knitr::opts_chunk$set(echo = TRUE) knitr::opts_chunk$set(eval = FALSE)
onnx/models is a repository for storing the pre-trained ONNX models. Every ONNX backend should support running these models out of the box. After downloading and extracting the tarball of each model, there should be:
test_data_*.npz
), they are numpy serialized archive.In this tutorial, you'll learn how to use a backend to load and run a ONNX model.
First, install ONNX TensorFlow backend by following the instructions here.
Then download and extract the tarball of ResNet-50.
Next, we load the necessary R and Python libraries (via reticulate):
library(onnx) library(reticulate) np <- import("numpy", convert = FALSE) backend <- import("onnx_tf.backend")
We can then use the loaded numpy Python library to define a helper function to load testing sample from numpy serialized archive.
load_npz_samples <- function(npz_path) { sample <- np$load(normalizePath(npz_path), encoding = 'bytes') list( inputs = sample$items()[[0]][[1]][[0]], outputs = sample$items()[[1]][[1]] ) }
Finally, we can load the ONNX model and the testing samples, and then run the model using ONNX TensorFlow backend:
# Specify paths to ONNX model and testing samples onnx_model_dir <- "~/Downloads/resnet50" model_pb_path <- file.path(onnx_model_dir, "model.onnx") npz_path <- file.path(onnx_model_dir, "test_data_0.npz") # Load ONNX model model <- load_from_file(model_pb_path) # Load testing sample from numpy serialized archive samples <- load_npz_samples(npz_path) inputs <- samples$inputs expected_outputs <- samples$outputs # Run the model with an onnx backend actual_outputs <- backend$run_model(model, inputs)
We can also use numpy to verify the result:
np$testing$assert_almost_equal(expected_outputs, actual_outputs, decimal = 6)
That's it! Isn't it easy? Next you can go ahead and try out different ONNX models as well as different ONNX backends, e.g. PyTorch, MXNet, Caffe2, CNTK, Chainer, etc.
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