在約束滿足問題中，破壞指數量級數量的所有對稱通常過於昂貴。在實踐中，我們通常只有效地破壞對稱的一個子集。我們稱之為目標對稱。在靜態對稱破壞中，我們的目標是發佈一套約束去破壞這些目標對稱，以達到減少解集以及搜索空間的效果。一個問題中的所有對稱之間是互相交織的。一個旨在特定對稱的破壞對稱約束几乎總會產生副作用，而不僅僅破壞了預期的對稱。破壞相同目標對稱的不同約束可以有不同的副作用。傳統智慧告訴我們應該選擇一個破壞更多對稱從而有更多副作用的破壞對稱約束。雖然這樣的說法在許多方面上都是有效的，我們應該更加注意副作用發生的地方。 / 給與一個約束滿足問題，一個對稱被一個約束保留當且僅當該對稱仍然是新的約束滿足問題的對稱。這個新的約束滿足問題是有原問題加上該約束組成的。我們給出定律和例子，以表明發佈儘量保留目標對稱以及限制它的副作用發生在非目標對稱上的破壞約束是有利的。這些好處來自于被破壞的對稱數目以及一個對稱被破壞（或消除）的程度，并導致一個較小的解集和搜索空間。但是，對稱不一定會被保留。我們顯示，旨在一個已經被消除的目標對稱的破壞對稱約束仍然可以被發佈。我們建議根據問題的約束以及其他破壞對稱約束來選擇破壞對稱約束，以繼續消除更多的對稱。我們進行了廣泛的實驗來確認我們的建議的可行性與效率。 / Breaking the exponential number of all symmetries of a constraint satisfaction problem is often too costly. In practice, we often aim at breaking a subset of the symmetries efficiently, which we call target symmetries. In static sym-metry breaking, the goal is to post a set of constraints to break these target symmetries in order to reduce the solution set and thus also the search space. Symmetries of a problem are all intertwined. A symmetry breaking constraint intended for a particular symmetry almost always breaks more than just the intended symmetry as a side-effect. Different constraints for breaking the same target symmetry can have different side-effects. Conventional wisdom suggests that we should select a symmetry breaking constraint that has more side-effects by breaking more symmetries. While this wisdom is valid in many ways, we should be careful where the side-effects take place. / A symmetry σ of a CSP P =(V, D, C) is preserved by a set of symmetry breaking constraints C{U+02E2}{U+1D47} i σ is a symmetry of P¹ =(V, D, CU C{U+02E2}{U+1D47}). We give theorems and examples to demonstrate that it is beneficial to post symmetry breaking constraints that preserve the target symmetries and restrict the side-effects to only non-target symmetries as much as possible. The benefits are in terms of the number of symmetries broken and the extent to which a symmetry is broken (or eliminated), resulting in a smaller solution set and search space. However, symmetry preservation may not always hold. We illustrate that symmetry breaking constraints, which aim at a target symmetry that is already eliminated, can still be posted. To continue eliminating more symmetries, we suggest to select symmetry breaking constraints based on problem constraints and other symmetry breaking constraints. Extensive experiments are also conducted to confirm the feasibility and efficiency of our proposal empirically. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Li, Jingying. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 101-112). / Abstracts also in Chinese. / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Constraint Satisfaction Problems --- p.1 / Chapter 1.2 --- Motivation and Goals --- p.3 / Chapter 1.3 --- Outline of Thesis --- p.5 / Chapter 2 --- Background --- p.8 / Chapter 2.1 --- Constraint Satisfaction Problems --- p.8 / Chapter 2.1.1 --- Backtracking Search --- p.9 / Chapter 2.1.2 --- Consistency Techniques --- p.12 / Chapter 2.1.3 --- Local Consistencies with Backtracking Search --- p.15 / Chapter 2.2 --- Symmetry Breaking in CSPs --- p.16 / Chapter 