The basic steps of our column generation scheme (CGS) are
as follows. The master problem is initialized with a solution to a simplified version of the NAM
presented below. We then solve its LP relaxation to get the dual prices for each constraint
containing the yickh variables. Once these values are available, we determine the reduced cost
for each case c and solve the corresponding subproblem. If the optimal objective function value
is negative, then a new column is identified and added to the master problem. By re-solving the
master problem, new values for the dual variables are found and the scheme is repeated. The process
continues until either no negative reduced cost is found or a stopping criterion (e.g., time
limit, iterations) is reached. Nurse-related applications
of column generation are addressed in [17,13,12].