Compile ONNX Models

Author: Joshua Z. Zhang

This article is an introductory tutorial to deploy ONNX models with Relay.

For us to begin with, ONNX package must be installed.

A quick solution is to install protobuf compiler, and

pip install onnx --user

or please refer to offical site. https://github.com/onnx/onnx

import onnx
import numpy as np
import tvm
import tvm.relay as relay

def download(url, path, overwrite=False):
    import os
    if os.path.isfile(path) and not overwrite:
        print('File {} existed, skip.'.format(path))
        return
    print('Downloading from url {} to {}'.format(url, path))
    try:
        import urllib.request
        urllib.request.urlretrieve(url, path)
    except:
        import urllib
        urllib.urlretrieve(url, path)

Load pretrained ONNX model

The example super resolution model used here is exactly the same model in onnx tutorial http://pytorch.org/tutorials/advanced/super_resolution_with_caffe2.html we skip the pytorch model construction part, and download the saved onnx model

model_url = ''.join(['https://gist.github.com/zhreshold/',
                     'bcda4716699ac97ea44f791c24310193/raw/',
                     '93672b029103648953c4e5ad3ac3aadf346a4cdc/',
                     'super_resolution_0.2.onnx'])
download(model_url, 'super_resolution.onnx', False)
# now you have super_resolution.onnx on disk
onnx_model = onnx.load('super_resolution.onnx')

Out:

File super_resolution.onnx existed, skip.

Load a test image

A single cat dominates the examples!

from PIL import Image
img_url = 'https://github.com/dmlc/mxnet.js/blob/master/data/cat.png?raw=true'
download(img_url, 'cat.png')
img = Image.open('cat.png').resize((224, 224))
img_ycbcr = img.convert("YCbCr")  # convert to YCbCr
img_y, img_cb, img_cr = img_ycbcr.split()
x = np.array(img_y)[np.newaxis, np.newaxis, :, :]

Out:

File cat.png existed, skip.

Compile the model with relay

target = 'llvm'

input_name = '1'
shape_dict = {input_name: x.shape}
sym, params = relay.frontend.from_onnx(onnx_model, shape_dict)

with relay.build_config(opt_level=1):
    intrp = relay.build_module.create_executor('graph', sym, tvm.cpu(0), target)

Execute on TVM

dtype = 'float32'
tvm_output = intrp.evaluate(sym)(tvm.nd.array(x.astype(dtype)), **params).asnumpy()

Display results

We put input and output image neck to neck

from matplotlib import pyplot as plt
out_y = Image.fromarray(np.uint8((tvm_output[0, 0]).clip(0, 255)), mode='L')
out_cb = img_cb.resize(out_y.size, Image.BICUBIC)
out_cr = img_cr.resize(out_y.size, Image.BICUBIC)
result = Image.merge('YCbCr', [out_y, out_cb, out_cr]).convert('RGB')
canvas = np.full((672, 672*2, 3), 255)
canvas[0:224, 0:224, :] = np.asarray(img)
canvas[:, 672:, :] = np.asarray(result)
plt.imshow(canvas.astype(np.uint8))
plt.show()
../../_images/sphx_glr_from_onnx_001.png

Total running time of the script: ( 0 minutes 1.417 seconds)

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