No Arabic abstract
Multimodal datasets contain an enormous amount of relational information, which grows exponentially with the introduction of new modalities. Learning representations in such a scenario is inherently complex due to the presence of multiple heterogeneous information channels. These channels can encode both (a) inter-relations between the items of different modalities and (b) intra-relations between the items of the same modality. Encoding multimedia items into a continuous low-dimensional semantic space such that both types of relations are captured and preserved is extremely challenging, especially if the goal is a unified end-to-end learning framework. The two key challenges that need to be addressed are: 1) the framework must be able to merge complex intra and inter relations without losing any valuable information and 2) the learning model should be invariant to the addition of new and potentially very different modalities. In this paper, we propose a flexible framework which can scale to data streams from many modalities. To that end we introduce a hypergraph-based model for data representation and deploy Graph Convolutional Networks to fuse relational information within and across modalities. Our approach provides an efficient solution for distributing otherwise extremely computationally expensive or even unfeasible training processes across multiple-GPUs, without any sacrifices in accuracy. Moreover, adding new modalities to our model requires only an additional GPU unit keeping the computational time unchanged, which brings representation learning to truly multimodal datasets. We demonstrate the feasibility of our approach in the experiments on multimedia datasets featuring second, third and fourth order relations.
Recent work has highlighted the advantage of jointly learning grounded sentence representations from multiple languages. However, the data used in these studies has been limited to an aligned scenario: the same images annotated with sentences in multiple languages. We focus on the more realistic disjoint scenario in which there is no overlap between the images in multilingual image--caption datasets. We confirm that training with aligned data results in better grounded sentence representations than training with disjoint data, as measured by image--sentence retrieval performance. In order to close this gap in performance, we propose a pseudopairing method to generate synthetically aligned English--German--image triplets from the disjoint sets. The method works by first training a model on the disjoint data, and then creating new triples across datasets using sentence similarity under the learned model. Experiments show that pseudopairs improve image--sentence retrieval performance compared to disjoint training, despite requiring no external data or models. However, we do find that using an external machine translation model to generate the synthetic data sets results in better performance.
Noisy neural networks (NoisyNNs) refer to the inference and training of NNs in the presence of noise. Noise is inherent in most communication and storage systems; hence, NoisyNNs emerge in many new applications, including federated edge learning, where wireless devices collaboratively train a NN over a noisy wireless channel, or when NNs are implemented/stored in an analog storage medium. This paper studies a fundamental problem of NoisyNNs: how to estimate the uncontaminated NN weights from their noisy observations or manifestations. Whereas all prior works relied on the maximum likelihood (ML) estimation to maximize the likelihood function of the estimated NN weights, this paper demonstrates that the ML estimator is in general suboptimal. To overcome the suboptimality of the conventional ML estimator, we put forth an $text{MMSE}_{pb}$ estimator to minimize a compensated mean squared error (MSE) with a population compensator and a bias compensator. Our approach works well for NoisyNNs arising in both 1) noisy inference, where noise is introduced only in the inference phase on the already-trained NN weights; and 2) noisy training, where noise is introduced over the course of training. Extensive experiments on the CIFAR-10 and SST-2 datasets with different NN architectures verify the significant performance gains of the $text{MMSE}_{pb}$ estimator over the ML estimator when used to denoise the NoisyNN. For noisy inference, the average gains are up to $156%$ for a noisy ResNet34 model and $14.7%$ for a noisy BERT model; for noisy training, the average gains are up to $18.1$ dB for a noisy ResNet18 model.
We propose {rm texttt{ResIST}}, a novel distributed training protocol for Residual Networks (ResNets). {rm texttt{ResIST}} randomly decomposes a global ResNet into several shallow sub-ResNets that are trained independently in a distributed manner for several local iterations, before having their updates synchronized and aggregated into the global model. In the next round, new sub-ResNets are randomly generated and the process repeats. By construction, per iteration, {rm texttt{ResIST}} communicates only a small portion of network parameters to each machine and never uses the full model during training. Thus, {rm texttt{ResIST}} reduces the communication, memory, and time requirements of ResNet training to only a fraction of the requirements of previous methods. In comparison to common protocols like data-parallel training and data-parallel training with local SGD, {rm texttt{ResIST}} yields a decrease in wall-clock training time, while being competitive with respect to model performance.
Distributed data-parallel algorithms aim to accelerate the training of deep neural networks by parallelizing the computation of large mini-batch gradient updates across multiple nodes. Approaches that synchronize nodes using exact distributed averaging (e.g., via AllReduce) are sensitive to stragglers and communication delays. The PushSum gossip algorithm is robust to these issues, but only performs approximate distributed averaging. This paper studies Stochastic Gradient Push (SGP), which combines PushSum with stochastic gradient updates. We prove that SGP converges to a stationary point of smooth, non-convex objectives at the same sub-linear rate as SGD, and that all nodes achieve consensus. We empirically validate the performance of SGP on image classification (ResNet-50, ImageNet) and machine translation (Transformer, WMT16 En-De) workloads. Our code will be made publicly available.
We describe TF-Replicator, a framework for distributed machine learning designed for DeepMind researchers and implemented as an abstraction over TensorFlow. TF-Replicator simplifies writing data-parallel and model-parallel research code. The same models can be effortlessly deployed to different cluster architectures (i.e. one or many machines containing CPUs, GPUs or TPU accelerators) using synchronous or asynchronous training regimes. To demonstrate the generality and scalability of TF-Replicator, we implement and benchmark three very different models: (1) A ResNet-50 for ImageNet classification, (2) a SN-GAN for class-conditional ImageNet image generation, and (3) a D4PG reinforcement learning agent for continuous control. Our results show strong scalability performance without demanding any distributed systems expertise of the user. The TF-Replicator programming model will be open-sourced as part of TensorFlow 2.0 (see https://github.com/tensorflow/community/pull/25).