## Learning deep learning (project 2, image classification)

In this class project, I built a network to classify images in the CIFAR-10 dataset. This dataset is freely available.

The dataset contains 60K color images (32×32 pixel) in 10 classes, with 6K images per class.

Here are the classes in the dataset, as well as 10 random images from each:

airplane | ||||||||||

automobile | ||||||||||

bird | ||||||||||

cat | ||||||||||

deer | ||||||||||

dog | ||||||||||

frog | ||||||||||

horse | ||||||||||

ship | ||||||||||

truck |

You can imagine it’s not possible to write down all rules to classify them, so we have to write a program which can learn.

The neural network I created contains 2 hidden layers. The first one is a convolutional layer with max pooling. Then drop out 70% of the connections. The second layer is a fully connected layer with 384 neurons.

def conv_net(x, keep_prob): """ Create a convolutional neural network model : x: Placeholder tensor that holds image data. : keep_prob: Placeholder tensor that hold dropout keep probability. : return: Tensor that represents logits """ # TODO: Apply 1, 2, or 3 Convolution and Max Pool layers # Play around with different number of outputs, kernel size and stride # Function Definition from Above: # conv2d_maxpool(x_tensor, conv_num_outputs, conv_ksize, conv_strides, pool_ksize, pool_strides) model = conv2d_maxpool(x, conv_num_outputs=18, conv_ksize=(4,4), conv_strides=(1,1), pool_ksize=(8,8), pool_strides=(1,1)) model = tf.nn.dropout(model, keep_prob) # TODO: Apply a Flatten Layer # Function Definition from Above: # flatten(x_tensor) model = flatten(model) # TODO: Apply 1, 2, or 3 Fully Connected Layers # Play around with different number of outputs # Function Definition from Above: # fully_conn(x_tensor, num_outputs) model = fully_conn(model,384) model = tf.nn.dropout(model, keep_prob) # TODO: Apply an Output Layer # Set this to the number of classes # Function Definition from Above: # output(x_tensor, num_outputs) model = output(model,10) # TODO: return output return model

Then I trained this network using Amazon AWS g2.2xlarge instance. This instance has GPU which is much faster for deep learning (than CPU). I did a simple experiment and find GPU is at least 3 times faster than CPU:

if all layers in gpu: 14 seconds to run 4 epochs,

if conv layer in cpu, other gpu, 36 seconds to run 4 epochs

This is apparently a very crude comparison but GPU is definitely much faster than CPU (at least the ones in AWS g2.2xlarge, cost: $0.65/hour)

Eventually I got ~70% accuracy on the test data, much better than random guess (10%). The time to train the model is ~30 minutes.

You can find my entire code at:

http://www.alivelearn.net/deeplearning/dlnd_image_classification_submission2.html