HW1 - (assume there are n processes in the system and Vt i...

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CS171- HW1 1) If events corresponding to vector timestamps Vt 1 , Vt 2 , . ..., Vt n   are mutually concurrent, then  prove that,  (Vt 1 [1], Vt 2 [2], . ..., Vt n [n]) = max(Vt 1 , Vt 2 , . ..., Vt n ). 2) If  events ei and  ej respectively  occurred at processes  pi  and pj and  are  assigned  vector  timestamps VT ei  and VT ej  , respectively, then show that ei   ej <=>  VT ei  [i] <  VT ej [i] 3) Consider the following simple method to collect a global snapshot (it may not always collect a  consistent global snapshot): an initiator process takes its snapshot and broadcasts a request to  take snapshot. When some other process receives this request, it takes a snapshot. Channels are  not FIFO. Prove that such a collected distributed snapshot will be consistent iff the following holds 
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Unformatted text preview: (assume there are n processes in the system and Vt i denotes the vector timestamp of the snapshot taken process p i ): (Vt 1 [1], Vt 2 [2], . ..., Vt n [n]) = max(Vt 1 , Vt 2 , . ..., Vt n ). Don't worry about the channel states. 4) Consider a distributed system where every node has its physical clock and all physical clocks are perfectly synchronized. Give an algorithm to record global state assuming the communication network is reliable. (Note that your algorithm should be simpler than the Chandy-Lamport algorithm). 5) What modifications should be done to the Chandy-Lamport snapshot algorithm so that it records a strongly consistent snapshot (I.e., all channel states are recorded empty)....
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This note was uploaded on 12/27/2011 for the course CMPSC 171 taught by Professor Agrawal during the Fall '09 term at UCSB.

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