arXiv subjects

Nick Brown

Publications and source records attributed to Nick Brown.

At least 19 recordsLinked to original sources

arXiv2026

Exploring spectral element methods on the Tenstorrent RISC-V accelerator

The growing availability of commodity RISC-V hardware has sparked interest in its use for High Performance Computing (HPC), with PCIe accelerator cards offering a practical near-term pathway to adoption. The Tenstorrent Wormhole is one example, with dedicated vector and matrix units across 128 Tensix cores, and is widely available. In this paper, we explore porting the AX kernel of Nekbone, a widely used HPC mini-application derived from the Gordon Bell Prize-winning Nek5000 spectral element solver, onto the Wormhole accelerator. This kernel evaluates the Poisson operator, and we describe the mapping of the algorithm onto the Tensix. The initial performance results reveal that the host-side data transposition, required for the z-direction gradient computation, is a severe bottleneck. Consequently, we investigated two optimisation strategies that yield dramatic improvements, achieving 242.97 GFLOPS for 100000 elements across 128 Tensix cores, outperforming a 24-core Xeon Platinum CPU and drawing approximately 7 times less power.

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arXiv2026

DSLHyPE-a DSL kernel language for the Exascale Hyperbolic PDE Engine ExaHyPE

We introduce a bilingual domain-specific language (DSL) for modelling compute kernels within a generic solver for hyperbolic partial differential equations (PDEs). Users express PDE terms, i.e.~the underlying physics, in a familiar native language such as C or C++, while the numerical scheme is specified in a Python-embedded DSL, DSLHyPE. DSLHyPE's compiler lowers the Python description to MLIR and introduces a translation pass that integrates it with native code likewise mapped to MLIR. Our approach keeps the numerical representation and the physics implementation separate for as long as possible, while delegating optimization to the compiler through existing MLIR optimization passes. This separation of concerns benefits researchers developing numerical schemes on top of existing PDE implementations or with applications involving nonlinear systems whose PDE terms must solve PDEs themselves. We demonstrate the feasibility of the approach using a gravitational-wave solver and a matter-evolution solver on x86 processors and H200 GPUs.

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arXiv2026

Lifting to tensors when compiling scientific computing workloads for AI Engines

It has been demonstrated that specialised architectures, such as FPGAs and AMD's AI Engines (AIEs), have the potential to deliver energy and performance advantages for scientific computing. Given the integration of AIEs into AMD's CPUs, this is an interesting potential avenue especially when executing on the edge or making better use of local compute constrained resources. However, a major challenge is in enabling existing codes to run on this architecture without extensive modification. Put simply, it requires significant expertise and time to port codes to the AIE's execution model. In this paper we explore a compilation pipeline for efficiently mapping loops in general purpose, scientific codes to AIEs. Lifting the semantics of an application into tensors, we demonstrate that this is able to capture the intention of general purpose loops annotated with OpenMP and such high-level tensor information provides a richness that is effective when mapping to the AIEs. Requiring only an OpenMP decorated loop, our approach significantly reduces code complexity when targeting the architecture. For six kernel benchmarks, representing AI and scientific computing, using our approach the NPU performs comparatively to the multicore CPU for float32, in all cases at reduced energy to solution. For two scientific computing kernels running across both the CPU and NPU together delivers up to a 40% improvement in performance and 15% reduction in energy usage compared to the CPU alone.

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arXiv2026

Interactive and Urgent HPC: State of the Research

When we think of how we use smartphones, e-commerce, collaboration platforms, LLMs, etc., most of our interactions with computers are interactive and often urgent. Similar trends of interactivity and urgency are coming to HPC, with applications from simulations to data analysis and machine learning requiring more parallel computational capability and more interactivity. This chapter overviews the progress made so far along with some vectors of what the path forward will bring for greater integration of interactive and urgent HPC policies, techniques, and technologies into our HPC ecosystems.

