The learning rate α t is set based on the bounded backtracking line search method . In general, for subgradient methods, line searches may not work well due to discontinuity in the gradient . However, it is only problematic when the signs of the errors change from the current value to the proposed value based on the new value of ζ. Therefore, the initial step size is set to be sufficiently small, similar to . This approach worked well in our numerical results. Subgradient of the loss for the parameters are expressed as follows.