The time-cost tradeoff problem (TCTP) is an important
issue in the scheduling of industrial projects; it is often possible
to expedite the completion of certain activities by increasing
the budget. This paper develops a new approach for the discrete
TCTP (DTCTP) in program evaluation and review technique networks
of project management, in which activities have multimode
discrete cost functions and activity durations are normally distributed.
Moreover, the first application of the ant colony system
(ACS) is applied to the stochastic DTCTP, solving it as a nonlinear
zero-one problem. To illustrate the suggested approach, a
numerical example is discussed and an overall efficiency measure
is developed to set the ACS parameters so as to reach more accurate
results with less computational time. The results obtained
from the computational study demonstrate the effectiveness of the
suggested approach for the DTCTP.