MFIT /EPSILON

        This option is used to specify the desired tolerance. Its  interpre-
    tation  is  method dependent. For SIMPLEX and POWELL, it means the rela-
    tive deviation of the mean squared difference of two fit iterations. For
    SLATEC,  which uses non-reduced chi-2, it is the absolute difference be-
    tween two iterations. For ANNEAL, its interpretation is totally  differ-
    ent.

    Use  default  value  0  to let the program guess. In subtle cases, or to
    gain speed in case a coarse result is desired, use  values  around  1D-5
    for  SIMPLEX  and POWELL, and of order 1 for SLATEC. For ANNEAL, see de-
    tails in the /METHOD option.

    Note that this is not the absolute error of the fit parameters.