3 research outputs found
Massively Parallel Single-Source SimRanks in Rounds
SimRank is one of the most fundamental measures that evaluate the structural
similarity between two nodes in a graph and has been applied in a plethora of
data management tasks. These tasks often involve single-source SimRank
computation that evaluates the SimRank values between a source node and all
other nodes. Due to its high computation complexity, single-source SimRank
computation for large graphs is notoriously challenging, and hence recent
studies resort to distributed processing. To our surprise, although SimRank has
been widely adopted for two decades, theoretical aspects of distributed
SimRanks with provable results have rarely been studied.
In this paper, we conduct a theoretical study on single-source SimRank
computation in the Massive Parallel Computation (MPC) model, which is the
standard theoretical framework modeling distributed systems such as MapReduce,
Hadoop, or Spark. Existing distributed SimRank algorithms enforce either
communication round complexity or machine space
for a graph of nodes. We overcome this barrier. Particularly, given a graph
of nodes, for any query node and constant error ,
we show that using rounds of communication among machines is
almost enough to compute single-source SimRank values with at most
absolute errors, while each machine only needs a space sub-linear to . To
the best of our knowledge, this is the first single-source SimRank algorithm in
MPC that can overcome the round complexity barrier with
provable result accuracy
The Changes of Functional Connectivity Strength in Electroconvulsive Therapy for Depression: A Longitudinal Study
Electroconvulsive therapy (ECT) is an effective treatment for depression, but the mechanism of ECT for depression is still unclear. Recently, neuroimaging studies have reported that the prefrontal cortex, hippocampus, angular gyrus, insular and other brain regions are involved in the mechanism of ECT for depression, and these regions are highly overlapped with the location of brain hubs. Here, we try to explore the effects of ECT on the functional connectivity of brain hubs in depression patients. In current study, depression patients were assessed at three time points: prior to ECT, at the completion of ECT and about 1 month after the completion of ECT. At each time point, resting-state functional magnetic resonance imaging, assessment of clinical symptoms and cognition function were performed respectively, which was compared with 20 normal controls. Functional connectivity strength (FCS) was used to identify brain hubs. The results showed that FCS of left angular gyrus in depression patients significantly increased after ECT, accompanied by improved mood. The changed FCS in depression patients recovered obviously at 1 month after the completion of ECT. It suggested that ECT could modulate functional connectivity of left angular gyrus in depression patients
Scaling Up Dynamic Graph Representation Learning via Spiking Neural Networks
Recent years have seen a surge in research on dynamic graph representation learning, which aims to model temporal graphs that are dynamic and evolving constantly over time. However, current work typically models graph dynamics with recurrent neural networks (RNNs), making them suffer seriously from computation and memory overheads on large temporal graphs. So far, scalability of dynamic graph representation learning on large temporal graphs remains one of the major challenges. In this paper, we present a scalable framework, namely SpikeNet, to efficiently capture the temporal and structural patterns of temporal graphs. We explore a new direction in that we can capture the evolving dynamics of temporal graphs with spiking neural networks (SNNs) instead of RNNs. As a low-power alternative to RNNs, SNNs explicitly model graph dynamics as spike trains of neuron populations and enable spike-based propagation in an efficient way. Experiments on three large real-world temporal graph datasets demonstrate that SpikeNet outperforms strong baselines on the temporal node classification task with lower computational costs. Particularly, SpikeNet generalizes to a large temporal graph (2.7M nodes and 13.9M edges) with significantly fewer parameters and computation overheads