Using a PID controller engine for controlling the pace of an online campaign in realtime

The invention uses a PID controller engine to provide a desired distribution of targeted ad placements, including controlling campaign pace in realtime to precisely spend a campaign budget over a prescribed runtime, while producing optimum results in a cost efficient manner based on desired targeting parameters. Those parameters include one or more probabilities that a viewer associated with an ad impression opportunity: belongs to one or more targeted demographic categories; will convert with respect to a product or service being offered; has an intention to buy the product or service; or exhibits one or more defined behaviors. Probabilities are determined by a truth-based machine-learning modelling engine. Upon receiving an ad slot opportunity package, a DSP makes a bid decision and determines a bid price, and then sends a bid response to the supply-side partner, all within 200 mS of receiving the ad slot opportunity or the bid will be ignored.