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Building and Running ExecuTorch with the Vulkan Backend

The ExecuTorch Vulkan Delegate is a native GPU delegate for ExecuTorch.

What you will learn in this tutorial:
  • How to export the Stories 110M parameter model with partial GPU delegation

  • How to execute the partially delegated model on Android


Note that all the steps below should be performed from the ExecuTorch repository root directory, and assumes that you have gone through the steps of setting up ExecuTorch.

You should also refer to the Prerequisites section of the Setting up the ExecuTorch LLaMA Android Demo App Tutorial in order to install the specified versions of the Android NDK and the Android SDK.

# Recommended version is Android NDK r25c.
export ANDROID_NDK=<path_to_ndk>
# Select an appropriate Android ABI
export ANDROID_ABI=arm64-v8a
# All subsequent commands should be performed from ExecuTorch repo root
cd <path_to_executorch_root>
# Make sure adb works
adb --version

Lowering the Stories 110M model to Vulkan


The resultant model will only be partially delegated to the Vulkan backend. In particular, only binary arithmetic operators (aten.add, aten.sub, aten.mul, aten.div) and the matrix multiplication operator (aten.mm) will be executed on the GPU via the Vulkan delegate. The rest of the model will be executed using Portable operators. This is because the Vulkan delegate is still early in development and currently has limited operator coverage.

First, download stories110M.pt and tokenizer.model from Github:

wget "https://huggingface.co/karpathy/tinyllamas/resolve/main/stories110M.pt"
wget "https://raw.githubusercontent.com/karpathy/llama2.c/master/tokenizer.model"

Next, create the params file:

echo '{"dim": 768, "multiple_of": 32, "n_heads": 12, "n_layers": 12, "norm_eps": 1e-05, "vocab_size": 32000}' > params.json

Then, create a tokenizer binary file:

python -m examples.models.llama2.tokenizer.tokenizer -t tokenizer.model -o tokenizer.bin

Finally, export the stories110M.pt file into an ExecuTorch program:

python -m examples.models.llama2.export_llama -c stories110M.pt -p params.json --vulkan

A vulkan_llama2.pte file should have been created as a result of the last step.

Push the tokenizer binary and vulkan_llama2.pte onto your Android device:

adb mkdir /data/local/tmp/llama/
adb push tokenizer.bin /data/local/tmp/llama/
adb push vulkan_llama2.pte /data/local/tmp/llama/

Build and Run the LLaMA runner binary on Android

First, build and install ExecuTorch libraries, then build the LLaMA runner binary using the Android NDK toolchain.

(rm -rf cmake-android-out && \
  cmake . -DCMAKE_INSTALL_PREFIX=cmake-android-out \
    -DCMAKE_TOOLCHAIN_FILE=$ANDROID_NDK/build/cmake/android.toolchain.cmake \
    -Bcmake-android-out && \
  cmake --build cmake-android-out -j16 --target install)

# Build LLaMA Runner library
(rm -rf cmake-android-out/examples/models/llama2 && \
  cmake examples/models/llama2 \
    -DCMAKE_TOOLCHAIN_FILE=$ANDROID_NDK/build/cmake/android.toolchain.cmake \
    -DCMAKE_INSTALL_PREFIX=cmake-android-out \
    -Bcmake-android-out/examples/models/llama2 && \
  cmake --build cmake-android-out/examples/models/llama2 -j16)

Finally, push and run the llama runner binary on your Android device.

adb push cmake-android-out/examples/models/llama2/llama_main /data/local/tmp/llama_main

adb shell /data/local/tmp/llama_main \
    --model_path=/data/local/tmp/llama/vulkan_llama2.pte \
    --tokenizer_path=/data/local/tmp/llama/tokenizer.bin \
    --prompt "hi" \--temperature=0

The following output will be produced:

hippo named Hippy lived in a big pond. Hippy was a very happy hippo. He liked to play...

Running with the LLaMA Android Demo App

It is also possible to run the partially delegated Vulkan model inside the LLaMA Android demo app.

First, make some modifications to the Android app setup script to make sure that the Vulkan backend is built when building and installing ExecuTorch libraries:

# Run from executorch root directory. You can also edit this in a code editor

Then, Follow the instructions at Setting up the ExecuTorch LLaMA Android Demo App to build and run the demo application on your Android device. Once the app starts up, you can load and run the vulkan_llama2.pte model with the app.


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