Reproduce ResNet-v2 using MXNet

Requirements

• Install MXNet on a machine with CUDA GPU, and it's better also installed with cuDNN v5
• Please fix the randomness if you want to train your own model and using this pull request

Trained models

The trained ResNet models achieve better error rates than the original ResNet-v1 models.

• ImageNet:single center crop (224x224) validation error rate(%)

  Network	Top-1 error	Top-5 error	Traind Model
  ResNet-18	30.90	11.01
  ResNet-34	--	--
  ResNet-50	24.56	7.33	baidu.yun or dropbox
  ResNet-101	22.68	6.58	data.dmlc.ml
  ResNet-152	22.25	6.42	data.dmlc.ml
  ResNet-200	--	--

• cifar10: single crop validation error rate(%):

  Network	top-1
  ResNet-164	4.68

How to Train

imagenet

you should create the *.rec file first, i recommend use this cmd parameters:

$im2rec_path train.lst train/ data/imagenet/train_480_q90.rec resize=480 quality=90

set resize=480 and quality=90(quality=100 will be best i think:)) here may use more disk memory(about ~103G), but this is very useful with scale augmentation during training[1][2], and can help reproducing a good result.

because you are training imagenet , so we should set data-type = imagenet, then the training cmd is like this(here i use 6 gpus for training):

python -u train_resnet.py --data-dir data/imagenet \
--data-type imagenet --depth 50 --batch-size 256  --gpus=0,1,2,3,4,5

change depth to different number to support different model, currently support ResNet-18, ResNet-34, ResNet-50, ResNet-101, ResNet-152, ResNet-200.

cifar10

same as above, first you should use im2rec to create the .rec file, then training with cmd like this:

python -u train_resnet.py --data-dir data/cifar10 --data-type cifar10 \
  --depth 164 --batch-size 128 --num-examples 50000 --gpus=0,1

change depth when training different model, only support(depth-2)%9==0, such as RestNet-110, ResNet-164, ResNet-1001...

retrain

When training large dataset(like imagenet), it's better for us to change learning rate manually, or the training is killed by some other reasons, so retrain is very important. the code here support retrain, suppose you want to retrain your resnet-50 model from epoch 70 and want to change lr=0.0005, wd=0.001, batch-size=256 using 8gpu, then you can try this cmd:

python -u train_resnet.py --data-dir data/imagenet --data-type imagenet --depth 50 --batch-size 256 \
--gpus=0,1,2,3,4,5,6,7 --model-load-epoch=70 --lr 0.0005 --wd 0.001 --retrain

Notes

• it's better training the model in imagenet with epoch > 100, because this will lead better result.
• when epoch is about 95, cancel the scale/color/ratio augmentation during training, this can be done by only comment out 6 lines of the code, like this:

train = mx.io.ImageRecordIter(
        # path_imgrec         = os.path.join(args.data_dir, "train_480_q90.rec"),
        path_imgrec         = os.path.join(args.data_dir, "train_256_q90.rec"),
        label_width         = 1,
        data_name           = 'data',
        label_name          = 'softmax_label',
        data_shape          = (3, 32, 32) if args.data_type=="cifar10" else (3, 224, 224),
        batch_size          = args.batch_size,
        pad                 = 4 if args.data_type == "cifar10" else 0,
        fill_value          = 127,  # only used when pad is valid
        rand_crop           = True,
        # max_random_scale    = 1.0 if args.data_type == "cifar10" else 1.0,  # 480
        # min_random_scale    = 1.0 if args.data_type == "cifar10" else 0.533,  # 256.0/480.0
        # max_aspect_ratio    = 0 if args.data_type == "cifar10" else 0.25,
        # random_h            = 0 if args.data_type == "cifar10" else 36,  # 0.4*90
        # random_s            = 0 if args.data_type == "cifar10" else 50,  # 0.4*127
        # random_l            = 0 if args.data_type == "cifar10" else 50,  # 0.4*127
        rand_mirror         = True,
        shuffle             = True,
        num_parts           = kv.num_workers,
        part_index          = kv.rank)

but you should prepare one train_256_q90.rec using im2rec like:

$im2rec_path train.lst train/ data/imagenet/train_256_q90.rec resize=256 quality=90

• it's better for running longer than 30 epoch before first decrease the lr(such as 60), so you may decide the epoch number by observe the val-acc curve, and set lr with retrain.

How to use Trained Models

TODO

Reference

[1] Kaiming He, et al. "Deep Residual Learning for Image Recognition." arXiv arXiv:1512.03385 (2015). [2] Kaiming He, et al. "Identity Mappings in Deep Residual Networks" arXiv:1603.05027 (2016) [3] caffe official training code and model, https://github.com/KaimingHe/deep-residual-networks [4] torch training code and model provided by facebook, https://github.com/facebook/fb.resnet.torch [5] MXNet resnet-v1 cifar10 examples,https://github.com/dmlc/mxnet/blob/master/example/image-classification/train_cifar10_resnet.py