problemset6 solutions

Since each of the columns in a given plane has within

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Unformatted text preview: he values in every ÝÞ -plane, alternating the order between planes (a ÝÞ -plane is the set of processors with µ½ ƽ Æ ). fixed Ü, ´Ü 4.Do two steps of the 1-dimensional odd-even sort on each Ü-row (an Ü-row is the set of processors with fixed Ý and Þ , ´ Ý Þ µ ½ Æ ). 5.Sort the values in every ÝÞ -plane. For each of the plane sorts in steps 1, 2, 3, and 5, we use the Æ ¢ Æ sort we discussed in class, which takes ¢´Æ µ time. Step 4 only takes 2 time, so we have a total running time of ¢´Æ µ. Now we need to argue correctness a bit. 1 We consider only 0-1 inputs as per the 0-1 lemma. After step 1, on each ÜÞ -plane, the ¼’s are moved towards the smallest value of Ü. Since the values are sorted, there can be at most one dirty Þ -column in each plane. Thus, every Ü-column within a single ÜÞ -plane has (almost) the same number of ¼’s (to within one). In step 2, we sort ÜÝ -planes. Thus, we pull one Ü-column from each of the ÜÞ -planes. Since each of the Ü-columns in a given ÜÞ plane has within one the same number of ¼’s, the ÜÝ -planes differ by at most Æ ¼’s. Thus, after we sort the values in each ÜÝ -plane, almost all the ÝÞ -planes are clean. In fact, we can only have two adjacent dirty ÝÞ -planes. More specifically, all the ÝÞ -pla...
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This document was uploaded on 03/20/2014 for the course EECS 6.896 at MIT.

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