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1. The Common Coder’s Scratch Programming Idioms and Their Impact on Project Remixing

   Long, Xingyu; Techapalokul, Peeratham; Tilevich, Eli (October 2021, Proceedings of ACM SIGPLAN SPLASH Educational Symposium 2021 (SPLASH-E 2021))

   null (Ed.)

   As Scratch has become one of the most popular educational programming languages, understanding its common programming idioms can benefit both computing educators and learners. This understanding can fine-tune the curricular development to help learners master the fundamentals of writing idiomatic code in their programming pursuits. Unfortunately, the research community’s understanding of what constitutes idiomatic Scratch code has been limited. To help bridge this knowledge gap, we systematically identified idioms as based on canonical source code, presented in widely available educational materials. We implemented a tool that automatically detects these idioms to assess their prevalence within a large dataset of over 70K Scratch projects in different experience backgrounds and project categories. Since communal learning and the practice of remixing are one of the cornerstones of the Scratch programming community, we studied the relationship between common programming idioms and remixes. Having analyzed the original projects and their remixes, we observed that different idioms may associate with dissimilar types of code changes. Code changes in remixes are desirable, as they require a meaningful programming effort that spurs the learning process. The ability to substantially change a project in its remixes hinges on the project’s code being easy to understand and modify. Our findings suggest that the presence of certain common idioms can indeed positively impact the degree of code changes in remixes. Our findings can help form a foundation of what comprises common Scratch programming idioms, thus benefiting both introductory computing education and Scratch programming tools. 

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2. Lightweight, Modular Verification for WebAssembly-to-Native Instruction Selection

   https://doi.org/10.1145/3617232.3624862  

   VanHattum, Alexa; Pardeshi, Monica; Fallin, Chris; Sampson, Adrian; Brown, Fraser (April 2024, ACM)

   Language-level guarantees---like module runtime isolation for WebAssembly (Wasm)---are only as strong as the compiler that produces a final, native-machine-specific executable. The process of lowering language-level constructions to ISA-specific instructions can introduce subtle bugs that violate security guarantees. In this paper, we present Crocus, a system for lightweight, modular verification of instruction-lowering rules within Cranelift, a production retargetable Wasm native code generator. We use Crocus to verify lowering rules that cover WebAssembly 1.0 support for integer operations in the ARM aarch64 backend. We show that Crocus can reproduce 3 known bugs (including a 9.9/10 severity CVE), identify 2 previously-unknown bugs and an underspecified compiler invariant, and help analyze the root causes of a new bug. 

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3. A Synthesis-Aided Compiler for DSP Architectures (WiP Paper)

   VanHattum, A.; Nigam, R.; Lee, V.; Bornholt, J.; Sampson, A. (January 2020, ACM SIGPLAN Conference on Languages, Compilers, and Tools for Embedded Systems (LCTES))

   Digital signal processors (DSPs) offer cutting-edge energy efficiency for embedded multimedia computations, but writing high-performance DSP code requires expert tuning. Programmers need to work at a low level of abstraction, manually tailoring vendor-specific instructions to enable vector and VLIW parallelism. Diospyros is a synthesizing compiler that searches for optimal data layouts to enable efficient vectorized code on DSPs. Preliminary results show that for small fixed-size matrix multiply and 2D convolution, Diospyros achieves a 6.4-7.6x speedup compared to vendor-provided optimized kernels, and a 6.5-31.3x speedup over loop-based kernels optimized with the vendor’s included compiler. 

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4. Enabling Portable and High-Performance SmartNIC Programs with Alkali

   Lin, Jiaxin Lin; Guo, Zhiyuan; Shah, Mihir; Ji, Tao; Zhang, Yiying; Kim, Daehyeok Kim; Akella, Aditya (April 2025, USENIX)

   Trends indicate that emerging SmartNICs, either from different vendors or generations from the same vendor, exhibit substantial differences in hardware parallelism and memory interconnects. These variations make porting programs across NICs highly complex and time-consuming, requiring programmers to significantly refactor code for performance based on each target NIC’s hardware characteristics. We argue that an ideal SmartNIC compilation framework should allow developers to write target-independent programs, with the compiler automatically managing cross-NIC porting and performance optimization. We present such a framework, Alkali, that achieves this by (1) proposing a new intermediate representation for building flexible compiler infrastructure for multiple NIC targets and (2) developing a new iterative parallelism optimization algorithm that automatically ports and parallelizes the input programs based on the target NIC’s hardware characteristics. Experiments across a wide range of NIC applications demonstrate that Alkali enables developers to easily write portable, high-performance NIC programs. Our compiler optimization passes can automatically port these programs and make them run efficiently across all targets, achieving performance within 9.8% of hand-tuned expert implementations. 

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5. “You Have Said Too Much”: Java-Like Verbosity Anti-Patterns in Python Codebases

   Ma, Yuzhi; Tilevich, Eli (October 2021, Proceedings of ACM SIGPLAN SPLASH Educational Symposium 2021 (SPLASH-E 2021))

   null (Ed.)

   As a popular language for teaching introductory programming, Java can profoundly influence beginner programmers with its coding style and idioms. Despite its many advantages, the paradigmatic coding style in Java is often described as verbose. As a result, when writing code in more concise languages, such programmers tend to emulate the familiar Java coding idioms, thus neglecting to take advantage of the more succinct counterparts in those languages. As a result of such verbosity, not only the overall code quality suffers, but the verbose non-idiomatic patterns also render code hard to understand and maintain. In this paper, we study the incidences of Java-like verbosity as they occur in Python codebases. We present a collection of Java-Like Verbosity Anti-patterns and our pilot study of their presence in representative open-source Python codebases. We discuss our findings as a call for action to computing educators, particularly those who work with introductory students. We need novel pedagogical interventions that encourage budding programmers to write concise idiomatic code in any language. 

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