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Below is the precedence graph for a set of tasks to be executed on a parallel processing system $S$.

What is the efficiency of this precedence graph on $S$ if each of the tasks $T_1, \dots, T_8$ takes the same time and the system $S$ has five processors?

  1. $25\%$
  2. $40\%$
  3. $50\%$
  4. $90\%$
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6 Answers

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Total processes that ran = 8

Total processes that could've had ran = 20.

Efficiency = 8/20 = 0.4 = 40%

 

Option B

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T1 exec. first and take 1 out of 5 processor to execute.. Efficiency   = 1/5 * 100 = 20%

T2 takes 1 out of 5 processor to execute.. Eff.  = 1/5*100 = 20%

T3,T4 and T5 will execute in parallel and all will take same amt. Of time... So they will use 3 out of 5 processors to execute.. Eff.  = 3/5*100 = 60%

T6,T7 and T8 will also do the same... And will take 3 out of 5 processors to execute... Eff. = 3/5* 100 = 60%

Avg eff.  = (20+20+60+60)/4 = 160/4 = 40% ans
Answer:

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