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A3T-GCN: Attention Temporal Graph Convolutional Network for Traffic Forecasting

arXiv.org Machine Learning

Accurate real-time traffic forecasting is a core technological problem against the implementation of the intelligent transportation system. However, it remains challenging considering the complex spatial and temporal dependencies among traffic flows. In the spatial dimension, due to the connectivity of the road network, the traffic flows between linked roads are closely related. In terms of the temporal factor, although there exists a tendency among adjacent time points in general, the importance of distant past points is not necessarily smaller than that of recent past points since traffic flows are also affected by external factors. In this study, an attention temporal graph convolutional network (A3T-GCN) traffic forecasting method was proposed to simultaneously capture global temporal dynamics and spatial correlations. The A3T-GCN model learns the short-time trend in time series by using the gated recurrent units and learns the spatial dependence based on the topology of the road network through the graph convolutional network. Moreover, the attention mechanism was introduced to adjust the importance of different time points and assemble global temporal information to improve prediction accuracy. Experimental results in real-world datasets demonstrate the effectiveness and robustness of proposed A3T-GCN. The source code can be visited at https://github.com/lehaifeng/T-GCN/A3T.


Unified Analysis of Stochastic Gradient Methods for Composite Convex and Smooth Optimization

arXiv.org Machine Learning

We present a unified theorem for the convergence analysis of stochastic gradient algorithms for minimizing a smooth and convex loss plus a convex regularizer. We do this by extending the unified analysis of Gorbunov, Hanzely \& Richt\'arik (2020) and dropping the requirement that the loss function be strongly convex. Instead, we only rely on convexity of the loss function. Our unified analysis applies to a host of existing algorithms such as proximal SGD, variance reduced methods, quantization and some coordinate descent type methods. For the variance reduced methods, we recover the best known convergence rates as special cases. For proximal SGD, the quantization and coordinate type methods, we uncover new state-of-the-art convergence rates. Our analysis also includes any form of sampling and minibatching. As such, we are able to determine the minibatch size that optimizes the total complexity of variance reduced methods. We showcase this by obtaining a simple formula for the optimal minibatch size of two variance reduced methods (\textit{L-SVRG} and \textit{SAGA}). This optimal minibatch size not only improves the theoretical total complexity of the methods but also improves their convergence in practice, as we show in several experiments.


Weakly-correlated synapses promote dimension reduction in deep neural networks

arXiv.org Machine Learning

Neural correlation is a common characteristic transformation of sensory inputs. All incoming synapses in most neural computations [1], playing vital to a hidden neuron form a receptive field (RF) of that roles in stimulus coding [2, 3], information storage [4] hidden neuron. The correlation among synapses is modeled and various cognition tasks that can be implemented by the inter-RF correlation (Figure 1). We do not by recurrent neural networks [5, 6]. Neural correlation need a prior knowledge about the synaptic correlation was recently shown by a mean-field theory [7] to be able strength. In fact, our mean-field theory yields different to manipulate the dimensionality of layered representations scaling behaviors of synaptic correlation with respect to in deep computations, which was empirically revealed the number of neurons at each layer, for both binary and to be a fundamental process in deep artificial continuous synaptic weights. The scaling behaviors are neural networks [8]. This theory demonstrates that a exactly a requirement of mathematically well-defined dimensionality.


FedMGDA+: Federated Learning meets Multi-objective Optimization

arXiv.org Machine Learning

Deep learning has achieved impressive successes on a number of domain applications, thanks largely to innovations on algorithmic and architectural design, and equally importantly to the tremendous amount of computational power one can harness through GPUs, computer clusters and dedicated software and hardware. Edge devices, such as smart phones, tablets, routers, car devices, home sensors, etc., due to their ubiquity and moderate computational power, impose new opportunities and challenges for deep learning. On the one hand, edge devices have direct access to privacy sensitive data that users may be reluctant to share (with say data centers), and they are much more powerful than their predecessors, capable of conducting a significant amount of on-device computations. On the other hand, edge devices are largely heterogeneous in terms of capacity, power, data, availability, communication, memory, etc., posing new challenges beyond conventional in-house training of machine learning models. Thus, a new paradigm, known as federated learning (FL) [1] that aims at harvesting the prospects of edge devices, has recently emerged. Developing new FL algorithms and systems on edge devices has since become a hot research topic in machine learning. From the beginning of its birth, FL has close ties to conventional distributed optimization. However, FL emerged from the pressing need to address news challenges in the mobile era that existing distributed optimization algorithms were not designed for per se. We mention the following characteristics ofFL that are most relevant to our work, and refer to the excellent surveys [2, 3, 4] and the references therein for more challenges and applications inFL.


