Add README

Author: dreiss

README.md

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+# PyTorch Java Demo
+
+This repository is a demonstration of how to use PyTorch from Java.
+
+## Setup
+
+Download and unpack libtorch nightly (or 1.4 or greater once it is released).
+From the pytorch.org homepage under "Quick Start Locally",
+make sure "LibTorch" is the selected package.
+As of this writing, only Linux is supported.  Mac and Windows will follow.
+
+Run `export LIBTORCH_HOME=/path/to/libtorch`.
+The `build.gradle` file will use this to set `java.library.path`
+when running the application.
+If you are using PyTorch in your own environment,
+`LIBTORCH_HOME` is not necessary.
+Instead, you will need to set `java.library.path` to `/path/to/libtorch/lib`.
+
+Run `./gradlew run` to build and run the demo application.
+It will load `demo-model.pt` and run it on some simple data.
+[This notebook](TorchScriptForJavaDemo.ipynb) was used to generate the model.
+
+More information about the Java API and TorchScript:
+- [TorchScript tutorial](https://pytorch.org/tutorials/beginner/Intro_to_TorchScript_tutorial.html)
+- [TorchScript reference](https://pytorch.org/docs/stable/jit.html)
+- [Loading TorchScript in C++](https://pytorch.org/tutorials/advanced/cpp_export.html)
+- [PyTorch-style JavaDoc](https://pytorch.org/docs/stable/packages.html)
+- [Standard JavaDoc](https://dreiss.github.io/pytorch/android/pytorch_android/javadoc-out/)
+- [PyTorch Android tutorial](https://pytorch.org/mobile/android/)