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arXiv · 2411.18330

QUADOL: A Quality-Driven Approximate Logic Synthesis Method Exploiting Dual-Output LUTs for Modern FPGAs

Jian Shi·Xuan Wang·Chang Meng·Weikang Qian
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Abstract

Approximate computing is a new computing paradigm. One important area of it is designing approximate circuits for FPGA. Modern FPGAs support dual-output LUT, which can significantly reduce the area of FPGA designs. Several existing works explored the use of dual-output in approximate computing. However, they are limited to small-scale arithmetic circuits. To address the problem, this work proposes QUADOL, a quality-driven ALS method by exploiting dual-output LUTs for modern FPGAs. We propose a technique to approximately merge two single-output LUTs (i.e., a LUT pair) into a dual-output LUT. In addition, we transform the problem of selecting multiple LUT pairs for simultaneous approximate merging into a maximum matching problem to maximize the area reduction. Since QUADOL exploits a new dimension, i.e., approximately merging a LUT pair into a dual-output LUT, it can be integrated with any existing ALS methods to strengthen them. Therefore, we also introduce QUADOL+, which is a generic framework to integrate QUADOL into existing ALS methods. The experimental results showed that QUADOL+ can reduce the LUT count by up to 18% compared to the state-of-the-art ALS methods for FPGA. Moreover, the approximate multipliers optimized by QUADOL+ dominate most prior FPGA-based approximate multipliers in the area-error plane.

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Jian Shi, Xuan Wang, Chang Meng, Weikang Qian. 2025-09-09. QUADOL: A Quality-Driven Approximate Logic Synthesis Method Exploiting Dual-Output LUTs for Modern FPGAs. https://arxiv.org/abs/2411.18330

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