Midterm (Fall 2002)
(1) †This exam is closed book, closed notes, and closed neighbor.
(2) You have 70
minutes to complete this exam.† If you
finish early, you may turn in your exam at the front of the room and
leave.† However if you finish during the
last ten minutes of the exam please remain seated until the end of the exam so
you don't disturb others.
(3) Write all
answers in the supplied exam booklet. Start each new problem (but not
sub-problem) on a new page.
(4) Partial credit
will be given for most questions assuming I can figure out what you were doing.
(5) Please write
neatly. Print your answers if your handwriting is hard to read. If you write
something, and wish to cross it out, simply put an X through it.
(20 points) Define and explain the following terms:
A. Spin Lock
B. Directory based
(20 points) The Earth Simulator employs parallelism on at least three levels
(vector, SMP, cluster).†
A. Explain the
granularity of what is being done in parallel at each level.
B. Explain how it
can use each of these levels as part of a single application (e.g., explain how
the HPF climate code was parallelized).
3. (20 points) Consider a
hardware counter that increments by one every cycle the processor is stalled waiting
for memory operations, it interrupts the processor when it overflows, and it is
writeable (but not readable).† How could you implement the memory hierarchy
metric of Mtool using this counter?
(20 points) Amdahlís law provides a limit on the speedup possible by using
parallel computing. Describe the limit implied by Amdahlís law. People
sometimes report speedups that would appear to exceed the limits of Amdahlís
law. Describe two different reasons such speedups might be seen and explain why
the donít violate Amdahlís law.
(20 points) Conducting experimental measurements for papers is difficult.† Explain three different flaws in the
methodology from any of the papers read so far, and how they could have been
corrected.† You may use as many (or as
few) as you like any one paper.