onnx / onnx/models

Mobilenet does not accept batched inputs

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Description

Bug Report

Which model does this pertain to?

Mobilenet

Describe the bug

The documentation of mobilenet says that the expected input shape is (N x 3 x H x W), where N is the batch size, and H and W are expected to be at least 224.

But when downloading the mobilenetv2-7.onnx model and running a simple inference session on it, it fails when running on any batch size > 1

Reproduction instructions

System Information

OS Platform and Distribution: Ubuntu 22.04.5 LTS
ONNX version: 1.17.0
Backend/Runtime version: onnxruntime 1.21.0

Provide a code snippet to reproduce your errors.

import onnxruntime
import requests
import numpy as np

MODEL_PATH = 'mobilenet.onnx'
model_url = "https://github.com/onnx/models/raw/refs/heads/main/validated/vision/classification/mobilenet/model/mobilenetv2-7.onnx"

# Download the model
response = requests.get(model_url)
with open(MODEL_PATH, 'wb') as f:
    f.write(response.content)

# Load model
sess = onnxruntime.InferenceSession(MODEL_PATH)
input_name = sess.get_inputs()[0].name
input_shape = sess.get_inputs()[0].shape
input_type = sess.get_inputs()[0].type

print("Input shape:", input_shape)
print("Input type:", input_type)

# Create a batched input (batch size = 4)
batched_input = np.random.rand(4, 3, 224, 224).astype(np.float32)

# Try inference - should raise an error
try:
    output = sess.run(None, {input_name: batched_input})
except Exception as e:
    print("\n❌ Inference failed with batched input:")
    print(e)
Result
❌ Inference failed with batched input:
[ONNXRuntimeError] : 2 : INVALID_ARGUMENT : Got invalid dimensions for input: data for the following indices
 index: 0 Got: 4 Expected: 1
 Please fix either the inputs/outputs or the model.

Contributor guide

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First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start in the linked validated/vision/classification/mobilenet/ directory and inspect the mobilenetv2-7.onnx input metadata. Run the provided Python reproduction with onnxruntime using a batch larger than one. Done means the model accepts the documented (N, 3, H, W) input and the documentation matches the verified behavior.

Written by the indexing model from the issue text.

Assessment

Tech stack
numpy, python
Domain
machine-learning
Issue type
Bug
Difficulty
3/5
Estimated time
1-2 days
Activity status
Stale
Clarity
Clearly specified
Newbie friendliness
35/100

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