run_control command.
&frequency_map
    STRING output = NULL;
    double xmin = 1e-6;
    double xmax = 0.1;
    double ymin = 1e-6;
    double ymax = 0.1;
    long nx = 21;
    long ny = 21;
    long verbosity = 1;
    long include_changes = 0;
&end
output -- The (incomplete) name of an SDDS file to send output to.  
 Recommended value: ``%s.fma''.
xmin, xmax -- Limits of grid of initial x coordinates for tracking.             
 xmin should typically be a small, positive value so that there                               
 is some betatron oscillation from which to get the tune.                                            
ymin, ymax -- Limits of grid of initial y coordinates for tracking.             
 ymin should typically be a small, positive value so that there                               
 is some betatron oscillation from which to get the tune.                       
nx -- Number of values of x coordinate in the grid.
ny -- Number of values of y coordinate in the grid.
verbosity -- If nonzero, prints possibly useful information while running.
include_changes -- If nonozero, then computes not only the tunes, but also
        the changes in the tunes.  It is recommended to leave this at the default value of
        0, since the resolution of the tunes is higher then.