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Qualcomm AI Engine Backend#

In this tutorial we will walk you through the process of getting started to build ExecuTorch for Qualcomm AI Engine Direct and running a model on it.

Qualcomm AI Engine Direct is also referred to as QNN in the source and documentation.

What you will learn in this tutorial:

In this tutorial you will learn how to lower and deploy a model for Qualcomm AI Engine Direct.

Tutorials we recommend you complete before this:

What’s Qualcomm AI Engine Direct?#

Qualcomm AI Engine Direct is designed to provide unified, low-level APIs for AI development.

Developers can interact with various accelerators on Qualcomm SoCs with these set of APIs, including Kryo CPU, Adreno GPU, and Hexagon processors. More details can be found here.

Currently, this ExecuTorch Backend can delegate AI computations to Hexagon processors through Qualcomm AI Engine Direct APIs.

Prerequisites (Hardware and Software)#

Host OS#

The QNN Backend is currently verified on the following Linux host operating systems:

Ubuntu 22.04 LTS (x64)
CentOS Stream 9
Windows Subsystem for Linux (WSL) with Ubuntu 22.04

In general, we verify the backend on the same OS versions that the QNN SDK is officially validated against.
The exact supported versions are documented in the QNN SDK.

Windows (WSL) Setup#

To install Ubuntu 22.04 on WSL, run the following command in PowerShell or Windows Terminal:

wsl --install -d ubuntu 22.04

This command will install WSL and set up Ubuntu 22.04 as the default Linux distribution.

For more details and troubleshooting, refer to the official Microsoft WSL installation guide: 👉 Install WSL | Microsoft Learn

Hardware:#

You will need an Android / Linux device with adb-connected running on one of below Qualcomm SoCs:

SA8295
SM8450 (Snapdragon 8 Gen 1)
SM8475 (Snapdragon 8 Gen 1+)
SM8550 (Snapdragon 8 Gen 2)
SM8650 (Snapdragon 8 Gen 3)
SM8750 (Snapdragon 8 Elite)
SSG2115P
SSG2125P
SXR1230P (Linux Embedded)
SXR2230P
SXR2330P

This example is verified with SM8550 and SM8450.

Software:#

Follow ExecuTorch recommended Python version.
A compiler to compile AOT parts, e.g., the GCC compiler comes with Ubuntu LTS. g++ version need to be 13 or higher.
Android NDK. This example is verified with NDK 26c.
(Optional) Target toolchain for linux embedded platform.
Qualcomm AI Engine Direct SDK
- Click the “Get Software” button to download the latest version of the QNN SDK.
- Although newer versions are available, we have verified and recommend using QNN 2.37.0 for stability.
- You can download it directly from the following link: QNN 2.37.0

The directory with installed Qualcomm AI Engine Direct SDK looks like:

├── benchmarks
├── bin
├── docs
├── examples
├── include
├── lib
├── LICENSE.pdf
├── NOTICE.txt
├── NOTICE_WINDOWS.txt
├── QNN_NOTICE.txt
├── QNN_README.txt
├── QNN_ReleaseNotes.txt
├── ReleaseNotes.txt
├── ReleaseNotesWindows.txt
├── sdk.yaml
└── share

Setting up your developer environment#

Conventions#

$QNN_SDK_ROOT refers to the root of Qualcomm AI Engine Direct SDK, i.e., the directory containing QNN_README.txt.

$ANDROID_NDK_ROOT refers to the root of Android NDK.

$EXECUTORCH_ROOT refers to the root of executorch git repository.

Setup environment variables#

We set LD_LIBRARY_PATH to make sure the dynamic linker can find QNN libraries.

Further, we set PYTHONPATH because it’s easier to develop and import ExecuTorch Python APIs.

export LD_LIBRARY_PATH=$QNN_SDK_ROOT/lib/x86_64-linux-clang/:$LD_LIBRARY_PATH
export PYTHONPATH=$EXECUTORCH_ROOT/..

