A technique for selecting context models (CMs) for a CM ensemble (CME) in a context mixing compressor includes measuring compression ratios (CRs) of the compressor on a dataset for each CM included in a base set of CMs. A first CM that has a maximum CR for the dataset is added to the CME. In response to a desired number of the CMs not being in the CME, subsequent CRs for the compressor are measured on the dataset for each of the CMs in the base set of CMs that are not in the CME in conjunction with one or more CMs in the CME. In response to a desired number of the CMs not being in the CME, subsequent CMs that in conjunction with the one or more CMs in the CME result in a maximum subsequent CR for the dataset are added to the CME.