
Preprint
costs. What’s more, federated learning also borrows tools such as differential privacy [
9
], secure multiparty computation
[4], homomorphic encryption [10] to offer enhanced security.
Graph Neural Networks (GNN) and their variants are showing dominant performance on many ML tasks [
11
]. For
example, Graph Convolutional Network (GCN) has been widely applied in many different domains such as semi-
supervised classification [
12
], multi-view networks [
13
] and link prediction [
14
], etc. However, the efficiency of
graph-based networks relies on the rich information among the elements contained in a graph. Once faced with a
perturbed topological structure or incomplete node attribute, the network either can no longer provide satisfied learning
performance [
15
] or needs a complex node attribute completion system [
16
]. The nature of graph-based networks
results in the hard implementation of federated learning, especially when the transmission of original user data, such as
features and labels of nodes, is prohibitive between processors.
Based on the observation that the embedding representation differs from initial data space, we propose our
Fe
derated
G
r
aph-b
a
sed Networks with
S
hared Embedding (
Feras
) model in this paper. Instead of exchanging raw data information
at the beginning, we facilitate embedding communication in the middle of the network. On the one hand, computations
are performed on edge hosts synchronously to speed up training without leaking raw data, on the other hand, node
information is propagated through the entire graph via embedding, which is critical to retain the network performance.
The rest of the paper proceeds as follows: we begin by discussing the latest related research of distributed learning
and training methods, then go introducing four main rules in application scenarios and proposing algorithm structure.
The next section is mainly concerned with the theoretical analysis and experiment results are reported in the following.
Some concluding remarks are put in the end.
2 Background
2.1 Fedeated learnig
Federated learning was first proposed by Google [
17
] in 2016 for Android mobiles phones. Its main idea is to train
centralized model with decentralized data. Indeed, devices use local data to train models and upload parameters to
server for aggregation. One of the most important features of federated learning is security and privacy [
8
]. Even
though sensitive data are not directly shared between devices, it is still urgent to protect the communication between
server and device. Represented by homomorphic encryption [
18
,
19
,
20
] and secure multiparty computation [
21
,
22
],
encryption methods provide a very safe and reliable solution while their computation cost is relatively high. Perturbation
methods, such as differential privacy [
23
,
24
], use a designed noise mechanism to protect sensitive information, while
no extra computation cost is demanded, there may exist risks on prediction accuracy. However, information can still be
leaked indirectly with intermediate results from updating process, [
25
,
26
] exploit some attacks and provide defense
mechanisms.
Most recently, a large scale of work has been done to implement federated learning in graph-based networks. [
27
]
addresses non-iid issue in graph data and confronts tasks with new label domains. [
28
] develops a multi-task federated
learning method without a server. [
29
] suggests FedGNN, a recommendation federated system based on GNN. [
30
]
proposes FedSAGE, which is a sub-graph level federated learning technique utilizing graph mining model GraphSAGE
[31]. [32] introduces a federated spatio-temporal model to improve the forecasting capacity of GNN. Nevertheless, to
the best of our knowledge, there is still no study concentrating on node embedding aggregation on sampling-based
graph neural network framework.
2.2 Related work
GraphSAINT [
33
] adopts an innovative way to build mini-batches. Instead of sampling across the layers, GraphSAINT
samples sub-graphs at first and then constructs a full GCN on it, which prevents neighbor explosion problem. It also
establishes an algorithm to reduce sampling bias and variance. From comparison experiments conducted on datasets in
[
33
], GraphSAINT shows absolute advantages on accuracy and convergence rate compared with other popular samplers
(GraphSAGE [31], FastGCN [34], ClusterGCN [35], etc).
A stochastic shared embedding (SSE) for graph-based networks is investigated in [
36
] to mitigate over-parameterization
problems. Embeddings are trainable vectors that are exchanged according to transition probability for each backprop-
agate step. Our proposed
Feras
is very different from SSE since [
36
] does not consider privacy issues and runs all
computations on the same server.
To prove the convergence of parallelized stochastic gradient descent, [
37
] offers a novel idea by borrowing the good
convergent property of contraction mappings, which inspired the mathematical demonstration of our paper even though
proof in [37] is drawn for traditional neural network and no embedding sharing mechanism is acknowledged.
2