | |
| 255 | |
| 256 BinaryConstraint(this.v1, this.v2, Strength strength) : super(strength) { | |
| 257 addConstraint(); | |
| 258 } | |
| 259 | |
| 260 /** | |
| 261 * Decides if this constraint can be satisfied and which way it | |
| 262 * should flow based on the relative strength of the variables related, | |
| 263 * and record that decision. | |
| 264 */ | |
| 265 void chooseMethod(int mark) { | |
| 266 if (v1.mark == mark) { | |
| 267 direction = | |
| 268 (v2.mark != mark && Strength.stronger(strength, v2.walkStrength)) | |
| 269 ? FORWARD | |
| 270 : NONE; | |
| 271 } | |
| 272 if (v2.mark == mark) { | |
| 273 direction = | |
| 274 (v1.mark != mark && Strength.stronger(strength, v1.walkStrength)) | |
| 275 ? BACKWARD | |
| 276 : NONE; | |
| 277 } | |
| 278 if (Strength.weaker(v1.walkStrength, v2.walkStrength)) { | |
| 279 direction = | |
| 280 Strength.stronger(strength, v1.walkStrength) ? BACKWARD : NONE; | |
| 281 } else { | |
| 282 direction = | |
| 283 Strength.stronger(strength, v2.walkStrength) ? FORWARD : BACKWARD; | |
| 284 } | |
| 285 } | |
| 286 | |
| 287 /// Add this constraint to the constraint graph. | |
| 288 void addToGraph() { | |
| 289 v1.addConstraint(this); | |
| 290 v2.addConstraint(this); | |
| 291 direction = NONE; | |
| 292 } | |
| 293 | |
| 294 /// Answer true if this constraint is satisfied in the current solution. | |
| 295 bool isSatisfied() => direction != NONE; | |
| 296 | |
| 297 /// Mark the input variable with the given mark. | |
| 298 void markInputs(int mark) { | |
| 299 input().mark = mark; | |
| 300 } | |
| 301 | |
| 302 /// Returns the current input variable | |
| 303 Variable input() => direction == FORWARD ? v1 : v2; | |
| 304 | |
| 305 /// Returns the current output variable. | |
| 306 Variable output() => direction == FORWARD ? v2 : v1; | |
| 307 | |
| 308 /** | |
| 309 * Calculate the walkabout strength, the stay flag, and, if it is | |
| 310 * 'stay', the value for the current output of this | |
| 311 * constraint. Assume this constraint is satisfied. | |
| 312 */ | |
| 313 void recalculate() { | |
| 314 Variable ihn = input(), out = output(); | |
| 315 out.walkStrength = Strength.weakest(strength, ihn.walkStrength); | |
| 316 out.stay = ihn.stay; | |
| 317 if (out.stay) execute(); | |
| 318 } | |
| 319 | |
| 320 /// Record the fact that this constraint is unsatisfied. | |
| 321 void markUnsatisfied() { | |
| 322 direction = NONE; | |
| 323 } | |
| 324 | |
| 325 bool inputsKnown(int mark) { | |
| 326 Variable i = input(); | |
| 327 return i.mark == mark || i.stay || i.determinedBy == null; | |
| 328 } | |
| 329 | |
| 330 void removeFromGraph() { | |
| 331 if (v1 != null) v1.removeConstraint(this); | |
| 332 if (v2 != null) v2.removeConstraint(this); | |
| 333 direction = NONE; | |
| 334 } | |
| 335 } | |
| 336 | |
| 337 /** | |
| 338 * Relates two variables by the linear scaling relationship: "v2 = | |
| 339 * (v1 * scale) + offset". Either v1 or v2 may be changed to maintain | |
| 340 * this relationship but the scale factor and offset are considered | |
| 341 * read-only. | |
| 342 */ | |
| 343 | |
| 344 class ScaleConstraint extends BinaryConstraint { | |
| 345 final Variable scale; | |
| 346 final Variable offset; | |
| 347 | |
| 348 ScaleConstraint( | |
| 349 Variable src, this.scale, this.offset, Variable dest, Strength strength) | |
| 350 : super(src, dest, strength); | |
| 351 | |
| 352 /// Adds this constraint to the constraint graph. | |
| 353 void addToGraph() { | |
| 354 super.addToGraph(); | |
| 355 scale.addConstraint(this); | |
| 356 offset.addConstraint(this); | |