Recovering Accurate Labeling Information from Partially Valid Data for Effective Multi-Label Learning

arXiv.org Machine Learning

Partial Multi-label Learning (PML) aims to induce the multi-label predictor from datasets with noisy supervision, where each training instance is associated with several candidate labels but only partially valid. To address the noisy issue, the existing PML methods basically recover the ground-truth labels by leveraging the ground-truth confidence of the candidate label, \ie the likelihood of a candidate label being a ground-truth one. However, they neglect the information from non-candidate labels, which potentially contributes to the ground-truth label recovery. In this paper, we propose to recover the ground-truth labels, \ie estimating the ground-truth confidences, from the label enrichment, composed of the relevance degrees of candidate labels and irrelevance degrees of non-candidate labels. Upon this observation, we further develop a novel two-stage PML method, namely \emph{\underline{P}artial \underline{M}ulti-\underline{L}abel \underline{L}earning with \underline{L}abel \underline{E}nrichment-\underline{R}ecovery} (\baby), where in the first stage, it estimates the label enrichment with unconstrained label propagation, then jointly learns the ground-truth confidence and multi-label predictor given the label enrichment. Experimental results validate that \baby outperforms the state-of-the-art PML methods.


List-Decodable Mean Estimation via Iterative Multi-Filtering

arXiv.org Machine Learning

We study the problem of {\em list-decodable mean estimation} for bounded covariance distributions. Specifically, we are given a set $T$ of points in $\mathbb{R}^d$ with the promise that an unknown $\alpha$-fraction of points in $T$, where $0< \alpha < 1/2$, are drawn from an unknown mean and bounded covariance distribution $D$, and no assumptions are made on the remaining points. The goal is to output a small list of hypothesis vectors such that at least one of them is close to the mean of $D$. We give the first practically viable estimator for this problem. In more detail, our algorithm is sample and computationally efficient, and achieves information-theoretically near-optimal error. While the only prior algorithm for this setting inherently relied on the ellipsoid method, our algorithm is iterative and only uses spectral techniques. Our main technical innovation is the design of a soft outlier removal procedure for high-dimensional heavy-tailed datasets with a majority of outliers.


California's earthquake 'swarm' triggered by fluid, scientists say

Daily Mail - Science & tech

A strange'swarm' of small earthquakes in California that lasted nearly four years was triggered by fluid spilling into the fault system from underground reservoirs, scientists say. The naturally occurring injection of underground fluid drove the earthquake swarm near Cahuilla in Southern California, which occurred in bursts around the region from early 2016 to late 2019. US scientists have made their conclusions based on earthquake detection algorithms that catalogued more than 22,000 individual seismic events that made up the'swarm'. Using machine learning to plot the location, depth and size of the tremors, the researchers generated a 3D representation of the underlying fault zone. The results suggested dynamic pressure changes from natural fluid injections deep below the surface largely controlled the prolonged evolution of the Cahuilla swarm.


ASIC Clouds

Communications of the ACM

Specialized replicated compute accelerators (RCA) are multiplied up by having multiple copies per ASICs, multiple ASICs per server, multiple servers per rack, and multiple racks per datacenter. Server controller can be an FPGA, microcontroller, or a Xeon processor. Power delivery and cooling system are customized based on ASIC needs. If required, there would be DRAMs on the PCB as well. Each ASIC interconnects its RCAs using a customized on-chip network.



Domain-Specific Hardware Accelerators

Communications of the ACM

From the simple embedded processor in your washing machine to powerful processors in data center servers, most computing today takes place on general-purpose programmable processors or CPUs. CPUs are attractive because they are easy to program and because large code bases exist for them. The programmability of CPUs stems from their execution of sequences of simple instructions, such as ADD or BRANCH; however, the energy required to fetch and interpret an instruction is 10x to 4000x more than that required to perform a simple operation such as ADD. This high overhead was acceptable when processor performance and efficiency were scaling according to Moore's Law.32 One could simply wait and an existing application would run faster and more efficiently. Our economy has become dependent on these increases in computing performance and efficiency to enable new features and new applications. Today, Moore's Law has largely ended,12 and we must look to alternative architectures with lower overhead, such as domain-specific accelerators, to continue scaling of performance and efficiency. There are several ways to realize domain-specific accelerators as discussed in the sidebar on accelerator options. A domain-specific accelerator is a hardware computing engine that is specialized for a particular domain of applications. Accelerators have been designed for graphics,26 deep learning,16 simulation,2 bioinformatics,49 image processing,38 and many other tasks. Accelerators can offer orders of magnitude improvements in performance/cost and performance/W compared to general-purpose computers. For example, our bioinformatics accelerator, Darwin,49 is up to 15,000x faster than a CPU at reference-based, long-read assembly. The performance and efficiency of accelerators is due to a combination of specialized operations, parallelism, efficient memory systems, and reduction of overhead. Domain-specific accelerators7 are becoming more pervasive and more visible, because they are one of the few remaining ways to continue to improve performance and efficiency now that Moore's Law has ended.22 Most applications require modifications to achieve high speed up on domain-specific accelerators. These applications are highly tuned to balance the performance of conventional processors with their memory systems. When specialization reduces the cost of processing to near zero, they become memory limited.