Find input shape from onnx file

Question

How can I find the input size of an onnx model? I would eventually like to script it from python.

With tensorflow I can recover the graph definition, find input candidate nodes from it and then obtain their size. Can I do something similar with ONNX (or even simpler)?

Thank you

Asked By: Nick Skywalker

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Source

Answer 1

Yes, provided the input model has the information. Note that inputs of an ONNX model may have an unknown rank or may have a known rank with dimensions that are fixed (like 100) or symbolic (like “N”) or completely unknown. You can access this as below:

import onnx

model = onnx.load(r"model.onnx")

# The model is represented as a protobuf structure and it can be accessed
# using the standard python-for-protobuf methods

# iterate through inputs of the graph
for input in model.graph.input:
    print (input.name, end=": ")
    # get type of input tensor
    tensor_type = input.type.tensor_type
    # check if it has a shape:
    if (tensor_type.HasField("shape")):
        # iterate through dimensions of the shape:
        for d in tensor_type.shape.dim:
            # the dimension may have a definite (integer) value or a symbolic identifier or neither:
            if (d.HasField("dim_value")):
                print (d.dim_value, end=", ")  # known dimension
            elif (d.HasField("dim_param")):
                print (d.dim_param, end=", ")  # unknown dimension with symbolic name
            else:
                print ("?", end=", ")  # unknown dimension with no name
    else:
        print ("unknown rank", end="")
    print()

Answered By: G. Ramalingam

Answer 2

Please do NOT use input as a variable name because it’s a built-in function.

The first idea that comes to mind is that using the google.protobuf.json_format.MessageToDict() method if I need the name, data_type, or some properties of a protobuf object. For example:

form google.protobuf.json_format import MessageToDict

model = onnx.load("path/to/model.onnx")
for _input in model.graph.input:
    print(MessageToDict(_input))

will gives the output like:

{'name': '0', 'type': {'tensorType': {'elemType': 2, 'shape': {'dim': [{'dimValue': '4'}, {'dimValue': '3'}, {'dimValue': '384'}, {'dimValue': '640'}]}}}}

I’m not very clear whether every model.graph.input is a RepeatedCompositeContainer object or not, but it would be necessary to use the for loop when it is a RepeatedCompositeContainer.

Then you need to get the shape information from the dim field.

model = onnx.load("path/to/model.onnx")
for _input in model.graph.input:
    m_dict = MessageToDict(_input))
    dim_info = m_dict.get("type").get("tensorType").get("shape").get("dim")  # ugly but we have to live with this when using dict
    input_shape = [d.get("dimValue") for d in dim_info]  # [4,3,384,640]

If you need the only dim, please use message object instead.

model = onnx.load("path/to/model.onnx")
for _input in model.graph.input:
    dim = _input.type.tensor_ype.shape.dim
    input_shape = [MessgeToDict(d).get("dimValue") for d in dim]
    # if you prefer the python naming style, using the line below
    # input_shape = [MessgeToDict(d, preserving_proto_field_name=True).get("dim_value") for d in dim]

One line version:

model = onnx.load("path/to/model.onnx")
input_shapes = [[d.dim_value for d in _input.type.tensor_type.shape.dim] for _input in model.graph.input]

Refs:

https://github.com/googleapis/python-vision/issues/70

AttributeError: 'google.protobuf.pyext._message.RepeatedCompositeCo' object has no attribute 'append'

Answered By: Xingdong Liu

Answer 3

If you use onnxruntime instead of onnx for inference.

Try using the below code.

import onnxruntime as ort
model = ort.InferenceSession("model.onnx", providers=['CUDAExecutionProvider', 'CPUExecutionProvider'])
input_shape = model.get_inputs()[0].shape

Answered By: developer0hye

Find input shape from onnx file

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