In this exercise, we time some methods for multiplying a lower triangular matrix by its transpose.
  • Run these Matlab commands:
    L = tril(rand(250));
    A = L*L';
    t1 = toc
  • Now write either a row-oriented algorithm to compute B = L L' or a column-oriented algorithm.
  • Run your algorithm and compare the time with t1.
  • If you want to verify the correctness of your algorithm, see if
    is small.
  • Algorithm MatMatDot (p180) and MatMatSax (p181) can be used to help you design your algorithm. Just modify them so that they don't touch any zeros in the matrix L.
  • Send a plain-text email with a copy of your program and its output by midnight on Monday.