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Unformatted text preview: CS 290N / CS 219: Sparse Matrix Algorithms // Homework 1 Due by class time Wednesday, October 7 Please turn in all your homework on paper, either in class or in the homework box in the Computer Science Department office. For programs, turn in (1) code listing; (2) sample output and any plots, showing thorough testing; (3) a transcript of a Matlab session showing how it’s used. Problem 1. [10 points] Let A and B be two nby n matrices. Show that the number of nonzero scalar multiplications required to compute C = AB is (using Matlab notation) n summationdisplay i =1 nnz ( A (: , i )) * nnz ( B ( i , :)) . Problem 2. [30 points] Let G be the 9vertex “grid graph” corresponding to the two dimensional model problem on a 3by3 mesh. Suppose the vertices of G are numbered 1 through 9 by rows from upper left to bottom right. 2(a) [5 points] Draw the sequence of ten socalled “elimination graphs” (beginning with G and ending with the empty graph) that result from playing the vertex elimination game on G with the given vertex numbering....
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 Fall '09
 Chong

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