Mercurial > ift6266
diff writeup/nips2010_submission.tex @ 519:eaa595ea2402
section 3 quickpass
author | Dumitru Erhan <dumitru.erhan@gmail.com> |
---|---|
date | Tue, 01 Jun 2010 11:32:04 -0700 |
parents | 460a4e78c9a4 |
children | 18a6379999fd |
line wrap: on
line diff
--- a/writeup/nips2010_submission.tex Tue Jun 01 11:15:37 2010 -0700 +++ b/writeup/nips2010_submission.tex Tue Jun 01 11:32:04 2010 -0700 @@ -309,7 +309,7 @@ \begin{figure}[h] \resizebox{.99\textwidth}{!}{\includegraphics{images/example_t.png}}\\ \caption{Illustration of the pipeline of stochastic -transformations applied to the image of a lower-case t +transformations applied to the image of a lower-case \emph{t} (the upper left image). Each image in the pipeline (going from left to right, first top line, then bottom line) shows the result of applying one of the modules in the pipeline. The last image @@ -361,11 +361,11 @@ Our main source of characters is the NIST Special Database 19~\citep{Grother-1995}, widely used for training and testing character recognition systems~\citep{Granger+al-2007,Cortes+al-2000,Oliveira+al-2002-short,Milgram+al-2005}. -The dataset is composed with 814255 digits and characters (upper and lower cases), with hand checked classifications, +The dataset is composed of 814255 digits and characters (upper and lower cases), with hand checked classifications, extracted from handwritten sample forms of 3600 writers. The characters are labelled by one of the 62 classes -corresponding to "0"-"9","A"-"Z" and "a"-"z". The dataset contains 8 series of different complexity. -The fourth series, $hsf_4$, experimentally recognized to be the most difficult one is recommended -by NIST as testing set and is used in our work and some previous work~\citep{Granger+al-2007,Cortes+al-2000,Oliveira+al-2002-short,Milgram+al-2005} +corresponding to ``0''-``9'',``A''-``Z'' and ``a''-``z''. The dataset contains 8 parts (partitions) of varying complexity. +The fourth partition, $hsf_4$, experimentally recognized to be the most difficult one is the one recommended +by NIST as a testing set and is used in our work as well as some previous work~\citep{Granger+al-2007,Cortes+al-2000,Oliveira+al-2002-short,Milgram+al-2005} for that purpose. We randomly split the remainder into a training set and a validation set for model selection. The sizes of these data sets are: 651668 for training, 80000 for validation, and 82587 for testing. @@ -373,15 +373,16 @@ Here we use all the classes both in the training and testing phase. This is especially useful to estimate the effect of a multi-task setting. Note that the distribution of the classes in the NIST training and test sets differs -substantially, with relatively many more digits in the test set, and uniform distribution -of letters in the test set, not in the training set (more like the natural distribution -of letters in text). +substantially, with relatively many more digits in the test set, and more uniform distribution +of letters in the test set, compared to the training set (in the latter, the letters are distributed +more like the natural distribution of letters in text). %\item {\bf Fonts.} -In order to have a good variety of sources we downloaded an important number of free fonts from: {\tt http://anonymous.url.net} -%real adress {\tt http://cg.scs.carleton.ca/~luc/freefonts.html} -in addition to Windows 7's, this adds up to a total of $9817$ different fonts that we can choose uniformly. +In order to have a good variety of sources we downloaded an important number of free fonts from: +{\tt http://cg.scs.carleton.ca/~luc/freefonts.html} +% TODO: pointless to anonymize, it's not pointing to our work +Including operating system's (Windows 7) fonts, there is a total of $9817$ different fonts that we can choose uniformly from. The {\tt ttf} file is either used as input of the Captcha generator (see next item) or, by producing a corresponding image, directly as input to our models. @@ -392,8 +393,8 @@ a random character class generator and various kinds of transformations similar to those described in the previous sections. In order to increase the variability of the data generated, many different fonts are used for generating the characters. Transformations (slant, distortions, rotation, translation) are applied to each randomly generated character with a complexity -depending on the value of the complexity parameter provided by the user of the data source. Two levels of complexity are -allowed and can be controlled via an easy to use facade class. +depending on the value of the complexity parameter provided by the user of the data source. +%Two levels of complexity are allowed and can be controlled via an easy to use facade class. %TODO: what's a facade class? %\item {\bf OCR data.} @@ -402,6 +403,7 @@ additional source. This set is part of a larger corpus being collected by the Image Understanding Pattern Recognition Research group lead by Thomas Breuel at University of Kaiserslautern ({\tt http://www.iupr.com}), and which will be publicly released. +%TODO: let's hope that Thomas is not a reviewer! :) Seriously though, maybe we should anonymize this %\end{itemize} \vspace*{-1mm} @@ -444,12 +446,13 @@ (making the use of SVMs computationally inconvenient because of their quadratic scaling behavior). The MLP has a single hidden layer with $\tanh$ activation functions, and softmax (normalized -exponentials) on the output layer for estimating P(class | image). -The hyper-parameters are the following: number of hidden units, taken in -$\{300,500,800,1000,1500\}$. The optimization procedure is as follows. Training -examples are presented in minibatches of size 20. A constant learning +exponentials) on the output layer for estimating$ P(class | image)$. +The number of hidden units is taken in $\{300,500,800,1000,1500\}$. +The optimization procedure is as follows: training +examples are presented in minibatches of size 20, a constant learning rate is chosen in $10^{-3},0.01, 0.025, 0.075, 0.1, 0.5\}$ -through preliminary experiments, and 0.1 was selected. +through preliminary experiments (measuring performance on a validation set), +and $0.1$ was then selected. {\bf Stacked Denoising Auto-Encoders (SDA).} Various auto-encoder variants and Restricted Boltzmann Machines (RBMs) @@ -472,8 +475,8 @@ teach (see tutorial and code there: {\tt http://deeplearning.net/tutorial}), provides immediate and efficient inference, and yielded results comparable or better than RBMs in series of experiments -\citep{VincentPLarochelleH2008}. During training of a Denoising -Auto-Encoder, it is presented with a stochastically corrupted version +\citep{VincentPLarochelleH2008}. During training, a Denoising +Auto-Encoder is presented with a stochastically corrupted version of the input and trained to reconstruct the uncorrupted input, forcing the hidden units to represent the leading regularities in the data. Once it is trained, its hidden units activations can