composable_kernel/example/ck_tile/04_img2col

Image to Column (im2col) with CK Tile

This example demonstrates the im2col transformation using the CK Tile programming model, a key step for converting convolution into GEMM for efficient GPU execution.

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Algorithm and Math

Given an input image tensor X and convolution kernel size, im2col rearranges sliding windows of X into columns:

• For each patch, flatten and stack as a column in the output matrix.
• Enables convolution as matrix multiplication: \text{im2col}(X) \times W.

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Tile Programming Model

• Tiles: Each thread block processes a tile (block of patches).
• Pipeline: Modular, can be extended for fused operations (e.g., quantization, activation).

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Build & Run

mkdir build && cd build
# you can replace <arch> with the appropriate architecture (for example gfx90a or gfx942) or leave it blank
../script/cmake-ck-dev.sh  ../ <arch>
make tile_example_img2col -j
./bin/tile_example_img2col -?

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Source Structure

• Kernel: image_to_column.hpp (tile-programming kernel template)
• Executable: image_to_column.cpp (argument parsing, kernel launch)
• Build: CMakeLists.txt

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Related CK Tile Examples

• 03_gemm: GEMM with tiles (im2col output as input)
• 05_reduce: Reductions with tiles
• 06_permute: Permutation with tiles

For distribution, see include/ck_tile/tile_program/tile_distribution/.

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Back to CK Tile Examples