% m3_CGconvergence.m - explore CG convergence

   A = diag(100:199);
   b = ones(100,1);
   x = cg(A,b);
   whos
   x(1:4)

   A = diag( sparse(1000000:1999999) );
   b = ones(1000000,1);
   x = cg(A,b);
   whos
   x(1:4)

% - - - - - -  - - - - - - - - - - -   [pause]

   A = randn(1000);
   A = A'*A;
   b = ones(1000,1);
   kappa = cond(A)
   e = eig(A); max(e)/min(e)
   sqrt(kappa)
   cg(A,b);

   A = A + 100*eye(1000);
   kappa = cond(A)
   sqrt(kappa)
   cg(A,b);