executions. As an alternative, WebPPL supports sharing parameters between WebPPL processes using MongoDB. This can be used to persist parameters across runs, speed up optimization by running multiple identical identical processes in parallel, and optimize multiple objectives simultaneously. To use the MongoDB store, select it at startup time as follows: webppl model.wppl --param-store mongo Parameters are --param-store mongo --param-id my-parameter-set To use the MongoDB store, MongoDB must be running. By default, WebPPL will look for MongoDB at localhost:27017 and use the collection parameters. This can