c
c------------------------------------------------------------------
c Begin file /home/sting/foster/timesdif/mkdifs.f
c------------------------------------------------------------------
c
      subroutine mkdifs(fld,pnt)
c
c Find differences: fld = fld - pnt
c
c On input:
c   pnt contains control for all fields (ntimefld), whereas fld 
c     contains perturbed only for fields to be plotted (nplfld)
c On output:
c   pnt is unchanged, fld contains differences
c
      include "gettime.h"
      include "timesdif.h"
      dimension pnt(imx,kmx,jmx,ntimefld),fld(imx,kmx,jmx,nplfld)
c
      ixp = 0
      eps = 1.e-20
      do ip=1,ntimefld
        if (ipltime(ip).le.0) goto 100
        ixp = ixp+1
        if (wtime(ip).gt.0..or.ip.eq.itxne) then
c
c Find percent diffs:
c 4/9/92: fix to avoid zero lower bounds:
c
          do j=1,jmx
            do k=1,kmx
              do i=1,imx
                if (pnt(i,k,j,ip).gt.eps) then
                  fld(i,k,j,ixp) = (fld(i,k,j,ixp) - pnt(i,k,j,ip)) /
     +              pnt(i,k,j,ip) * 100.
                else
                  fld(i,k,j,ixp) = cpspval
                endif
              enddo
            enddo
          enddo
c
c Find raw diffs:
c
        else
          fld(:,:,:,ixp) = fld(:,:,:,ixp) - pnt(:,:,:,ip)
        endif
 100    continue
      enddo
c 
      return
      end