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69 lines
2.3 KiB
Markdown
69 lines
2.3 KiB
Markdown
# Client Example: im2col and col2im Transformations
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## Theory
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This client example demonstrates **im2col (image-to-column) and col2im (column-to-image) transformations**. These operations are used to convert image data into a matrix form suitable for GEMM-based convolution and reconstruct images from column representations.
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**Mathematical Formulation:**
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- **im2col**: Rearranges image blocks into columns, mapping a 3D/4D tensor to a 2D matrix.
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- **col2im**: Reverses the process, mapping a 2D matrix back to an image tensor.
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**Algorithmic Background:**
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- im2col is used to lower convolution to matrix multiplication (GEMM).
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- col2im is used to reconstruct the original image or feature map from the column representation.
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- These transformations are essential for efficient convolution implementations on GPUs.
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## How to Run
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### Prerequisites
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Please follow the instructions in the main [Build Guide](../../README.md#building-ck) section as a prerequisite to building and running this example.
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### Build and run
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```bash
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cd composable_kernel/client_example/27_im2col_col2im
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mkdir build && cd build
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cmake -DCMAKE_CXX_COMPILER=/opt/rocm/bin/hipcc ..
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make -j
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# Example run (image to column)
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./image_to_column
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# Example run (column to image)
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./column_to_image
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```
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## Source Code Structure
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### Directory Layout
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```
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client_example/27_im2col_col2im/
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├── image_to_column.cpp # im2col: image to column transformation
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├── column_to_image.cpp # col2im: column to image transformation
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├── CMakeLists.txt # Build configuration for the example
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```
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### Key Functions
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- **main()** (in each `.cpp`):
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Sets up input tensors, configures transformation parameters, launches the im2col or col2im kernel, and verifies the result.
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- **im2col/col2im kernel invocation**:
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Uses the Composable Kernel device API to launch the transformation.
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---
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## Additional Details
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- Supports various image and patch sizes.
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- Example parameters can be adjusted in the source for different workloads.
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---
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## Related Examples
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- [52_im2col_col2im](../../example/52_im2col_col2im/README.md): im2col/col2im in the main example directory
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- [09_convnd_fwd](../../example/09_convnd_fwd/README.md): N-dimensional convolution using im2col
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---
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[Back to Client Examples](../README.md)
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