def columns_tag_from_columns(columns):
    """Generate a columns tag, to customize phase names based on the number of columns of data extracted in the fit,
    which is used to speed up parallel CTI fits.

    This changes the phase name 'phase_name' as follows:

    columns = None -> phase_name
    columns = 10 -> phase_name_col_10
    columns = 60 -> phase_name_col_60
    """
    if columns == None:
        return ''
    else:
        return '_col_' + str(int(columns))