Build#

An example script for the below building instructions is here. We recommend to use the script because the ExecuTorch build-command can change from time to time. The above script is actively used. It is updated more frequently than this tutorial. An example usage is

cd $EXECUTORCH_ROOT
# android target
./backends/qualcomm/scripts/build.sh
# (optional) linux embedded target
./backends/qualcomm/scripts/build.sh --enable_linux_embedded
# for release build
./backends/qualcomm/scripts/build.sh --release

Deploying and running on device#

AOT compile a model#

Refer to this script for the exact flow. We use deeplab-v3-resnet101 as an example in this tutorial. Run below commands to compile:

cd $EXECUTORCH_ROOT

python -m examples.qualcomm.scripts.deeplab_v3 -b build-android -m SM8550 --compile_only --download

You might see something like below:

[INFO][Qnn ExecuTorch] Destroy Qnn context
[INFO][Qnn ExecuTorch] Destroy Qnn device
[INFO][Qnn ExecuTorch] Destroy Qnn backend

opcode         name                      target                       args                           kwargs
-------------  ------------------------  ---------------------------  -----------------------------  --------
placeholder    arg684_1                  arg684_1                     ()                             {}
get_attr       lowered_module_0          lowered_module_0             ()                             {}
call_function  executorch_call_delegate  executorch_call_delegate     (lowered_module_0, arg684_1)   {}
call_function  getitem                   <built-in function getitem>  (executorch_call_delegate, 0)  {}
call_function  getitem_1                 <built-in function getitem>  (executorch_call_delegate, 1)  {}
output         output                    output                       ([getitem_1, getitem],)        {}

The compiled model is ./deeplab_v3/dlv3_qnn.pte.

Test model inference on QNN HTP emulator#

We can test model inferences before deploying it to a device by HTP emulator.

Let’s build qnn_executor_runner for a x64 host:

# assuming the AOT component is built.
cd $EXECUTORCH_ROOT/build-x86
cmake ../examples/qualcomm \
  -DCMAKE_PREFIX_PATH="$PWD/lib/cmake/ExecuTorch;$PWD/third-party/gflags;" \
  -DCMAKE_FIND_ROOT_PATH_MODE_PACKAGE=BOTH \
  -DPYTHON_EXECUTABLE=python3 \
  -Bexamples/qualcomm

cmake --build examples/qualcomm -j$(nproc)

# qnn_executor_runner can be found under examples/qualcomm/executor_runner
# The full path is $EXECUTORCH_ROOT/build-x86/examples/qualcomm/executor_runner/qnn_executor_runner
ls examples/qualcomm/executor_runner

To run the HTP emulator, the dynamic linker needs to access QNN libraries and libqnn_executorch_backend.so. We set the below two paths to LD_LIBRARY_PATH environment variable:

$QNN_SDK_ROOT/lib/x86_64-linux-clang/
$EXECUTORCH_ROOT/build-x86/lib/

The first path is for QNN libraries including HTP emulator. It has been configured in the AOT compilation section.

The second path is for libqnn_executorch_backend.so.

So, we can run ./deeplab_v3/dlv3_qnn.pte by:

cd $EXECUTORCH_ROOT/build-x86
export LD_LIBRARY_PATH=$EXECUTORCH_ROOT/build-x86/lib/:$LD_LIBRARY_PATH
examples/qualcomm/executor_runner/qnn_executor_runner --model_path ../deeplab_v3/dlv3_qnn.pte

We should see some outputs like the below. Note that the emulator can take some time to finish.

I 00:00:00.354662 executorch:qnn_executor_runner.cpp:213] Method loaded.
I 00:00:00.356460 executorch:qnn_executor_runner.cpp:261] ignoring error from set_output_data_ptr(): 0x2
I 00:00:00.357991 executorch:qnn_executor_runner.cpp:261] ignoring error from set_output_data_ptr(): 0x2
I 00:00:00.357996 executorch:qnn_executor_runner.cpp:265] Inputs prepared.

I 00:01:09.328144 executorch:qnn_executor_runner.cpp:414] Model executed successfully.
I 00:01:09.328159 executorch:qnn_executor_runner.cpp:421] Write etdump to etdump.etdp, Size = 424
[INFO] [Qnn ExecuTorch]: Destroy Qnn backend parameters
[INFO] [Qnn ExecuTorch]: Destroy Qnn context
[INFO] [Qnn ExecuTorch]: Destroy Qnn device
[INFO] [Qnn ExecuTorch]: Destroy Qnn backend

Run model inference on an Android smartphone with Qualcomm SoCs#

Step 1. We need to push required QNN libraries to the device.

