Cited by 149Advanced Neural Network ApplicationsParallel Computing and Optimization TechniquesLow-power high-performance VLSI design

Softermax: Hardware/Software Co-Design of an Efficient Softmax for Transformers

Open access
Stevens, Jacob R., Venkatesan, Rangharajan, Dai, Steve, Khailany, Brucek, Raghunathan, Anand·2021·2021 58th ACM/IEEE Design Automation Conference (DAC)

Abstract

Transformers have transformed the field of natural language processing. Their superior performance is largely attributed to the use of stacked “self-attention” layers, each of which consists of matrix multiplies as well as softmax operations. As a result, unlike other neural networks, the softmax operation accounts for a significant fraction of the total run-time of Transformers. To address this, we propose Softermax, a hardware-friendly softmax design. Softermax consists of base replacement, low-precision softmax computations, and an online normalization calculation. We show Softermax results in 2.35x the energy efficiency at 0.90x the size of a comparable baseline, with negligible impact on network accuracy.

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Crossref · 10.1109/dac18074.2021.9586134

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  • Non-linear operations like Softmax, LayerNorm, and GELU present computational challenges on conventional hardware due to their complexity, potentially restricting end-to-end transformer inference.

    “Non-linear operations like Softmax, LayerNorm, and GELU, though less prevalent, present computational challenges on conventional hardware due to their complexity, potentially restricting the enhancement of end-to-end transformer inference [31].”

    From Model Quantization and Hardware Acceleration for Vision Transformers: A Comprehensive Survey (2024) · cites this paper as [31]

    The “Softmax Bottlenecks” section (page not supplied) explains why softmax is inefficient on CPUs and GPUs, and the Conclusion says its time and energy costs limit Transformer implementations. The paper does not establish the same hardware challenges for LayerNorm or GELU, so the claim’s broader list of operations is not fully supported. (LLM, conf=0.88)

    Experimental — accuracy not yet measured
  • A large portion of the inference time in ViT models is consumed by floating-point non-linear activations, normalizations, and the associated quantization and dequantization operations.

    “A large portion of the inference time in ViT models is consumed by floating-point non-linear activations, normalizations, and the associated quantization and dequantization operations [31].”

    From Model Quantization and Hardware Acceleration for Vision Transformers: A Comprehensive Survey (2024) · cites this paper as [31]

    The Introduction says attention operations, particularly softmax, account for a large fraction of Transformer runtime; its runtime example is BERT-Large, not a ViT model. The Softmax Bottlenecks section also notes a possible slight performance penalty from casting between data types. The paper does not establish that floating-point activations, normalizations, and quantization/dequantization operations collectively consume a large portion of ViT inference time. (LLM, conf=0.86)

    Experimental — accuracy not yet measured
  • Various approximation methods that hold floating-point arithmetic lower certain computational costs but cannot meet the demands of integer arithmetic.

    “In addition, various approximation methods that hold floating-point arithmetic are presented [36, 50]; while they lower certain computational costs, they cannot meet the demands of integer arithmetic.”

    From I-ViT: Integer-only Quantization for Efficient Vision Transformer Inference (2023) · cites this paper as [36]

    In “Low-precision Softmax Operations” (page unavailable), the paper says 32-bit floating-point units are costly in area and power and proposes lower-precision operations. “Softmax Bottlenecks” discusses earlier approximate units, but does not establish that those methods retain floating-point arithmetic or cannot meet integer-arithmetic requirements. The Experimental Setup instead describes Softermax’s compatibility with 8-bit integer datapaths. (LLM, conf=0.78)

    Experimental — accuracy not yet measured
  • Softmax cannot follow the dyadic arithmetic pipeline due to non-linearity, and the exponential arithmetic in Softmax is typically unsupported by integer-only logic units.

    “Due to the non-linearity, Softmax cannot follow the dyadic arithmetic pipeline discussed above, and the exponential arithmetic in Eq. 11 is typically unsupported by integer-only logic units [36].”

    From I-ViT: Integer-only Quantization for Efficient Vision Transformer Inference (2023) · cites this paper as [36]

    The Softermax Software section describes the natural exponential as nonlinear and says it creates hardware overhead. Low-precision Softmax Operations says commodity hardware does not support low-precision special-function units such as power and division. The paper does not specifically say that Softmax cannot follow a dyadic arithmetic pipeline or that exponential arithmetic is unsupported by integer-only logic units (page numbers unavailable in our copy). (LLM, conf=0.84)

    Experimental — accuracy not yet measured

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Cites

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2 of the 23 references couldn’t be matched to a known paper.

Research works printed but not linked: 1

  1. A. Radford, J. Wu, R. Child et al., "Language models are unsupervised multitask learners," OpenAI blog, vol. 1, no. 8, p. 9, 2019.

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Authors
Stevens, J. R., Venkatesan, R., Dai, S., Khailany, B., & Raghunathan, A.
Affiliations
  • Purdue University West Lafayette (US)
  • Nvidia (United Kingdom) (GB)
Venue
2021 58th ACM/IEEE Design Automation Conference (DAC)
Publisher
IEEE
Published
2021-12-05
Pages
469-474
ISSN
0738-100X (ISSN-L)
OpenAlex
W3137649401
Cited by
148
References
23
Citations by year
2026: 22 · 2025: 68 · 2024: 35 · 2023: 16 · 2022: 5 · 2021: 2
FWCI
4.74
Type
conference paper
Language
en
Open access
Locations
  • ACM/IEEE Design Automation Conference (DAC) (publishedVersion)
  • arXiv (Cornell University) (submittedVersion, cc-by-nc-nd)
  • arXiv (Cornell University) (submittedVersion)
  • arXiv (Cornell University)
Topics
  • Physical Sciences › Computer Science › Computer Vision and Pattern Recognition › Advanced Neural Network Applications
  • Physical Sciences › Computer Science › Hardware and Architecture › Parallel Computing and Optimization Techniques
  • Physical Sciences › Engineering › Electrical and Electronic Engineering › Low-power high-performance VLSI design
Keywords
softmax, transformer models, hardware-software co-design, self-attention, low-precision arithmetic, energy efficiency, neural network acceleration

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