regularise_l1 Subroutine

  pure subroutine regularise_l1(this, params, gradient, learning_rate)
    !! Regularise the parameters using L1 regularisation
    implicit none

    ! Arguments
    class(l1_regulariser_type), intent(in) :: this
    !! Instance of the L1 regulariser
    real(real32), dimension(:),  intent(in) :: params
    !! Parameters to regularise
    real(real32), dimension(:), intent(inout) :: gradient
    !! Gradient of the parameters
    real(real32), intent(in) :: learning_rate
    !! Learning rate

    gradient = gradient + learning_rate * this%l1 * sign(1._real32,params)

  end subroutine regularise_l1