There are many designs and implementations of Transactional Memory, and that is not a coincidence: different ones perform best on different workloads. One cannot expect the developer to be aware of such concerns, as it is even contradictory with the simplicity advocated by the use of the transactional abstraction. With ProteusTM, the developer writes transactions and the underlying implementation uses techniques to automatically change Transactional Memory algorithms, parallelism degree, and others.