composable_kernel/example/ck_tile/16_batched_gemm/README.md

Batched GEMM with CK Tile

This example demonstrates batched matrix multiplication (Batched GEMM) using the CK Tile programming model, enabling efficient parallel computation of multiple independent GEMMs in a single kernel launch.

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Algorithm and Math

Given:

• A: [\text{batch}, M, K]
• B: [\text{batch}, K, N]
• C: [\text{batch}, M, N]

For each batch b:

C^{(b)} = A^{(b)} \times B^{(b)}

• Tilewise Batched GEMM: Each thread block processes a tile of C for a specific batch, loading corresponding tiles from A and B, performing blockwise matrix multiply-accumulate, and writing results.

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Tile Programming Model

• Tiles: Each thread block processes a tile of C for a given batch.
• Pipeline: Modular, supports different memory/computation pipelines.

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Features

• Flexible Layouts: Supports row/column-major and custom strides for A, B, C.
• Batching: Efficiently computes multiple GEMMs in parallel.
• Precision: Supports fp16, bf16, fp8, bf8.
• Validation: CPU/GPU validation and error tolerance options.

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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_batched_gemm -j

This will result in an executable build/bin/tile_example_batched_gemm

Arguments

args:
               -m    m dimension (default:512)
               -n    n dimension (default:1024)
               -k    k dimension (default:2048)
         -stride_a    Tensor A stride (default:0)
         -stride_b    Tensor B stride (default:0)
         -stride_c    Tensor C stride (default:0)
         -a_layout    A tensor data layout - Row by default (default:R)
         -b_layout    B tensor data layout - Row by default (default:C)
         -c_layout    C tensor data layout - Row by default (default:R)
   -batch_stride_a    Batch A stride (default:1048576)
   -batch_stride_b    Batch B stride (default:2097152)
   -batch_stride_c    Batch C stride (default:524288)
      -batch_count    Batch count (default:8)
               -v    0. No validation, 1. Validation on CPU, 2. Validation on GPU (default:2)
            -prec    data type. fp16/bf16/fp8/bf8 (default:fp16)
         -warmup    number of iterations before benchmark the kernel (default:50)
         -repeat    number of iterations to benchmark the kernel (default:100)
            -timer    gpu:gpu timer, cpu:cpu timer (default:gpu)
         -split_k    splitK value (default:1)
            -json    0: No Json, 1: Dump Results in Json format (default:0)
         -jsonfile    json file name to dump results (default:cktile_batched_gemm.json)

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Source Structure

• Kernel: batched_gemm.hpp (tile-programming kernel template)
• Executable: batched_gemm.cpp
• Build: CMakeLists.txt, run_batched_gemm_example.inc

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Related CK Tile Examples

• 03_gemm: Single GEMM with tiles
• 15_fused_moe: Fused MoE block (uses group/batched GEMM)
• 13_moe_sorting: MoE sorting for expert dispatch

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

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Back to CK Tile Examples