This procedure does the following: The fit parameter specified by the integer grid_test_para is varied from the value grid_test_min to the value given by grid_test_max. Grid_test_no_points are used to cover this parameter range. For each value the fit deviation is computed. After the procedure the fit parameter is set to the best value found on this grid of tried values. This feature can be used before an automatic fit to find good starting values for some of the fit parameters.