| 357 } | |
| 358 | |
| 359 void removeFromGraph() { | |
| 360 super.removeFromGraph(); | |
| 361 if (scale != null) scale.removeConstraint(this); | |
| 362 if (offset != null) offset.removeConstraint(this); | |
| 363 } | |
| 364 | |
| 365 void markInputs(int mark) { | |
| 366 super.markInputs(mark); | |
| 367 scale.mark = offset.mark = mark; | |
| 368 } | |
| 369 | |
| 370 /// Enforce this constraint. Assume that it is satisfied. | |
| 371 void execute() { | |
| 372 if (direction == FORWARD) { | |
| 373 v2.value = v1.value * scale.value + offset.value; | |
| 374 } else { | |
| 375 v1.value = (v2.value - offset.value) ~/ scale.value; | |
| 376 } | |
| 377 } | |
| 378 | |
| 379 /** | |
| 380 * Calculate the walkabout strength, the stay flag, and, if it is | |
| 381 * 'stay', the value for the current output of this constraint. Assume | |
| 382 * this constraint is satisfied. | |
| 383 */ | |
| 384 void recalculate() { | |
| 385 Variable ihn = input(), out = output(); | |
| 386 out.walkStrength = Strength.weakest(strength, ihn.walkStrength); | |
| 387 out.stay = ihn.stay && scale.stay && offset.stay; | |
| 388 if (out.stay) execute(); | |
| 389 } | |
| 390 } | |
| 391 | |
| 392 /** | |
| 393 * Constrains two variables to have the same value. | |
| 394 */ | |
| 395 class EqualityConstraint extends BinaryConstraint { | |
| 396 EqualityConstraint(Variable v1, Variable v2, Strength strength) | |
| 397 : super(v1, v2, strength); | |
| 398 | |
| 399 /// Enforce this constraint. Assume that it is satisfied. | |
| 400 void execute() { | |
| 401 output().value = input().value; | |
| 402 } | |
| 403 } | |
| 404 | |
| 405 /** | |
| 406 * A constrained variable. In addition to its value, it maintain the | |
| 407 * structure of the constraint graph, the current dataflow graph, and | |
| 408 * various parameters of interest to the DeltaBlue incremental | |
| 409 * constraint solver. | |
| 410 **/ | |
| 411 class Variable { | |
| 412 List<Constraint> constraints = <Constraint>[]; | |
| 413 Constraint determinedBy; | |
| 414 int mark = 0; | |
| 415 Strength walkStrength = WEAKEST; | |
| 416 bool stay = true; | |
| 417 int value; | |
| 418 final String name; | |
| 419 | |
| 420 Variable(this.name, this.value); | |
| 421 | |
| 422 /** | |
| 423 * Add the given constraint to the set of all constraints that refer | |
| 424 * this variable. | |
| 425 */ | |
| 426 void addConstraint(Constraint c) { | |
| 427 constraints.add(c); | |
| 428 } | |
| 429 | |
| 430 /// Removes all traces of c from this variable. | |
| 431 void removeConstraint(Constraint c) { | |
| 432 constraints.remove(c); | |
| 433 if (determinedBy == c) determinedBy = null; | |
| 434 } | |
| 435 } | |
| 436 | |
| 437 class Planner { | |
| 438 int currentMark = 0; | |
| 439 | |
| 440 /** | |
| 441 * Attempt to satisfy the given constraint and, if successful, | |
| 442 * incrementally update the dataflow graph. Details: If satifying | |
| 443 * the constraint is successful, it may override a weaker constraint | |
| 444 * on its output. The algorithm attempts to resatisfy that | |
| 445 * constraint using some other method. This process is repeated | |
| 446 * until either a) it reaches a variable that was not previously | |
| 447 * determined by any constraint or b) it reaches a constraint that | |
| 448 * is too weak to be satisfied using any of its methods. The | |
| 449 * variables of constraints that have been processed are marked with | |
| 450 * a unique mark value so that we know where we've been. This allows | |
| 451 * the algorithm to avoid getting into an infinite loop even if the | |
