0c7665a331
## Summary ### Rationale `ck_tile::sequence` is the most fundamental metaprogramming type in ck_tile — it underpins tensor dimensions, strides, loop bounds, and index calculations. Six of its metafunctions use recursive template instantiation, producing O(N) to O(N²) intermediate types that the compiler must process. When these are used inside deeply nested GEMM pipelines with large dimension counts, the cumulative instantiation overhead becomes a significant contributor to frontend compile time. Measurements on `test_gemm_pipeline_compv6` show 84,288 `InstantiateFunction` calls in the frontend alone. Reducing template instantiation depth in these core utilities has a multiplicative effect because they are called from hundreds of sites. ### What changed | Metafunction | Before | After | |---|---|---| | `sequence::modify` | O(N) recursive split/merge | O(1) pack expansion | | `sequence_gen` | O(log N) recursive binary split | O(1) via `__make_integer_seq` | | `uniform_sequence_gen` | Delegates to `sequence_gen` | O(1) via `__make_integer_seq` | | `sequence_reverse_inclusive_scan` | O(N) recursive | O(1) constexpr for-loop + pack expansion | | `sequence_inclusive_scan` | Computed via reverse + flip | O(1) constexpr for-loop (unified impl) | | `sequence_exclusive_scan` | O(N) recursive merge chain | O(1) constexpr for-loop + pack expansion | | `sequence_map_inverse` | O(N²) recursive modify calls | O(1) constexpr for-loop + pack expansion | Supporting changes: - Portable `__type_pack_element` fallback with `__has_builtin` guard (hipRTC-safe, no `<tuple>` dependency) - Renamed reserved `__integer_sequence` to `integer_sequence_wrapper` - Adopted `static_array` from develop (PR #4355) for constexpr computation - Unified forward and reverse inclusive scan into a single `sequence_inclusive_scan_impl` with `bool Reverse` template parameter - Added `sequence_inclusive_scan` struct (new public API for forward scan direction) - Replaced recursive `sequence_exclusive_scan` (3 template specializations) with `sequence_exclusive_scan_impl` using the same constexpr for-loop pattern as inclusive scan - Rewired `exclusive_scan_sequence` and `prefix_sum_sequence` to use new impl - Added `CK_TILE_HOST_DEVICE` to `exclusive_scan_sequence` and `prefix_sum_sequence` to match sibling scan function annotations ### Technical debt and housekeeping - Unified all `namespace impl` to `namespace detail` across sequence.hpp for consistency - Removed dead comment block (orphaned `integer_sequence` alternative) - Added defensive `static_assert(sizeof...(Is) > 0)` in `sequence_map_inverse::build_inverse` - Converted all multi-line Doxygen blocks from `///` to `/** */` per style guide - Corrected `constexpr static` to `static constexpr` keyword ordering in `static_array` - Added blank line between `#pragma once` and first `#include` in `static_array.hpp` - Trimmed redundant 4-line comment on `sequence_gen_helper` to a one-liner - Moved `sequence_gen` Doxygen comment below `namespace detail` block so it directly precedes the struct it documents - Added Doxygen `@brief`/`@tparam`/`@pre` documentation for `sequence_gen` and `sequence_map_inverse` public APIs - Added `@brief` documentation to `static_array` explaining relationship to `ck_tile::array` - Added scope comment at `namespace detail` openings **Note:** `private:`/`public:` access modifier indentation is enforced at 4 spaces by `.clang-format`. The style guide calls for left-alignment, but the formatter overrides this. Requires a `.clang-format` config change to resolve — not addressable in code. ### `static_array` hardening (from develop's PR #4355) - Added zero-length array guard (`T elems[N > 0 ? N : 1]`) - Added `CK_TILE_HOST_DEVICE` annotations to `operator[]` and `size()` - Added `#include "ck_tile/core/config.hpp"` (IWYU for `CK_TILE_HOST_DEVICE`) ### Value Combined with the `static_ford` changes, measured impact on `test_gemm_pipeline_compv6`: - **Frontend: -28.9%** (InstantiateFunction: 84,288 → 69,439) - **Backend: -13.1%** (CodeGen Functions: 3,170 → 2,203) - **Wall-clock: -16.3%** (611.6s → 512.2s) ### Files changed (4) - `sequence.hpp`: Metafunction optimizations, namespace unification, documentation, style fixes - `static_array.hpp`: Zero-length guard, `CK_TILE_HOST_DEVICE`, documentation, style fixes - `test_sequence.cpp`: 50 unit tests with runtime `EXPECT_EQ` assertions (new file) - `CMakeLists.txt`: Register new test target ## Test plan - [x] 50 runtime unit tests covering all optimized and pre-existing sequence APIs - [x] Edge cases: empty sequences, single-element, larger sizes (N=8), negative values, non-trivial init values - [x] Both functor signatures tested (`operator()(index_t)` and `operator()(number<I>)`) - [x] Both scan reducers (`plus`, `multiplies`) with forward, reverse, inclusive, and exclusive directions - [x] Exclusive scan: sum, product, single, empty, non-zero init - [x] Prefix sum: N+1 output verification, single, empty - [x] Permutation round-trip verification for `sequence_map_inverse` - [x] Full sequence public API coverage: modify, gen, uniform_gen, scans (inclusive, exclusive, prefix sum), map_inverse, make_index_sequence, size/sum/product, push/pop, reverse, extract, merge, arithmetic operators, equality, transform - [x] Portable `__type_pack_element` fallback tested implicitly (same `at_index_t` interface) 🤖 Generated with [Claude Code](https://claude.com/claude-code) ## Submission Checklist - [ ] Look over the contributing guidelines at https://github.com/ROCm/ROCm/blob/develop/CONTRIBUTING.md#pull-requests. --------- Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com> Co-authored-by: Max Podkorytov <4273004+tenpercent@users.noreply.github.com>
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.