function [x,n]=fastdown(A,b,x0,eps)if(nargin == 3)    eps = 1.0e-6;endr  = b-A*x0;d  = dot(r,r)/dot(A*r,r);x  = x0+d*r;n=1;while(norm(x-x0)>eps)    x0 = x;    r  = b-A*x0;    d  = dot(r,r)/dot(A*r,r);    x  = x0+d*r;    n  = n + 1;end