composable_kernel/example/14_gemm_quantization/README.md

GEMM with Quantization

Theory

This example demonstrates GEMM (General Matrix Multiplication) with quantized inputs or weights. Quantization is a technique to reduce memory and computation by representing values with lower-precision integer types (e.g., int8), commonly used for efficient inference in deep learning.

Mathematical Formulation:

• Quantized GEMM: C = \text{dequant}(A_q) \times \text{dequant}(B_q)
• A_q, B_q: quantized matrices (e.g., int8)
• \text{dequant}(x_q) = (x_q - z) \cdot s (scale s, zero-point z)
• C: output matrix (often in higher precision, e.g., float32 or float16)

Algorithmic Background:

• Quantized values are dequantized on-the-fly during GEMM computation.
• Accumulation is performed in higher precision for accuracy.
• Supports symmetric and asymmetric quantization.

How to Run

Prerequisites

Please follow the instructions in the main Build Guide section as a prerequisite to building and running this example.

Build and run

cd composable_kernel/example/14_gemm_quantization
mkdir build && cd build
cmake -DCMAKE_CXX_COMPILER=/opt/rocm/bin/hipcc ..
make -j

# Example run
./gemm_quantization_xdl --verify=1 --time=1

Source Code Structure

Directory Layout

example/14_gemm_quantization/
├── gemm_quantization_xdl.cpp         # Main example: sets up, runs, and verifies quantized GEMM
include/ck/tensor_operation/gpu/device/
│   └── device_gemm_quantized.hpp       # Device-level quantized GEMM API
include/ck/tensor_operation/gpu/device/impl/
│   └── device_gemm_quantized_impl.hpp  # Implementation
include/ck/tensor_operation/gpu/grid/
│   └── gridwise_gemm_quantized.hpp     # Grid-level quantized GEMM kernel
include/ck/tensor_operation/gpu/element/
    └── quantization_operations.hpp     # Quantization/dequantization utilities

Key Classes and Functions

• DeviceGemmQuantized (in device_gemm_quantized.hpp):
  Device API for quantized GEMM.
• gridwise_gemm_quantized (in gridwise_gemm_quantized.hpp):
  Implements the tiled/blocking quantized GEMM kernel.
• quantization_operations (in quantization_operations.hpp):
  Defines quantization and dequantization functions.

This example demonstrates how Composable Kernel supports efficient quantized matrix multiplication for deep learning inference.