C2PAx: Complexity-Aware Constant Parameter Approximation for Energy-Efficient Tree-Based Machine Learning Accelerators

Tree-based machine learning models, like random forests and decision trees, are low-complexity solutions that provide an efficient prediction for a wide range of applications. These models are particularly interesting for energy-constrained platforms since they can be implemented with simple logical...

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Bibliographic Details
Published in:IEEE transactions on circuits and systems. I, Regular papers Regular papers, 2022-07, Vol.69 (7), p.2683-2693
Main Authors: de Abreu, Brunno Alves, Paim, Guilherme, Grellert, Mateus, Bampi, Sergio
Format: Article
Language:English
Subjects:
Accelerators
Accuracy
Approximate computing
Approximation
Brain modeling
Comparators
Complexity
Decision trees
Energy consumption
Energy efficiency
hardware accelerators
Integrated circuit modeling
Integrated circuits
Machine learning
Mathematical models
Optimization
Parameters
Power consumption
Power dissipation
Proposals
Radio frequency
Random forests
Very large scale integration
VLSI design
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Summary:Tree-based machine learning models, like random forests and decision trees, are low-complexity solutions that provide an efficient prediction for a wide range of applications. These models are particularly interesting for energy-constrained platforms since they can be implemented with simple logical operations. Tree-based accelerators are also intrinsically resilient to errors, and this can be leveraged to boost energy efficiency with approximate computing techniques. The key operations in these models are comparisons to constants, making comparators excellent candidates for approximation. This paper presents a technique to approximate comparisons to constants called C2PAx, which is capable of reducing the area and energy of tree-based accelerators. The method consists in finding alternative constants that reduce circuit area while keeping an efficient prediction performance. It is also shown that the selection of the constant parameters directly influences both hardware complexity and model performance, demanding cross-layer optimization. For that, we extend an existing framework that generates VLSI tree-based accelerators, inserting our approximation proposal that allows selecting the constant parameters that maximize energy efficiency at the cost of minor accuracy drops. Simulation results demonstrate that C2PAx outperforms the Don't Care logic approximation technique when accuracy and energy are jointly considered. C2PAx trades accuracy for significant reductions in the VLSI area, power, delay, and energy consumption compared to precise models.
ISSN:1549-8328
1558-0806
DOI:10.1109/TCSI.2022.3169028