TheRock/rocm-libraries/projects/composablekernel/docs/conceptual/ck_tile/index.rst

.. _ck_tile_conceptual:

CK Tile Conceptual Documentation
================================

Welcome to the conceptual documentation for CK Tile, the core abstraction layer of Composable Kernel that enables efficient GPU programming through compile-time coordinate transformations and tile-based data distribution.

See the :ref:`ck_tile_index` for the complete CK Tile documentation structure.

Overview
--------

CK Tile provides a mathematical framework for expressing complex GPU computations through:

- **Automatic Memory Coalescing**: Ensures optimal memory access patterns without manual optimization
- **Thread Cooperation**: Coordinates work distribution across the GPU's hierarchical execution model
- **Zero-Overhead Abstractions**: Compile-time optimizations ensure no runtime performance penalty
- **Portable Performance**: Same code achieves high performance across different GPU architectures

Why CK Tile?
------------

Traditional GPU programming requires manual management of:

- Thread-to-data mapping calculations
- Memory coalescing patterns
- Bank conflict avoidance
- Boundary condition handling

CK Tile automates all of these concerns through a unified abstraction that maps logical problem coordinates to physical GPU resources.


Learning Path
-------------

1. **Start Here**: :ref:`ck_tile_introduction`
   
   The fundamental problems CK Tile solves and why it's essential for efficient GPU programming.

2. **Foundation**: :ref:`ck_tile_buffer_views`
   
   How CK Tile provides structured access to raw GPU memory across different address spaces.

3. **Multi-Dimensional Views**: :ref:`ck_tile_tensor_views`
   
   How to work with multi-dimensional data structures and memory layouts.

4. **Core API**: :ref:`ck_tile_tile_distribution`
   
   The tile distribution system that maps work to GPU threads.

5. **Mathematical Framework**: :ref:`ck_tile_coordinate_systems`
   
   The coordinate transformation system that powers CK Tile's abstractions.

6. **Reference**: :ref:`ck_tile_terminology`
   
   Glossary of all terms and concepts used in CK Tile.


Key Concepts at a Glance
------------------------

**Coordinate Spaces**

- **P-space**: Processing element coordinates (thread, warp, block)
- **Y-space**: Local tile access patterns
- **X-space**: Physical tensor coordinates
- **D-space**: Linearized memory addresses

**Core Components**

- **BufferView**: Type-safe access to GPU memory
- **TileDistribution**: Automatic work distribution
- **TileWindow**: Efficient data loading/storing
- **Encoding**: Compile-time distribution specification

Quick Example
-------------

.. code-block:: cpp

   // Define how to distribute a 256x256 tile across threads
   using Encoding = tile_distribution_encoding<
       sequence<>,                              // No replication
       tuple<sequence<4,2,8,4>,                // M dimension hierarchy
             sequence<4,2,8,4>>,               // N dimension hierarchy
       tuple<sequence<1,2>, sequence<1,2>>,    // Thread mapping
       tuple<sequence<1,1>, sequence<2,2>>,    // Minor indices
       sequence<1,1,2,2>,                      // Y-space mapping
       sequence<0,3,0,3>                       // Y-space minor
   >;
   
   // Create distribution and load data
   auto distribution = make_static_tile_distribution(Encoding{});
   auto window = make_tile_window(tensor_view, tile_size, origin, distribution);
   auto tile = window.load();
   
   // Process tile efficiently
   sweep_tile(tile, [](auto idx) { /* computation */ });


Next Steps
----------

To dive deeper, start with :ref:`ck_tile_introduction` to understand the motivation and core concepts behind CK Tile.

For practical examples, see the `example/ck_tile <https://github.com/ROCm/rocm-libraries/tree/develop/projects/composablekernel/example/ck_tile>`_ directory in the Composable Kernel repository.