Files
composable_kernel/include/ck/utility/sequence_helper.hpp
Max Podkorytov 1dd47118e2 [rocm-libraries] ROCm/rocm-libraries#4828 (commit 7de19bb)
Add generate_identity_sequences helper and replace lambdas
 with named functors (#4828)
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## Summary

- Add `generate_identity_sequences<N>()` helper that returns
`Tuple<Sequence<0>, Sequence<1>, ..., Sequence<N-1>>`
- Replace lambdas with named functors in `transform_tensor_descriptor`
- Add `unpack_and_merge_sequences` helper functor
- Reduces `transform_tensor_descriptor` instantiations from 388 to 32
(92% reduction)

## Motivation

Multiple call sites use `generate_tuple([](auto i) { return
Sequence<i>{}; }, Number<N>{})` pattern. A named helper reduces lambda
instantiations.

Additionally, each lambda in `transform_tensor_descriptor` creates a
unique closure type, causing the function to be instantiated separately
for every call site. Named functors share a single type, so the compiler
reuses the same instantiation.

## Changes

### Part 1: generate_identity_sequences helper
- Replaces common lambda pattern for generating identity sequences
- Each lambda expression creates a unique closure type, causing separate
template instantiations at every call site
- Named helper shares a single type across all uses

### Part 2: Named functors in transform_tensor_descriptor
- Add `unpack_and_merge_sequences` helper to replace lambda in
`GetNumOfHiddenDimension`
- Use `generate_identity_sequences` in `matrix_padder.hpp`

## Test Plan

- [x] Added 7 unit tests:
  - 4 tests for `generate_identity_sequences`
  - 3 tests for `unpack_and_merge_sequences`
- [ ] Waiting for full CI

## Related PRs

This PR merges the functionality from:
- ROCm/composable_kernel#3588 (generate_identity_sequences helper)
- ROCm/composable_kernel#3589 (Named functors in
transform_tensor_descriptor)

Part of PR stack for issue #4229 (Reduce CK/CKTile Build Times)

**Note:** This PR supersedes #4283, ROCm/composable_kernel#3588 and
ROCm/composable_kernel#3589, which can be closed once this is merged.
2026-02-28 20:11:11 +00:00

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// Copyright (c) Advanced Micro Devices, Inc., or its affiliates.
// SPDX-License-Identifier: MIT
#pragma once
#include "ck/utility/functional4.hpp"
#include "ck/utility/tuple.hpp"
namespace ck {
template <index_t... Is>
__host__ __device__ constexpr auto make_sequence(Number<Is>...)
{
return Sequence<Is...>{};
}
// F returns index_t
template <typename F, index_t N>
__host__ __device__ constexpr auto generate_sequence(F, Number<N>)
{
return typename sequence_gen<N, F>::type{};
}
// F returns Number<>
template <typename F, index_t N>
__host__ __device__ constexpr auto generate_sequence_v2(F&& f, Number<N>)
{
return unpack([&f](auto&&... xs) { return make_sequence(f(xs)...); },
typename arithmetic_sequence_gen<0, N, 1>::type{});
}
template <index_t... Is>
__host__ __device__ constexpr auto to_sequence(Tuple<Number<Is>...>)
{
return Sequence<Is...>{};
}
// Functor wrapper for merge_sequences to enable reuse across call sites
struct merge_sequences_functor
{
template <typename... Seqs>
__host__ __device__ constexpr auto operator()(Seqs... seqs) const
{
return merge_sequences(seqs...);
}
};
// Unpacks tuple of sequences and merges them into a single sequence
template <typename TupleOfSequences>
__host__ __device__ constexpr auto unpack_and_merge_sequences(TupleOfSequences tuple_of_sequences)
{
return unpack(merge_sequences_functor{}, tuple_of_sequences);
}
} // namespace ck