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[CK_TILE] Add SageAttention v2 forward kernel with multi-granularity quantization (#6574) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit ## Summary Add a CK_TILE forward kernel implementing [SageAttention v2](https://arxiv.org/abs/2411.10958) — an attention algorithm that applies multi-granularity quantization to Q/K/V before computing attention, trading minimal accuracy loss for higher throughput on low-precision hardware. ### Quantization design | Tensor | Supported data types | Scale granularity options | |--------|---------------------|--------------------------| | Q | fp8 / int8 / int4 | per-tensor, per-block (128 tokens), per-warp (32 tokens), per-thread (4 tokens) | | K | fp8 / int8 / int4 | per-tensor, per-block (128 tokens), per-warp (64 tokens), per-thread (16 tokens) | | V | fp8 | per-channel (always) | | O | bf16 | — | Three precision combinations are supported: `fp8/bf16` (QKV fp8, O bf16), `i8/fp8/bf16` (QK int8, V fp8, O bf16), and `i4/fp8/bf16` (QK int4, V fp8, O bf16). ### Architecture support - **gfx9** (CDNA2/3, e.g. gfx90a, gfx942) — full tile set - **gfx950** (CDNA4) — restricted tile set (N-per-block capped at 64 for fp8-family dtypes) ### Implementation - Two pipeline variants: `QRKSVS` (synchronous) and `QRKSVS_ASYNC` (async copy) - Masking support: no mask, causal (top-left / bottom-right), and generic windowed - Batch and group (variable-length) modes - Head dimension: d=128, d_v=128 - Python codegen under `example/ck_tile/49_sageattention/codegen/` generates kernel instances per target/dtype/tile combination - Smoke tests included via `tile_example_sageattn_fwd` ### Test commands \`\`\`bash # fp8 QKV ./build/bin/tile_example_sageattn_fwd -v=1 -b=16 -h=8 -s=1024 -d=128 -kname=1 -prec=fp8bf16 -qscale=3 -init=3 # int8 QK, fp8 V ./build/bin/tile_example_sageattn_fwd -v=1 -b=16 -h=8 -s=1024 -d=128 -kname=1 -prec=i8fp8bf16 -qscale=3 -init=3 \`\`\` \`-qscale\` values: 1=per-tensor, 2=per-block, 3=per-warp, 4=per-thread
CK Tile Example Suite
This directory contains a comprehensive suite of examples demonstrating the CK Tile programming model for high-performance GPU kernels. Each example illustrates a key deep learning or HPC operation, implemented using tile-based parallelism, modular pipelines, and data movement policy.
What is CK Tile?
CK Tile is a composable GPU programming API that expresses kernels as a composition of "tiles"—rectangular blocks of computation and data movement. The pipeline & policy orchestrates data movement (global <-> LDS <-> registers), computation, and synchronization, enabling high efficiency and flexibility.
Example Index
| Example | Operation | Description |
|---|---|---|
| 01_fmha | Fused Multi-Head Attention | Tile-based FMHA with masking, quantization, and epilogue fusion |
| 02_layernorm2d | LayerNorm2D | Blockwise layer normalization with fusion and quantization |
| 03_gemm | GEMM | Matrix multiplication with tilewise parallelism |
| 04_img2col | im2col | Image-to-column transformation for GEMM-based convolution |
| 05_reduce | Reduction | Tilewise sum, max, mean reductions |
| 06_permute | Permute | Generic tensor permutation (up to rank-8) |
| 09_topk_softmax | TopK-Softmax | Rowwise softmax and top-k selection for MoE gating |
| 10_rmsnorm2d | RMSNorm2D | Root mean square normalization for LLMs |
| 11_add_rmsnorm2d_rdquant | Add + RMSNorm2D + RDQuant | Fused add, RMSNorm, and rowwise dynamic quantization |
| 12_smoothquant | SmoothQuant | Per-channel scaling and quantization for int8 inference |
| 13_moe_sorting | MoE Sorting | Token-to-expert rearrangement for MoE dispatch |
| 14_moe_smoothquant | MoE-SmoothQuant | Expert-dependent quantization fused with top-k selection |
| 15_fused_moe | Fused MoE | End-to-end fused MoE block: sorting, group-GEMM, activation, weighting |
| 16_batched_gemm | Batched GEMM | Parallel computation of multiple GEMMs |
| 17_grouped_gemm | Grouped GEMM | Multiple independent GEMMs with different shapes |
| 18_flatmm | FLATMM | Flattened matrix multiplication for packed layouts |
| 19_gemm_multi_d | Multi-D GEMM | GEMM with multiple side inputs (bias, residual, etc.) |
| 35_batched_transpose | Batched Transpose | NCHW <-> NHWC and other layout conversions |
| 36_copy | Copy | Minimal example for tile-based memory movement |
| 37_transpose | Block Transpose | High-performance tiled transpose for large tensors |
Technical Highlights
- Tile Distribution: See
include/ck_tile/tile_program/tile_distribution/for mapping tiles to thread blocks. - Block Tile Pipelines: See
include/ck_tile/tile_program/block_tile_pipeline/for memory/computation pipelines. - Policies and Utilities: Many examples use custom policies for tile/block size and memory access.
How to Build & Run
mkdir build && cd build
sh ../script/cmake-ck-dev.sh ../ <arch>
make -j
Each example produces its own executable in build/bin/.
Learning and Extending
- Start Simple: Try 03_gemm or 36_copy to learn tile basics.
- Explore Fusion: See 11_add_rmsnorm2d_rdquant, 15_fused_moe, or 14_moe_smoothquant for advanced fusion.
- Experiment: Modify tile sizes, layouts, or pipelines to explore performance and flexibility.