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arXiv2026

An MLIR Lowering Pipeline for Stencils at Wafer-Scale

The Cerebras Wafer-Scale Engine (WSE) delivers performance at an unprecedented scale of over 900,000 compute units, all connected via a single-wafer on-chip interconnect. Initially designed for AI, the WSE architecture is also well-suited for High Performance Computing (HPC). However, its distributed asynchronous programming model diverges significantly from the simple sequential or bulk-synchronous programs that one would typically derive for a given mathematical program description. Targeting the WSE requires a bespoke re-implementation when porting existing code. The absence of WSE support in compilers such as MLIR, meant that there was little hope for automating this process. Stencils are ubiquitous in HPC, and in this paper we explore the hypothesis that domain specific information about stencils can be leveraged by the compiler to automatically target the WSE without requiring application-level code changes. We present a compiler pipeline that transforms stencil-based kernels into highly optimized CSL code for the WSE, bridging the semantic gap between the mathematical representation of the problem and the WSE's asynchronous execution model. Based upon five benchmarks across three HPC programming technologies, running on both the Cerebras WSE2 and WSE3, our approach delivers comparable, if not slightly better, performance than manually optimized code. Furthermore, without requiring any application level code changes, performance on the WSE3 is around 14 times faster than 128 Nvidia A100 GPUs and 20 times faster than 128 nodes of a CPU-based Cray-EX supercomputer when using our approach.

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arXiv2025

An MLIR pipeline for offloading Fortran to FPGAs via OpenMP

With the slowing of Moore's Law, heterogeneous computing platforms such as Field Programmable Gate Arrays (FPGAs) have gained increasing interest for accelerating HPC workloads. In this work we present, to the best of our knowledge, the first implementation of selective code offloading to FPGAs via the OpenMP target directive within MLIR. Our approach combines the MLIR OpenMP dialect with a High-Level Synthesis (HLS) dialect to provide a portable compilation flow targeting FPGAs. Unlike prior OpenMP FPGA efforts that rely on custom compilers, by contrast we integrate with MLIR and so support any MLIR-compatible front end, demonstrated here with Flang. Building upon a range of existing MLIR building blocks significantly reduces the effort required and demonstrates the composability benefits of the MLIR ecosystem. Our approach supports manual optimisation of offloaded kernels through standard OpenMP directives, and this work establishes a flexible and extensible path for directive-based FPGA acceleration integrated within the MLIR ecosystem.

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arXiv2025

Is RISC-V ready for High Performance Computing? An evaluation of the Sophon SG2044

The pace of RISC-V adoption continues to grow rapidly, yet for the successes enjoyed in areas such as embedded computing, RISC-V is yet to gain ubiquity in High Performance Computing (HPC). The Sophon SG2044 is SOPHGO's next generation 64-core high performance CPU that has been designed for workstation and server grade workloads. Building upon the SG2042, subsystems that were a bottleneck in the previous generation have been upgraded. In this paper we undertake the first performance study of the SG2044 for HPC. Comparing against the SG2042 and other architectures, we find that the SG2044 is most advantageous when running at higher core counts, delivering up to 4.91 greater performance than the SG2042 over 64-cores. Two of the most important upgrades in the SG2044 are support for RVV v1.0 and an enhanced memory subsystem. This results in the SG2044 significantly closing the performance gap with other architectures, especially for compute-bound workloads.

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arXiv2025

RISC-V for HPC: An update of where we are and main action points

This extended abstract is submitted on behalf of the RISC-V HPC SIG who have been undertaking an analysis to explore the current state and limitations of the RISC-V ecosystem for HPC. Whilst it is right to celebrate that there has been great progress made in recent years, we also highlight limitations and where effort should be focussed.

