Unformatted text preview: our PING may be answered by diﬀerent machines/processes in diﬀerent invocaFons). D is not certain either (in the case of PING, the informaFon being exchanged is always the same). In the absence of event synchronizaFon and signiﬁcant latency being incurred by remote method invocaFons, any interleaving is possible. Consider, by enumeraFon, all the possible interleavings and the ﬁnal values of x and y: (1, 2, 3) implies x = 0 y =
2 (1, 3, 2) implies x = 0 y =
3 (2, 1, 3) implies x = 0 y =
2 (2, 3, 1) implies x = 0 y =
2 (3, 1, 2) implies x = 0 y =
3 (3, 2, 1) implies x = 0 y =
3 The value of y is not determined because diﬀerent interleavings lead to diﬀerent values of y at the end of the block, but the same is not true of x: it end with the same value no ma`er the interleaving. Note that you could have concluded the fact about the ﬁnal value of x irrespecFve of the iniFal values and of the possible interleavings, because x is assigned only once and by a value that is not changed insi...
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This document was uploaded on 02/10/2014.
 Spring '10

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