routine    

is the name of a subroutine you have defined, which is called when the mutation operator is applied. This parameter must be a string literal; a variable is not accepted.

nparents

is optional, and specifies the number of parent solutions the operator requires. If not specified, 2 is assumed.

nchildren

is optional, and specifies the number of children solutions the operator will generate. If not specified, 2 is assumed.