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arXiv2025

Exploring Fast Fourier Transforms on the Tenstorrent Wormhole

Whilst numerous areas of computing have adopted the RISC-V Instruction Set Architecture (ISA) wholesale in recent years, it is yet to become widespread in HPC. RISC-V accelerators offer a compelling option where the HPC community can benefit from the specialisation offered by the open nature of the standard but without the extensive ecosystem changes required when adopting RISC-V CPUs. In this paper we explore porting the Cooley-Tukey Fast Fourier Transform (FFT) algorithm to the Tenstorrent Wormhole PCIe RISC-V based accelerator. Built upon Tenstorrent's Tensix architecture, this technology decouples the movement of data from compute, potentially offering increased control to the programmer. Exploring different optimisation techniques to address the bottlenecks inherent in data movement, we demonstrate that for a 2D FFT whilst the Wormhole n300 is slower than a server-grade 24-core Xeon Platinum CPU, the Wormhole draws around 8 times less power and consumes around 2.8 times less energy than the CPU when computing the Fourier transform.

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arXiv2025

Programming RISC-V accelerators via Fortran

A range of RISC-V based accelerators are available and coming to market, and there is strong potential for these to be used for High Performance Computing (HPC) workloads. However, such accelerators tend to provide bespoke programming models and APIs that require codes to be rewritten. In scientific computing, where many of the simulation code are highly complex, extensive, and written in Fortran, this is not realistic. In this extended abstract we present an approach that enables driving such architectures via Fortran, avoiding code redevelopment.

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arXiv2025

Investigations of multi-socket high core count RISC-V for HPC workloads

Whilst RISC-V has become popular in fields such as embedded computing, it is yet to find mainstream success in High Performance Computing (HPC). However, the 64-core RISC-V Sophon SG2042 is a potential game changer as it provides a commodity available CPU with much higher core count than existing technologies. In this work we benchmark the SG2042 CPU hosted in an experimental, dual-socket, system to explore the performance properties of the CPU when running a common HPC benchmark suite across sockets. Earlier benchmarks found that, on the Milk-V Pioneer workstation, whilst the SG2042 performs well for compute bound codes, it struggles when pressure is placed on the memory subsystem. The performance results reported here confirm that, even on a different system, these memory performance limitations are still present and hence inherent in the CPU. However, a multi-socket configuration does enable the CPU to scale to a larger number of threads which, in the main, delivers an improvement in performance and-so this is a realistic system configuration for the HPC community.

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arXiv2025

Seamless acceleration of Fortran intrinsics via AMD AI engines

A major challenge that the HPC community faces is how to continue delivering the performance demanded by scientific programmers, whilst meeting an increased emphasis on sustainable operations. Specialised architectures, such as FPGAs and AMD's AI Engines (AIEs), have been demonstrated to provide significant energy efficiency advantages, however a major challenge is that to most effectively program these architectures requires significant expertise and investment of time which is a major blocker. Fortran in the lingua franca of scientific computing, and in this paper we explore automatically accelerating Fortran intrinsics via the AIEs in AMD's Ryzen AI CPU. Leveraging the open source Flang compiler and MLIR ecosystem, we describe an approach that lowers the MLIR linear algebra dialect to AMD's AIE dialects, and demonstrate that for suitable workloads the AIEs can provide significant performance advantages over the CPU without any code modifications required by the programmer.

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arXiv2024

Pragma driven shared memory parallelism in Zig by supporting OpenMP loop directives

The Zig programming language, which is designed to provide performance and safety as first class concerns, has become popular in recent years. Given that Zig is built upon LLVM, and-so enjoys many of the benefits provided by the ecosystem, including access to a rich set of backends, Zig has significant potential for high performance workloads. However, it is yet to gain acceptance in HPC and one of the reasons for this is that support for the pragma driven shared memory parallelism is missing. In this paper we describe enhancing the Zig compiler to add support for OpenMP loop directives. Then exploring performance using NASA's NAS Parallel Benchmark (NPB) suite. We demonstrate that not only does our integration of OpenMP with Zig scale comparatively to Fortran and C reference implementations of NPB, but furthermore Zig provides up to a 1.25 times performance increase compared to Fortran.

