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Optimistic make is a version of make that executes the commands necessary to bring targets up-to-date prior to the time the user types a make request. Side effects of these optimistic computations (such as file or screen updates) are concealed until the make request is issued. If the inputs read by the optimistic computations are identical to the inputs the computation would read at the time the make request is issued, the results of the optimistic computations are used immediately, resulting in improved response time. Otherwise, the necessary computations are reexecuted. We have implemented optimistic make in the V-System on a collection of SUN-3 workstations. Statistics collected from this implementation are used to synthesize a workload for a discrete-event simulation and to validate its results. The simulation shows a speedup distribution over pessimistic make with a median of 1.72 and a mean of 8.28. The speedup distribution is strongly dependent on the ratio between the target out-of-date times and the command execution times. In particular, with faster machines the median of the speedup distribution grows to 5.1, and then decreases again. The extra machine resources used by optimistic make are well within the limit of available resources, given the large idle times observed in many workstation environments