Thursday, March 26, 2015

Speedup Tips for OSX

Go into accessibility settings and turn on "reduce transparency".

Wednesday, March 25, 2015

IFT6266 Week 8

After looking at batch normalization, I really think that the gamma and beta terms are correcting for the bias in the minibatch estimates of mean and variance, but have not confirmed. I am also toying with ideas along the same lines as Julian, except using reinforcement learning to choose the optimal minibatch that gives the largest expected reduction in training or validation error rather than controlling hyperparameters as he is doing. One possible option would be something like CACLA for real valued things, and LSPI for "switches".

Batch normalization (and nesterov momentum) seem to help. After only 11 epochs, an ~50% smaller network is able to reach equivalent validation performance.

Epoch 11
Train Accuracy  0.874000
Valid Accuracy  0.802000
Loss 0.364031

The code for the batch normalization layer is here:
https://github.com/kastnerkyle/ift6266h15/blob/master/normalized_convnet.py#L46

With the same sized network as before, things stay pretty consistently around 80% but begin to massively overfit. The best validation scores, with .95 nesterov momentum are:

Epoch 10
Train Accuracy  0.875050
Valid Accuracy  0.813800
Loss 0.351992

Epoch 36
Train Accuracy  0.967650
Valid Accuracy  0.815800

Epoch 96
Train Accuracy  0.992100
Valid Accuracy  0.822000

I next plan to try batch normalization on fully connected and convolutional VAE. First trying with MNIST, then LFW, then probably cats and dogs. It would be nice to try to either a) mess with batch normalization and do it properly *or* simplify the equations somehow b) do some reinforcement learning like Julian is doing, but on the minibatch selection process. However, time is short!

Thursday, March 12, 2015

IFT6266 Week 7

With a 50% probability of introducing a horizontal flip, the network gets very close to passing the 80% threshold with early stopping.

Epoch 93
Train Accuracy  0.951350
Valid Accuracy  0.794200

With the addition of per pixel mean and standard deviation normalization the network successfully gets over 80% validation accuracy (barely)!

Epoch 74
Train Accuracy  0.878000
Valid Accuracy  0.803800

The working version of the network can be seen here:
https://github.com/kastnerkyle/ift6266h15/blob/master/convnet.py

Note that addition of ZCA did not seem to help in this case!

With these changes, I will move on to implementing other models/ideas. First up, batch normalization, then spatially sparse convolution and possibly fractional maxpooling.

Wednesday, March 11, 2015

IFT6266 Week 6

The network has been working this entire time, there was just bug in my prediction accuracy percentage printing! See this snippet for an example


In [3]: import numpy as np
In [4]: a = np.array([1., 2., 3., 4., 5.])
In [5]: b = np.array([[1.], [2.], [3.], [4.], [5.]])

In [6]: a
Out[6]: array([ 1., 2., 3., 4., 5.])

In [7]: b
Out[7]:
array([[ 1.],
[ 2.],
[ 3.],
[ 4.],
[ 5.]])

In [8]: (a == b).mean()
Out[8]: 0.20000000000000001
The correct way to print these is (a.flatten() == b.flatten()).astype('float32').mean()

For a task with 2 classes, this will always give ~50% accuracy but the number will change slightly due to small changes in the prediction!

It is an obvious bug in hindsight, but it took a long time to find. Now after 100 epochs, the results are as follows:

Epoch 99
Train Accuracy  0.982200
Valid Accuracy  0.751000
Loss 0.021493

The general network architecture is:
Resize all images to 64x64, then crop the center 48x48
No flipping, random subcrops, or anything

32 kernels, 4x4 with 2x2 pooling and 2x2 strides
64 kernels, 2x2 with 2x2 pooling
128 kernels, 2x2 with 2x2 pooling
512x128 fully-connected
128x64 fully connected
64x2 fully connected
All initialized uniformly [-0.1, 0.1] 
ReLU activations at every layer
Softmax cost

I plan to try:
Adding random horizontal flipping
ZCA with 0.1 bias
dropout or batch normalization
PReLU
dark knowledge / knowledge distillation

Monday, March 2, 2015

Install Konsole/gnome-terminal for better Vim experience in OS X

Go to the App Store and install Xcode

Next, go to https://www.macports.org to download and install MacPorts

After this do

For gnome terminal:
sudo port install gnome-terminal 

otherwise
sudo port install konsole

For both apps, you will also need
sudo port install xorg-server

In the Applications file under MacPorts, there should be an X11 app. Launch this before trying to launch either gnome-terminal or console.

Sunday, February 15, 2015

IFT6266 Week 5

The convent has gone no farther this week since massively overfitting, but I had a few interesting discussions with Roland about computationally efficient pooling which should be useful once I solve my current issues.

I also got the convolutional VAE working for MNIST. If I can get a good run for CIFAR10 it might also be useful to slap a one or two layer MLP on the hidden space representation to see if that gets above 80% for cats and dogs. If not it would also be fun to train on the dataset itself, folding in all the data and then finetune for prediction. This is a sidetrack from "the list" but could be fruitful.

Here are some samples from the ConvVAE on MNIST (also a link to the current code here https://gist.github.com/kastnerkyle/f3f67424adda343fef40/9b6bf8c66c112d0ca8eb87babb717930a7d42913 ).


Monday, February 9, 2015

IFT6266 Week 4

I got the convolutional-deconvolutional VAE working as a standalone script now - training it on LFW to see the results. The code can be found here: https://gist.github.com/kastnerkyle/f3f67424adda343fef40

I have also completed coding a convnet in pure theano which heavily overfits the dogs and cats data. See convnet.py here: https://github.com/kastnerkyle/ift6266h15

Current training stats:
Epoch 272
Train Accuracy  0.993350
Valid Accuracy  0.501600
Loss 0.002335

The architecture is:
load in data as color and resize all to 48x48
1000 epochs, batch size 128
SGD with 0.01 learning rate, no momentum

layer 1 - 10 filters, 3x3 kernel, 2x2 max pool, relu
layer 2 - 10 filters, 3x3 kernel, 1x1 max pool, relu
layer 3 - 10 filters, 3x3 kernel, 1x1 max pool, relu
layer 4 - fully connected 3610x100,  relu
layer 5 - softmax

The next step is quite obviously to add dropout. With this much overfitting I am hopeful that this architecture can get me above 80%. Other things to potentially add include ZCA preprocessing, maxout instead of relu, network-in-network, inception layers, and more. Also considering bumping the default image size to 64x64, random subcrops, image flipping, and other preprocessing tricks.

Once above 80%, I want to experiment with some of the "special sauce" from Dr. Ben Graham - fractional max pooling and spatially sparse convolution. His minibatch dropout also seems quite nice!