Steering language generation towards objectives or away from undesired content has been a long-standing goal in utilizing language models (LM). Recent work has demonstrated reinforcement learning and weighted decoding as effective approaches to achieve a higher level of language control and quality with pros and cons. In this work, we propose a novel critic decoding method for controlled language generation (CriticControl) that combines the strengths of reinforcement learning and weighted decoding. Specifically, we adopt the actor-critic framework to train an LM-steering critic from non-differentiable reward models. And similar to weighted decoding, our method freezes the language model and manipulates the output token distribution using called critic, improving training efficiency and stability. Evaluation of our method on three controlled generation tasks, namely topic control, sentiment control, and detoxification, shows that our approach generates more coherent and well-controlled texts than previous methods. In addition, CriticControl demonstrates superior generalization ability in zero-shot settings. Human evaluation studies also corroborate our findings.

Controllable Text Generation (CTG) is emerging area in the field of natural language generation (NLG). It is regarded as crucial for the development of advanced text generation technologies that are more natural and better meet the specific constraints in practical applications. In recent years, methods using large-scale pre-trained language models (PLMs), in particular the widely used transformer-based PLMs, have become a new paradigm of NLG, allowing generation of more diverse and fluent text. However, due to the lower level of interpretability of deep neural networks, the controllability of these methods need to be guaranteed. To this end, controllable text generation using transformer-based PLMs has become a rapidly growing yet challenging new research hotspot. A diverse range of approaches have emerged in the recent 3-4 years, targeting different CTG tasks which may require different types of controlled constraints. In this paper, we present a systematic critical review on the common tasks, main approaches and evaluation methods in this area. Finally, we discuss the challenges that the field is facing, and put forward various promising future directions. To the best of our knowledge, this is the first survey paper to summarize CTG techniques from the perspective of PLMs. We hope it can help researchers in related fields to quickly track the academic frontier, providing them with a landscape of the area and a roadmap for future research.

Large pretrained language models generate fluent text but are notoriously hard to controllably sample from. In this work, we study constrained sampling from such language models: generating text that satisfies user-defined constraints, while maintaining fluency and the model's performance in a downstream task. We propose MuCoLa -- a sampling procedure that combines the log-likelihood of the language model with arbitrary (differentiable) constraints in a single energy function, and then generates samples in a non-autoregressive manner. Specifically, it initializes the entire output sequence with noise and follows a Markov chain defined by Langevin Dynamics using the gradients of the energy function. We evaluate MuCoLa on text generation with soft and hard constraints as well as their combinations obtaining significant improvements over competitive baselines for toxicity avoidance, sentiment control, and keyword-guided generation.

Pretrained language models have demonstrated extraordinary capabilities in language generation. However, real-world tasks often require controlling the distribution of generated text in order to mitigate bias, promote fairness, and achieve personalization. Existing techniques for controlling the distribution of generated text only work with quantified distributions, which require pre-defined categories, proportions of the distribution, or an existing corpus following the desired distributions. However, many important distributions, such as personal preferences, are unquantified. In this work, we tackle the problem of generating text following arbitrary distributions (quantified and unquantified) by proposing Nano, a few-shot human-in-the-loop training algorithm that continuously learns from human feedback. Nano achieves state-of-the-art results on single topic/attribute as well as quantified distribution control compared to previous works. We also show that Nano is able to learn unquantified distributions, achieves personalization, and captures differences between different individuals' personal preferences with high sample efficiency.

基于变压器的语言模型能够生成流利的文本，并在各种自然语言生成任务中有效地适应。但是，已证明在大型未标记的网络文本语料库中鉴定的语言模型已被证明会遭受堕落的有毒内容和社会偏见行为的损害，从而阻碍了他们的安全部署。提出了各种排毒方法来减轻语言模型的毒性；但是，这些方法是在包含与性别，种族或宗教相关的特定社会身份的提示条件下进行排毒语言模型的。在这项研究中，我们提出了增强氧化。一种基于强化学习的方法，用于降低语言模型中的毒性。我们应对语言模型中的安全性挑战，并提出了一种新的奖励模型，该模型能够检测有毒内容并减轻对毒性预测中社会身份的意外偏见。该实验表明，用于语言模型排毒的增强方法化方法优于自动评估指标中现有的排毒方法，这表明我们在语言模型排毒中的方法能力和对生成内容中社会认同的意外偏见的能力较小。

