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Tianshi Chen

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8 papers

1 author row

IJCAI Conference 2024 Conference Paper

Automated CPU Design by Learning from Input-Output Examples

Shuyao Cheng
Pengwei Jin
Qi Guo
Zidong Du
Rui Zhang
Xing Hu
Yongwei Zhao
Yifan Hao

Designing a central processing unit (CPU) requires intensive manual work of talented experts to implement the circuit logic from design specifications. Although considerable progress has been made in electronic design automation (EDA) to relieve human efforts, all existing EDA tools require hand-crafted formal program codes (e. g. , Verilog, Chisel, or C) as the input. To automate the CPU design without human programming, we are motivated to learn the CPU design from only input-output (IO) examples. The key challenge is that the learned CPU design should have almost zero tolerance for inaccuracy, which makes well-known approximate algorithms such as neural networks ineffective. We propose a new AI approach to generate the CPU design in the form of a large-scale Boolean function, from only external IO examples instead of formal program code. This approach employs a novel graph structure called Binary Speculative Diagram (BSD) to approximate the CPU-scale Boolean function accurately. We propose an efficient BSD expansion method based on Boolean Distance, a new metric to quantitatively measure the structural similarity between Boolean functions, gradually increasing the design accuracy up to 100%. Our approach generates an industrial-scale RISC-V CPU design within 5 hours, reducing the design cycle by about 1000x without human involvement. The taped-out chip, Enlightenment-1, the world's first CPU designed by AI, successfully runs the Linux operating system and performs comparably against the human-design Intel 80486SX CPU. Our approach even autonomously discovers human knowledge of the von Neumann architecture.

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NeurIPS Conference 2021 Conference Paper

Distilling Object Detectors with Feature Richness

Du Zhixing
Rui Zhang
Ming Chang
Xishan Zhang
Shaoli Liu
Tianshi Chen
Yunji Chen

In recent years, large-scale deep models have achieved great success, but the huge computational complexity and massive storage requirements make it a great challenge to deploy them in resource-limited devices. As a model compression and acceleration method, knowledge distillation effectively improves the performance of small models by transferring the dark knowledge from the teacher detector. However, most of the existing distillation-based detection methods mainly imitating features near bounding boxes, which suffer from two limitations. First, they ignore the beneficial features outside the bounding boxes. Second, these methods imitate some features which are mistakenly regarded as the background by the teacher detector. To address the above issues, we propose a novel Feature-Richness Score (FRS) method to choose important features that improve generalized detectability during distilling. The proposed method effectively retrieves the important features outside the bounding boxes and removes the detrimental features within the bounding boxes. Extensive experiments show that our methods achieve excellent performance on both anchor-based and anchor-free detectors. For example, RetinaNet with ResNet-50 achieves 39. 7% in mAP on the COCO2017 dataset, which even surpasses the ResNet-101 based teacher detector 38. 9% by 0. 8%. Our implementation is available at https: //github. com/duzhixing/FRS.

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AAAI Conference 2020 Conference Paper

DWM: A Decomposable Winograd Method for Convolution Acceleration

Di Huang
Xishan Zhang
Rui Zhang
Tian Zhi
Deyuan He
Jiaming Guo
Chang Liu
Qi Guo

Winograd’s minimal ﬁltering algorithm has been widely used in Convolutional Neural Networks (CNNs) to reduce the number of multiplications for faster processing. However, it is only effective on convolutions with kernel size as 3x3 and stride as 1, because it suffers from signiﬁcantly increased FLOPs and numerical accuracy problem for kernel size larger than 3x3 and fails on convolution with stride larger than 1. In this paper, we propose a novel Decomposable Winograd Method (DWM), which breaks through the limitation of original Winograd’s minimal ﬁltering algorithm to a wide and general convolutions. DWM decomposes kernels with large size or large stride to several small kernels with stride as 1 for further applying Winograd method, so that DWM can reduce the number of multiplications while keeping the numerical accuracy. It enables the fast exploring of larger kernel size and larger stride value in CNNs for high performance and accuracy and even the potential for new CNNs. Comparing against the original Winograd, the proposed DWM is able to support all kinds of convolutions with a speedup of ∼2, without affecting the numerical accuracy.

