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We discuss the concept of FPGA-unfriendliness, the property of certain algorithms, programs, or domains which may limit their applicability to FPGAs. Specifically, we look at graph analysis, which has recently seen increased interest in combination with High-Level Synthesis, but has yet to find great success compared to established acceleration mechanisms. To this end, we make use of Xilinx's Vitis Graph Library to implement Single-Source Shortest Paths (SSSP) and PageRank (PR), and present a custom kernel written from the ground up for Distinctiveness Centrality (DC, a novel graph centrality measure). We use public datasets to test these implementations, and analyse power consumption and execution time. Our comparisons against published data for GPU and CPU execution show FPGA slowdowns in execution time between around 18.5x and 328x for SSSP, and around 1.8x and 195x for PR, respectively. In some instances, we obtained FPGA speedups versus CPU of up to 2.5x for PR. Regarding DC, results show speedups from 0.1x to 3.5x, and energy efficiency increases from 0.8x to 6x. Lastly, we provide some insights regarding the applicability of FPGAs in FPGA-unfriendly domains, and comment on the future as FPGA and HLS technology advances.

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Learning computer programming is a complex activity and requires a lot of practice. The viral pandemic that we are facing has intensified these difficulties. In this context, programming learning platforms play a crucial role. Most of them are characterized by providing a wide range of exercises with progressive complexity, multi-language support, sophisticated interfaces and automatic evaluation and gamification services. Nevertheless, despite the various features provided, others features, which influence user experience, are not emphasized, such as performance and usability. This article presents an user experience evaluation of the LearnJS playground, a JavaScript learning platform which aims to foster the practice of coding. The evaluation highlights two facets of the code playground: performance and a usability. In the former, lab and field data were collected based on Google Lighthouse and PageSpeed Insights reports. In the later, an inquiry was distributed among students from a Web Technologies course with a set of questions based on flexibility, usability and consistency heuristics. Both evaluation studies have a twofold goal: to improve the learning environment in order to be officially used in the next school year and to foster the awareness of user experience in all phases of the software development life-cycle as a key facet in Web applications engagement and loyalty. © Ricardo Queirós, Mário Pinto, and Teresa Terroso; licensed under Creative Commons License CC-BY 4.0 Second International Computer Programming Education Conference (ICPEC 2021).

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In this paper, we discuss the design considerations and goals of an interactive digital musical instrument (DMI) for novice pianists. It aims to promote the practice of melodic improvisation by guiding pianists in the selection of notes. The DMI includes two major components: a generative jazz model (software) and an illuminating keyboard controller (hardware). Visual feedback in the form of illuminated keyboard controller keys guides notes selection. Illuminated keys correspond to scale degrees that comply with a harmonic structure generated on-the-fly. The generative nature of the engine allows high degrees of novelty while guaranteeing a structurally-coherent harmonic structure anchored in the blues/jazz idiom. Preliminary experimental results inform critical directions for future design iterations of the proposed system.