CUTLASS is a collection of CUDA C++ template abstractions for implementing high-performance matrix-multiplication (GEMM) at all levels and scales within CUDA. It incorporates strategies for hierarchical decomposition and data movement similar to those used to implement cuBLAS. CUTLASS decomposes these "moving parts" into reusable, modular software components abstracted by C++ template classes. These thread-wide, warp-wide, block-wide, and device-wide primitives can be specialized and tuned via custom tiling sizes, data types, and other algorithmic policy. The resulting flexibility simplifies their use as building blocks within custom kernels and applications.
To support a wide variety of applications, CUTLASS provides extensive support for mixed-precision computations, providing specialized data-movement and multiply-accumulate abstractions for 8-bit integer, half-precision floating point (FP16), single-precision floating point (FP32), and double-precision floating point (FP64) types. Furthermore, CUTLASS demonstrates CUDA's WMMA API for targeting the programmable, high-throughput Tensor Cores provided by NVIDIA's Volta architecture and beyond.
For more exposition, see our Parallel Forall blog post CUTLASS: Fast Linear Algebra in CUDA C++.
CUTLASS primitives are very efficient. When used to construct device-wide GEMM kernels, they exhibit performance comparable to cuBLAS for scalar GEMM computations. The above figure shows CUTLASS performance relative to cuBLAS for large matrix dimensions (M=10240, N=K=4096) running on an NVIDIA Tesla V100 GPU when compiled with CUDA 9.0.
CUTLASS is arranged as a header-only library with several example test programs that demonstrate instantiating a GEMM task within a CUDA kernel. Comments inline with the source explain the individual components.
The repository is organized in the following arrangement.
cutlass/ Root of header-only source library for matrix multiply
gemm/ Implementation of GEMM __device__ code and supporting components
util/ Utility components for CUDA device-side CUDA development
A test program is provided to illustrate the use of CUTLASS. This is implemented in the following directory.
cutlass_test Root of test programs depicting CUTLASS kernels
util/ Utilities
gemm.cu Simple example calling CUTLASS and CUBLAS GEMM kernels
Makefile Build script for test programs
There are different sample targets for different GEMM data types and transposititions. Be sure to specify your target architecture.
make <sgemm|dgemm|hgemm|igemm|wgemm> sm=<60|61|70> \
[transpose=<nn|nt|tn|tt>] [verbose=<0|1>] [keep=<0|1>]
Program usage:
<s|d|h|i|w>gemm_<nn|nt|tn|tt>
[--help]
[--schmoo=<#schmoo-samples> || --m=<height> --n=<width> --k=<depth>]
[--i=<timing iterations>]
[--device=<device-id>]
[--alpha=<alpha> --beta=<beta>]
CUTLASS is released by NVIDIA Corporation under the "New BSD" open-source license:
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