| 452 * constraint graph has an inadvertent cycle. | |
| 453 */ | |
| 454 void incrementalAdd(Constraint c) { | |
| 455 int mark = newMark(); | |
| 456 for (Constraint overridden = c.satisfy(mark); | |
| 457 overridden != null; | |
| 458 overridden = overridden.satisfy(mark)); | |
| 459 } | |
| 460 | |
| 461 /** | |
| 462 * Entry point for retracting a constraint. Remove the given | |
| 463 * constraint and incrementally update the dataflow graph. | |
| 464 * Details: Retracting the given constraint may allow some currently | |
| 465 * unsatisfiable downstream constraint to be satisfied. We therefore collect | |
| 466 * a list of unsatisfied downstream constraints and attempt to | |
| 467 * satisfy each one in turn. This list is traversed by constraint | |
| 468 * strength, strongest first, as a heuristic for avoiding | |
| 469 * unnecessarily adding and then overriding weak constraints. | |
| 470 * Assume: [c] is satisfied. | |
| 471 */ | |
| 472 void incrementalRemove(Constraint c) { | |
| 473 Variable out = c.output(); | |
| 474 c.markUnsatisfied(); | |
| 475 c.removeFromGraph(); | |
| 476 List<Constraint> unsatisfied = removePropagateFrom(out); | |
| 477 Strength strength = REQUIRED; | |
| 478 do { | |
| 479 for (int i = 0; i < unsatisfied.length; i++) { | |
| 480 Constraint u = unsatisfied[i]; | |
| 481 if (u.strength == strength) incrementalAdd(u); | |
| 482 } | |
| 483 strength = strength.nextWeaker(); | |
| 484 } while (strength != WEAKEST); | |
| 485 } | |
| 486 | |
| 487 /// Select a previously unused mark value. | |
| 488 int newMark() => ++currentMark; | |
| 489 | |
| 490 /** | |
| 491 * Extract a plan for resatisfaction starting from the given source | |
| 492 * constraints, usually a set of input constraints. This method | |
| 493 * assumes that stay optimization is desired; the plan will contain | |
| 494 * only constraints whose output variables are not stay. Constraints | |
| 495 * that do no computation, such as stay and edit constraints, are | |
| 496 * not included in the plan. | |
| 497 * Details: The outputs of a constraint are marked when it is added | |
| 498 * to the plan under construction. A constraint may be appended to | |
| 499 * the plan when all its input variables are known. A variable is | |
| 500 * known if either a) the variable is marked (indicating that has | |
| 501 * been computed by a constraint appearing earlier in the plan), b) | |
| 502 * the variable is 'stay' (i.e. it is a constant at plan execution | |
| 503 * time), or c) the variable is not determined by any | |
| 504 * constraint. The last provision is for past states of history | |
| 505 * variables, which are not stay but which are also not computed by | |
| 506 * any constraint. | |
| 507 * Assume: [sources] are all satisfied. | |
| 508 */ | |
| 509 Plan makePlan(List<Constraint> sources) { | |
| 510 int mark = newMark(); | |
| 511 Plan plan = new Plan(); | |
| 512 List<Constraint> todo = sources; | |
| 513 while (todo.length > 0) { | |
| 514 Constraint c = todo.removeLast(); | |
| 515 if (c.output().mark != mark && c.inputsKnown(mark)) { | |
| 516 plan.addConstraint(c); | |
| 517 c.output().mark = mark; | |
| 518 addConstraintsConsumingTo(c.output(), todo); | |
| 519 } | |
| 520 } | |
| 521 return plan; | |
| 522 } | |
| 523 | |
| 524 /** | |
| 525 * Extract a plan for resatisfying starting from the output of the | |
| 526 * given [constraints], usually a set of input constraints. | |
| 527 */ | |
| 528 Plan extractPlanFromConstraints(List<Constraint> constraints) { | |
| 529 List<Constraint> sources = <Constraint>[]; | |
