SampleMidterm2-2010 - CS 140 Sample Midterm 2 Questions...

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CS 140 Sample Midterm 2 Questions -- March 2010 You may use your textbook and notes, but no other books or computers. Problem 1 [30 points total] : Short answers. (1a) [10 points] Draw a graph that has two maximal independents sets of different sizes, and identify both maximal independent sets. (Your graph should have 5 vertices or less.) (1b) [10 points] Give two reasons why many computations on large graphs perform poorly on conventional distributed-memory parallel computers. (1c) [10 points] Why doesn't everyone use shared-memory parallel computers instead of distributed-memory parallel computers? Problem 2 [35 points total] This problem is about Jacobi iteration to solve the temperature problem on an k -by- k grid (with n = k 2 points), using a message-passing distributed memory machine. As usual, the effect of one iteration is to replace each value x i with the average of its four neighboring values, using the boundary values if the point x i is next to the edge of the region. For this problem, each processor has k/p rows of the grid. Assume k is divisible by p . Here’s a picture for k = 20 and p = 4 : To analyze the computation and communication time, use the following assumptions: Computation time only counts + , - , * , and / operations on floating point numbers, and each arithmetic operation takes one unit of time. Communication time counts both startup and data time, so the time to send or receive a
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This note was uploaded on 12/27/2011 for the course CMPSC 140 taught by Professor Gilbert during the Fall '11 term at UCSB.

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SampleMidterm2-2010 - CS 140 Sample Midterm 2 Questions...

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