S.. To place a copy Suppose we want to replicate a file over a collection of...
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S.. To place a copy Suppose we want to replicate a file over a collection of n servers, labeled S₁, S₂, of the file at server si results in a placement cost of i, for an integer ; > 0. Now, if a user requests the file from server Si, and no copy of the file is present at Si, then the servers Si- Si- Si... are searched in order until a copy of the file is finally found, say at server S, where j> i. This results in an access cost of j-i. (Note that the lower-indexed servers Si-1, Si-2, ... are not consulted in this search.) The access cost is 0 if Si holds a copy of the file. We will require that a copy of the file be placed at server Sn, so that all such searches will terminate, at the latest, at Sn. We'd like to place copies of the files at the servers so as to minimize the sum of placement and access costs. Formally, we say that a configuration is a choice, for each server Si with i = 1,2,...,n-1, of whether to place a copy of the file at S; or not. (Recall that a copy is always placed at S..) The total cost of a configuration is the sum of all placement costs for servers with a copy of the file, plus the sum of all access costs associated with all n servers. Give a polynomial-time algorithm to find a configuration of the minimum total cost. What is the running time of your algorithm? S.. To place a copy Suppose we want to replicate a file over a collection of n servers, labeled S₁, S₂, of the file at server si results in a placement cost of i, for an integer ; > 0. Now, if a user requests the file from server Si, and no copy of the file is present at Si, then the servers Si- Si- Si... are searched in order until a copy of the file is finally found, say at server S, where j> i. This results in an access cost of j-i. (Note that the lower-indexed servers Si-1, Si-2, ... are not consulted in this search.) The access cost is 0 if Si holds a copy of the file. We will require that a copy of the file be placed at server Sn, so that all such searches will terminate, at the latest, at Sn. We'd like to place copies of the files at the servers so as to minimize the sum of placement and access costs. Formally, we say that a configuration is a choice, for each server Si with i = 1,2,...,n-1, of whether to place a copy of the file at S; or not. (Recall that a copy is always placed at S..) The total cost of a configuration is the sum of all placement costs for servers with a copy of the file, plus the sum of all access costs associated with all n servers. Give a polynomial-time algorithm to find a configuration of the minimum total cost. What is the running time of your algorithm?
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Related Book For
Income Tax Fundamentals 2013
ISBN: 9781285586618
31st Edition
Authors: Gerald E. Whittenburg, Martha Altus Buller, Steven L Gill
Posted Date:
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