新任助教講演会(Lectures from New Assistant Professors)

日時(Datetime) 令和4年6月17日(金)3限 (13:30 -- 15:00), 2022/06/17, Friday
場所(Location) エーアイ大講義室(L1)
司会(Chair) 黄 銘(Ming Huang)

講演者(Presenter) Kan Yirong, コンピューティング・アーキテクチャ研究室 (Computing Architecture Lab.)
題目(Title) Multi-Grained Reconfigurable Architecture Powered by Elastic Neural Network for Approximate Computing
概要(Abstract) Beyond the boom of artificial intelligence, the next generation of computing architectures with high speed and low cost are always demanded. In this lecture, we introduce a multi-grained reconfigurable architecture for accelerating arbitrary functions in fully parallel with high speed and low cost. The proposed architecture is reconfigurable in fine-grained (arbitrary functions), mid-grained (flexible function feature, accuracy, and number of operands), and coarse-grained (organization of kernels). By implementing a large scale of novel bisection neural network (BNN) on hardware, the reconfiguration is conducted by partitioning entire BNN into any specific pieces without redundancy. Each piece of BNN retrieves the arbitrary function approximately. By reconfiguring the BNN topology in software, we can easily adjust dimensions of the computing kernel without rewiring, and achieve a wide range of trade-offs between accuracy and efficiency in hardware. In this manner, the multi-grained reconfigurable architecture is achieved. For proof-of-concept, a demo accelerator is built on FPGA. The processing element is designed in 16-bit fixed point scheme including two synapses and one neuron. In order to better support this architecture, we have also proposed a series of system-level optimization techniques, including design flow, on-chip interconnection, and configuration strategies, etc. From the FPGA implementation results,compared with CPU baseline, proposed architecture achieves speedups of 5.1x to 30.3x. Compared with other traditional function approximation methods, our method provides fewer parameter storage requirements. The comparison against related works proves that our accelerator has reduced the area-latency product by at least 9.5% with a loss of accuracy by at most 8.9%.

講演者(Presenter) 柏 祐太郎(Yutaro Kashiwa), 総合情報基盤センター (Information Initiative Center)
題目(Title) Does Refactoring Break Tests and to What Extent?
概要(Abstract) Refactoring as a process is aimed at improving the quality of a software system while preserving its external behavior. In practice, refactoring comes in the form of many specific and diverse refactoring operations, which have different scopes and thus a different potential impact on both the production and the test code. We present a large-scale quantitative study complemented by a qualitative analysis involving 615,196 test cases to understand how and to what extent different refactoring operations impact a system’s test suites. Our findings show that while the vast majority of refactoring operations do not or very seldom induce test breaks, some specific refactoring types (e.g., “RENAME ATTRIBUTE” and “RENAME CLASS”) have a higher chance of breaking test suites. Meanwhile, “ADD PARAMETER” and “CHANGE RETURN TYPE” refactoring operations often require additional lines of changes to fix the test suite they break. While some modern IDEs provide features to automatically apply these two types of refactoring operations, they are not always able to avoid test breaks, thus demanding extra-human efforts.