79 lines
2.3 KiB
TeX
79 lines
2.3 KiB
TeX
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% HOMEWORK #2
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% re: processes
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%
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\documentstyle[11pt,fullpage]{article}
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\pagestyle{empty}
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\begin{document}
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\begin{center}
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{\large\bf BACI Projects for an OS Course}
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\end{center}
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\begin{enumerate}
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\item {\bf A's and B's:} For the following
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program outline in Ben-Ari Concurrent Pascal,
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\begin{tabbing}
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xxxxxx \= xxx \= \kill
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\> PROGRAM As\_and\_Bs; \\
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\\
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\> VAR \\
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\>\> \{ semaphore declarations \} \\
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\\
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\> PROCEDURE A; \\
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\> BEGIN (P's and V's only) END; \\
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\\
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\> PROCEDURE B; \\
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\> BEGIN (P's and V's only) END; \\
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\\
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\> BEGIN \\
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\>\> \{ semaphore initializations \} \\
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\>\> COBEGIN A;A;A;B;B; COEND; \\
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\> END.
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\end{tabbing}
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complete the program using {\it general} semaphores so that the
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processes ALWAYS terminate in the order A (any copy), B (any copy), A
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(any copy), A, B. In addition to the program,
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hand in the results of FIVE executions of the
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program using the -apt option.
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Include an explanation (or proof, if you prefer) of why the
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program works like it should.
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\item {\bf Binary Semaphores:}
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Repeat problem 1 using only BINARY semaphores. In addition, you
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can use assignment, incrementing, and decrementing auxiliary INTEGER
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variables, along with IF-(testing INTEGER expressions)-THEN-ELSE.
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Consider why this problem can not be solved without counting
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variables.
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\item {\bf More A's and B's:}
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Repeat the A and B problem using four concurrent processes
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(A, A, A, and B) such that they terminate in the order A (any copy),
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B, A, A.
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\item {\bf Even More A's and B's:}
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Repeat the A and B problem using eight concurrent processes (A, A, A, A,
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B, B, B, B) such that they terminate in the order AABABABB. {\bf
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Tough one!}
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\item {\small\bf Busy Waiting versus Semaphores:}
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Using the program developed in the
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general semaphore project above (ABAAB), consider
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the performance effect of its execution with your fair and
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your unfair (random) semaphore implementations.
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That is, calculate the total number of
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busy waiting loops that occur in each implementation.
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Compare the performance of these two semaphore implementations
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with a busy waiting implementation, i.e., an implementation that
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uses the exchange operation for synchronization. In each case,
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use a large number of executions (say,
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1000) to obtain better statistics.
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Discuss your results, explaining why one implementation is preferred
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over another.
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\end{enumerate}
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\end{document}
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