MX: Enhancing RISC-V's Vector ISA for Ultra-Low Overhead, Energy-Efficient Matrix Multiplication
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Date
2024
Publication Type
Conference Paper
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yes
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Abstract
Dense Matrix Multiplication (MatMul) is arguably one of the most ubiquitous compute-intensive kernels, spanning linear algebra, DSP, graphics, and machine learning applications. Thus, MatMul optimization is crucial not only in high-performance processors but also in embedded low-power platforms. Several Instruction Set Architectures (ISAs) have recently included matrix extensions to improve MatMul performance and efficiency at the cost of added matrix register files and units. In this paper, we propose Matrix eXtension (MX), a lightweight approach that builds upon the open-source RISC-V Vector (RVV) ISA to boost MatMul energy efficiency. Instead of adding expensive dedicated hardware, MX uses the pre-existing vector register file and functional units to create a hybrid vector/matrix engine at a negligible area cost (<3%) , which comes from a compact near-FPU tile buffer for higher data reuse, and no clock frequency overhead. We implement MX on a compact and highly energy-optimized RVV processor and evaluate it in both a Dual- and 64-Core cluster in a 12-nm technology node. MX boosts the Dual-Core's energy efficiency by 10% for a double-precision 64×64×64 matrix multiplication with the same FPU utilization (≈97%) and by 25 % on the 64-Core cluster for the same benchmark on 32-bit data, with a 56% performance gain.
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published
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Book title
2024 Design, Automation & Test in Europe Conference & Exhibition (DATE)
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Pages / Article No.
10546720
Publisher
IEEE
Event
27th Design, Automation and Test in Europe Conference and Exhibition (DATE 2024)
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Methods
Software
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Date created
Subject
RISC-V; Matrix; Vector; Efficiency
Organisational unit
03996 - Benini, Luca / Benini, Luca