Design and analysis of algorithm chapter two.pptx
- 1. ARBA MINCH UNIVERSITY INSTITUTE OF TECHNOLOGY FACULTY OF COMPUTING AND SOFTWARE ENGNEERING DEPARTMENT OF COMPUTER SCIENCE Presentation on :The Chandy–Lamport algorithm Prepared by 1.Tekle Dargaso ------------------PRAMIT/094/13
- 2. The Chandy–Lamport algorithm The Chandy–Lamport algorithm is a snapshot algorithm that is used in distributed systems for recording a consistent global state of an asynchronous system. It was developed by and named after Leslie Lamport and K. Mani Chandy. • The assumptions of the algorithm are as follows: There are no failures and all messages arrive intact and only once The communication channels are unidirectional and FIFO ordered There is a communication path between any two processes in the system Any process may initiate the snapshot algorithm The snapshot algorithm does not interfere with the normal execution of the processes Each process in the system records its local state and the state of its incoming channels
- 3. How Algorithm Works • The Chandy–Lamport algorithm works like this: The observer process (the process taking a snapshot): Saves its own local state Sends a snapshot request message bearing a snapshot token to all other processes A process receiving the snapshot token for the first time on any message: Sends the observer process its own saved state Attaches the snapshot token to all subsequent messages (to help propagate the snapshot token) When a process that has already received the snapshot token receives a message that does not bear the snapshot token, this process will forward that message to the observer process.