Discriminator Goal

[renswny]

Is the discriminator's goal to determine relevant vs. non-relevant query-document pairs, or true vs. generated query-document pairs? If the former is true, shouldn't the stopping criteria for IRGAN be the discriminator converging to 1 (relevant) everywhere, instead of 0.5? If the latter is true, shouldn't the generator perform positive sampling instead of negative sampling in order to fool the discriminator? Thanks in advance for the clarification!

[wnzhang]

The discriminator tries to detect whether a query-doc pair is from true data distribution or the generated one, not about the (non)-relevancy. The generator tries to create a CONDITIONAL distribution of documents given the user's query P(d|q;theta), thus when such a distribution perfectly fits the true preference distribution P_data(d|q), the discriminator cannot distinguish whether a query-doc pair is from P(d|q;theta) or P_data(d|q). Thus the prediction of D should be 0.5 instead of 1.0.