Category: Publications
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FlashAttention-3: Fast and Accurate Attention with Asynchrony and Low-precision
In this blogpost, we describe three main techniques that we use to speed up attention on Hopper GPUs in FlashAttention-3: exploiting asynchrony of the Tensor Cores and TMA to (1) overlap overall computation and data movement via warp-specialization and (2) interleave block-wise matmul and softmax operations, and (3) incoherent processing that leverages hardware support for… Go to article…
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CUTLASS Tutorial: Mastering the NVIDIA® Tensor Memory Accelerator (TMA)
TMA (Tensor Memory Accelerator) is a new feature introduced in the NVIDIA Hopper™ architecture for doing asynchronous memory copy between a GPU’s global memory (GMEM) and the shared memory (SMEM) of its threadblocks (i.e., CTAs). Compared to prior approaches, TMA offers a number of advantages, such as (1) improving GPU utilization through facilitating warp-specialized kernel… Go to article…
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Sharing NVIDIA® GPUs at the System Level: Time-Sliced and MIG-Backed vGPUs
While some modern applications for GPUs aim to consume all GPU resources and even scale to multiple GPUs (deep learning training, for instance), other applications require only a fraction of GPU resources (like some deep learning inferencing) or don’t use GPUs all the time (for example, a developer working on an NVIDIA CUDA® application may… Go to article…
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Tutorial: Matrix Transpose in CUTLASS
The goal of this tutorial is to elicit the concepts and techniques involving memory copy when programming on NVIDIA® GPUs using CUTLASS and its core backend library CuTe. Specifically, we will study the task of matrix transpose as an illustrative example for these concepts. We choose this task because it involves no operation other than… Go to article…
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Tutorial: Python bindings for CUDA libraries in PyTorch
PyTorch today is one of the most popular AI frameworks. Developed by Meta (then Facebook) and open-sourced in 2017, it features approachable, “pythonic” interfaces. This ease-of-use makes it especially potent for research and development, where a researcher might need to go through multiple iterations of novel AI workloads that they are developing. However, developing in… Go to article…
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Delivering 1 PFLOP/s of Performance with FP8 FlashAttention-2
We recently released an update to our FlashAttention-2 forward pass implementation on NVIDIA Hopper™ architecture that incorporates a number of new optimizations and improvements, including a software pipelining scheme and FP8 support. In this article, we will explain a challenge with achieving layout conformance of register fragments for WGMMA instructions that we encountered in the… Go to article…
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A note on the algebra of CuTe Layouts
The core abstraction of NVIDIA’s CUTLASS library for high-performance linear algebra is the CuTe Layout. In this technical note, we give a rigorous, mathematical treatment of the algebra of these layouts and certain layout operations. Currently, the main goal is to lay down conditions for when the operations of complementation, composition, and logical division are… Go to article…
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A Case Study in CUDA Kernel Fusion: Implementing FlashAttention-2 on NVIDIA Hopper Architecture using the CUTLASS Library
We provide an optimized implementation of the forward pass of FlashAttention-2, a popular memory-aware scaled dot-product attention algorithm, as a custom fused CUDA® kernel targeting NVIDIA Hopper™ architecture and written using the open-source CUTLASS library. In doing so, we explain the challenges and techniques involved in fusing online-softmax with back-to-back GEMM kernels, utilizing the Hopper-specific… Go to article…
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Developing CUDA Kernels for GEMM on NVIDIA Hopper Architecture using CUTLASS
We explain how to develop NVIDIA CUDA® kernels for optimized general matrix multiplication (GEMM) on NVIDIA Hopper™ architecture using the template collection CUTLASS and its core library CuTe. Our main contribution is to provide an implementation of a GEMM kernel that uses the Tensor Memory Accelerator (TMA) and Warp Group Matrix-Multiply-Accumulate (WGMMA) operations introduced with… Go to article…