Recent work has demonstrated that pretrained transformers are overconfident in text classification tasks, which can be calibrated by the famous post-hoc calibration method temperature scaling (TS). Character or word spelling mistakes are frequently encountered in real applications and greatly threaten transformer model safety. Research on calibration under noisy settings is rare, and we focus on this direction. Based on a toy experiment, we discover that TS performs poorly when the datasets are perturbed by slight noise, such as swapping the characters, which results in distribution shift. We further utilize two metrics, predictive uncertainty and maximum mean discrepancy (MMD), to measure the distribution shift between clean and noisy datasets, based on which we propose a simple yet effective transferable TS method for calibrating models dynamically. To evaluate the performance of the proposed methods under noisy settings, we construct a benchmark consisting of four noise types and five shift intensities based on the QNLI, AG-News, and Emotion tasks. Experimental results on the noisy benchmark show that (1) the metrics are effective in measuring distribution shift and (2) transferable TS can significantly decrease the expected calibration error (ECE) compared with the competitive baseline ensemble TS by approximately 46.09%.

Recent studies show that deep neural networks are vulnerable to adversarial attacks in the form of subtle perturbations to the input image, which leads the model to output wrong prediction. Such an attack can easily succeed by the existing white-box attack methods, where the perturbation is calculated based on the gradient of the target network. Unfortunately, the gradient is often unavailable in the real-world scenarios, which makes the black-box adversarial attack problems practical and challenging. In fact, they can be formulated as high-dimensional black-box optimization problems at the pixel level. Although evolutionary algorithms are well known for solving black-box optimization problems, they cannot efficiently deal with the high-dimensional decision space. Therefore, we propose an approximated gradient sign method using differential evolution (DE) for solving black-box adversarial attack problems. Unlike most existing methods, it is novel that the proposed method searches the gradient sign rather than the perturbation by a DE algorithm. Also, we transform the pixel-based decision space into a dimension-reduced decision space by combining the pixel differences from the input image to neighbor images, and two different techniques for selecting neighbor images are introduced to build the transferred decision space. In addition, six variants of the proposed method are designed according to the different neighborhood selection and optimization search strategies. Finally, the performance of the proposed method is compared with a number of the state-of-the-art adversarial attack algorithms on CIFAR-10 and ImageNet datasets. The experimental results suggest that the proposed method shows superior performance for solving black-box adversarial attack problems, especially nontargeted attack problems.

For complex system design [e.g., satellite layout optimization design (SLOD)] in practical engineering, when launching a new optimization instance with another parameter configuration from the intuition of designers, it is always executed from scratch which wastes much time to repeat the similar search process. Inspired by transfer learning which can reuse past experiences to solve relevant tasks, many researchers pay more attention to explore how to learn from past optimization instances to accelerate the target one. In real-world applications, there have been numerous similar source instances stored in the database. The primary question is how to measure the transferability from numerous sources to avoid the notorious negative transferring. To obtain the relatedness between source and target instance, we develop an optimization instance representation method named centroid distribution, which is by the aid of the probabilistic model learned by elite candidate solutions in estimation of distribution algorithm (EDA) during the evolutionary process. Wasserstein distance is employed to evaluate the similarity between the centroid distributions of different optimization instances, based on which, we present a novel framework called multisource selective transfer optimization with three strategies to select sources reasonably. To choose the suitable strategy, four selection suggestions are summarized according to the similarity between the source and target centroid distribution. The framework is beneficial to choose the most suitable sources, which could improve the search efficiency in solving multiobjective optimization problems. To evaluate the effectiveness of the proposed framework and selection suggestions, we conduct two experiments: 1) comprehensive empirical studies on complex multiobjective optimization problem benchmarks and 2) a real-world SLOD problem. Suggestions for strategy selection coincide with the experiment results, based on which, we propose a mixed strategy to deal with the negative transfer in the experiments successfully. The results demonstrate that our proposed framework achieves competitive performance on most of the benchmark problems in convergence speed and hypervolume values and performs best on the real-world applications among all the comparison algorithms.

The satellite layout optimization design (SLOD) problem is a kind of three-dimensional layout problems with complex performance constraints and known as a NP-hard problem. To solve SLOD problems efficiently and effectively, two types of hybrid optimization algorithm based on differential evolution (DE) are proposed in this paper. Concerning the design requirements of satellite attitude control subsystem, the SLOD problem is formulated, aiming to improve the overall mass characteristics of satellite. To explore the layout design space globally, the DE algorithm is utilized as the main framework of the proposed hybrid algorithm. Then in order to improve the local exploitation capability and algorithm robustness, sequential quadratic programming (SQP), as a gradient-based method, is combined with DE in two unique ways, comprising two types of hybrid algorithm. In the first type of hybrid algorithm (denoted by DESQP), SQP is performed when iteration process of DE has finished and only the final solution of DE is used as the initial point of SQP, the purpose of which is to locate the most promising area of optimum with DE first and then make a rapid exploitation around the quasi-optimum. In the second type of hybrid algorithm (denoted by DESQPDE), SQP is performed in the specific iteration of DE and all the current-generation population individuals are used as the initial points, the purpose of which is to accelerate the evolution process while holding the diversity of the population and to enhance the robustness. Finally, the efficacy and robustness of the proposed hybrid algorithms are compared with classical DE and also validated by two three-dimensional satellite layout cases with 14 and 40 components, respectively.