slopeLimiter.F90

module slopeLimiter
  
#include "definition.h"
  
  !use grid_data


contains

  subroutine minmod(a,b,delta)
    implicit none
    real, intent(IN) :: a, b
    real, intent(OUT) :: delta

    delta = 0.5 * (sign(1.0,a) + sign(1.0,b))*min(abs(a),abs(b))

    return
  end subroutine minmod

  
  subroutine mc(a,b,delta)
    implicit none
    real, intent(IN) :: a, b
    real, intent(OUT) :: delta
    delta = (sign(1.,a)+sign(1.,b))*min(abs(a),.25*abs(a+b),abs(b))
    return
  end subroutine mc

  
  subroutine vanLeer(a,b,delta)
    implicit none
    real, intent(IN) :: a, b
    real, intent(OUT) :: delta

    if (a*b > 0) then
       delta = 2.*a*b/(a+b)
    else 
       delta = 0.
    endif
    
    return
  end subroutine vanLeer
  
end module slopeLimiter