  Federated learning (FL) enables distributed participants to collectively
learn a strong global model without sacrificing their individual data privacy.
Mainstream FL approaches require each participant to share a common network
architecture and further assume that data are are sampled IID across
participants. However, in real-world deployments participants may require
heterogeneous network architectures; and the data distribution is almost
certainly non-uniform across participants. To address these issues we introduce
FedH2L, which is agnostic to both the model architecture and robust to
different data distributions across participants. In contrast to approaches
sharing parameters or gradients, FedH2L relies on mutual distillation,
exchanging only posteriors on a shared seed set between participants in a
decentralized manner. This makes it extremely bandwidth efficient, model
agnostic, and crucially produces models capable of performing well on the whole
data distribution when learning from heterogeneous silos.