2.2.1 --- Symmetry Classes --- p.18 / Chapter 2.2.2 --- Breaking Symmetries --- p.22 / Chapter 2.2.3 --- Variable and Value Symmetries --- p.23 / Chapter 2.2.4 --- Symmetry Breaking Constraints --- p.26 / Chapter 3 --- Effects of Symmetry Breaking Constraints --- p.29 / Chapter 3.1 --- Removing Symmetric Search Space --- p.29 / Chapter 3.1.1 --- Properties --- p.30 / Chapter 3.1.2 --- Canonical Variable Orderings --- p.31 / Chapter 3.1.3 --- Regenerating All Solutions --- p.33 / Chapter 3.1.4 --- Remaining Solution Set Sizes --- p.36 / Chapter 3.2 --- Constraint Interactions in Propagation --- p.43 / Chapter 4 --- Choices of Symmetry Breaking Constraints --- p.45 / Chapter 4.1 --- Side-Effects --- p.45 / Chapter 4.2 --- Symmetry Preservation --- p.50 / Chapter 4.2.1 --- De nition and Properties --- p.50 / Chapter 4.2.2 --- Solution Reduction --- p.54 / Chapter 4.2.3 --- Preservation Examples --- p.55 / Chapter 4.2.4 --- Preserving Order --- p.64 / Chapter 4.3 --- Eliminating Eliminated Symmetries --- p.65 / Chapter 4.3.1 --- Further Elimination --- p.65 / Chapter 4.3.2 --- Aggressive Elimination --- p.71 / Chapter 4.4 --- Interactions with Problem Constraints --- p.72 / Chapter 4.4.1 --- Further Simplification --- p.72 / Chapter 4.4.2 --- Increasing Constraint Propagation --- p.73 / Chapter 5 --- Experiments --- p.75 / Chapter 5.1 --- Symmetry Preservation --- p.75 / Chapter 5.1.1 --- Diagonal Latin Square Problem --- p.76 / Chapter 5.1.2 --- NN-Queen Problem --- p.77 / Chapter 5.1.3 --- Error Correcting Code - Lee Distance (ECCLD) --- p.78 / Chapter 5.2 --- Eliminating Eliminated Symmetries --- p.80 / Chapter 5.2.1 --- Equidistance Frequency Permutation Array Problem --- p.80 / Chapter 5.2.2 --- Cover Array Problem --- p.82 / Chapter 5.2.3 --- Sports League Scheduling Problem --- p.83 / Chapter 6 --- Related Work --- p.86 / Chapter 6.1 --- Symmetry Breaking Approaches --- p.86 / Chapter 6.2 --- Reducing Overhead and Increasing Propagation --- p.90 / Chapter 6.3 --- Selecting and Generating Choices --- p.91 / Chapter 6.3.1 --- Reducing Conflict with Search Heuristic --- p.92 / Chapter 6.3.2 --- Choosing the Subset of Symmetries --- p.93 / Chapter 6.4 --- Detecting Symmetries --- p.93 / Chapter 7 --- Conclusion and Remarks --- p.95 / Chapter 7.1 --- Conclusion --- p.95 / Chapter 7.2 --- Discussions --- p.97 / Chapter 7.3 --- Future Work --- p.99 / Bibliography --- p.101
| Identifer | oai:union.ndltd.org:cuhk.edu.hk/oai:cuhk-dr:cuhk_328533 |
| Date | January 2012 |
| Contributors | Li, Jingying., Chinese University of Hong Kong Graduate School. Division of Computer Science and Engineering. |
| Source Sets | The Chinese University of Hong Kong |
| Language | English, Chinese |
| Detected Language | English |
| Type | Text, bibliography |
| Format | electronic resource, electronic resource, remote, 1 online resource (xi, 112 leaves) : ill. (some col.) |
| Rights | Use of this resource is governed by the terms and conditions of the Creative Commons “Attribution-NonCommercial-NoDerivatives 4.0 International” License (http://creativecommons.org/licenses/by-nc-nd/4.0/) |
Page generated in 0.0055 seconds