Roles: Guest, Host, Arbiter

[henrydrp10]

Hello,

I don't really know the meaning of each role, and haven't been able to find it online. I am currently trying to perform horizontal Federated Learning on a Gradient Boosting Decision Tree - HomoSecureBoost. From my understanding, there is a server, who aggregates the local results of the workers, who train subsets of the dataset locally. What do the roles (guest, host and arbiter) actually represent? Why is the RMSE value different between the hosts and the guest at evaluation? Any help is appreciated as soon as possible, thank you.