the mad program

EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH

Define Variable Parameter

VARY: Define Variable Parameter

A parameter to be varied is specified by the command

VARY,NAME=variable,STEP=real,LOWER=real,UPPER=real;

It has four attributes:

NAME: The name of the parameter or attribute to be varied,
STEP: The approximate initial step size for varying the parameter. If the step is not entered, MAD tries to find a reasonable step, but this may not always work.
LOWER: Lower limit for the parameter (optional),
UPPER: Upper limit for the parameter (optional).
SLOPE: allowed change rate (optional, available only using JACOBIAN routine). Limit the parameter to increase (SLOPE=1) decrease (SLOPE=-1) only.
OPT: optimal value for the parameter (optional, available only using JACOBIAN routine).

Examples:

VARY,NAME=PAR1,STEP=1.0E-4;                         ! vary global parameter PAR1 
VARY,NAME=QL11->K1,STEP=1.0E-6;                     ! vary attribute K1 of the QL11 
VARY,NAME=Q15->K1,STEP=0.0001,LOWER=0.0,UPPER=0.08; ! vary with limits

If the upper limit is smaller than the lower limit, the two limits are interchanged. If the current value is outside the range defined by the limits, it is brought back to range. If a parameter comes outside the limits during the matching process the matching module resets the parameter to a value inside the limits and informs the user with a message. If such a 'rescaling' occurs more than 20 times the matching process terminates. The user should either eliminate the corresponding parameters from the list of varied parameters or change the corresponding upper and lower limits before restarting the matching process. After a matching operation all varied attributes retain their value after the last successful matching iteration. Using JACOBIAN routine, STRATEGY=3, in case the number of parameters is greater the the number of constraint, if a parameter comes outside the limits, it is excluded automatically from the set of variables and a new solution is searched.

Oliver Brüning, June, 2002. Riccardo de Maria, February, 2006.