深度神经语言模型的最新进展与大规模数据集的能力相结合，加速了自然语言生成系统的发展，这些系统在多种任务和应用程序上下文中产生流利和连贯的文本（在各种成功程度上）。但是，为所需的用户控制这些模型的输出仍然是一个开放的挑战。这不仅对于自定义生成语言的内容和样式至关重要，而且对于他们在现实世界中的安全可靠部署至关重要。我们提出了一项关于受约束神经语言生成的新兴主题的广泛调查，在该主题中，我们通过区分条件和约束（后者是在输出文本上而不是输入的可检验条件），正式定义和分类自然语言生成问题，目前是可检验的）约束文本生成任务，并查看受限文本生成的现有方法和评估指标。我们的目的是强调这个新兴领域的最新进展和趋势，以告知最有希望的方向和局限性，以推动受约束神经语言生成研究的最新作品。

许多文献表明，基于及时的学习是使用大型预训练的语言模型的有效方法。最近的作品还展示了通过插入适当的提示来指导聊天机器人输出的可能性。基于梯度的方法通常用于扰动提示。但是，某些语言模型甚至无法为公众提供。在这项工作中，我们首先探讨了提示和加强学习（RL）与转向模型的生成的组合，而无需访问任何模型的参数。其次，为了减少培训工作并增强对看不见的任务的普遍性，我们应用多任务学习以使模型学会更好地对新任务进行推广。实验结果表明，我们提出的方法可以成功控制几个最新的（SOTA）对话模型，而无需访问其参数。此外，该模型证明了与基线模型更少的步骤快速适应看不见的任务的强大能力。

预处理的基于变压器的语言模型（LMS）显示出显着的自然语言生成能力。凭借其巨大的潜力，控制这种LM的文本生成引起了人们的关注。尽管有一些研究试图控制生成的文本的高级属性（例如情感和主题），但仍然缺乏对其在单词和短语级别上的内容的更精确的控制。在这里，我们建议内容调节器（COCON）以细粒度的水平控制LM的输出文本。在我们的自我监督方法中，Cocon Block学会了通过调节从LM中扣留的内容输入来帮助LM完成部分观察到的文本序列。通过实验，我们表明Cocon可以自然地将目标内容纳入生成的文本中，并以零拍的方式控制高级文本属性。

控制语言模型的主要方法在控制高级属性（例如主题和情感）方面具有突出性。但是，这些方法通常需要特定于条件的数据或计算昂贵。我们提出了一种新的简单引导解码方法，伽玛采样，该方法不需要任何培训数据来实现可控制的文本生成，同时保持快速生成速度。伽玛采样将与属性相关的信息（由人类或语言模型本身提供）引入采样过程中，以指导语言模型，以生成具有所需属性的文本。由于不涉及培训，因此可以轻松地将伽马抽样应用于任何语言模型以进行可控文本。通过实验，我们表明，伽马取样的GPT2-MALL（1.17亿）优于PPLM（345m）和CTRL（1.6B）的多样性，属性相关性以及生成样品的整体质量。

Existing reference-free metrics have obvious limitations for evaluating controlled text generation models. Unsupervised metrics can only provide a task-agnostic evaluation result which correlates weakly with human judgments, whereas supervised ones may overfit task-specific data with poor generalization ability to other datasets. In this paper, we propose an unsupervised reference-free metric called CTRLEval, which evaluates controlled text generation from different aspects by formulating each aspect into multiple text infilling tasks. On top of these tasks, the metric assembles the generation probabilities from a pre-trained language model without any model training. Experimental results show that our metric has higher correlations with human judgments than other baselines, while obtaining better generalization of evaluating generated texts from different models and with different qualities.

