subroutine Chi2(iflag, m, n, X, Fvec, Fjac, ldFjac)

c***********************************************************************
c     Chi2 is designed to be called by snls1. It returns a vector
c     of deviation Fvec(m) which would be minimized in snls1.
c 
c     iflag is assighed by snls1. if iflag = 0, Chi2 only prints,
c        	 iflag != 0, chi2 only calculates, doesn't print.
c***********************************************************************
c     
      integer i, ner
      integer n, m, ldfjac
      double precision er1, er2, ep11, xtol
c      double precision Diag(3), Qtf(3)
c      double precision Wa1(3), Wa2(3), Wa3(3), Wa4(450)
c     
      integer Nifty, nfit, iflag, Fidx
      double precision X(n), Xpole(2), Fvec(m), Fjac(ldFjac,n)
      double precision exp_xs, th_xs, zero, Scale(6)
      double precision f0,mgb,alpha,c1,c2,Mbare,mpion,Mass,rcbm

      common /control/ Nifty(15)
      common /bag/ rcbm,f0,mgb,alpha,c1,c2,Mbare(3),Fidx(3)
      common /mass/ mpion, Mass(2)

      common /data/ exp_xs(20, 6), th_xs(20, 6), nfit
      external Det1Mvg
      parameter (zero = 0.0d0)
      data xtol /1.0d-2/, epsfcn /1.0d-6/, ep11 /940.d0/
      data Scale /1.d5,1.d6,1.d6,1.d5,1.d5,1.d4/

c*********************************************************

      call GetFit(x)
     
c     print x Fvec if iflag == 0
      if (iflag .eq. 0) then
         write(8, 900)
         call PrtPot()
     
      else
c     calculate chi-square if iflag != 0
c       chi-square from scattering data
c       nfit is assgined in obs (to be 5)

        call Obs(er1, er2, ner)

	do i = 1, nfit
  	Fvec(i) = ((exp_xs(i,6) - th_xs(i,6))/exp_xs(i,6))**2 
	enddo

c	constraints from P11 phase shift
	Fvec(4) = abs((exp_xs(2,3) - th_xs(2,3))/exp_xs(2,3))
	Fvec(5) = ((exp_xs(5,3) - th_xs(5,3))/exp_xs(5,3))**2

c       chi-square from p11 pole (nucleon mass)
         Xpole(1) = ep11 - mpion - Mass(1)
         Xpole(2) = 0.
	 Nifty(6) = 3
         call GetPole(Xpole,xtol,epsfcn)
	 Nifty(6) = 6

	 Fvec(nfit+1) = (Xpole(1)+mpion+Mass(1)-ep11)**2
c	 Fvec(nfit+2) = (X(2)/ep11)**2
	 do i = 1, nfit+1
	        Fvec(i) = Scale(i)*Fvec(i)
         enddo 
	 write(*,999) f0,Mbare(1),Mbare(2),
     &		Xpole(1)+mpion+Mass(1),Fvec(3),Fvec(6)
	endif

 999  format('CHI2::f0,Mbare=',3e12.5,2x,'POLE=',3e12.4)
 900  format('0', 10('-'), 'Chi2, Beginning of printing mode ', 10('-'))
 940  format('0', 'Chi-Square = ', e13.7,
     &     3x, 'Chi-Square/per-freedom = ', e13.7)
 945  format('0', 'Chi-Square = ', e13.7)
     
      return
      end