This is the implementation of SqueezeNet, however there are many other common factors that were taken care such as:

1. Data Augmentation is outside of main class and can be defined in a semi declarative way using albumentations library inside the transformation.py class.
2. Automatic Loading and Saving models from and to checkpoint.
3. Integration with Tensor Board. The Tensor Board data is being written after a checkpoint save. This is to make sure that, upon restarting the training, the plots are properly drawn. A. Both Training Loss and Validation Accuracy is being written. The code will be modified to also include Training Accuracy and Validation Loss. B. The model is also being stored as graph for visualization.
4. Logging has been enabled in both console and external file. The external file name can be configured using the configuration in properties.py.
5. Multi-GPU Training has been enabled using torch.nn.DataParallel() function.
6. Mixed Precision has been enabled using Nvidia's apex library as the PyTorch 1.6 is not released yet. None: At this moment both Multi-GPU and Mixed Precision can not be using together. This will be fixed once PyTorch 1.6 has been released.
7. The network layers sizes can be printed to console for verification.

There are few functionality which were not implemented here,such as

1. Simple and Complex Bypass
2. Deep Compression

This implementation is focused on Vanilla SqueezeNet

The SqueezeNet paper used ImageNet dataset, however this implementation used another dataset named Caltech256 which is very similar to Imagenet but consists of only 256 Categories and around 30K images. Any decent GPU should be able to train using this dataset in much lesser time than ImageNet.

In order to use ImagNet instead of Caltech256, please find the below blog post for more details.

How to prepare imagenet dataset for image classification

Below is the URL of the Caltech256 Dataset.

Download Caltech 256 Dataset

The pre-processing steps are similar to AlexNet. As SqueezeNet hasn't recommended any additional improvements.

1. Create Train/Validation Dataset ( Test labels are not given )
2. Resize the smaller side of the image to 256 and scale the larger side accordingly..
3. Calculate RGB Mean ( only on train set ) and finally save the global mean to a file named rgb_val.json.
   • The RGB mean values is used during training to normalize each images in ClassificationDataset class.
4. Moves the processed images to a different dir
5. Create a file name categories.csv with the list if class labels and corresponding ids.
6. Create train/val csv file with image name ( randomly generated ) and class id.

The common.preprocessing.image_dir_preprocessor.py class performs the pre processing tasks.

None: In case of ImageNet, parallel processing is recommended. Please refer the below blog post for more details.

http://www.adeveloperdiary.com/data-science/computer-vision/imagenet-preprocessing-using-tfrecord-and-tensorflow-2-0-data-api/

There were only few types of data augmentation used. Following Data Augmentations are implemented using the albumentations library in the SqueezeNet.transformation.py file.

1. Random Crop of 224x224
2. RGB Mean Normalization
3. ShiftScaleRotate
4. Horizontal Flip

1. Random Crop of 224x224 ( Same as training )
2. RGB Mean Normalization

Here are some of the changed applied in this implementation.

1. Use Xavier Normal initialization instead of initializing just from a normal distribution.
2. Use of SqueezeNet 1.1 Architecture which reduces the computation by 2.4 times.

Here are the layers defined by the authors.

The Fire module is defined as:

Here is the layer structure of SqueezeNet 1.1 architecture.

• Used Adam with CosineAnnealingLR learning rate scheduler.
• Initial Learning Rate for Adam has been set to 0.001
• The initial hyper-parameters of CosineAnnealingLR are set as following:
  • T_max : 5
  • eta_min : 1e-5
• After 70 epochs the eta_min hyper-parameter of CosineAnnealingLR was changed to 1e-6.

Here is the plot of Training/Validation Loss/Accuracy after 90 Epochs. We can get more accuracy by using a larger model or more advanced optimization technique.

The is the plot of the learning rate decay.

As shown below, the implemented model was able to achieve 46.60% Accuracy while training from scratch which is similar to AlexNet.

• The network was trained using 2 x NVIDIA 2080ti and 32Bit Floating Point.
• 80 training epochs took ~40 Minutes to complete.