Self-training (ST) has prospered again in language understanding by augmenting the fine-tuning of pre-trained language models when labeled data is insufficient. However, it remains challenging to incorporate ST into attribute-controllable language generation. Augmented by only self-generated pseudo text, generation models over-emphasize exploitation of the previously learned space, suffering from a constrained generalization boundary. We revisit ST and propose a novel method, DuNST to alleviate this problem. DuNST jointly models text generation and classification with a shared Variational AutoEncoder and corrupts the generated pseudo text by two kinds of flexible noise to disturb the space. In this way, our model could construct and utilize both pseudo text from given labels and pseudo labels from available unlabeled text, which are gradually refined during the ST process. We theoretically demonstrate that DuNST can be regarded as enhancing exploration towards the potential real text space, providing a guarantee of improved performance. Experiments on three controllable generation tasks show that DuNST could significantly boost control accuracy while maintaining comparable generation fluency and diversity against several strong baselines.

本文提出了一种简单的方法，用于使用自由形式分类器（即CAIF采样）基于加权逻辑来控制文本生成。使用任意文本分类器，我们将语言模型逻辑的一小部分调整为指导文本生成，以远离分类器预测。我们试验了避免毒性和情感控制任务，并表明该方法在PPL和DESS准确度指标上基于生成的文本的外部分类器而显着优于最近的PPLM，GEDI和DEXPERTS。此外，与其他方法相比，它更容易实施和调整，并且限制和要求较少。

真实世界的文本应用程序通常涉及组成广泛的文本控制操作，例如编辑文本W.R.T.属性，操纵关键字和结构，并生成所需属性的新文本。事先的工作通常会学习/芬太尼语言模型（LM）以执行操作的个人或特定子集。最近的研究以插件方式研究了合并操作，通常在复杂序列空间中以昂贵的搜索或优化进行了研究。本文提出了一种新的有效方法，用于在紧凑的文本潜在空间中进行可复合的文本操作。文本潜在矢量的低维度和不同性使我们能够基于给定的任意插入运算符（例如属性分类器）基于普通微分方程（ODE）开发有效的采样器。通过通过有效的适应性将预告片的LMS（例如GPT2）连接到潜在空间，然后我们将采样向量解码为所需的文本序列。灵活的方法允许使用来自不同域中的任何相关数据获取的各种控制操作员（情感，时态，形式，关键字等）。实验表明，在我们的方法中构成这些操作员可以生成或编辑高质量文本，从而在发电质量和效率方面显着改善了以前的方法。

We present Second Thought, a new learning paradigm that enables language models (LMs) to re-align with human values. By modeling the chain-of-edits between value-unaligned and value-aligned text, with LM fine-tuning and additional refinement through reinforcement learning, Second Thought not only achieves superior performance in three value alignment benchmark datasets but also shows strong human-value transfer learning ability in few-shot scenarios. The generated editing steps also offer better interpretability and ease for interactive error correction. Extensive human evaluations further confirm its effectiveness.

程序合成或代码生成旨在生成满足问题规范的程序。使用大规模预处理的语言模型（LMS）的最新方法显示出令人鼓舞的结果，但它们有一些关键的局限性。特别是，他们经常遵循标准监督的微调程序，仅从对自然语言问题描述和基础真相计划对培训代码生成模型。这种范式在很大程度上忽略了问题规范中的一些重要但潜在的信号，例如单位测试，因此在求解复杂的看不见的编码任务时通常会导致性能差。为了解决这些局限性，我们提出了“ Coderl”，这是通过验证的LMS和深入强化学习（RL）实现程序合成任务的新框架。具体而言，在培训期间，我们将代码生成的LM视为参与者网络，并引入批评网络，该网络经过培训，以预测生成的程序的功能正确性，并为演员提供密集的反馈信号。在推理期间，我们引入了一种新一代程序，具有关键的抽样策略，该过程允许模型根据示例单位测试和评论家分数的反馈自动重新生成程序。对于模型骨架，我们扩展了Codet5的编码器架构，具有增强的学习目标，更大的模型大小和更好的预处理数据。我们的方法不仅在具有挑战性的应用程序基准上实现了新的SOTA结果，而且还显示出强大的零弹性传输能力，并在简单的MBPP基准上具有新的SOTA结果。

