curvefit_lmdif_func Subroutine

  subroutine curvefit_lmdif_func(model_func,a,xdata,ydata,tol,info)
    interface
       function model_func(x,a)
         real(8),dimension(:)       :: x
         real(8),dimension(:)       :: a
         real(8),dimension(size(x)) :: model_func
       end function model_func
    end interface
    real(8),dimension(:)           :: a
    real(8),dimension(:)           :: xdata
    real(8),dimension(size(xdata)) :: ydata
    integer                        :: m
    real(8),optional               :: tol
    integer,optional               :: info
    real(8)                        :: tol_
    integer                        :: info_
    integer                        :: n
    real(8),dimension(size(xdata)) :: fvec
    !
    tol_ = 1.d-15;if(present(tol))tol_=tol
    !
    n=size(a)
    m=size(xdata)
    !
    call lmdif1(curvefit_lmdif_func2sub,m,n,a,fvec,tol_,info_)
    !
    if(present(info))info=info_
  contains
    subroutine curvefit_lmdif_func2sub(m,n,a,fvec,iflag)
      integer ::  m
      integer ::  n
      real(8) ::  a(n)
      real(8) ::  fvec(m)
      integer ::  iflag
      fvec = model_func(xdata,a) - ydata
      if(iflag<0)stop "CURVEFIT_LMDIF_func2sub ERROR: iflag < 0 "
    end subroutine curvefit_lmdif_func2sub
  end subroutine curvefit_lmdif_func