Workers can be assigned parameters to measure in parallel using multiprocessing, and measurement duration is set to be variable. Upon receiving a measurement, Atlas re-trains its surrogate model, but also conditions its recommendations on pending experiments, i.e. those that have been assigned to a worker but whose measurement has not completed (the reader is referred to Section III A for additional information on setting pending parameter constraints in Atlas). This is achieved with a built-in mechanism to generate fictitious measurements, y ′ for pending parameters, x ′ . Specifically, we adopt the hallucination or kriging believer strategy first reported by Ginsbourger et al., which imputes the expected value of each pending parameter,