while 1
    for i = 1:n
        for j = 1:n
            if M(i,j) != 0
                this_sum = PR_old(j)/X(j) + this_sum;
            endif
        endfor
        PR(i) = (1 - d)/n + d*this_sum;
        endfor
        PR_old = PR;
        R_old = R;
        R = PR;
        this_sum = 0;
        if norm(R-R_old) < eps
            return
        endif
    endwhile