philim.f.html CLAWPACK  
 Source file:   philim.f
 Directory:   /Users/rjl/git/rjleveque/clawpack-4.6.3/book/chap9/acoustics/layered
 Converted:   Mon Jan 21 2013 at 20:15:48   using clawcode2html
 This documentation file will not reflect any later changes in the source file. 

 
c
c
c     =====================================================
      double precision function philim(a,b,meth)
c     =====================================================
      implicit real*8(a-h,o-z)
c
c     # Compute a limiter based on wave strengths a and b.
c     # meth determines what limiter is used.
c     # a is assumed to be nonzero.
c
      if (a .eq. 0.d0) then
         philim = 0.d0
	 return
	 endif

      r = b/a

c
   10 continue
c     --------
c     # minmod
c     --------
      philim = dmax1(0.d0, dmin1(1.d0, r))
      return
c
   20 continue
c     ----------
c     # superbee
c     ----------
      philim = dmax1(0.d0, dmin1(1.d0, 2.d0*r), dmin1(2.d0, r))
      return
c
   30 continue
c     ----------
c     # van Leer
c     ----------
      philim = (r + dabs(r)) / (1.d0 + dabs(r))
      return
c
   40 continue
c     ------------------------------
c     # monotinized centered 
c     ------------------------------
      c = (1.d0 + r)/2.d0
      philim = dmax1(0.d0, dmin1(c, 2.d0, 2.d0*r))
      return
c
   50 continue
c     ------------------------------
c     # Beam-Warming
c     ------------------------------
      philim = r

      return
      end