PyTorch iOS Examples

Requirements

• XCode 11.0 or above
• iOS 12.0 or above

Quick Start with a HelloWorld Example

HelloWorld is a simple image classification application that demonstrates how to use PyTorch C++ libraries on iOS. The code is written in Swift and uses Objective-C as a bridge.

Model Preparation

The model we are going to use is Resnet18, a pre-trained image classification model that has been packaged in TorchVision. To install it, run the command below.

We highly recommend following the Pytorch Github page to set up the Python development environment on your local machine.

pip install torchvision

Once we have TorchVision installed successfully, navigate to the HelloWorld folder and run trace_model.py to generate our model. The script contains the code of tracing and saving a torchscript model that can be run on mobile devices.

python trace_model.py

If everything works well, model.pt should be generated in the HelloWorld folder. Now copy the model file to our application folder HelloWorld/model.

Install LibTorch via Cocoapods

The PyTorch C++ library is available in Cocoapods, to integrate it to our project, we can run

pod install

Now open the HelloWorld.xcworkspace in XCode, select an iOS simulator and launch it (cmd + R). If everything works well, we should see a wolf picture on the simulator screen along with the prediction results.

PyTorch demo app

For more complex use cases, we recommend to check out the PyTorch demo application. The demo app contains two showcases. A camera app that runs a quantized model to predict the images coming from device’s rear-facing camera in real time. And a text-based app that uses a text classififcation model to predict the topic from the input string.

LICENSE

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.