Version: 0.10.0

# ONNX model inferencing on Spark

## ONNX​

ONNX is an open format to represent both deep learning and traditional machine learning models. With ONNX, AI developers can more easily move models between state-of-the-art tools and choose the combination that is best for them.

SynapseML now includes a Spark transformer to bring a trained ONNX model to Apache Spark, so you can run inference on your data with Spark's large-scale data processing power.

## Usage​

1. Create a com.microsoft.azure.synapse.ml.onnx.ONNXModel object and use setModelLocation or setModelPayload to load the ONNX model.

For example:

val onnx = new ONNXModel().setModelLocation("/path/to/model.onnx")
2. Use ONNX visualization tool (for example, Netron) to inspect the ONNX model's input and output nodes.

3. Set the parameters properly to the ONNXModel object.

The com.microsoft.azure.synapse.ml.onnx.ONNXModel class provides a set of parameters to control the behavior of the inference.

ParameterDescriptionDefault Value
feedDictMap the ONNX model's expected input node names to the input DataFrame's column names. Make sure the input DataFrame's column schema matches with the corresponding input's shape of the ONNX model. For example, an image classification model may have an input node of shape [1, 3, 224, 224] with type Float. It is assumed that the first dimension (1) is the batch size. Then the input DataFrame's corresponding column's type should be ArrayType(ArrayType(ArrayType(FloatType))).None
fetchDictMap the output DataFrame's column names to the ONNX model's output node names.None
miniBatcherSpecify the MiniBatcher to use.FixedMiniBatchTransformer with batch size 10
softMaxDictA map between output DataFrame columns, where the value column will be computed from taking the softmax of the key column. If the 'rawPrediction' column contains logits outputs, then one can set softMaxDict to Map("rawPrediction" -> "probability") to obtain the probability outputs.None
argMaxDictA map between output DataFrame columns, where the value column will be computed from taking the argmax of the key column. This can be used to convert probability or logits output to the predicted label.None
deviceTypeSpecify a device type the model inference runs on. Supported types are: CPU or CUDA. If not specified, auto detection will be used.None
optimizationLevelSpecify the optimization level for the ONNX graph optimizations. Supported values are: NO_OPT, BASIC_OPT, EXTENDED_OPT, ALL_OPT.ALL_OPT
4. Call transform method to run inference on the input DataFrame.