翻訳と辞書 Words near each other ・ Hapoel Tel Aviv F.C. (women) ・ Hapoel Tel Aviv F.C. in European football ・ Hapoel Tiberias F.C. ・ Hapoel Tirat HaCarmel F.C. ・ Hapoel Tirat Shalom F.C. ・ Hapoel Tzafririm Holon F.C. ・ Hapoel Umm al-Fahm F.C. ・ Hapoel Yehud F.C. ・ Hapoel Yeruham F.C. ・ Hapoel Zikhron Ya'akov F.C. ・ Hapoli ・ Happan ・ Happawara ・ Happe ・ Happencourt ・ Happened-before ・ Happenin' All Over Again ・ Happening ・ Happening '68 ・ Happening (disambiguation) ・ Happening (song) ・ Happening bar ・ Happening for Love ・ Happening Live! ・ Happening Now ・ Happenings (Bobby Hutcherson album) ・ Happenings (Hank Jones and Oliver Nelson album) ・ Happenings 1000 Years Time Ago ・ Happenings Ten Years Time Ago ・ Happenstance Dictionary Lists mini英和辞書 mini和英辞書 Webster 1913 Latin-English FOLDOC Wikipedia English ウィキペディア

翻訳と辞書　辞書検索 [ 開発暫定版 ] スポンサード リンク Happened-before ： ウィキペディア英語版 Happened-before In computer science, the happened-before relation (denoted: $\backslash to\; \backslash ;$) is a relation between the result of two events, such that if one event should happen before another event, the result must reflect that, even if those events are in reality executed out of order (usually to optimize program flow). This involves ordering events based on the potential causal relationship of pairs of events in a concurrent system, especially asynchronous distributed systems. It was formulated by Leslie Lamport.〔Lamport, Leslie (1978). ("Time, Clocks and the Ordering of Events in a Distributed System" ), ''Communications of the ACM'', 21(7), 558-565.〕 In Java specifically, a happens-before relationship is a guarantee that memory written to by statement A is visible to statement B, that is, that statement A completes its write before statement B starts its read.() The happened-before relation is formally defined as the least strict partial order on events such that: * If events $a\; \backslash ;$ and $b\; \backslash ;$ occur on the same process, $a\; \backslash to\; b\backslash ;$ if the occurrence of event $a\; \backslash ;$ preceded the occurrence of event $b\; \backslash ;$. * If event $a\; \backslash ;$ is the sending of a message and event $b\; \backslash ;$ is the reception of the message sent in event $a\; \backslash ;$, $a\; \backslash to\; b\backslash ;$. If there are other causal relationships between events in a given system, such as between the creation of a process and its first event, these relationships are also added to the definition. Like all strict partial orders, the happened-before relation is ''transitive'', ''irreflexive'' and ''antisymmetric'', i.e.: * $\backslash forall\; a,\; b,\; c$, if $a\; \backslash to\; b\backslash ;$ and $b\; \backslash to\; c\backslash ;$, then $a\; \backslash to\; c\backslash ;$ (transitivity). This means that for any three events $a,\; b,\; c$, if $a$ happened before $b$, and $b$ happened before $c$, then $a$ must have happened before $c$. * $\backslash forall\; a,\; a\; \backslash nrightarrow\; a$ (irreflexivity). This means that no event can happen before itself. * $\backslash forall\; a,\; b,$ where $a\; \backslash neq\; b$, if $a\; \backslash to\; b$ then $b\; \backslash nrightarrow\; a$ (antisymmetry). This means that for any two distinct events $a,\; b$, if $a$ happened before $b$ then $b$ cannot have happened before $a$. The processes that make up a distributed system have no knowledge of the happened-before relation unless they use a logical clock, like a Lamport clock or a vector clock. This allows one to design algorithms for mutual exclusion, and tasks like debugging or optimising distributed systems. ==See also== * Java Memory Model * Lamport timestamps 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「Happened-before」の詳細全文を読む スポンサード リンク 翻訳と辞書 : 翻訳のためのインターネットリソース Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.