# make sure you have write-permission on below path.
DEVICE_DIR=/data/local/tmp/executorch_qualcomm_tutorial/
adb shell "mkdir -p ${DEVICE_DIR}"
adb push ${QNN_SDK_ROOT}/lib/aarch64-android/libQnnHtp.so ${DEVICE_DIR}
adb push ${QNN_SDK_ROOT}/lib/aarch64-android/libQnnSystem.so ${DEVICE_DIR}
adb push ${QNN_SDK_ROOT}/lib/aarch64-android/libQnnHtpV69Stub.so ${DEVICE_DIR}
adb push ${QNN_SDK_ROOT}/lib/aarch64-android/libQnnHtpV73Stub.so ${DEVICE_DIR}
adb push ${QNN_SDK_ROOT}/lib/aarch64-android/libQnnHtpV75Stub.so ${DEVICE_DIR}
adb push ${QNN_SDK_ROOT}/lib/aarch64-android/libQnnHtpV79Stub.so ${DEVICE_DIR}
adb push ${QNN_SDK_ROOT}/lib/hexagon-v69/unsigned/libQnnHtpV69Skel.so ${DEVICE_DIR}
adb push ${QNN_SDK_ROOT}/lib/hexagon-v73/unsigned/libQnnHtpV73Skel.so ${DEVICE_DIR}
adb push ${QNN_SDK_ROOT}/lib/hexagon-v75/unsigned/libQnnHtpV75Skel.so ${DEVICE_DIR}
adb push ${QNN_SDK_ROOT}/lib/hexagon-v79/unsigned/libQnnHtpV79Skel.so ${DEVICE_DIR}

Step 2. We also need to indicate dynamic linkers on Android and Hexagon where to find these libraries by setting ADSP_LIBRARY_PATH and LD_LIBRARY_PATH. So, we can run qnn_executor_runner like

adb push ./deeplab_v3/dlv3_qnn.pte ${DEVICE_DIR}
adb push ${EXECUTORCH_ROOT}/build-android/examples/qualcomm/executor_runner/qnn_executor_runner ${DEVICE_DIR}
adb push ${EXECUTORCH_ROOT}/build-android/lib/libqnn_executorch_backend.so ${DEVICE_DIR}
adb shell "cd ${DEVICE_DIR} \
           && export LD_LIBRARY_PATH=${DEVICE_DIR} \
           && export ADSP_LIBRARY_PATH=${DEVICE_DIR} \
           && ./qnn_executor_runner --model_path ./dlv3_qnn.pte"

You should see something like below:

I 00:00:00.257354 executorch:qnn_executor_runner.cpp:213] Method loaded.
I 00:00:00.323502 executorch:qnn_executor_runner.cpp:262] ignoring error from set_output_data_ptr(): 0x2
I 00:00:00.357496 executorch:qnn_executor_runner.cpp:262] ignoring error from set_output_data_ptr(): 0x2
I 00:00:00.357555 executorch:qnn_executor_runner.cpp:265] Inputs prepared.
I 00:00:00.364824 executorch:qnn_executor_runner.cpp:414] Model executed successfully.
I 00:00:00.364875 executorch:qnn_executor_runner.cpp:425] Write etdump to etdump.etdp, Size = 424
[INFO] [Qnn ExecuTorch]: Destroy Qnn backend parameters
[INFO] [Qnn ExecuTorch]: Destroy Qnn context
[INFO] [Qnn ExecuTorch]: Destroy Qnn backend

The model is merely executed. If we want to feed real inputs and get model outputs, we can use

cd $EXECUTORCH_ROOT
# android
python -m examples.qualcomm.scripts.deeplab_v3 -b build-android -m SM8550 --download -s <device_serial>
# (optional) linux embedded
python -m examples.qualcomm.scripts.deeplab_v3 -b build-oe-linux -m SXR1230P --download -s <device_serial> -t aarch64-oe-linux-gcc-9.3

The <device_serial> can be found by adb devices command.

After the above command, pre-processed inputs and outputs are put in $EXECUTORCH_ROOT/deeplab_v3 and $EXECUTORCH_ROOT/deeplab_v3/outputs folder.

The command-line arguments are written in utils.py. The model, inputs, and output location are passed to qnn_executorch_runner by --model_path, --input_list_path, and --output_folder_path.

Run Android LlamaDemo with QNN backend#

$DEMO_APP refers to the root of the executorch android demo, i.e., the directory containing build.gradle.kts.

