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13 lines
784 B
13 lines
784 B
2 years ago
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Exercise 3.43: Suppose that the balances in
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three accounts start out as $10, $20, and $30, and that multiple processes run,
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exchanging the balances in the accounts. Argue that if the processes are run
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sequentially, after any number of concurrent exchanges, the account balances
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should be $10, $20, and $30 in some order. Draw a timing diagram like the one
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in Figure 3.29 to show how this condition can be violated if the
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exchanges are implemented using the first version of the account-exchange
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program in this section. On the other hand, argue that even with this
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exchange program, the sum of the balances in the accounts will be
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preserved. Draw a timing diagram to show how even this condition would be
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violated if we did not serialize the transactions on individual accounts.
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