Add compile library tutorial (#277)

* Add compile library tutorial

* Clean output

* Refactor with sphinx gallery

* Refactor

* Change title and other minor fixes

nnvm/tutorials/define_and_compile_model.py

+"""
+Quick Start - End-to-End Tutorial for NNVM/TVM Pipeline
+=======================================================
+**Author**: `Yao Wang <https://github.com/kevinthesun>`_
+
+This example shows how to build a neural network with NNVM python frontend and
+generate runtime library for Nvidia GPU and Raspberry Pi with TVM. (Thanks to
+Tianqi's `tutorial for cuda <http://nnvm.tvmlang.org/tutorials/get_started.html>`_ and
+Ziheng's `tutorial for Raspberry Pi <http://nnvm.tvmlang.org/tutorials/deploy_model_on_rasp.html>`_)
+To run this notebook, you need to install tvm and nnvm following
+`these instructions <https://github.com/dmlc/nnvm/blob/master/docs/how_to/install.md>`_.
+Notice that you need to build tvm with cuda and llvm.
+"""
+
+######################################################################
+# Overview for Supported Hardware Backend of TVM
+# -----------------------------
+# The image below shows hardware backend currently supported by TVM:
+#
+# .. image:: https://github.com/dmlc/web-data/raw/master/tvm/tutorial/tvm_support_list.png
+#      :align: center
+#      :scale: 100%
+#
+# In this tutorial, we'll choose cuda and llvm as target backends.
+# To begin with, let's import NNVM and TVM.
+import tvm
+import nnvm.compiler
+import nnvm.testing
+
+
+######################################################################
+# Define Neural Network in NNVM
+# -----------------------------
+# First, let's define a neural network with nnvm python frontend.
+# For simplicity, we'll use pre-defined resnet-18 network in NNVM.
+# Parameters are initialized with Xavier initializer.
+# NNVM also supports other model formats such as MXNet, CoreML and ONNX.
+#
+# In this tutorial, we assume we will do inference on our device
+# and the batch size is set to be 1. Input images are RGB color
+# images of size 224 * 224. We can call the :any:`nnvm.symbol.debug_str`
+# to show the network structure.
+
+batch_size = 1
+num_class = 1000
+image_shape = (3, 224, 224)
+data_shape = (batch_size,) + image_shape
+out_shape = (batch_size, num_class)
+
+net, params = nnvm.testing.resnet.get_workload(batch_size=batch_size, image_shape=image_shape)
+print(net.debug_str())
+
+######################################################################
+# Compilation
+# ----------------------------
+# Next step is to compile the model using the NNVM/TVM pipeline.
+# Users can specify the optimization level of the compilation.
+# Currently this value can be 0 to 2, which corresponds to
+# "SimplifyInference", "OpFusion" and "PrecomputePrune" respectively.
+# In this example we set optimization level to be 0
+# and use Raspberry Pi as compile target.
+#
+# :any:`nnvm.compiler.build` returns three components: the execution graph in
+# json format, the TVM module library of compiled functions specifically
+# for this graph on the target hardware, and the parameter blobs of
+# the model. During the compilation, NNVM does the graph-level
+# optimization while TVM does the tensor-level optimization, resulting
+# in an optimized runtime module for model serving.
+#
+# We'll first compile for Nvidia GPU.
+
+opt_level = 0
+target = tvm.target.cuda()
+with nnvm.compiler.build_config(opt_level=opt_level):
+    graph, lib, params = nnvm.compiler.build(
+        net, target, shape={"data": data_shape}, params=params)
+
+######################################################################
+# Save Compiled Module
+# ----------------------------
+# After compilation, we can save the graph, lib and params into separate files
+# and deploy them to Nvidia GPU.
+
+from tvm.contrib import util
+
+temp = util.tempdir()
+path_lib = temp.relpath("deploy_lib.so")
+lib.export_library(path_lib)
+with open(temp.relpath("deploy_graph.json"), "w") as fo:
+    fo.write(graph.json())
+with open(temp.relpath("deploy_param.params"), "wb") as fo:
+    fo.write(nnvm.compiler.save_param_dict(params))
+print(temp.listdir())
+
+######################################################################
+# Deploy locally to Nvidia GPU
+# ------------------------------
+# Now we can load the module back.
+
+import numpy as np
+from tvm.contrib import graph_runtime
+
+loaded_lib = tvm.module.load(path_lib)
+loaded_json = open(temp.relpath("deploy_graph.json")).read()
+loaded_params = bytearray(open(temp.relpath("deploy_param.params"), "rb").read())
+module = graph_runtime.create(loaded_json, loaded_lib, tvm.gpu(0))
+module.load_params(loaded_params)
+
+input_data = tvm.nd.array(np.random.uniform(size=data_shape).astype("float32"))
+module.run(data=input_data)
+out = module.get_output(0, out=tvm.nd.empty(out_shape))
+# Print first 10 elements of output
+print(out.asnumpy()[0][0:10])
+
+######################################################################
+# Compile and Deploy the Model to Raspberry Pi Remotely with RPC
+# ------------------------------
+# Following the steps above, we can also compile the model for Raspberry Pi.
+# TVM provides rpc module to help with remote deploying.
+#
+# For demonstration, we simply start an RPC server on the same machine,
+# if :code:`use_rasp` is False. If you have set up the remote
+# environment, please change the three lines below: change the
+# :code:`use_rasp` to True, also change the host and port with your
+# device's host address and port number.
+
+# If we run the example locally for demonstration, we can simply set the 
+# compilation target as `llvm`. 
+# To run it on the Raspberry Pi, you need to specify its instruction set. 
+# `llvm -target=armv7l-none-linux-gnueabihf -mcpu=cortex-a53 -mattr=+neon`
+# is the recommended compilation configuration, thanks to Ziheng's work.
+
+from tvm.contrib import rpc
+
+use_rasp = False
+host = 'rasp0'
+port = 9090
+
+if not use_rasp:
+    # run server locally
+    host = 'localhost'
+    port = 9090
+    server = rpc.Server(host=host, port=port)
+
+# compile and save model library
+if use_rasp:
+    target = "llvm -target=armv7l-none-linux-gnueabihf -mcpu=cortex-a53 -mattr=+neon"
+else:
+    target = "llvm"
+# use `with tvm.target.rasp` for some target-specified optimization
+with tvm.target.rasp():
+    graph, lib, params = nnvm.compiler.build(
+        net, target, shape={"data": data_shape}, params=params)
+
+temp = util.tempdir()
+path_lib = temp.relpath("deploy_lib_rasp.o")
+lib.save(path_lib)
+
+# connect the server
+remote = rpc.connect(host, port)
+
+# upload the library to remote device and load it
+remote.upload(path_lib)
+rlib = remote.load_module('deploy_lib_rasp.o')
+
+ctx = remote.cpu(0)
+# upload the parameter
+rparams = {k: tvm.nd.array(v, ctx) for k, v in params.items()}
+
+# create the remote runtime module
+module = graph_runtime.create(graph, rlib, ctx)
+# set parameter
+module.set_input(**rparams)
+# set input data
+input_data = np.random.uniform(size=data_shape)
+module.set_input('data', tvm.nd.array(input_data.astype('float32')))
+# run
+module.run()
+
+out = module.get_output(0, out=tvm.nd.empty(out_shape, ctx=ctx))
+# Print first 10 elements of output
+print(out.asnumpy()[0][0:10])
+
+if not use_rasp:
+    # terminate the local server
+    server.terminate()
+