Step 1: Rebuild ExecuTorch AAR

# Build the AAR
cd $EXECUTORCH_ROOT
export BUILD_AAR_DIR=$EXECUTORCH_ROOT/aar-out
./scripts/build_android_library.sh

Step 2: Copy AAR to Android Project

cp $EXECUTORCH_ROOT/aar-out/executorch.aar \
   $DEMO_APP/app/libs/executorch.aar

Step 3: Build Android APK

cd $DEMO_APP
./gradlew clean assembleDebug -PuseLocalAar=true

Step 4: Install on Device

adb install -r app/build/outputs/apk/debug/app-debug.apk

Step 5: Push model

adb shell mkdir -p /data/local/tmp/llama
adb push model.pte /data/local/tmp/llama
adb push tokenizer.bin /data/local/tmp/llama

Step 6: Run the Llama Demo

Open the App on Android
Select QUALCOMM backend
Select model.pte Model
Select tokenizer.bin Tokenizer
Select Model Type
Click LOAD MODEL
It should show Successfully loaded model.

Verification Steps#

Step 1. Verify AAR Contains Your Changes

# Check for debug strings in the AAR
unzip -p $DEMO_APP/app/libs/executorch.aar jni/arm64-v8a/libexecutorch.so | \
  strings | grep "QNN"   # Replace "QNN" with your actual debug string if needed

If found, your changes are in the AAR.

Step 2. Verify APK Contains Correct Libraries

# Check QNN library version in APK
cd $DEMO_APP
unzip -l app/build/outputs/apk/debug/app-debug.apk | grep "libQnnHtp.so"

Expected size for QNN 2.37.0: ~2,465,440 bytes

Step 3. Monitor Logs During Model Loading

adb logcat -c
adb logcat | grep -E "ExecuTorch"

Common Issues and Solutions#

Issue 1: Error 18 (InvalidArgument)#

Cause: Wrong parameter order in Runner constructor or missing QNN config
Solution: Check $EXECUTORCH_ROOT/examples/qualcomm/oss_scripts/llama/runner/runner.h for the correct constructor signature.

Issue 2: Error 1 (Internal) with QNN API Version Mismatch#

Symptoms:

W [Qnn ExecuTorch]: Qnn API version 2.33.0 is mismatched
E [Qnn ExecuTorch]: Using newer context binary on old SDK
E [Qnn ExecuTorch]: Can't create context from binary. Error 5000

Cause: Model compiled with QNN SDK version X but APK uses QNN runtime version Y
Solution:
- Update build.gradle.kts with matching QNN runtime version
Note: The version numbers below (2.33.0 and 2.37.0) are examples only. Please check for the latest compatible QNN runtime version or match your QNN SDK version to avoid API mismatches.

Before:
```
implementation("com.qualcomm.qti:qnn-runtime:2.33.0")
```
After:
```
implementation("com.qualcomm.qti:qnn-runtime:2.37.0")
```
- Or recompile model with matching QNN SDK version

Issue 3: Native Code Changes Not Applied#

Symptoms:
- Debug logs don’t appear
- Behavior doesn’t change
Cause:
- Gradle using Maven dependency instead of local AAR
Solution:
- Always build with -PuseLocalAar=true flag

Issue 4: Logs Not Appearing#

Cause: Wrong logging tag filter
Solution: QNN uses “ExecuTorch” tag:
```
adb logcat | grep "ExecuTorch"
```

Supported model list#

Please refer to $EXECUTORCH_ROOT/examples/qualcomm/scripts/ and $EXECUTORCH_ROOT/examples/qualcomm/oss_scripts/ to the list of supported models.

Each script demonstrates:

Model export (torch.export)
Quantization (PTQ/QAT)
Lowering and compilation to QNN delegate

Deployment on device or HTP emulator

How to Support a Custom Model in HTP Backend#

Step-by-Step Implementation Guide#

Please reference the simple example and more complicated examples for reference

Step 1: Prepare Your Model#

import torch

# Initialize your custom model
model = YourModelClass().eval()  # Your custom PyTorch model

# Create example inputs (adjust shape as needed)
example_inputs = (torch.randn(1, 3, 224, 224),)  # Example input tensor

Step 2: [Optional] Quantize Your Model#

Choose between quantization approaches, post training quantization (PTQ) or quantization aware training (QAT):

from executorch.backends.qualcomm.quantizer.quantizer import QnnQuantizer
from torchao.quantization.pt2e.quantize_pt2e import prepare_pt2e, prepare_qat_pt2e, convert_pt2e

quantizer = QnnQuantizer()
m = torch.export.export(model, example_inputs, strict=True).module()

# PTQ (Post-Training Quantization)
if quantization_type == "ptq":
    prepared_model = prepare_pt2e(m, quantizer)
    # Calibration loop would go here
    prepared_model(*example_inputs)

# QAT (Quantization-Aware Training)
elif quantization_type == "qat":
    prepared_model = prepare_qat_pt2e(m, quantizer)
    # Training loop would go here
    for _ in range(training_steps):
        prepared_model(*example_inputs)

# Convert to quantized model
quantized_model = convert_pt2e(prepared_model)

The QNNQuantizer is configurable, with the default setting being 8a8w. For advanced users, refer to the QnnQuantizer documentation for details.

