41064d8684
[CK_TILE] Fix typo in fmha_fwd_kernel K-dram unmerge tuple sizes (#7141) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit ## Summary The qr_async_trload K-dram lambda's `else (XorLengthFold == 1)` branch in `fmha_fwd_kernel.hpp` writes the outer-tile dim of its 3-tuple unmerge/xor/merge as ```cpp number<FmhaPipeline::kQKHeaddim / kDramTileK / FmhaPipeline::kAlignmentK>{} ``` which divides one extra time. For every fp16/bf16 hdim=128 configuration the outer length collapses to **0**, e.g. `128 / 128 / 8 == 0`. The 3-tuple product no longer equals `kQKHeaddim`, so unmerge → xor → merge stops round-tripping the head dimension. This bug was masked by the async-load path: it only walks the descriptor via stride and silently absorbs a length=0 outer dim. Any consumer that actually traverses the descriptor (e.g. the TDM path on gfx1250) immediately faults on the resulting `tuple<int, constant<0>>`. The fix drops the extra `/ kAlignmentK` in all three call sites in the same lambda so the outer dim becomes `kQKHeaddim / kDramTileK` and the product is restored to `kQKHeaddim`. Strides are unaffected, so the async path is bit-identical. | Config (fp16/bf16) | hdim | kDramTileK | kAlignmentK | a (typo) | a (fixed) | product (typo) | product (fixed) | |---|---|---|---|---|---|---|---| | hdim128, kKLoadOnce | 128 | 128 | 8 | 0 | 1 | **0** | **128** | | hdim128, kK0=32 | 128 | 32 | 8 | 0 | 4 | **0** | **128** | | hdim64, kKLoadOnce | 64 | 64 | 8 | 0 | 1 | **0** | **64** | | hdim256, kK0=32 | 256 | 32 | 8 | 1 | 8 | **32** | **256** | Bug introduced in 2cc0af6a815a (PR #2888 \"[CK_TILE] FMHA FWD bug fix\"), where the original 2-tuple unmerge was generalized to a 3-tuple and the typo slipped in. ## Test plan - [x] Built `test_ck_tile_fmha_fwd` (umbrella, 5 gtest binaries) on gfx950 native at develop b3bdc63a509 with `dev-gfx950` preset (clang 22, ROCm 7.2.2). Compiles cleanly with `-Werror -Weverything`. - [x] Ran `ctest -R test_ck_tile_fmha_fwd` on gfx950 native, baseline vs patched: identical pass/fail (3 pass / 2 fail), identical failing case set (114 gtest fails + 2 GPU memory access faults, all in pre-existing fp16/bf16 group-mode `Alibi`/`Dropout` cases that reproduce on develop without this patch). Total wall time 403s → 393s. Per-case latency drift ±8% (noise). - [x] CI to verify on other gfx9 / gfx11 architectures.
Composable Kernel Tile
concept
ck_tile provides a programming model with templated abstractions to enable users to implement performance-critical kernels for machine learning workloads. introduces following basic concepts to help users building your own operator
- tensor coordinate transformation, this is the core concept of layout/index transform abstraction in both compiler time and run time.
- tile-based programming model, including tile-level api and the concept of distributed tensor.
ck_tile is independently from the old ck, located under /include/ck_tile. You don't need to include anything from old CK, ck_tile has similiar (indeed almost the same) implementations for users to build operators. We will have a transition period to pull everything from old ck into ck_tile, stay tuned.
component
ck_tile is splitted into several componenets including core, host, ops/gemm, ops/fmha... each component you only need to include a single header (e.g #include "ck_tile/core.hpp", #include "ck_tile/ops/fmha.hpp") then you are able to use the function/structure inside (different from old ck)
[core]
ck_tile/core contains all the basic data structure and function to build the kernel, you can only include this header and build your own operators that utilizing all the basic building blocks introduced in ck.
core/container
- array, store runtime variables with fixed length (tensor index, register buffer, etc...)
- tuple, same as std::tuple, hold different type of data, and one of the solution to achieve multiple buffer.
- sequence, compile time integer sequence used to build various internal structures, or to describe tile size
- other convenient structure build on top of above 3
core/numeric
- gpu data type like
fp16_t,bf16_t,fp8_t... and the conversion between each other - constexpr integer similiar to std::integral_constant to be used as compile time integer.
- math functions and numeric utilities
core/algorithm
- coordinate transformation system, used to build tensor transform and compile time indexing. This is the core idea introduced in old
ckto describe how a tensor is build by several basic transform primitives likemerge/unmerge/embedetc... and how we indexing into a ND tensor that finally mapped to 1D memory offset.
core/tensor
- tensor descriptor, to describe how a ND tensor
- distributed tensor, describe the storage of this tensor, and the distribution of how a collection of threads collaborately work for this tensor.
- tile level API, including
load_tile,store_tile,shuffle_tile,slice_tile, etc...
[host]
ck_tile/host contains all the host side utilities to launch a kernel, create the device buffer, and some reference implementations. This can be used to create examples (like that under ck_tile example folder) and simple executable to invoke this kernel, so if you only need ck_tile to build your own device library then it's OK to not include this. Based on this, it is recommended to include the specific header you needed under this folder to avoid including unwanted headers (e.g, only include ck_tile/host/kernel_launch.hpp), unless you are writing a host executable.
[ops/gemm, ops/fmha, ops/reduce...]
our implementation of different device operators.
- warp, warp tile level operator
- block, block tile level operator
- pipeline, pipeline that can achieve a customized tile level mainloop (or epilogue). By switching different pipeline to the kernel template you can have different kind of pipeline optimizations.
- kernel, template interface for users to instantiate a particular kernel
[ops/epilogue]
epilogue part of our kernel. We may extend this epilogue part to let users to build their own cutomized epilogues.
[ref]
reference implementation of cpu or gpu. This folder is supposed to include a specific header on demand.
examples
currently we put all ck_tile related example under /example/ck_tile folder. Please check each example's subfolder.