13. The system of claim 11 , wherein the plurality of matching information items are a second plurality of matching information items; and the one or more processors are further configured to: receive the search request; generate a first plurality of matching information items; preprocess the first plurality of matching information items; and select from the first plurality of matching information items the second plurality of matching information items.
11. A system for generating ranked search results, comprising: one or more processors configured to: receive a plurality of matching information items that match a search request; rank at least some of the plurality of matching information items using a linear ranking model that linearly combines a first plurality of feature values for the at least some of the plurality of matching information items to obtain a first set of ranked results; rank at least some of the first set of ranked results using a nonlinear ranking model that nonlinearly combines a second plurality of feature values for at least some of the first set of ranked results to obtain a second set of ranked results; and provide a search response based at least in part on the second set of ranked results; one or more memories coupled to the one or more processors, configured to provide the processors with instructions.