lec11a - Sparse Matrices sparse . many elements are zero...

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Sparse Matrices sparse … many elements are zero dense … few elements are zero
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Example Of Sparse Matrices diagonal tridiagonal lower triangular (?) These are structured sparse matrices. May be mapped into a 1D array so that a mapping function can be used to locate an element.
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Unstructured Sparse Matrices Airline flight matrix. airports are numbered 1 through n flight(i,j) = list of nonstop flights from airport i to airport j n = 1000 (say) n x n array of list references => 4 million bytes total number of flights = 20,000 (say) need at most 20,000 list references => at most 80,000 bytes
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Unstructured Sparse Matrices Web page matrix. web pages are numbered 1 through n web(i,j) = number of links from page i to page j Web analysis. authority page … page that has many links to it hub page … links to many authority pages
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n = 2 billion (and growing by 1 million a day) n x n array of int s => 16 * 10 18 bytes (16 * 10 9 GB)
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This note was uploaded on 01/18/2012 for the course COP 3530 taught by Professor Davis during the Fall '08 term at University of Florida.

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lec11a - Sparse Matrices sparse . many elements are zero...

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