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95 lines
3.1 KiB
Markdown
95 lines
3.1 KiB
Markdown
# Permute with CK Tile
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This example demonstrates generic tensor permutation which is similiar to [torch.permute](https://pytorch.org/docs/stable/generated/torch.permute.html) (combined with [torch.contiguous](https://pytorch.org/docs/stable/generated/torch.Tensor.contiguous.html)). Currently we implement a generic permute kernel that support up to rank 8 arbitrary permutation with a single kernel instance. Performance is not the first consideration, we prefer a simple and general kernel implementation using `ck_tile` in this example.
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---
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## Algorithm and Math
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Given a tensor $X$ of shape $[d_0, d_1, ..., d_{n-1}]$ and a permutation $\pi$, compute:
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$$
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Y_{i_0, i_1, ..., i_{n-1}} = X_{i_{\pi(0)}, i_{\pi(1)}, ..., i_{\pi(n-1)}}
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$$
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- **Tilewise Permute**: Each thread block processes a tile (block) of the input, computes the permuted indices, and writes to the output.
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---
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## Tile Programming Model
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- **Tiles**: Each thread block processes a tile of the input tensor.
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- **Alternative Implementation**: For rank-7 tensors, a swizzled layout is supported for matrix core-friendly data loading.
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---
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## Build & Run
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### Arguments
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```
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args:
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-v weather do CPU validation or not (default:1)
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-prec data type. fp16/bf16/fp32 (default:fp16)
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-shape the shape of the input tensor (default:2,3,4)
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-perm permute perm (default:2,1,0)
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```
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```
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# in the root of ck_tile
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mkdir build && cd build
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../script/cmake-ck-dev.sh ../ <arch> # you can replace this <arch> to gfx90a, gfx942...
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make tile_example_permute -j
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```
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This will result in an executable `build/bin/tile_example_permute`
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### Further Examples
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```
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# torch
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x=torch.randn(2,3,4,6)
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y=x.permute(0,3,2,1).contiguous()
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# ck_tile
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./build/bin/tile_example_permute -shape=2,3,4,6 -perm=0,3,2,1
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```
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You can try the smoke_test:
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```
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# in the root of ck_tile, after you build this example
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sh example/ck_tile/06_permute/script/smoke_test.sh
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```
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### Alternative Implementation
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We have an alternative implementation under `alternative_impl/` folder, that can swizzle the tensor to be more friendly for data loading for matrix core layout. This can be enabled when dealing with a `rank-7` tensor, with a fixed pattern of either `0,1,4,2,5,3,6` or `0,1,2,4,5,3,6`. There are other shape limitation of this implementation, check the source code of `permute.cpp` for detail.
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```
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# example
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./build/bin/tile_example_permute -shape=3,6,4,32,16,2,8 -perm=0,1,4,2,5,3,6 # b_n0_k0_n1_k1_n2_k2
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./build/bin/tile_example_permute -shape=3,8,4,16,16,4,8 -perm=0,1,2,4,5,3,6 # b_n0_n1_k0_k1_n2_k2
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```
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---
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## Source Structure
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- **Kernel**: `permute.hpp` (tile-programming kernel template)
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- **Executable**: `permute.cpp` (argument parsing, kernel launch)
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- **Alternative**: `alternative_impl/` (swizzled layout for rank-7 tensors)
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- **Build**: `CMakeLists.txt`, `script/`
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---
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## Related CK Tile Examples
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- [03_gemm](../03_gemm/README.md): GEMM with tiles
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- [05_reduce](../05_reduce/README.md): Reductions with tiles
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- [35_batched_transpose](../35_batched_transpose/README.md): Batched transpose with tiles
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For distribution, `include/ck_tile/tile_program/tile_distribution/`.
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---
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[Back to CK Tile Examples](../README.md)
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