  Federated learning is an active research topic since it enables several
participants to jointly train a model without sharing local data. Currently,
cross-silo federated learning is a popular training setting that utilizes a few
hundred reliable data silos with high-speed access links to training a model.
While this approach has been widely applied in real-world scenarios, designing
a robust topology to reduce the training time remains an open problem. In this
paper, we present a new multigraph topology for cross-silo federated learning.
We first construct the multigraph using the overlay graph. We then parse this
multigraph into different simple graphs with isolated nodes. The existence of
isolated nodes allows us to perform model aggregation without waiting for other
nodes, hence effectively reducing the training time. Intensive experiments on
three public datasets show that our proposed method significantly reduces the
training time compared with recent state-of-the-art topologies while
maintaining the accuracy of the learned model. Our code can be found at
https://github.com/aioz-ai/MultigraphFL
