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Online Sparse Dictionary Learning Algorithm
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README.md

OSDL

Online Sparse Dictionary Learning Algorithm

This is the Matlab Package for the Online Sparse Dictionary Learning (OSDL) algorithm, presented in: J. Sulam, B. Ophir, M. Zibulevsky and M. Elad, "Trainlets: Dictionary Learning in High Dimensions," in IEEE Transactions on Signal Processing, vol. 64, no. 12, pp. 3180-3193, June15, 2016.

Version 1.1

INSTALLATION:

  • The OSDL requieres to have the OMP-BOX and the OMPS-BOX installed, which can be freely downloaded from http://www.cs.technion.ac.il/~ronrubin/software.html
  • Once these packages have their corresponding mex files compiled (check their instructions for further details), make sure they are added in the matlab path.

USAGE: The main function is OSDL.m, which performs dictionary learning on the indictaded training data and outputs a sparse dictionary (refer to the referenced paper for more details). OSDL has two basic modes of operation, in terms of the training data:

  1. If all training data can be stored in memory, it can be provided through the parameter Ytrain. Other details (such as mini-batch size, etc) can also be specified.
  2. If the training data cannot be stored in memory, OSDL can receive a directory to where there training data is stored. In this case, the data should be saved in a directory in separate .mat files. Each .mat file corresponds to a mini-batch. The name of the variable (with the training data in matrix form) in the files should be specified through the parameters dataname. For example, data could be stored in a 'Data/' directory in minibatches Data1.mat, Data2.mat, ... DataN.mat. Each file would contain a matrix variable called DataMiniBatch, containing the training samples for that mini-batch ordered columnwise.

A demo Script is provided to show the basic usage of OSDL.


UPDATES FROM V.1.0:

  • Subspace Pursuit (SP) included as an alternative pursuit option. This provides a faster and lighter alternative to OMP which which does not scale as well for high dimensional signals (dimension of 10,000+). Unlike OMP, the number of iterations of SP can be much smaller than the target sparsity, and this implementaion does not require to store in memory the Gram matrix, which can be prohibitely large in such cases. This enables efficient parallelization of the pursuit as well.

  • This version, unlike the previous one, does not require the MatrixMult package (thanks to Grisha Varksman).

  • Another external regularization option was added. In the previous version, one could select how many times per epoch the dictionary to be cleaned from unused or repeated atoms. Now it is possible to use an alternative method: selecting a random subset of atoms (given by the parameter DropAtoms between 0 and 1) for the first StopDropOut epochs.


All comments are welcomed at jsulam@cs.technion.ac.il

Jeremias Sulam Computer Science Department - Technion March, 2016.

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