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In computer science, partial order reduction is a technique for reducing the size of the state-space to be searched by a model checking algorithm. It exploits the commutativity of concurrently executed transitions, which result in the same state when executed in different orders. In explicit state space exploration, partial order reduction usually refers to the specific technique of expanding a representative subset of all enabled transitions. This technique has also been described as model checking with representatives . There are various versions of the method, the so-called stubborn set method , ample set method , and persistent set method . == Ample sets == Ample sets are an example of model checking with representatives. Their formulation relies on a separate notion of ''dependency''. Two transitions are considered independent only if whenever they are mutually enabled, they cannot disable another and the execution of both results in a unique state regardless of the order in which they are executed. Transitions that are not independent, are dependent. In practice dependency is approximated using static analysis. Ample sets for different purposes can be defined by giving conditions as to when a set of transitions is "ample" in a given state. C0 C1 If a transition depends on some transition relation in , this transition cannot be invoked until some transition in the ample set is executed. Conditions C0 and C1 are sufficient for preserving all the deadlocks in the state space. Further restrictions are needed in order to preserve more nuanced properties. For instance, in order to preserve properties of linear temporal logic, the following two conditions are needed: C2 If , each transition in the ample set is invisible C3 A cycle is not allowed if it contains a state in which some transition is enabled, but is never included in ample(s) for any states s on the cycle. These conditions are sufficient for an ample set, but not necessary conditions . 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「partial order reduction」の詳細全文を読む スポンサード リンク
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