The PTAS for the Problem of P_m|r_j,B|∑C_j

In this paper, we consider the scheduling problem on identicall parallel batch machines with jobs having release time. We get ploynomial time approximation scheme (PTAS) for this problem when the batch capcity and the number of machines are both constant. For the unit batch machine, we get PTAS with less run time. Some present result are extended.