4 votes 4 votes A particular parallel program computation requires $100$ sec when executed on a single processor, if $40\%$ of this computation is inherently sequential (i.e. will not benefit from additional processors), then theoretically best possible elapsed times of this program running with $2$ and $4$ processors, respectively, are: $20$ sec and $10$ sec $30$ sec and $15$ sec $50$ sec and $25$ sec $70$ sec and $55$ sec CO and Architecture isro2018 co-and-architecture parallel-programming + – Arjun asked Apr 22, 2018 • edited Dec 4, 2022 by Lakshman Bhaiya Arjun 4.9k views answer comment Share Follow See all 0 reply Please log in or register to add a comment.
Best answer 6 votes 6 votes 40% sequential means 40 seconds. Rest 60 % will be divided into 30 -30 % each parallely by the two processors hence total 40+30=70 sec If four processors then 15% each, hence total 40+15=55 sec Ans is D cs2019 answered Apr 23, 2018 • selected Apr 24, 2018 by srestha cs2019 comment Share Follow See all 3 Comments See all 3 3 Comments reply `JEET commented Jan 3, 2020 reply Follow Share What about $4$ processors case. 0 votes 0 votes Arjun commented Jan 3, 2020 reply Follow Share Already given right? 0 votes 0 votes `JEET commented Jan 3, 2020 reply Follow Share @Arjun Sir Yes, it is correct. I didn't t see that small line. 0 votes 0 votes Please log in or register to add a comment.
0 votes 0 votes Option (D) is correct. shahidhope answered Apr 23, 2018 shahidhope comment Share Follow See all 0 reply Please log in or register to add a comment.
0 votes 0 votes Ans should be option C. For 2 processors ___40 sec for sequential, by the time other processor will complete 40% remaining instructions. Now 20% instructions left. Both can perform 10% each. So total time is 50 sec. Similarly for 4 processors. maahisingh answered Apr 24, 2018 maahisingh comment Share Follow See 1 comment See all 1 1 comment reply kirtipurohit commented Jul 24, 2021 reply Follow Share For 4 processors, why can’t we do like, P1 P2 P3 P4 15 15 15 15 10 10 10 10 First, the 60% is divided into 4 and then, the 40% work is also divided into 4. So the total time elapsed can be 25 0 votes 0 votes Please log in or register to add a comment.
0 votes 0 votes D→ let us consider we have 100 instructions and takes 100s to complete given that 40 instructions are sequential and 60 are branch now when we use multiple processors time due branch will decrese whereas sequential instructions wont be affected when 2 processors are used 60 instructions will be run on 2 processors parallelly so it’ll take 30s time Time =40+30=70 when 4 processors are used 60 instructions will be run on 4 processors parallelly so it’ll take 15s time Time =40+15=55 shantanumapari17 answered Mar 22, 2021 shantanumapari17 comment Share Follow See all 0 reply Please log in or register to add a comment.