subroutine geom_to_var(n,x)
C
C Transfer the geometry parameters to the variable array.
C The positions of variables are as follows:
C 1. Virtual-bond torsional angles: 1 thru nres-3
C 2. Virtual-bond valence angles: nres-2 thru 2*nres-5
C 3. The polar angles alpha of local SC orientation: 2*nres-4 thru 
C    2*nres-4+nside
C 4. The torsional angles omega of SC orientation: 2*nres-4+nside+1
C    thru 2*nre-4+2*nside 
C
      implicit real*8 (a-h,o-z)
      include 'DIMENSIONS'
      include 'COMMON.VAR'
      include 'COMMON.GEO'
      include 'COMMON.CHAIN'
      double precision x(n)
cd    print *,'nres',nres,' nphi',nphi,' ntheta',ntheta,' nvar',nvar
      do i=4,nres
        x(i-3)=phi(i)
cd      print *,i,i-3,phi(i)
      enddo
      if (n.eq.nphi) return
      do i=3,nres
        x(i-2+nphi)=theta(i)
cd      print *,i,i-2+nphi,theta(i)
      enddo
      if (n.eq.nphi+ntheta) return
      do i=2,nres-1
	if (ialph(i,1).gt.0) then
	  x(ialph(i,1))=alph(i)
	  x(ialph(i,1)+nside)=omeg(i)
cd        print *,i,ialph(i,1),ialph(i,1)+nside,alph(i),omeg(i)
        endif
      enddo      
      return
      end
C--------------------------------------------------------------------
      subroutine var_to_geom(n,x)
C
C Update geometry parameters according to the variable array.
C
      implicit real*8 (a-h,o-z)
      include 'DIMENSIONS'
      include 'COMMON.VAR'
      include 'COMMON.CHAIN'
      include 'COMMON.GEO'
      include 'COMMON.IOUNITS'
      dimension x(n)
      logical change,reduce
      change=reduce(x)
      if (n.gt.nphi+ntheta) then
        do i=1,nside
          ii=ialph(i,2)
          alph(ii)=x(nphi+ntheta+i)
          omeg(ii)=pinorm(x(nphi+ntheta+nside+i))
        enddo      
      endif
      do i=4,nres
        phi(i)=x(i-3)
      enddo
      if (n.eq.nphi) return
      do i=3,nres
        theta(i)=x(i-2+nphi)
        if (theta(i).eq.pi) theta(i)=0.99d0*pi
        x(i-2+nphi)=theta(i)
      enddo
      return
      end
c-------------------------------------------------------------------------
      logical function convert_side(alphi,omegi)
      implicit none
      double precision alphi,omegi
      double precision pinorm
      include 'COMMON.GEO'
      convert_side=.false.
C Apply periodicity restrictions.
      if (alphi.gt.pi) then
        alphi=dwapi-alphi
        omegi=pinorm(omegi+pi)
        convert_side=.true.
      endif
      return
      end
c-------------------------------------------------------------------------
      logical function reduce(x)
C
C Apply periodic restrictions to variables.
C
      implicit real*8 (a-h,o-z)
      include 'DIMENSIONS'
      include 'COMMON.VAR'
      include 'COMMON.CHAIN'
      include 'COMMON.GEO'
      logical zm,zmiana,convert_side
      dimension x(nvar)
      zmiana=.false.
      do i=4,nres
        x(i-3)=pinorm(x(i-3))
      enddo
      if (nvar.gt.nphi+ntheta) then
        do i=1,nside
          ii=nphi+ntheta+i
          iii=ii+nside
          x(ii)=thetnorm(x(ii))
          x(iii)=pinorm(x(iii))
C Apply periodic restrictions.
          zm=convert_side(x(ii),x(iii))
          zmiana=zmiana.or.zm
        enddo      
      endif
      if (nvar.eq.nphi) return
      do i=3,nres
        ii=i-2+nphi
        iii=i-3
        x(ii)=dmod(x(ii),dwapi)
C Apply periodic restrictions.
        if (x(ii).gt.pi) then
          zmiana=.true.
          x(ii)=dwapi-x(ii)
          if (iii.gt.0) x(iii)=pinorm(x(iii)+pi)
          if (i.lt.nres) x(iii+1)=pinorm(x(iii+1)+pi)
          ii=ialph(i-1,1)
          if (ii.gt.0) then
            x(ii)=dmod(pi-x(ii),dwapi)
            x(ii+nside)=pinorm(-x(ii+nside))
            zm=convert_side(x(ii),x(ii+nside))
          endif
        else if (x(ii).lt.-pi) then
          zmiana=.true.
          x(ii)=dwapi+x(ii)
          ii=ialph(i-1,1)
          if (ii.gt.0) then
            x(ii)=dmod(pi-x(ii),dwapi)
            x(ii+nside)=pinorm(-pi-x(ii+nside))
            zm=convert_side(x(ii),x(ii+nside))
          endif
        else if (x(ii).lt.0.0d0) then
          zmiana=.true.
          x(ii)=-x(ii)
          if (iii.gt.0) x(iii)=pinorm(x(iii)+pi)
          if (i.lt.nres) x(iii+1)=pinorm(x(iii+1)+pi)
          ii=ialph(i-1,1)
          if (ii.gt.0) then
            x(ii+nside)=pinorm(-x(ii+nside))
            zm=convert_side(x(ii),x(ii+nside))
          endif
        endif 
      enddo
      reduce=zmiana
      return
      end
c--------------------------------------------------------------------------
      double precision function thetnorm(x)
C This function puts x within [0,2Pi].
      implicit none
      double precision x,xx
      include 'COMMON.GEO'
      xx=dmod(x,dwapi)
      if (xx.lt.0.0d0) xx=xx+dwapi
      if (xx.gt.0.9999d0*pi) xx=0.9999d0*pi
      thetnorm=xx
      return
      end 
C--------------------------------------------------------------------
      subroutine var_to_geom_restr(n,xx)
C
C Update geometry parameters according to the variable array.
C
      implicit real*8 (a-h,o-z)
      include 'DIMENSIONS'
      include 'COMMON.VAR'
      include 'COMMON.CHAIN'
      include 'COMMON.GEO'
      include 'COMMON.IOUNITS'
      dimension x(maxvar),xx(maxvar)
      logical change,reduce

      call xx2x(x,xx)
      change=reduce(x)
      do i=1,nside
          ii=ialph(i,2)
          alph(ii)=x(nphi+ntheta+i)
          omeg(ii)=pinorm(x(nphi+ntheta+nside+i))
      enddo      
      do i=4,nres
        phi(i)=x(i-3)
      enddo
      do i=3,nres
        theta(i)=x(i-2+nphi)
        if (theta(i).eq.pi) theta(i)=0.99d0*pi
        x(i-2+nphi)=theta(i)
      enddo
      return
      end
c-------------------------------------------------------------------------