Act13_Interference

# Act13_Interference - Illinois Institute of Technology Activities for Lecture 13 Interference Mon Activity 13.1 Interference A Why Interference

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Interference Mon Nov 29, 2010 Activity 13.1: Interference A. Why? Interference between threads can cause the threads to misbehave when run in parallel. B. Objectives At the end of today, you should: Be able to detect interference between two sequential threads. C. Questions For each of the following sets of threads, (a) list the triples to check for interference freedom, (b) say whether each triples is true or false, and (c) say whether the threads interfere or not. 1. { even(x) } x:= x+1 { odd(x) } and { x 0 } x:= x+2 { x 0 }. { even(x) x 0 } x:= x+1 { x 0 } { even(x) x 0 } x:= x+1 { x 0 } { x 0 even(x) } x:= x+2 { even(x) } { x 0 odd(x) } x:= x+2 { odd(x) } Are all true; there’s no interference. 2. { T } x:= 0 { x = 0 } and { x = 0 } x:= x+2 { x = 2 }. Does { T x = 0 } x:= 0 interfere with x = 0 (precondition of thread 2) { T x = 0 } x:= 0 { x = 0 } Does { T x = 0 } x:= 0 interfere with x = 2 (the postcondition of thread 2) { T x = 2 } x:= 0 { x = 2 } Does { x = 0 T } x:= x+2 interfere with T (the precondition of thread 1)? { x = 0

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## This note was uploaded on 04/17/2011 for the course CS 536 taught by Professor Cs536 during the Fall '08 term at Illinois Tech.

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Act13_Interference - Illinois Institute of Technology Activities for Lecture 13 Interference Mon Activity 13.1 Interference A Why Interference

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