rpack.f90

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function rpack(x, x0, b, t, amp) result(f_rpack)
!-------------------------------------------------------------------
! polynomial to describe local changes of the radial coordinate
!       x0 : central x value
!       b  : the position of the maximum
!       t  : the total halfwidth
!------------------------------------------------------------------
  
  use itm_types

  implicit none
  
  real(r8) :: x, x0, b, t, amp
  real(r8) :: f_rpack
  
  real(r8) :: dx, p4
  
  dx = abs(x - x0)
  if (dx < b) then
    p4 = 2._r8 * dx / b - (dx / b)**2
  else
    dx = dx - b
    p4 = 1._r8 - 3._r8 * (dx / (t - b))**2 + 2._r8 * (dx &
     / (t - b))**3
  end if
  f_rpack = amp * p4
  if (x < x0) f_rpack = -f_rpack
  if (abs(x - x0) > t) f_rpack = 0._r8
  
end function rpack