| 530 for (int i = 0; i < constraints.length; i++) { | |
| 531 Constraint c = constraints[i]; | |
| 532 // if not in plan already and eligible for inclusion. | |
| 533 if (c.isInput() && c.isSatisfied()) sources.add(c); | |
| 534 } | |
| 535 return makePlan(sources); | |
| 536 } | |
| 537 | |
| 538 /** | |
| 539 * Recompute the walkabout strengths and stay flags of all variables | |
| 540 * downstream of the given constraint and recompute the actual | |
| 541 * values of all variables whose stay flag is true. If a cycle is | |
| 542 * detected, remove the given constraint and answer | |
| 543 * false. Otherwise, answer true. | |
| 544 * Details: Cycles are detected when a marked variable is | |
| 545 * encountered downstream of the given constraint. The sender is | |
| 546 * assumed to have marked the inputs of the given constraint with | |
| 547 * the given mark. Thus, encountering a marked node downstream of | |
| 548 * the output constraint means that there is a path from the | |
| 549 * constraint's output to one of its inputs. | |
| 550 */ | |
| 551 bool addPropagate(Constraint c, int mark) { | |
| 552 List<Constraint> todo = <Constraint>[c]; | |
| 553 while (todo.length > 0) { | |
| 554 Constraint d = todo.removeLast(); | |
| 555 if (d.output().mark == mark) { | |
| 556 incrementalRemove(c); | |
| 557 return false; | |
| 558 } | |
| 559 d.recalculate(); | |
| 560 addConstraintsConsumingTo(d.output(), todo); | |
| 561 } | |
| 562 return true; | |
| 563 } | |
| 564 | |
| 565 /** | |
| 566 * Update the walkabout strengths and stay flags of all variables | |
| 567 * downstream of the given constraint. Answer a collection of | |
| 568 * unsatisfied constraints sorted in order of decreasing strength. | |
| 569 */ | |
| 570 List<Constraint> removePropagateFrom(Variable out) { | |
| 571 out.determinedBy = null; | |
| 572 out.walkStrength = WEAKEST; | |
| 573 out.stay = true; | |
| 574 List<Constraint> unsatisfied = <Constraint>[]; | |
| 575 List<Variable> todo = <Variable>[out]; | |
| 576 while (todo.length > 0) { | |
| 577 Variable v = todo.removeLast(); | |
| 578 for (int i = 0; i < v.constraints.length; i++) { | |
| 579 Constraint c = v.constraints[i]; | |
| 580 if (!c.isSatisfied()) unsatisfied.add(c); | |
| 581 } | |
| 582 Constraint determining = v.determinedBy; | |
| 583 for (int i = 0; i < v.constraints.length; i++) { | |
| 584 Constraint next = v.constraints[i]; | |
| 585 if (next != determining && next.isSatisfied()) { | |
| 586 next.recalculate(); | |
| 587 todo.add(next.output()); | |
| 588 } | |
| 589 } | |
| 590 } | |
| 591 return unsatisfied; | |
| 592 } | |
| 593 | |
| 594 void addConstraintsConsumingTo(Variable v, List<Constraint> coll) { | |
| 595 Constraint determining = v.determinedBy; | |
| 596 for (int i = 0; i < v.constraints.length; i++) { | |
| 597 Constraint c = v.constraints[i]; | |
| 598 if (c != determining && c.isSatisfied()) coll.add(c); | |
| 599 } | |
| 600 } | |
| 601 } | |
| 602 | |
| 603 /** | |
| 604 * A Plan is an ordered list of constraints to be executed in sequence | |
| 605 * to resatisfy all currently satisfiable constraints in the face of | |
| 606 * one or more changing inputs. | |
| 607 */ | |
| 608 class Plan { | |
| 609 List<Constraint> list = <Constraint>[]; | |
| 610 | |
| 611 void addConstraint(Constraint c) { | |
| 612 list.add(c); | |
| 613 } | |
| 614 | |
| 615 int size() => list.length; | |
| 616 | |
| 617 void execute() { | |
| 618 for (int i = 0; i < list.length; i++) { | |
| 619 list[i].execute(); | |
| 620 } | |
| 621 } | |
| 622 } | |
| 623 | |
| 624 /** | |
