llama.cpp for OpenCL

Background
OS
Hardware
DataType Supports
Model Preparation
CMake Options
Android
Windows 11 Arm64
Known Issue
TODO

Background

OpenCL (Open Computing Language) is an open, royalty-free standard for cross-platform, parallel programming of diverse accelerators found in supercomputers, cloud servers, personal computers, mobile devices and embedded platforms. OpenCL specifies a programming language (based on C99) for programming these devices and application programming interfaces (APIs) to control the platform and execute programs on the compute devices. Similar to CUDA, OpenCL has been widely used to program GPUs and is supported by most GPU vendors.

Llama.cpp + OpenCL

The llama.cpp OpenCL backend is designed to enable llama.cpp on Qualcomm Adreno GPU firstly via OpenCL. Thanks to the portabilty of OpenCL, the OpenCL backend can also run on certain Intel GPUs although the performance is not optimal.

OS

OS	Status	Verified
Android	Support	Snapdragon 8 Gen 3, Snapdragon 8 Elite
Windows	Support	Windows 11 Arm64 with Snapdragon X Elite
Linux	Support	Ubuntu 22.04 WSL2 with Intel 12700H

Hardware

Adreno GPU

Verified devices

Adreno GPU	Status
Adreno 750 (Snapdragon 8 Gen 3)	Support
Adreno 830 (Snapdragon 8 Elite)	Support
Adreno X85 (Snapdragon X Elite)	Support

DataType Supports

DataType	Status
Q4_0	Support
Q6_K	Support, but not optimized

Model Preparation

You can refer to the general Prepare and Quantize guide for model prepration.

Currently we support Q4_0 quantization and have optimize for it. To achieve best performance on Adreno GPU, add --pure to llama-quantize. For example,

./llama-quantize --pure ggml-model-qwen2.5-3b-f16.gguf ggml-model-qwen-3b-Q4_0.gguf Q4_0

Since Q6_K is also supported, Q4_0 quantization without --pure will also work. However, the performance will be worse compared to pure Q4_0 quantization.

CMake Options

The OpenCL backend has the following CMake options that control the behavior of the backend.

CMake options	Default value	Description
`GGML_OPENCL_EMBED_KERNELS`	`ON`	Embed OpenCL kernels into the executable.
`GGML_OPENCL_USE_ADRENO_KERNELS`	`ON`	Use kernels optimized for Adreno.

Android

Ubuntu 22.04 is used for targeting Android. Make sure the following tools are accessible from command line,

Git
CMake 3.29
Ninja
Python3

I. Setup Environment

Install NDK

cd ~
wget https://dl.google.com/android/repository/commandlinetools-linux-8512546_latest.zip && \
unzip commandlinetools-linux-8512546_latest.zip && \
mkdir -p ~/android-sdk/cmdline-tools && \
mv cmdline-tools latest && \
mv latest ~/android-sdk/cmdline-tools/ && \
rm -rf commandlinetools-linux-8512546_latest.zip

yes | ~/android-sdk/cmdline-tools/latest/bin/sdkmanager "ndk;26.3.11579264"

Install OpenCL Headers and Library

mkdir -p ~/dev/llm
cd ~/dev/llm

git clone https://github.com/KhronosGroup/OpenCL-Headers && \
cd OpenCL-Headers && \
cp -r CL ~/android-sdk/ndk/26.3.11579264/toolchains/llvm/prebuilt/linux-x86_64/sysroot/usr/include

cd ~/dev/llm

git clone https://github.com/KhronosGroup/OpenCL-ICD-Loader && \
cd OpenCL-ICD-Loader && \
mkdir build_ndk26 && cd build_ndk26 && \
cmake .. -G Ninja -DCMAKE_BUILD_TYPE=Release \
  -DCMAKE_TOOLCHAIN_FILE=$HOME/android-sdk/ndk/26.3.11579264/build/cmake/android.toolchain.cmake \
  -DOPENCL_ICD_LOADER_HEADERS_DIR=$HOME/android-sdk/ndk/26.3.11579264/toolchains/llvm/prebuilt/linux-x86_64/sysroot/usr/include \
  -DANDROID_ABI=arm64-v8a \
  -DANDROID_PLATFORM=24 \
  -DANDROID_STL=c++_shared && \
ninja && \
cp libOpenCL.so ~/android-sdk/ndk/26.3.11579264/toolchains/llvm/prebuilt/linux-x86_64/sysroot/usr/lib/aarch64-linux-android

II. Build llama.cpp

cd ~/dev/llm

git clone https://github.com/ggml-org/llama.cpp && \
cd llama.cpp && \
mkdir build-android && cd build-android

cmake .. -G Ninja \
  -DCMAKE_TOOLCHAIN_FILE=$HOME/android-sdk/ndk/26.3.11579264/build/cmake/android.toolchain.cmake \
  -DANDROID_ABI=arm64-v8a \
  -DANDROID_PLATFORM=android-28 \
  -DBUILD_SHARED_LIBS=OFF \
  -DGGML_OPENCL=ON

ninja

Windows 11 Arm64

A Snapdragon X Elite device with Windows 11 Arm64 is used. Make sure the following tools are accessible from command line,

Git
CMake 3.29
Clang 19
Ninja
Visual Studio 2022
Powershell 7

Visual Studio provides necessary headers and libraries although it is not directly used for building. Alternatively, Visual Studio Build Tools can be installed instead of the full Visual Studio.

Powershell 7 is used for the following commands. If an older version of Powershell is used, these commands may not work as they are.

I. Setup Environment

Install OpenCL Headers and Library

mkdir -p ~/dev/llm

cd ~/dev/llm
git clone https://github.com/KhronosGroup/OpenCL-Headers && cd OpenCL-Headers
mkdir build && cd build
cmake .. -G Ninja `
  -DBUILD_TESTING=OFF `
  -DOPENCL_HEADERS_BUILD_TESTING=OFF `
  -DOPENCL_HEADERS_BUILD_CXX_TESTS=OFF `
  -DCMAKE_INSTALL_PREFIX="$HOME/dev/llm/opencl"
cmake --build . --target install

cd ~/dev/llm
git clone https://github.com/KhronosGroup/OpenCL-ICD-Loader && cd OpenCL-ICD-Loader
mkdir build && cd build
cmake .. -G Ninja `
  -DCMAKE_BUILD_TYPE=Release `
  -DCMAKE_PREFIX_PATH="$HOME/dev/llm/opencl" `
  -DCMAKE_INSTALL_PREFIX="$HOME/dev/llm/opencl"
cmake --build . --target install

II. Build llama.cpp

mkdir -p ~/dev/llm
cd ~/dev/llm

git clone https://github.com/ggml-org/llama.cpp && cd llama.cpp
mkdir build && cd build

cmake .. -G Ninja `
  -DCMAKE_TOOLCHAIN_FILE="$HOME/dev/llm/llama.cpp/cmake/arm64-windows-llvm.cmake" `
  -DCMAKE_BUILD_TYPE=Release `
  -DCMAKE_PREFIX_PATH="$HOME/dev/llm/opencl" `
  -DBUILD_SHARED_LIBS=OFF `
  -DGGML_OPENCL=ON
ninja

Known Issues

Currently OpenCL backend does not work on Adreno 6xx GPUs.

TODO

Optimization for Q6_K
Support and optimization for Q4_K