Complexity of master-slave tasking on heterogeneous trees

In this paper, we consider the problem of scheduling independent identical tasks on heterogeneous processors and network, where processing times and communications times are different. We assume that communication-computation overlap is possible for every processor, but only allow one send and one receive at a time. In this model, we prove that scheduling on a tree network is NP-hard in the strong sense, reducing to it the well-known 3-partition problem.