sll_m_primitives.F90

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module sll_m_primitives
!+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
#include "sll_working_precision.h"
 
   implicit none
 
   public :: &
      sll_s_function_to_primitive, &
      sll_s_primitive_to_function
 
   private
!+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 
contains
 
   subroutine sll_s_function_to_primitive(f, x, n, xm)
 
      sll_real64, dimension(:), intent(inout) :: f
      sll_real64, dimension(:), intent(in)    :: x
      sll_int32, intent(in)    :: n
      sll_real64, intent(out)   :: xm
 
      sll_int32  :: i
      sll_real64 :: dx
      sll_real64 :: tmp
      sll_real64 :: tmp2
 
      dx = 1._f64/real(n, f64)
 
!from f compute the mean
      xm = 0.0_f64
      do i = 1, n
         xm = xm + f(i)*(x(i + 1) - x(i))
      end do
 
      f(1) = (f(1) - xm)*(x(2) - x(1))
      tmp = f(1)
      f(1) = 0.0_f64
      do i = 2, n
         f(i) = (f(i) - xm)*(x(i + 1) - x(i))
         tmp2 = f(i)
         f(i) = f(i - 1) + tmp
         tmp = tmp2
      end do
      f(n + 1) = f(n) + tmp
 
   end subroutine sll_s_function_to_primitive
 
   subroutine sll_s_primitive_to_function(f, x, n, xm)
 
      sll_real64, dimension(:), intent(inout) :: f
      sll_real64, dimension(:), intent(in)    :: x
      sll_int32, intent(in)    :: n
      sll_real64, intent(in)    :: xm
 
      sll_int32                               :: i
      sll_real64                              :: tmp
      sll_real64                              :: dx
 
      dx = 1._f64/real(n, f64)
 
      tmp = f(1)
      do i = 1, n - 1
         f(i) = f(i + 1) - f(i) + xm*(x(i + 1) - x(i))
      end do
      f(n) = tmp - f(n) + xm*(x(1) + 1._f64 - x(n))
 
!from mean compute f
      do i = 1, n
         f(i) = f(i)/(x(i + 1) - x(i))
      end do
 
      f(n + 1) = f(1)
 
   end subroutine sll_s_primitive_to_function
 
end module sll_m_primitives