sll_m_initial_distribution_functions.F90

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module sll_m_initial_distribution_functions
!+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
#include "sll_working_precision.h"
 
   use sll_m_constants, only: &
      sll_kx, &
      sll_p_pi
 
   implicit none
 
   private
!+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 
contains
   elemental function landau(x, v)
      sll_real64, intent(in) :: x, v
      sll_real64 :: landau
      sll_real64, parameter :: eps = 0.01_f64
 
      ! sll_kx is defined in the sll_m_constants module.
      ! It is set at the mesh initialization
      landau = (1.0_f64 + eps*cos(sll_kx*x)) &
               /sqrt(2.0_f64*sll_p_pi)*exp(-0.5_f64*v*v)
   end function landau
 
   elemental function two_stream(x, v) result(fval)
      sll_real64, intent(in) :: x, v
      sll_real64 :: fval
      ! local variables
      sll_real64, parameter :: eps = 0.01_f64
      sll_real64, parameter :: xi = 0.90_f64
      sll_real64, parameter :: v0 = 2.4_f64
      sll_real64 :: vv
      ! sll_kx is defined in the sll_m_constants module.
      ! It is set at the mesh initialization
      vv = v*v
      fval = (1.0_f64 + eps*((cos(2*sll_kx*x) + cos(3*sll_kx*x))/1.2_f64 + cos(sll_kx*x)))* &
             (1.0_f64/sqrt(2*sll_p_pi))*((2 - 2*xi)/(3 - 2*xi))* &
             (1.0_f64 + .5_f64*vv/(1 - xi))*exp(-.5_f64*vv)
      !fval=(1+eps*eps*cos(sll_kx*x)+eps*cos(2*sll_kx*x))*0.5_f64/sqrt(2*pi) &
      !     *(exp(-.5_f64*(vx-v0)**2)+ exp(-.5_f64*(vx+v0)**2))
      !fval=(1+eps*cos(sll_kx*x))*0.5_f64/sqrt(2*pi)*(exp(-.5_f64*(vx-v0)**2) &
      !     + exp(-.5_f64*(vx+v0)**2))
      !fval= 1/sqrt (2 * sll_p_pi) * ( 0.9_f64 * exp (-.5_f64 * vx * vx) &
      !     + 0.2_f64 * exp(-0.5_f64 * (vx - 4.5_f64)*(vx - 4.5_f64)   &
      !     /(0.5_f64 * 0.5_f64))) * (1. + 0.03_f64 * cos (0.3_f64 * x))
      ! fval=(1+eps*cos(sll_kx*x))*1/sqrt(2*pi)*exp(-.5_f64*vv)
      ! fval=exp(-.5_f64*(xx+vv))
   end function two_stream
 
   ! Samuel : I've change elemental by pure because there is an error with
   ! gcc 4.7.0 in the unit_test because he does'nt like pointer to elemental
   ! function.
 
   pure function sll_m_gaussian(x, v) result(fval)
      sll_real64, intent(in) :: x, v
      sll_real64 :: fval
      ! local variables
      sll_real64, parameter :: xoffset = 0.5_f64
      sll_real64, parameter :: voffset = 0.5_f64
      sll_real64 :: xx, vv
 
      xx = (x - xoffset)**2
      vv = (v - voffset)**2
      fval = exp(-0.5_f64*(xx + vv)*40._f64)
   end function sll_m_gaussian
 
end module