• Run the following file:
  • common.preprocessing.image_dir_preprocessor.py
  • The properties can be changed at common.preprocessing.properties.py. Here is how the configurations are defined.

    # Provide the input preprocessing location
    INPUT_PATH = '/media/4TB/datasets/caltech/256_ObjectCategories'
    # Provide the output location to store the processed images
    OUTPUT_PATH = '/media/4TB/datasets/caltech/processed'
    # Validation split. Range - [ 0.0 - 1.0 ]
    VALIDATION_SPLIT = 0.2
    # Output image dimension. ( height,width )
    OUTPUT_DIM = (256, 256)
    # If RGB mean is needed, set this to True
    RGB_MEAN = True
    # If this is true, then the images will only be resized while preserving the aspect ratio.
    CENTER_CROP = False
    # If this is true then the smaller side will be resized to the dimension defined above
    SMALLER_SIDE_RESIZE = True        
    
    # Function to provide the logic to parse the class labels from the directory.
    def read_class_labels(path):
        return path.split('/')[-1].split('.')[-1]

• Run the following files:
  • SqueezeNet.train.py
  • SqueezeNet.test.py
    • The test.py will automatically pickup the last saved checkpoint by training
• The properties can be changed at SqueezeNet.properties.py. Here is how the configurations are defined.

config = dict()
config['PROJECT_NAME'] = 'SqueezeNet'
config['INPUT_DIR'] = '/media/4TB/datasets/caltech/processed'

config['TRAIN_DIR'] = f"{config['INPUT_DIR']}/train"
config['VALID_DIR'] = f"{config['INPUT_DIR']}/val"

config['TRAIN_CSV'] = f"{config['INPUT_DIR']}/train.csv"
config['VALID_CSV'] = f"{config['INPUT_DIR']}/val.csv"

config['CHECKPOINT_INTERVAL'] = 10
config['NUM_CLASSES'] = 256
config['EPOCHS'] = 80  

config['MULTI_GPU'] = True
config['FP16_MIXED'] = False

config["LOGFILE"] = "output.log"
config["LOGLEVEL"] = "INFO"

I am executing the script remotely from pycharm. Here is a sample output of the train.py

sudo+ssh://home@192.168.50.106:22/home/home/.virtualenvs/dl4cv/bin/python3 -u /home/home/Documents/synch/mini_projects/SqueezeNet/train.py
Building model ...
Training starting now ...
INFO:root:epoch=1, loss=5.2465, val acc=7.318, train acc=5.263, lr=0.001
INFO:root:epoch=2, loss=4.8779, val acc=9.49, train acc=8.318, lr=0.000905463412215599
INFO:root:epoch=3, loss=4.6193, val acc=11.336, train acc=11.036, lr=0.000657963412215599
INFO:root:epoch=4, loss=4.3906, val acc=14.325, train acc=14.075, lr=0.0003520365877844011
INFO:root:epoch=5, loss=4.1922, val acc=16.335, train acc=16.686, lr=0.00010453658778440106
INFO:root:epoch=6, loss=4.1104, val acc=16.661, train acc=17.85, lr=1e-05
INFO:root:epoch=7, loss=4.1201, val acc=17.168, train acc=17.586, lr=0.00010453658778440102
INFO:root:epoch=8, loss=4.1607, val acc=16.465, train acc=16.76, lr=0.0003520365877844012
INFO:root:epoch=9, loss=4.1984, val acc=16.825, train acc=16.336, lr=0.0006579634122155993
INFO:root:epoch=10, loss=4.1244, val acc=17.364, train acc=17.545, lr=0.0009054634122155996

[1] SQUEEZENET: ALEXNET-LEVEL ACCURACY WITH 50X FEWER PARAMETERS AND <0.5MB MODEL SIZE

[2] ImageNet Classification with Deep Convolutional Neural Networks

[3] Batch Normalization: Accelerating Deep Network Training by Reducing Internal Covariate Shift

[4] Understanding the difficulty of training deep feedforward neural networks