anchor.diff:      end do
       end do
       sumKm_dotVm = sumKm_dotVm / nGrid
  -    KZero = sumKm / nGrid
  +    KZero = sumKm / nGrid 
       call invSymMat(invKZero, KZero, .true.)
       res = matmul(invKZero, sumKm_dotVm)
   
  
positive.code:     nx = size(Bx, 1)
      ny = size(Bx, 2)
      nz = size(Bx, 3)
      sumKm = 0
      sumKm_dotVm = 0
      do k = 1, nz
  
negative.code:       stop 
      end if
  
      call getri(working, ipiv, info)
      inv = working
      if ((info .ne. 0)) then
        print *, 'Computation is failed because of the element #', info
        stop
      end if
    end subroutine invSymMat
  
    subroutine calcVHT(vHT, Bx, By, Bz, vx, vy, vz)
  