imagenet classification with deep convolutional neural networks presenter: weicong chen

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ImageNet Classification with Deep Convolutional Neural Networks Presenter: Weicong Chen

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ImageNet LSVRC-2010 Contest 1.2 million high-resolution images 1,000 different classes 50,000 validation images, 150,000 testing images Top-1 error 47.1% best in contest, 45.7% best published Top-5 errors 28.2% best in contest, 25.7% best published

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Page 1: ImageNet Classification with Deep Convolutional Neural Networks Presenter: Weicong Chen

ImageNet Classification with Deep Convolutional Neural

Networks

Presenter: Weicong Chen

Page 2: ImageNet Classification with Deep Convolutional Neural Networks Presenter: Weicong Chen

Deep Convolutional Neural Networks• Led by Geoffrey Hinton, University of Toronto

• Published in 2013

• Based on the datasets from ImageNet LSVRC-2010 Contest

• Using graphic cards to train the neural network

Page 3: ImageNet Classification with Deep Convolutional Neural Networks Presenter: Weicong Chen

ImageNet LSVRC-2010 Contest • 1.2 million high-resolution images

• 1,000 different classes

• 50,000 validation images, 150,000 testing images

• Top-1 error 47.1% best in contest, 45.7% best published

• Top-5 errors 28.2% best in contest, 25.7% best published

Page 4: ImageNet Classification with Deep Convolutional Neural Networks Presenter: Weicong Chen

Convolutional Neural Networks (CNN)

Page 5: ImageNet Classification with Deep Convolutional Neural Networks Presenter: Weicong Chen

Architecture

Page 6: ImageNet Classification with Deep Convolutional Neural Networks Presenter: Weicong Chen

Novel/Unusual features in architecture• ReLU (Rectified Linear Units ) Nonlinearity

Standard way: f(x) = tanh(x) or f(x) = (1 + e-x)-1 (logistic function)ReLU: f(x) = max(0, x)6 times faster than hyperbolic function

• Multiple GPUsLarger memoryParallel computingControl of communication

Page 7: ImageNet Classification with Deep Convolutional Neural Networks Presenter: Weicong Chen

Overfitting• Occurs when a statistical model describes random error or noise

instead of the underlying relationship

• Exaggerate minor fluctuations in the data

• Will generally have poor predictive performance

Page 8: ImageNet Classification with Deep Convolutional Neural Networks Presenter: Weicong Chen

Reducing overfitting• Data Augmentation1.Image translation and horizontal reflection

Randomly extracting patchesFour corner and one center patches with reflection for testing

2.Altering the intensities of the RGB channels in training imagesApproximately captures an important property of natural images reduces the top-1 error rate by over 1%

Page 9: ImageNet Classification with Deep Convolutional Neural Networks Presenter: Weicong Chen

Reducing Overfitting• Dropout

Zero the output of each hidden neuron with probability 0.5.

No longer contribute to forward pass and backward propagation

Neural network samples a different architecture every time

Reduce complex co-adaptations of neurons

Used in two fully-connected layers

Page 10: ImageNet Classification with Deep Convolutional Neural Networks Presenter: Weicong Chen

Result• Two NVIDIA GTX 580 3GB GPUs

• 6 days of training

• 90 cycles

• 60 million parameters

• 37.5% top-1 error (45.7% second best)

• 17% top-5 error (28.2% second best)

Page 11: ImageNet Classification with Deep Convolutional Neural Networks Presenter: Weicong Chen

Questions?