c
c
      subroutine invproc(nlay,thick,xcomp) 

*$noereference
      include 'p1werm.inc'
*$reference

c     + + + PURPOSE + + +
c     
c	  Invert the component passed to xcomp 
c	  
c     + + + KEYWORDS + + +
c     inversion, tillage 
c
c     + + + ARGUMENT DECLARATIONS + + +

      real xcomp(mnsz), thick(mnsz)
      integer nlay
c
c     + + + ARGUMENT DEFINITIONS + + +

c     nlay		- number of soil layers used
c     thick		- thickness of each layer in a subregion
c	  xcomp		- component that needs inverting
c

c     + + + LOCAL VARIABLES + + +

      integer   idx, odx
      real      ithick(mnsz), ixcomp(mnsz)
      real      othick(mnsz)
      real      dthick

c     + + + LOCAL VARIABLE DEFINITIONS + + +
c     idx      - input index for layers
c     odx      - output index for layers
c     ithick   - inverted thickness of layers
c     ixcomp   - inverted property of layers
c     othick   - temp thickness
c     dthick   - delta thickness
C
C create inverted layer thickness and property arrays
C and zero out output array
C
      do 10 idx=1, nlay
        ithick(idx) = thick(nlay-idx+1)
        ixcomp(idx) = xcomp(nlay-idx+1)
        xcomp(nlay-idx+1) = 0.0
        othick(idx) = thick(idx)
   10 continue

      idx = 1
      odx = 1

   20 dthick = min(ithick(idx), othick(odx))
      xcomp(odx) = xcomp(odx) + ixcomp(idx) * dthick
      ithick(idx) = ithick(idx) - dthick
      othick(odx) = othick(odx) - dthick
      if (ithick(idx).eq.0.0) idx = idx + 1
      if (othick(odx).eq.0.0) odx = odx + 1
      if (idx.le.nlay.and.odx.le.nlay) goto 20

      do 30 odx = 1, nlay
        xcomp(odx) = xcomp(odx) / thick(odx)
   30 continue

      return
      end
      

C ***c     + + + LOCAL VARIABLES + + +
C ***
C ***      integer i
C ***	  real dum(mnsz),dum1(mnsz),dum2(mnsz) 
C ***	  real inverse(mnsz), depth(mnsz), oldepth(0:mnsz)
C ***	  real x, new,  p(mnsz)  
C ***c
C ***c     + + + LOCAL VARIABLE DEFINITIONS + + +
C ***c
C ***c     dum		- dummy variable used in making a property array
C ***c     dum1		- dummy variable used in making a property array
C ***c     dum2		- dummy variable used in making a property array
C ***c     depth		- depth matrix containing inverted layer depths from the surface
C ***c     i			- loop variable for soil layers
C ***c     inverse	- inverse layer thickness matrix
C ***c	  new		- new inverted property value based on interpolation or
C ***c	  			  extrapolation
C ***c     oldepth	- depth matrix containing original layer depths from the surface
C ***c     p			- property matrix after inversion
C ***c     x			- variable containing the original depths from the surface
C ***c				  used in the call to polint
C ***	   
C ***c     Do the inversion process. 
C ***c     Initialize the dummy variables to zero.
C ***
C ***	  dum(1) = 0.0
C ***	  dum1(1) = 0.0
C ***	  dum2(1) = 0.0
C ***	  oldepth(0) = 0.0
C ***
C ***	  do 100 i=1,nlay
C ***c      invert the layers (layer thickness) 
C ***	    inverse(i) = thick((nlay+1)-i)
C ***c      invert the property passed to xcomp  
C ***		p(i) = xcomp((nlay+1)-i)
C ***c     form a property array for the depth (thichness) and component based
C ***c     on the inverted matrix 
C ***	  dum(i+1) = thick(i)
C ***	  dum1(i+1) = inverse(i) 
C ***	  depth(i)=inverse(i)/2.0+dum1(i)/2.0+dum2(i) 
C ***	  dum2(i+1)= depth(i)
C ***	  oldepth(i)=thick(i)/2.0+dum(i)/2.0+oldepth(i-1)
C ***100   continue
C ***c
C ***c     make a call to subroutine polint which takes the current
C ***c     property matrix and depth matrix and either interpolates
C ***c     or extrapolates the property matrix to correspond to the
C ***c     original layer thickness before the inversion process 
C ***c     was performed.  Make call for each layer (nlay). 
C ***c
C ***      do 200 i=1,nlay
C ***        x=oldepth(i) 
C ***	    call polint(depth, p, nlay, x, new)
C ***c
C ***c     set the component for a layer equal to the interpolated
C ***c     or extrapolated value calculated in polint.for 
C ***c
C ***	    xcomp(i) = new
C ***200   continue   
C ***	  end