46     *search_direction = -current.gradient;  in NextDirection()
69         gradient_change = current.gradient - previous.gradient;  in NextDirection()
70         beta = (current.gradient.dot(gradient_change) /  in NextDirection()
74         gradient_change = current.gradient - previous.gradient;  in NextDirection()
75         beta =  (current.gradient.dot(gradient_change) /  in NextDirection()
82     *search_direction =  -current.gradient + beta * previous.search_direction;  in NextDirection()
84         current.gradient.dot(*search_direction);  in NextDirection()
88       *search_direction = -current.gradient;  in NextDirection()
121         current.gradient - previous.gradient);  in NextDirection()
124     low_rank_inverse_hessian_.RightMultiply(current.gradient.data(),  in NextDirection()
128     if (search_direction->dot(current.gradient) >= 0.0) {  in NextDirection()
132                    << search_direction->dot(current.gradient);  in NextDirection()
175     const Vector delta_gradient = current.gradient - previous.gradient;  in NextDirection()
320         (-1.0 * current.gradient);  in NextDirection()
322     if (search_direction->dot(current.gradient) >= 0.0) {  in NextDirection()
326                    << search_direction->dot(current.gradient);  in NextDirection()