comparison_report - 1 Performance Comparison of Suzuki...

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1 Abstract —Suzuki Kasami’s and Raymond’s Tree are distributed Algorithms that realize mutual exclusion among N nodes in a computer network by usage of a single token. Suzuki Kasami’s Algorithm requires 0 or at most N number of messages to enter into critical section. Raymond’s Tree Algorithm requires O(Log N) message under light demand and reduced number of messages exchanged per critical section to approximately 4 messages under saturated demand. Suzuki Kasami’s Algorithm Operates on a fully connected network, however Raymond’s uses a spanning tree of the network. Additional Keywords: — critical section, message exchange, delay, privilege message. I. INTRODUCTION The algorithms are used for N computer network nodes, communicating by message passing rather than shared memory. Message delivery is guaranteed by the communication network however neither the time (state) nor the order of message arrival can be predicted. Nodes may enter critical section out of order. The performance parameters to be measured for a mutual exclusion algorithm other than number of messages are Synchronization delay(Sd): The time measured between when one site leaves and next one enter. Response Time: The time interval a site waits its CS execution to be over after request has been sent. Throughput=1/(Sd + E): Where Sd is the average synchronization delay and E is the average critical section execution time. Suzuki Kasami’s Algorithm: A node having the token is allowed to enter into the critical section. A single node has the privilege and a node requesting critical section broadcast’s a message to all the other nodes. A site sends the privilege if the token is idle with the site. The site having token can continuously enter critical section until it sends the token to some other site. The request message has the format REQUEST(j,n), which means site j is requesting its nth critical section. Each node maintains an array RN of size N for recording latest sequence number received from each of the other nodes. The PRIVILEGE message has the format PRIVILEGE (Q, LN), where Q is queue of nodes requesting critical section and LN is an array of size N where LN[j] is the latest critical section executed by a node j. If RN[j] = LN[j]+1 means a node j has sent a request for its new sequence of critical section, and the node having the privilege adds this to the queue and if token is idle sends the node sends the PRIVILEDGE(LN,Q) to the node requesting critical section. Number of message per Critical section entry is (N-1) REQUEST messages plus 1 PRIVILEGE message so N messages in all or 0 if the node having the token wants to enter critical section. Raymond’s Tree Algorithm:
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This note was uploaded on 05/11/2011 for the course CS 591 taught by Professor Annieliu during the Spring '11 term at SUNY Stony Brook.

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comparison_report - 1 Performance Comparison of Suzuki...

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