c	***********************************************************************
	subroutine interdp(yy,zz,m,y,z,n,opt)
c	interpolation soubroutine. input values: y(n) at z(n). 
c	output values: yy(m) at zz(m). options: 1 -> lineal; 2 -> logarithmic
c       jul 2011:  malv+fgg   Adapted to LMD-MGCM
c	***********************************************************************
        implicit none
	integer n,m,i,j,opt
	real*8 zz(m),yy(m),z(n),y(n), zmin,zzmin,zmax,zzmax

!	write (*,*) ' d interpolating '
	call mindp (z,n,zmin)
	call mindp (zz,m,zzmin)
	call maxdp (z,n,zmax)
	call maxdp (zz,m,zzmax)

	if(zzmin.lt.zmin)then
		write (*,*) 'from d interp: new variable out of limits'
		write (*,*) zzmin,'must be .ge. ',zmin
		stop
!	elseif(zzmax.gt.zmax)then
!		write (*,*) 'from interp: new variable out of limits'
!		write (*,*) zzmax, 'must be .le. ',zmax
!		stop
	end if

	do 1,i=1,m

	do 2,j=1,n-1
	if(zz(i).ge.z(j).and.zz(i).lt.z(j+1)) goto 3
 2	continue
c	in this case (zz(m).eq.z(n)) and j leaves the loop with j=n-1+1=n
	if(opt.eq.1)then
	 	yy(i)=y(n-1)+(y(n)-y(n-1))*(zz(i)-z(n-1))/(z(n)-z(n-1))
	elseif(opt.eq.2)then
		if(y(n).eq.0.0d0.or.y(n-1).eq.0.0d0)then
			yy(i)=0.0d0
		else
			yy(i)=dexp(dlog(y(n-1))+dlog(y(n)/y(n-1))*
     @			(zz(i)-z(n-1))/(z(n)-z(n-1)))
		end if
	else
		write (*,*) 
     @           ' from d interp error: opt must be 1 or 2, opt= ',opt
	end if
	goto 1
 3	continue
	if(opt.eq.1)then
	 	yy(i)=y(j)+(y(j+1)-y(j))*(zz(i)-z(j))/(z(j+1)-z(j))
!	write (*,*) ' '
!	write (*,*) ' z(j),z(j+1) =', z(j),z(j+1)
!	write (*,*) ' t(j),t(j+1) =', y(j),y(j+1)
!	write (*,*) ' zz, tt =  ', zz(i), yy(i)
	elseif(opt.eq.2)then
		if(y(j+1).eq.0.0d0.or.y(j).eq.0.0d0)then
			yy(i)=0.0d0
		else
			yy(i)=dexp(dlog(y(j))+dlog(y(j+1)/y(j))*
     @			(zz(i)-z(j))/(z(j+1)-z(j)))
		end if
	else
		write (*,*) ' from interp error: opt must be 1 or 2, opt= ',
     @                      opt
	end if
 1	continue
	return
	end