Supported Quantization Schemes#

8a8w (default)
16a16w
16a8w
16a4w
16a4w_block

Customization Options#

Per-node annotation: Use custom_quant_annotations.
Per-module (nn.Module) annotation: Use submodule_qconfig_list.

Additional Features#

Node exclusion: Discard specific nodes via discard_nodes.
Blockwise quantization: Configure block sizes with block_size_map.

For practical examples, see test_qnn_delegate.py.

Step 3: Configure Compile Specs#

During this step, you will need to specify the target SoC, data type, and other QNN compiler spec.

from executorch.backends.qualcomm.utils.utils import (
    generate_qnn_executorch_compiler_spec,
    generate_htp_compiler_spec,
    QcomChipset,
    to_edge_transform_and_lower_to_qnn,
)

# HTP Compiler Configuration
backend_options = generate_htp_compiler_spec(
    use_fp16=not quantized,  # False for quantized models
)

# QNN Compiler Spec
compile_spec = generate_qnn_executorch_compiler_spec(
    soc_model=QcomChipset.SM8650,  # Your target SoC
    backend_options=backend_options,
)

Step 4: Lower and Export the Model#

# Lower to QNN backend
delegated_program = to_edge_transform_and_lower_to_qnn(
    quantized_model if quantized else model,
    example_inputs,
    compile_spec
)

# Export to ExecuTorch format
executorch_program = delegated_program.to_executorch()

# Save the compiled model
model_name = "custom_model_qnn.pte"
with open(model_name, "wb") as f:
    f.write(executorch_program.buffer)
print(f"Model successfully exported to {model_name}")

Deep Dive#

Partitioner API#

The QnnPartitioner identifies and groups supported subgraphs for execution on the QNN backend.
It uses QnnOperatorSupport to check node-level compatibility with the Qualcomm backend via QNN SDK APIs.

The partitioner tags supported nodes with a delegation_tag and handles constants, buffers, and mutable states appropriately. Please checkout QNNPartitioner for the latest changes. It mostly supports the following 4 inputs, and only compile spec is required

class QnnPartitioner(Partitioner):
    """
    QnnPartitioner identifies subgraphs that can be lowered to QNN backend, by tagging nodes for delegation,
    and manages special cases such as mutable buffers and consumed constants.
    """

    def __init__(
        self,
        compiler_specs: List[CompileSpec],
        skip_node_id_set: set = None,
        skip_node_op_set: set = None,
        skip_mutable_buffer: bool = False,
    ):
        ...

Quantization#

Quantization in the QNN backend supports multiple data bit-widths and training modes (PTQ/QAT). The QnnQuantizer defines quantization configurations and annotations compatible with Qualcomm hardware.

Supported schemes include:

8a8w (default)
16a16w
16a8w
16a4w
16a4w_block

Highlights:

QuantDtype enumerates bit-width combinations for activations and weights.
ModuleQConfig manages per-layer quantization behavior and observers.
QnnQuantizer integrates with PT2E prepare/convert flow to annotate and quantize models.

Supports:

Per-channel and per-block quantization
Custom quant annotation via custom_quant_annotations
Skipping specific nodes or ops
Per-module customization via submodule_qconfig_list

For details, see: backends/qualcomm/quantizer/quantizer.py

Operator Support#

[The full operator support matrix](https://github.com/pytorch/executorch/tree/f32cdc3de6f7176d70a80228f1a60bcd45d93437/backends/qualcomm/builders#operator-support-status is tracked and frequently updated in the ExecuTorch repository.

It lists:

Supported PyTorch ops (aten.*, custom ops)
Planned ops
Deprecated ops

This matrix directly corresponds to the implementations in: executorch/backends/qualcomm/builders/node_visitors/*.py

Custom Ops Support#

You can extend QNN backend support for your own operators. Follow the tutorial:

It covers:

Writing new NodeVisitor for your op
Registering via @register_node_visitor
Creating and linking libQnnOp*.so for the delegate
Testing and verifying custom kernels on HTP

FAQ#

If you encounter any issues while reproducing the tutorial, please file a github issue on ExecuTorch repo and tag use #qcom_aisw tag

Debugging tips#

Before trying any complicated models, try out a simple model example and see it if works one device.