Quiz 2 Key COP 5615 Fall 2011 1) (4) Consider Lamport Logical Clocks that only increment on message send and on message receive. Show that if m1 happens before m2 then T(m1) < T(m2), but that T(m3) < T(m4) does not imply that m3 happens before m4. 2) (6) Suppose that building a house requires steps of pouring a foundation (F), framing (M), Plumbing (P), Electrical (E), Drywall (D), Roofing (R), Painting (N), Carpeting (C), Tiling (T), installing kitchen cabinets (K), installing appliances (A), and installing baseboards (B). F must finish before anything else starts, and M must finish before P, R, or E starts. R, P, and E must finish before D or T starts. D must finish before N or K, but K requires that T be done first. K must finish before A, N must finish before C, and C must finish before B. (a) Draw the precedence graph for building a house. Label all nodes. (2 – all arcs right, labels right) (b) Suppose all tasks take a unit time; what is the critical path through the graph? (1) (c) What is the minimum number of workers needed to complete the
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