已经研究了对比学习，以提高学习句嵌入的表现。当前的最先进的方法是SIMCSE，它将丢失作为数据增强方法，并馈送预训练的变压器编码器两次相同的输入句。相应的输出，两个句子嵌入来自不同丢弃掩码的相同句子，可用于构建正对。使用丢弃掩模应用的网络可以被视为ITSEF的子网，其预期比例由差动率决定。在本文中，我们推动具有不同预期尺度的子网，了解相同句子的类似嵌入。 SIMCSE未能这样做，因为它们将丢失率修复到调谐的超参数。我们通过从分布蚀刻前进过程中采样辍学率来实现这一目标。由于这种方法可能使优化更加困难，我们还提出了一种简单的句子掩模策略来采样更多子网。我们在几个流行的语义文本相似性数据集中评估了所提出的S-SIMCSE。实验结果表明，S-SIMCSE优于最先进的SIMCSE超过$ 1 \％$ ON BERT $ _ {base} $

深度卷积神经网络（CNNS）通常是复杂的设计，具有许多可学习的参数，用于准确性原因。为了缓解在移动设备上部署它们的昂贵成本，最近的作品使挖掘预定识别架构中的冗余作出了巨大努力。然而，尚未完全研究现代CNN的输入分辨率的冗余，即输入图像的分辨率是固定的。在本文中，我们观察到，用于准确预测给定图像的最小分辨率使用相同的神经网络是不同的。为此，我们提出了一种新颖的动态分辨率网络（DRNET），其中基于每个输入样本动态地确定输入分辨率。其中，利用所需网络共同地探索具有可忽略的计算成本的分辨率预测器。具体地，预测器学习可以保留的最小分辨率，并且甚至超过每个图像的原始识别准确性。在推断过程中，每个输入图像将被调整为其预测的分辨率，以最小化整体计算负担。然后，我们对几个基准网络和数据集进行了广泛的实验。结果表明，我们的DRNET可以嵌入到任何现成的网络架构中，以获得计算复杂性的相当大降低。例如，DR-RESET-50实现了类似的性能，计算减少约34％，同时增加了1.4％的准确度，与原始Resnet-50上的计算减少相比，在ImageNet上的原始resnet-50增加了10％。

作为对话系统的基本组成部分，响应选择旨在挑选候选人之间的最佳反应，以继续对话。在现有研究中，这项任务通常被视为二进制分类问题，其中每个候选人分别排名以获取适当性。为了提高其性能，我们将此任务重构为一个多项选择问题，允许在一次性推断中进行最佳选择。这个新的视图激励我们提出一个名为全景 - 编码器的架构（我们的工作将是再现性和未来研究的开放来源。）具有新的候选人注意机制（CAM），这允许在响应之间进行情境方面的关注并导致良好-Gremator比较。此外，我们研究并纳入了一些已被证明有效改善响应选择的技术。三个基准测试的实验表明，我们的方法推动了最先进的，同时实现了大约3x的推理速度。

Increasing model size when pretraining natural language representations often results in improved performance on downstream tasks. However, at some point further model increases become harder due to GPU/TPU memory limitations and longer training times. To address these problems, we present two parameterreduction techniques to lower memory consumption and increase the training speed of BERT (Devlin et al., 2019). Comprehensive empirical evidence shows that our proposed methods lead to models that scale much better compared to the original BERT. We also use a self-supervised loss that focuses on modeling inter-sentence coherence, and show it consistently helps downstream tasks with multi-sentence inputs. As a result, our best model establishes new state-of-the-art results on the GLUE, RACE, and SQuAD benchmarks while having fewer parameters compared to BERT-large. The code and the pretrained models are available at https://github.com/google-research/ALBERT. * Work done as an intern at Google Research, driving data processing and downstream task evaluations.

Compressed videos often exhibit visually annoying artifacts, known as Perceivable Encoding Artifacts (PEAs), which dramatically degrade video visual quality. Subjective and objective measures capable of identifying and quantifying various types of PEAs are critical in improving visual quality. In this paper, we investigate the influence of four spatial PEAs (i.e. blurring, blocking, bleeding, and ringing) and two temporal PEAs (i.e. flickering and floating) on video quality. For spatial artifacts, we propose a visual saliency model with a low computational cost and higher consistency with human visual perception. In terms of temporal artifacts, self-attention based TimeSFormer is improved to detect temporal artifacts. Based on the six types of PEAs, a quality metric called Saliency-Aware Spatio-Temporal Artifacts Measurement (SSTAM) is proposed. Experimental results demonstrate that the proposed method outperforms state-of-the-art metrics. We believe that SSTAM will be beneficial for optimizing video coding techniques.

