Offline evaluation of ranking functions

An example system includes a processor to receive production log data and pre-process the production log data to generate an exploration data set. The production log data includes continuous updates of a ranking function associated with different actions for a same query issued by a same user in different impressions. The processor can perform offline estimation of online metrics for ranking functions using the exploration data set, evaluate a proposed ranking function by comparing the estimated online metrics to a set of baseline metrics of a baseline ranking function, detect that the proposed ranking function is a preferred ranking function having a higher detected metric score than the baseline ranking function based on a comparison of the estimated online metrics with the baseline metrics of the baseline ranking function, and execute an action on an information retrieval system based on the preferred ranking function.