“…Other gradient descent-based optimization methods have also been implemented on neuromorphic systems for training, and they tend to be variations of back-propagation that have been adapted or simplified in some way [639], [645], [709], [716], [718], [719], [723], [792], [812], [844], [1030], [1122], [1300]- [1303]. Back-propagation methods have also been developed in chip-in-the-loop training methods [686], [702], [732], [815], [859]; in this case, most of the learning takes place on a host machine or off-chip, but the evaluation of the solution network is done on the chip. These methods can help to take into account some of the device's characteristics, such as component variation.…”