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.