sdk example tutorial (#846)

Summary:
Pull Request resolved: #846

This diff creates README.md for sdk example (mainly focus on bp for now) and add sdk-related info to example/README.md.

Reviewed By: tarun292, guangy10

Differential Revision: D50197309

fbshipit-source-id: 5ba5227f33afa373f250e6b9ac61cdb60643ce9b

Author: Gasoonjia

examples/README.md

@@ -19,6 +19,7 @@ examples
 ├── qualcomm                          # Contains demos of Qualcomm QNN backend
 ├── xtensa                            # Contains demos of exporting and running a simple model on Xtensa Hifi4 DSP
 ├── demo-apps                         # Contains demo apps for Android and iOS
+├── sdk                               # Contains demos of BundledProgram and ETDump
 ├── third-party                       # Third-party libraries required for working on the demos
 └── README.md                         # This file
 ```
@@ -59,6 +60,10 @@ You will find demos of [ExecuTorch QNN Backend](./qualcomm) in the [`qualcomm/`]
 The [`xtensa/`](./xtensa) directory hosts a demo that showcases the process of exporting and executing a model on Xtensa Hifi4 DSP. You can utilize [this tutorial](../docs/source/build-run-xtensa.md) to guide you in configuring the demo and running it.
 
 
+## Demo of ExecuTorch SDK
+
+You will find demos of [ExecuTorch SDK](./sdk/) in the [`sdk/`](./sdk/) directory. The examples focuses on exporting and executing BundledProgram for ExecuTorch model verification, and ETDump generation.
+
 ## Dependencies
 
 Various models and workflows listed in this directory have dependencies on some other packages. You need to follow the setup guide in [Setting up ExecuTorch from GitHub](/docs/website/docs/tutorials/00_setting_up_executorch.md) to have appropriate packages installed.

examples/sdk/README.md

@@ -0,0 +1,61 @@
+# SDK Examples
+This directory contains examples of BundledProgram and ETDump generation.
+
+## Directory structure
+```bash
+examples/sdk
+├── scripts                           # Python scripts to illustrate export workflow of bundled program.
+├── sdk_executor_runner               # Contains an example for both BundledProgram to verify ExecuTorch model, and generate ETDump for runtime results.
+└── README.md                         # Current file
+```
+
+## BundledProgram
+
+We will use an example model (in `torch.nn.Module`) and its representative inputs, both from [`models/`](../models) directory, to generate a [BundledProgram(`.bp`)](../../docs/source/sdk-bundled-io.md) file using the [script](scripts/export_bundled_program.py). Then we will use [sdk_example_runner](sdk_example_runner/sdk_example_runner.cpp) to execute the `.bp` model on the ExecuTorch runtime and verify the model on BundledProgram API.
+
+
+1. Sets up the basic development environment for ExecuTorch by [Setting up ExecuTorch from GitHub](../../docs/source/getting-started-setup.md).
+
+2. Using the [script](scripts/export_bundled_program.py) to generate a BundledProgram binary file by retreiving a `torch.nn.Module` model and its representative inputs from the list of available models in the [`models/`](../models) dir。
+
+```bash
+cd executorch # To the top level dir
+
+# To get a list of example models
+python3 -m examples.sdk.scripts.export_bundled_program -h
+
+# To generate a specific `.bp` model
+python3 -m examples.sdk.scripts.export_bundled_program -m mv2 # for MobileNetv2
+
+# This should generate ./mv2_bundled.bp file, if successful.
+```
+
+3. Once we have the BundledProgram binary (`.bp`) file, then let's run and verify it with ExecuTorch runtime and BundledProgram APIs using the [sdk_example_runner](sdk_example_runner/sdk_example_runner.cpp).
+
+```bash
+buck2 run examples/sdk/sdk_example_runner:sdk_example_runner -- --bundled_program_path mv2_bundled.bp --output_verification
+```
+
+
+## Generate ETDump
+
+Next step is to generate an ``ETDump``. ``ETDump`` contains runtime results
+from executing the model. To generate, users have two options:
+
+**Option 1:**
+
+Use Buck::
+```bash
+   python3 -m examples.sdk.scripts.export_bundled_program -m mv2
+   buck2 run -c executorch.event_tracer_enabled=true examples/sdk/sdk_example_runner:sdk_example_runner -- --bundled_program_path mv2_bundled.bp
+```
+ **Option 2:**
+
+ Use CMake::
+```bash
+   cd executorch
+   rm -rf cmake-out && mkdir cmake-out && cd cmake-out && cmake -DBUCK2=buck2 -DEXECUTORCH_BUILD_SDK=1 -DEXECUTORCH_BUILD_EXTENSION_DATA_LOADER=1 ..
+   cd ..
+   cmake --build cmake-out -j8 -t sdk_example_runner
+   ./cmake-out/examples/sdk/sdk_example_runner --bundled_program_path mv2_bundled.bp
+   ```