Logical clocks and logical time

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    06-Dec-2014

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<ul><li> 1. Logical Time and Clocks1 | Internal use only </li> <li> 2. The need for logical time Unlike conventional sequential programs. the computations performed by distributed systems do not yield a linear sequence of events system inherently define a partial ordering genuinely concurrent events have no influence on one another. another2 | Internal use only </li> <li> 3. The relation happened before, Condition 1: Sequential behaviour. If events e and f occur in the same process instance p, and f occurs after e, then e f ( e happened before f ) Condition 2: Process creation . If event e and process instance q occur in process instance p. event f occurs in q, and q begins after e, then e f3 | Internal use only </li> <li> 4. Happened before ... Condition 3: Process termination. If event e and process instance q occur in process instance p. event f occurs in q. and e occurs after q terminates. then f e4 | Internal use only </li> <li> 5. Condition 4 : Synchronous (un-buffered) message-passing. If event e is a synchronous input (output) and event f is the corresponding output (input), and there is an event g such that e g, then f g. If there is an event h such that h e, then hf5 | Internal use only </li> <li> 6. Condition 5 Asynchronous (buffered) message-passing. If event e is an asynchronous send and event f is the corresponding receive, then e f6 | Internal use only </li> <li> 7. Condition 6 Transitivity : ef fg Then e g7 | Internal use only </li> <li> 8. Concurrent Events a -/-&gt; e , e -/-&gt; a since they occur at different processes Such events are called concurrent Therefore a || e8 | Internal use only </li> <li> 9. 9 | Internal use only </li> <li> 10. Lamport Logical Clocks10 | Internal use only </li> <li> 11. Vector time11 | Internal use only </li> <li> 12. May be Continued ... So any12 | Internal use only </li> <li> 13. Thank You !!13 | Internal use only </li> </ul>

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