apply_clip Subroutine

  pure subroutine apply_clip(this, length, gradient, bias)
    !! Function to apply clipping to gradients
    implicit none

    ! Arguments
    class(clip_type), intent(in) :: this
    !! Instance of the clip type
    integer, intent(in) :: length
    !! Length of the gradient
    real(real32), dimension(length), intent(inout) :: gradient
    !! Gradient to be clipped
    real(real32), dimension(:), optional, intent(inout) :: bias
    !! Bias to be clipped

    ! Local variables
    real(real32) :: scale
    !! Scaling factor for the gradient
    real(real32), dimension(:), allocatable :: bias_
    !! Copy of the bias

    if(present(bias))then
       bias_ = bias
    else
       allocate(bias_(1), source=0._real32)
    end if

    ! Clip values to within limits of (min,max)
    if(this%l_min_max)then
       gradient = max(this%min,min(this%max,gradient))
       bias_   = max(this%min,min(this%max,bias_))
    end if

    ! Clip values to a maximum L2-norm
    if(this%l_norm)then
       scale = min(1._real32, &
            this%norm/sqrt(sum(gradient**2._real32) + &
            sum(bias_)**2._real32))
       if(scale.lt.1._real32)then
          gradient = gradient * scale
          bias_   = bias_ * scale
       end if
    end if

    if(present(bias)) bias = bias_

  end subroutine apply_clip