1. Clone the repository.

git clone https://github.com/NVIDIA/DeepLearningExamples
cd DeepLearningExamples/PyTorch/Classification/

2. Download and preprocess the dataset.

The ResNeXt101-32x4d script operates on ImageNet 1k, a widely popular image classification dataset from the ILSVRC challenge.

PyTorch can work directly on JPEGs, therefore, preprocessing/augmentation is not needed.

To train your model using mixed or TF32 precision with Tensor Cores or using FP32, perform the following steps using the default parameters of the resnext101-32x4d model on the ImageNet dataset. For the specifics concerning training and inference, see the Advanced section.

1. Download the images.

2. Extract the training data:

mkdir train && mv ILSVRC2012_img_train.tar train/ && cd train
tar -xvf ILSVRC2012_img_train.tar && rm -f ILSVRC2012_img_train.tar
find . -name "*.tar" | while read NAME ; do mkdir -p "${NAME%.tar}"; tar -xvf "${NAME}" -C "${NAME%.tar}"; rm -f "${NAME}"; done
cd ..

3. Extract the validation data and move the images to subfolders:

mkdir val && mv ILSVRC2012_img_val.tar val/ && cd val && tar -xvf ILSVRC2012_img_val.tar
wget -qO- https://raw.githubusercontent.com/soumith/imagenetloader.torch/master/valprep.sh | bash

The directory in which the train/ and val/ directories are placed, is referred to as <path to imagenet> in this document.

3. Build the ResNeXt101-32x4d PyTorch NGC container.

docker build . -t nvidia_resnext101-32x4d

4. Start an interactive session in the NGC container to run training/inference.

nvidia-docker run --rm -it -v <path to imagenet>:/imagenet --ipc=host nvidia_resnext101-32x4d

5. Start training

To run training for a standard configuration (DGXA100/DGX1V, AMP/TF32/FP32, 90/250 Epochs), run one of the scripts in the ./resnext101-32x4d/training directory called ./resnext101-32x4d/training/{AMP, TF32, FP32}/{ DGXA100, DGX1V }_resnext101-32x4d_{AMP, TF32, FP32}_{ 90, 250 }E.sh.

Ensure ImageNet is mounted in the /imagenet directory.

Example: bash ./resnext101-32x4d/training/AMP/DGX1_resnext101-32x4d_AMP_250E.sh <path were to store checkpoints and logs>

6. Start inference

You can download pretrained weights from NGC:

wget --content-disposition https://api.ngc.nvidia.com/v2/models/nvidia/resnext101_32x4d_pyt_amp/versions/20.06.0/zip -O resnext101_32x4d_pyt_amp_20.06.0.zip

unzip resnext101_32x4d_pyt_amp_20.06.0.zip

To run inference on ImageNet, run:

python ./main.py --arch resnext101-32x4d --evaluate --epochs 1 --pretrained-from-file nvidia_resnext101-32x4d_200821.pth.tar -b <batch size> <path to imagenet>

To run inference on JPEG image using pretrained weights:

python classify.py --arch resnext101-32x4d --pretrained-from-file nvidia_resnext101-32x4d_200821.pth.tar --precision AMP|FP32 --image <path to JPEG image>