In contrast to the control-theoretic methods, the lack of stability guarantee remains a significant problem for model-free reinforcement learning (RL) methods. Jointly learning a policy and a Lyapunov function has recently become a promising approach to ensuring the whole system with a stability guarantee. However, the classical Lyapunov constraints researchers introduced cannot stabilize the system during the sampling-based optimization. Therefore, we propose the Adaptive Stability Certification (ASC), making the system reach sampling-based stability. Because the ASC condition can search for the optimal policy heuristically, we design the Adaptive Lyapunov-based Actor-Critic (ALAC) algorithm based on the ASC condition. Meanwhile, our algorithm avoids the optimization problem that a variety of constraints are coupled into the objective in current approaches. When evaluated on ten robotic tasks, our method achieves lower accumulated cost and fewer stability constraint violations than previous studies.

Off-Policy evaluation (OPE) is concerned with evaluating a new target policy using offline data generated by a potentially different behavior policy. It is critical in a number of sequential decision making problems ranging from healthcare to technology industries. Most of the work in existing literature is focused on evaluating the mean outcome of a given policy, and ignores the variability of the outcome. However, in a variety of applications, criteria other than the mean may be more sensible. For example, when the reward distribution is skewed and asymmetric, quantile-based metrics are often preferred for their robustness. In this paper, we propose a doubly-robust inference procedure for quantile OPE in sequential decision making and study its asymptotic properties. In particular, we propose utilizing state-of-the-art deep conditional generative learning methods to handle parameter-dependent nuisance function estimation. We demonstrate the advantages of this proposed estimator through both simulations and a real-world dataset from a short-video platform. In particular, we find that our proposed estimator outperforms classical OPE estimators for the mean in settings with heavy-tailed reward distributions.

Mitosis nuclei count is one of the important indicators for the pathological diagnosis of breast cancer. The manual annotation needs experienced pathologists, which is very time-consuming and inefficient. With the development of deep learning methods, some models with good performance have emerged, but the generalization ability should be further strengthened. In this paper, we propose a two-stage mitosis segmentation and classification method, named SCMitosis. Firstly, the segmentation performance with a high recall rate is achieved by the proposed depthwise separable convolution residual block and channel-spatial attention gate. Then, a classification network is cascaded to further improve the detection performance of mitosis nuclei. The proposed model is verified on the ICPR 2012 dataset, and the highest F-score value of 0.8687 is obtained compared with the current state-of-the-art algorithms. In addition, the model also achieves good performance on GZMH dataset, which is prepared by our group and will be firstly released with the publication of this paper. The code will be available at: https://github.com/antifen/mitosis-nuclei-segmentation.

Motivated by the human-machine interaction such as training chatbots for improving customer satisfaction, we study human-guided human-machine interaction involving private information. We model this interaction as a two-player turn-based game, where one player (Alice, a human) guides the other player (Bob, a machine) towards a common goal. Specifically, we focus on offline reinforcement learning (RL) in this game, where the goal is to find a policy pair for Alice and Bob that maximizes their expected total rewards based on an offline dataset collected a priori. The offline setting presents two challenges: (i) We cannot collect Bob's private information, leading to a confounding bias when using standard RL methods, and (ii) a distributional mismatch between the behavior policy used to collect data and the desired policy we aim to learn. To tackle the confounding bias, we treat Bob's previous action as an instrumental variable for Alice's current decision making so as to adjust for the unmeasured confounding. We develop a novel identification result and use it to propose a new off-policy evaluation (OPE) method for evaluating policy pairs in this two-player turn-based game. To tackle the distributional mismatch, we leverage the idea of pessimism and use our OPE method to develop an off-policy learning algorithm for finding a desirable policy pair for both Alice and Bob. Finally, we prove that under mild assumptions such as partial coverage of the offline data, the policy pair obtained through our method converges to the optimal one at a satisfactory rate.

Knowledge tracing (KT) aims to leverage students' learning histories to estimate their mastery levels on a set of pre-defined skills, based on which the corresponding future performance can be accurately predicted. In practice, a student's learning history comprises answers to sets of massed questions, each known as a session, rather than merely being a sequence of independent answers. Theoretically, within and across these sessions, students' learning dynamics can be very different. Therefore, how to effectively model the dynamics of students' knowledge states within and across the sessions is crucial for handling the KT problem. Most existing KT models treat student's learning records as a single continuing sequence, without capturing the sessional shift of students' knowledge state. To address the above issue, we propose a novel hierarchical transformer model, named HiTSKT, comprises an interaction(-level) encoder to capture the knowledge a student acquires within a session, and a session(-level) encoder to summarise acquired knowledge across the past sessions. To predict an interaction in the current session, a knowledge retriever integrates the summarised past-session knowledge with the previous interactions' information into proper knowledge representations. These representations are then used to compute the student's current knowledge state. Additionally, to model the student's long-term forgetting behaviour across the sessions, a power-law-decay attention mechanism is designed and deployed in the session encoder, allowing it to emphasize more on the recent sessions. Extensive experiments on three public datasets demonstrate that HiTSKT achieves new state-of-the-art performance on all the datasets compared with six state-of-the-art KT models.