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thumbnail A wait-for graph in computer science is a directed graph used for deadlock detection in operating systems and relational database systems. In computer science, a system that allows concurrent operation of multiple processes and locking of resources and which does not provide mechanisms to avoid or prevent deadlock must support a mechanism to detect deadlocks and an algorithm for recovering from them. One such deadlock detection algorithm makes use of a wait-for graph to track which other processes a process is currently blocking on. In a wait-for graph, processes are represented as nodes, and an edge from process to implies is holding a resource that needs and thus is waiting for to release its lock on that resource. If the process is waiting for more than a single resource to become available (the trivial case), multiple edges may represent a conjunctive (and) or disjunctive (or) set of different resources or a certain number of equivalent resources from a collection. In the conjunctive case, graph cycles imply the possibility of a deadlock, whereas in the disjunctive case knots are indicative of deadlock possibility. There is no simple algorithm for detecting the possibility of deadlock in the final case. (Srinavasan, Rajaram 2011) The wait-for-graph scheme is applicable to a resource allocation system with multiple instances of each resource type. ==References== * 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「Wait-for graph」の詳細全文を読む スポンサード リンク
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