We consider a task graph model taking into account the communication a
mong tasks of a parallel system. First, we assume that the available n
umber of processors is adequate for dealing with the whole width of th
e task graph (i.e. the number of processors is unbounded), and we prop
ose a scheduling strategy, called Line-Schedule, which executes the ta
sks of a d-dimensional grid graph (d-D grid in short) in the optimal t
ime. We continue by proving that Line-Schedule is the only strategy ab
le to execute a d-D grid in the optimal time. Furthermore, we compute
the minimum number of processors required to execute a d-D grid optima
lly. (C) 1998 Elsevier Science B.V. All rights reserved.