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TIST Journal 2013 Journal Article

Effective and efficient microprocessor design space exploration using unlabeled design configurations

Tianshi Chen
Yunji Chen
Qi Guo
Zhi-Hua Zhou
Ling Li
Zhiwei Xu

Ever-increasing design complexity and advances of technology impose great challenges on the design of modern microprocessors. One such challenge is to determine promising microprocessor configurations to meet specific design constraints, which is called Design Space Exploration (DSE). In the computer architecture community, supervised learning techniques have been applied to DSE to build regression models for predicting the qualities of design configurations. For supervised learning, however, considerable simulation costs are required for attaining the labeled design configurations. Given limited resources, it is difficult to achieve high accuracy. In this article, inspired by recent advances in semisupervised learning and active learning, we propose the COAL approach which can exploit unlabeled design configurations to significantly improve the models. Empirical study demonstrates that COAL significantly outperforms a state-of-the-art DSE technique by reducing mean squared error by 35% to 95%, and thus, promising architectures can be attained more efficiently.

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TCS Journal 2012 Journal Article

A large population size can be unhelpful in evolutionary algorithms

Tianshi Chen
Ke Tang
Guoliang Chen
Xin Yao

The utilization of populations is one of the most important features of evolutionary algorithms (EAs). There have been many studies analyzing the impact of different population sizes on the performance of EAs. However, most of such studies are based on computational experiments, except for a few cases. The common wisdom so far appears to be that a large population would increase the population diversity and thus help an EA. Indeed, increasing the population size has been a commonly used strategy in tuning an EA when it did not perform as well as expected for a given problem. He and Yao (2002) [8] showed theoretically that for some problem instance classes, a population can help to reduce the runtime of an EA from exponential to polynomial time. This paper analyzes the role of population further in EAs and shows rigorously that large populations may not always be useful. Conditions, under which large populations can be harmful, are discussed in this paper. Although the theoretical analysis was carried out on one multimodal problem using a specific type of EAs, it has much wider implications. The analysis has revealed certain problem characteristics, which can be either the problem considered here or other problems, that lead to the disadvantages of large population sizes. The analytical approach developed in this paper can also be applied to analyzing EAs on other problems.

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IJCAI Conference 2011 Conference Paper

Effective and Efficient Microprocessor Design Space Exploration Using Unlabeled Design Configurations

Qi Guo
Tianshi Chen
Yunji Chen
Zhi-Hua Zhou
Weiwu Hu
Zhiwei Xu

During the design of a microprocessor, Design Space Exploration (DSE) is a critical step which determines the appropriate design configuration of the microprocessor. In the computer architecture community, supervised learning techniques have been applied to DSE to build models for predicting the qualities of design configurations. For supervised learning, however, considerable simulation costs are required for attaining the labeled design configurations. Given limited resources, it is difficult to achieve high accuracy. In this paper, inspired by recent advances in semi-supervised learning, we propose the COMT approach which can exploit unlabeled design configurations to improve the models. In addition to an improved predictive accuracy, COMT is able to guide the design of microprocessors, owing to the use of comprehensible model trees. Empirical study demonstrates that COMT significantly outperforms state-of-the-art DSE technique through reducing mean squared error by 30% to 84%, and thus, promising architectures can be attained more efficiently.

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AAAI Conference 2011 Conference Paper

Towards Maximizing the Area Under the ROC Curve for Multi-Class Classification Problems

Ke Tang
Rui Wang
Tianshi Chen

The Area Under the ROC Curve (AUC) metric has achieved a big success in binary classiﬁcation problems since they measure the performance of classiﬁers without making any speciﬁc assumptions about the class distribution and misclassiﬁcation costs. This is desirable because the class distribution and misclassiﬁcation costs may be unknown during training process or even change in environment. MAUC, the extension of AUC to multi-class problems, has also attracted a lot of attention. However, despite the emergence of approaches for training classiﬁers with large AUC, little has been done for MAUC. This paper analyzes MAUC in-depth, and reveals that the maximization of MAUC can be achieved by decomposing the multi-class problem into a number of independent sub-problems. These sub-problems are formulated in the form of a “learning to rank” problem, for which well-established methods already exist. Based on the analysis, a method that employs RankBoost algorithm as the sub-problem solver is proposed to achieve classiﬁcation systems with maximum MAUC. Empirical studies have shown the advantages of the proposed method over other eight relevant methods. Due to the importance of MAUC to multi-class cost-sensitive learning and class imbalanced learning problems, the proposed method is a general technique for both problems. It can also be generalized to accommodate other learning algorithms as the subproblem solvers.

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TCS Journal 2010 Journal Article

Choosing selection pressure for wide-gap problems

Tianshi Chen
Jun He
Guoliang Chen
Xin Yao

To exploit an evolutionary algorithm’s performance to the full extent, the selection scheme should be chosen carefully. Empirically, it is commonly acknowledged that low selection pressure can prevent an evolutionary algorithm from premature convergence, and is thereby more suitable for wide-gap problems. However, there are few theoretical time complexity studies that actually give the conditions under which a high or a low selection pressure is better. In this paper, we provide a rigorous time complexity analysis showing that low selection pressure is better for the wide-gap problems with two optima.

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