| 625 * This is the standard DeltaBlue benchmark. A long chain of equality | |
| 626 * constraints is constructed with a stay constraint on one end. An | |
| 627 * edit constraint is then added to the opposite end and the time is | |
| 628 * measured for adding and removing this constraint, and extracting | |
| 629 * and executing a constraint satisfaction plan. There are two cases. | |
| 630 * In case 1, the added constraint is stronger than the stay | |
| 631 * constraint and values must propagate down the entire length of the | |
| 632 * chain. In case 2, the added constraint is weaker than the stay | |
| 633 * constraint so it cannot be accomodated. The cost in this case is, | |
| 634 * of course, very low. Typical situations lie somewhere between these | |
| 635 * two extremes. | |
| 636 */ | |
| 637 void chainTest(int n) { | |
| 638 planner = new Planner(); | |
| 639 Variable prev = null, first = null, last = null; | |
| 640 // Build chain of n equality constraints. | |
| 641 for (int i = 0; i <= n; i++) { | |
| 642 Variable v = new Variable("v$i", 0); | |
| 643 if (prev != null) new EqualityConstraint(prev, v, REQUIRED); | |
| 644 if (i == 0) first = v; | |
| 645 if (i == n) last = v; | |
| 646 prev = v; | |
| 647 } | |
| 648 new StayConstraint(last, STRONG_DEFAULT); | |
| 649 EditConstraint edit = new EditConstraint(first, PREFERRED); | |
| 650 Plan plan = planner.extractPlanFromConstraints(<Constraint>[edit]); | |
| 651 for (int i = 0; i < 100; i++) { | |
| 652 first.value = i; | |
| 653 plan.execute(); | |
| 654 if (last.value != i) { | |
| 655 print("Chain test failed:"); | |
| 656 print("Expected last value to be $i but it was ${last.value}."); | |
| 657 } | |
| 658 } | |
| 659 } | |
| 660 | |
| 661 /** | |
| 662 * This test constructs a two sets of variables related to each | |
| 663 * other by a simple linear transformation (scale and offset). The | |
| 664 * time is measured to change a variable on either side of the | |
| 665 * mapping and to change the scale and offset factors. | |
| 666 */ | |
| 667 void projectionTest(int n) { | |
| 668 planner = new Planner(); | |
| 669 Variable scale = new Variable("scale", 10); | |
| 670 Variable offset = new Variable("offset", 1000); | |
| 671 Variable src = null, dst = null; | |
| 672 | |
| 673 List<Variable> dests = <Variable>[]; | |
| 674 for (int i = 0; i < n; i++) { | |
| 675 src = new Variable("src", i); | |
| 676 dst = new Variable("dst", i); | |
| 677 dests.add(dst); | |
| 678 new StayConstraint(src, NORMAL); | |
| 679 new ScaleConstraint(src, scale, offset, dst, REQUIRED); | |
| 680 } | |
| 681 change(src, 17); | |
| 682 if (dst.value != 1170) print("Projection 1 failed"); | |
| 683 change(dst, 1050); | |
| 684 if (src.value != 5) print("Projection 2 failed"); | |
| 685 change(scale, 5); | |
| 686 for (int i = 0; i < n - 1; i++) { | |
| 687 if (dests[i].value != i * 5 + 1000) print("Projection 3 failed"); | |
| 688 } | |
| 689 change(offset, 2000); | |
| 690 for (int i = 0; i < n - 1; i++) { | |
| 691 if (dests[i].value != i * 5 + 2000) print("Projection 4 failed"); | |
| 692 } | |
| 693 } | |
| 694 | |
| 695 void change(Variable v, int newValue) { | |
| 696 EditConstraint edit = new EditConstraint(v, PREFERRED); | |
| 697 Plan plan = planner.extractPlanFromConstraints(<EditConstraint>[edit]); | |
| 698 for (int i = 0; i < 10; i++) { | |
| 699 v.value = newValue; | |
| 700 plan.execute(); | |
| 701 } | |
| 702 edit.destroyConstraint(); | |
| 703 } | |
| 704 | |
| 705 Planner planner; | |
| OLD | NEW |
|---|
Chromium Code Reviews
Issue 2825063002:
Move kernel baseline tests to front_end. (Closed)
