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Homework Help: Matlab Cg algorithm

  1. Dec 27, 2008 #1
    1. The problem statement, all variables and given/known data
    http://img184.imageshack.us/img184/8454/26645063th6.png [Broken]

    2. Relevant equations

    The code
    Code (Text):

    u = [ 0 ;zeros(n-2,1); 0]; % this has to be zero.
    k = 0;
    r = b;

    while k<100
        k = k+1
        if k==1
            p = z;
            r_1 = b;
            z_1 = z;
            beta = (r_1'*z_1)/(r_2'*z_2);
            p = z_1+ beta*p;
        alpha = (r_1'*z_1)/(p'*A*p);
        u = u + alpha*p;
        r= r_1-alpha*A*p;

    r_2 = r_1;
    r_1 = r;

    z_2 = z_1;
    z_1 = z;


    3. The attempt at a solution
    Somewhere is a mistake in the code (aside the fact that A and b aren't shown), because it doesn't converge. But I can't find it. Can someone help me?
    Last edited by a moderator: May 3, 2017
  2. jcsd
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