TransformCode: A Contrastive Learning Framework for Code Embedding via Subtree transformation

Large-scale language models have made great progress in the field of software engineering in recent years. They can be used for many code-related tasks such as code clone detection, code-to-code search, and method name prediction. However, these large-scale language models based on each code token have several drawbacks: They are usually large in scale, heavily dependent on labels, and require a lot of computing power and time to fine-tune new datasets.Furthermore, code embedding should be performed on the entire code snippet rather than encoding each code token. The main reason for this is that encoding each code token would cause model parameter inflation, resulting in a lot of parameters storing information that we are not very concerned about. In this paper, we propose a novel framework, called TransformCode, that learns about code embeddings in a contrastive learning manner. The framework uses the Transformer encoder as an integral part of the model. We also introduce a novel data augmentation technique called abstract syntax tree transformation: This technique applies syntactic and semantic transformations to the original code snippets to generate more diverse and robust anchor samples. Our proposed framework is both flexible and adaptable: It can be easily extended to other downstream tasks that require code representation such as code clone detection and classification. The framework is also very efficient and scalable: It does not require a large model or a large amount of training data, and can support any programming language.Finally, our framework is not limited to unsupervised learning, but can also be applied to some supervised learning tasks by incorporating task-specific labels or objectives. To explore the effectiveness of our framework, we conducted extensive experiments on different software engineering tasks using different programming languages and multiple datasets.

Elongated Physiological Structure Segmentation via Spatial and Scale Uncertainty-aware Network

Robust and accurate segmentation for elongated physiological structures is challenging, especially in the ambiguous region, such as the corneal endothelium microscope image with uneven illumination or the fundus image with disease interference. In this paper, we present a spatial and scale uncertainty-aware network (SSU-Net) that fully uses both spatial and scale uncertainty to highlight ambiguous regions and integrate hierarchical structure contexts. First, we estimate epistemic and aleatoric spatial uncertainty maps using Monte Carlo dropout to approximate Bayesian networks. Based on these spatial uncertainty maps, we propose the gated soft uncertainty-aware (GSUA) module to guide the model to focus on ambiguous regions. Second, we extract the uncertainty under different scales and propose the multi-scale uncertainty-aware (MSUA) fusion module to integrate structure contexts from hierarchical predictions, strengthening the final prediction. Finally, we visualize the uncertainty map of final prediction, providing interpretability for segmentation results. Experiment results show that the SSU-Net performs best on cornea endothelial cell and retinal vessel segmentation tasks. Moreover, compared with counterpart uncertainty-based methods, SSU-Net is more accurate and robust.

Using Metamorphic Relations to Verify and Enhance Artcode Classification

Software testing is often hindered where it is impossible or impractical to determine the correctness of the behaviour or output of the software under test (SUT), a situation known as the oracle problem. An example of an area facing the oracle problem is automatic image classification, using machine learning to classify an input image as one of a set of predefined classes. An approach to software testing that alleviates the oracle problem is metamorphic testing (MT). While traditional software testing examines the correctness of individual test cases, MT instead examines the relations amongst multiple executions of test cases and their outputs. These relations are called metamorphic relations (MRs): if an MR is found to be violated, then a fault must exist in the SUT. This paper examines the problem of classifying images containing visually hidden markers called Artcodes, and applies MT to verify and enhance the trained classifiers. This paper further examines two MRs, Separation and Occlusion, and reports on their capability in verifying the image classification using one-way analysis of variance (ANOVA) in conjunction with three other statistical analysis methods: t-test (for unequal variances), Kruskal-Wallis test, and Dunnett's test. In addition to our previously-studied classifier, that used Random Forests, we introduce a new classifier that uses a support vector machine, and present its MR-augmented version. Experimental evaluations across a number of performance metrics show that the augmented classifiers can achieve better performance than non-augmented classifiers. This paper also analyses how the enhanced performance is obtained.