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arXiv2024

Fully integrating the Flang Fortran compiler with standard MLIR

Fortran is the lingua franca of HPC code development and as such it is crucial that we as a community have open source Fortran compilers capable of generating high performance executables. Flang is LLVM's Fortran compiler and leverages MLIR which is a reusable compiler infrastructure which, as part of LLVM, has become popular in recent years. However, whilst Flang leverages MLIR it does not fully integrate with it and instead provides bespoke translation and optimisation passes to target LLVM-IR. In this paper we first explore the performance of Flang against other compilers popular in HPC for a range of benchmarks before describing a mapping between Fortran and standard MLIR, exploring the performance of this. The result of this work is an up to three times speed up compared with Flang's existing approach across the benchmarks and experiments run, demonstrating that the Flang community should seriously consider leveraging standard MLIR.

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arXiv2024

Accelerating stencils on the Tenstorrent Grayskull RISC-V accelerator

The RISC-V Instruction Set Architecture (ISA) has enjoyed phenomenal growth in recent years, however it still to gain popularity in HPC. Whilst adopting RISC-V CPU solutions in HPC might be some way off, RISC-V based PCIe accelerators offer a middle ground where vendors benefit from the flexibility of RISC-V yet fit into existing systems. In this paper we focus on the Tenstorrent Grayskull PCIe RISC-V based accelerator which, built upon Tensix cores, decouples data movement from compute. Using the Jacobi iterative method as a vehicle, we explore the suitability of stencils on the Grayskull e150. We explore best practice in structuring these codes for the accelerator and demonstrate that the e150 provides similar performance to a Xeon Platinum CPU (albeit BF16 vs FP32) but the e150 uses around five times less energy. Over four e150s we obtain around four times the CPU performance, again at around five times less energy.

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arXiv2024

Implementing OpenMP for Zig to enable its use in HPC context

This extended abstract explores supporting OpenMP in the Zig programming language. Whilst, C and Fortran are currently the main languages used to implement HPC applications, Zig provides a similar level of performance complimented with several modern language features, such as enforcing memory safety. However, Zig lacks support for OpenMP which is the de facto threaded programming technology. Leveraging Zig's LLVM compiler tooling, we have added partial support for OpenMP to the Zig compiler and demonstrated that the performance attained by using Zig with OpenMP is comparable to, and in come cases exceeds, that of conventional HPC languages. Consequently we demonstrate that Zig is a viable and important programming technology to use for HPC, and this work paves the way for more HPC features to be added to Zig, ultimately providing HPC developers with the option of using a safer, more modern language for creating high performance applications.

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arXiv2024

Performance characterisation of the 64-core SG2042 RISC-V CPU for HPC

Whilst RISC-V has grown phenomenally quickly in embedded computing, it is yet to gain significant traction in High Performance Computing (HPC). However, as we move further into the exascale era, the flexibility offered by RISC-V has the potential to be very beneficial in future supercomputers especially as the community places an increased emphasis on decarbonising its workloads. Sophon's SG2042 is the first mass produced, commodity available, high-core count RISC-V CPU designed for high performance workloads. First released in summer 2023, and at the time of writing now becoming widely available, a key question is whether this is a realistic proposition for HPC applications. In this paper we use NASA's NAS Parallel Benchmark (NPB) suite to characterise performance of the SG2042 against other CPUs implementing the RISC-V, x86-64, and AArch64 ISAs. We find that the SG2042 consistently outperforms all other RISC-V solutions, delivering between a 2.6 and 16.7 performance improvement at the single core level. When compared against the x86-64 and AArch64 CPUs, which are commonplace for high performance workloads, we find that the SG2042 performs comparatively well with computationally bound algorithms but decreases in relative performance when the algorithms are memory bandwidth or latency bound. Based on this work, we identify that performance of the SG2042's memory subsystem is the greatest bottleneck.

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arXiv2024

RISC-V for HPC: Where we are and where we need to go

Funded by the UK ExCALIBUR H&ES exascale programme, since early 2022 we have provided a RISC-V testbed for HPC to offer free access for scientific software developers to experiment with RISC-V for their workloads. Based upon our experiences of providing access to RISC-V for the HPC community, and our involvement with the RISC-V community at large, in this extended abstract we summarise the current state of RISC-V for HPC and consider the high priority areas that should be addressed to help drive adoption.

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