Agnetis, Alessandro; Flamini, Marta; Nicosia, Gaia; … - In: European Journal of Operational Research 202 (2010) 3, pp. 669-674
We consider the problem of scheduling n tasks subject to chain-precedence constraints on two identical machines with the objective of minimizing the makespan. The problem is known to be strongly NP-hard. Here, we prove that it is binary NP-hard even with three chains. Furthermore, we...