practice_quiz2_f17_answers.pdf - Performance Engineering of...

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Performance Engineering of Software Systems Thursday, November 15, 2018 Massachusetts Institute of Technology 6.172 Prof. Charles E. Leiserson and Prof. Julian Shun Practice Quiz 2 Practice Quiz 2 Name: Kerberos: Instructions • DO NOT open this quiz booklet until you are instructed to do so. • This quiz booklet contains 17 pages, including this one. You have 80 minutes to earn 80 points. • This quiz is closed book, but you may use one handwritten, double-sided 8 1/2 00 × 11 00 crib sheet and the Master Method card handed out in lecture. • When the quiz begins, please write your name and Kerberos on this coversheet, and write your name or Kerberos on the top of each page, since the pages may be separated for grading. • Some of the questions are true/false, and some are multiple choice. You need not explain these answers unless you wish to receive partial credit if your answer is wrong. For these kinds of questions, since incorrect answers will be penalized, do not guess unless you are reasonably sure . • Good luck! Number Question Parts Points Score Grader 0 Name on Every Page 17 1 1 True or False 9 18 2 Heap space for Cilk programs 3 7 3 Concurrent free lists 2 8 4 Parallel Strassen 5 15 5 Space usage for Strassen 6 18 6 Cache-oblivious Strassen 3 13 Total 80 1
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6.172 Practice Quiz 2 Name or Kerberos 2 1 True or false (9 parts, 18 points) Incorrect answers will be penalized, so do not guess unless you are reasonably sure. You need not justify your answer, unless you want to leave open the possibility of receiving partial credit if your answer is wrong. Comments will have no impact on a correct answer. 1.1 There are generally fewer conflict misses in a set-associative cache than a direct-mapped cache. True False Answer: True 1.2 If there is a TLB miss, then the corresponding cache line is not already in cache. True False Answer: False 1.3 When dealing with multiple pages, a new block should be allocated from the free list for the emptiest page to incur the fewest TLB misses. True False Answer: False 1.4 It is generally more important for a memory allocator to quickly allocate small blocks than to quickly allocate large blocks. True False Answer: True
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6.172 Practice Quiz 2 Name or Kerberos 3 1.5 Streaming writes allow for higher memory bandwidth utilization by bypassing cache with the additional cost of higher latency. True False Answer: True 1.6 On x86 , sequentially consistent behavior can always be achieved through the use of memory fences. True False Answer: True 1.7 If a program that runs on 2 threads protects its critical sections using Peterson’s algorithm, then it is free of determinacy races. True False Answer: False 1.8 If a program that runs on 2 threads protects its critical sections using Peterson’s algorithm, then it is free of data races.
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  • Spring '05
  • Wen
  • CPU cache, Strassen, Strassen algorithm

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