Natural Language Generation (NLG) represents a large collection of tasks in the field of NLP. While many of these tasks have been tackled well by the cross-entropy (CE) loss, the task of dialog generation poses a few unique challenges for this loss function. First, CE loss assumes that for any given input, the only possible output is the one available as the ground truth in the training dataset. In general, this is not true for any task, as there can be multiple semantically equivalent sentences, each with a different surface form. This problem gets exaggerated further for the dialog generation task, as there can be multiple valid responses (for a given context) that not only have different surface forms but are also not semantically equivalent. Second, CE loss does not take the context into consideration while processing the response and, hence, it treats all ground truths with equal importance irrespective of the context. But, we may want our final agent to avoid certain classes of responses (e.g. bland, non-informative or biased responses) and give relatively higher weightage for more context-specific responses. To circumvent these shortcomings of the CE loss, in this paper, we propose a novel loss function, CORAL, that directly optimizes recently proposed estimates of human preference for generated responses. Using CORAL, we can train dialog generation models without assuming non-existence of response other than the ground-truth. Also, the CORAL loss is computed based on both the context and the response. Extensive comparisons on two benchmark datasets show that the proposed methods outperform strong state-of-the-art baseline models of different sizes.

我们提出了两种小型无监督方法，用于消除文本中的毒性。我们的第一个方法结合了最近的两个想法：（1）使用小型条件语言模型的生成过程的指导和（2）使用释义模型进行风格传输。我们使用良好的令人措辞的令人愉快的释放器，由风格培训的语言模型引导，以保持文本内容并消除毒性。我们的第二种方法使用BERT用他们的非攻击性同义词取代毒性单词。我们通过使BERT替换具有可变数量的单词的屏蔽令牌来使该方法更灵活。最后，我们介绍了毒性去除任务的风格转移模型的第一个大规模比较研究。我们将模型与许多用于样式传输的方法进行比较。使用无监督的样式传输指标的组合以可参考方式评估该模型。两种方法都建议产生新的SOTA结果。

文本样式传输是自然语言生成中的重要任务，旨在控制生成的文本中的某些属性，例如礼貌，情感，幽默和许多其他特性。它在自然语言处理领域拥有悠久的历史，最近由于深神经模型带来的有希望的性能而重大关注。在本文中，我们对神经文本转移的研究进行了系统调查，自2017年首次神经文本转移工作以来跨越100多个代表文章。我们讨论了任务制定，现有数据集和子任务，评估，以及丰富的方法在存在并行和非平行数据存在下。我们还提供关于这项任务未来发展的各种重要主题的讨论。我们的策据纸张列表在https://github.com/zhijing-jin/text_style_transfer_survey

大规模的预训练的语言模型在自然语言生成任务上取得了巨大的成功。但是，很难控制预先训练的语言模型来生成具有所需属性的句子，例如主题和情感等。最近，贝叶斯可控的语言模型（BCLM）已被证明在可控制的语言生成中有效。 BCLM并没有微调预训练的语言模型的参数，而是使用外部歧视器来指导预训练的语言模型的生成。但是，BCLMS训练和推断之间的不匹配限制了模型的性能。为了解决这个问题，在这项工作中，我们为可控语言生成提出了一个“双子座歧视者”，以减轻小计算成本的不匹配问题。我们在两个可控的语言生成任务上测试了我们的方法：情感控制和主题控制。在这两项任务上，我们的方法都达到了新的最先进的结果，从而可以自动评估。

This work presents a thorough review concerning recent studies and text generation advancements using Generative Adversarial Networks. The usage of adversarial learning for text generation is promising as it provides alternatives to generate the so-called "natural" language. Nevertheless, adversarial text generation is not a simple task as its foremost architecture, the Generative Adversarial Networks, were designed to cope with continuous information (image) instead of discrete data (text). Thus, most works are based on three possible options, i.e., Gumbel-Softmax differentiation, Reinforcement Learning, and modified training objectives. All alternatives are reviewed in this survey as they present the most recent approaches for generating text using adversarial-based techniques. The selected works were taken from renowned databases, such as Science Direct, IEEEXplore, Springer, Association for Computing Machinery, and arXiv, whereas each selected work has been critically analyzed and assessed to present its objective, methodology, and experimental results.