LTM (Lifelong Topic Model)

LTM is an open-source Java package implementing the algorithm proposed in the paper (Chen and Liu, ICML 2014), created by Zhiyuan (Brett) Chen. For more details, please refer to this paper.

If you use this package, please cite the paper: Zhiyuan Chen and Bing Liu. Topic Modeling using Topics from Many Domains, Lifelong Learning and Big Data. In Proceedings of ICML 2014, pages 703-711.

If you have any question or bug report, please send it to Zhiyuan (Brett) Chen ([email protected]).

Table of Contents

• Quick Start
• Commandline Arguments
• Input and Output
• Efficiency
• Contact Information

## Quick Start

First, Clone the repo: git clone https://github.com/czyuan/LTM.git.

Then, 2 quick start options are available:

1. Import the directory into Eclipse (recommended).

If you get the exception Java.Lang.OutOfMemoryError, please increase the Java heap memory for Eclipse: http://www.mkyong.com/eclipse/eclipse-java-lang-outofmemoryerror-java-heap-space/.

2. Use Maven

a. Then, change the current working directory to Src.

cd LTM/Src

b. Build the package.

mvn clean package

c. Increase the Java heap memory for Maven.

export MAVEN_OPTS=-Xmx1024m

d. Run the program.

mvn exec:java -Dexec.mainClass="launch.MainEntry"

## Commandline Arguments The commandline arguments are stored in the file "global/CmdOption.java". If no argument is provided, the program uses the default arguments. There are several arguments that are subject to change:

1. -i: the path of input domains directory.
2. -o: the path of output model directory.
3. -nthreads: the number of threads used in the program. The program runs in parallel supporting multithreading.
4. -nTopics: the number of topics used in Topic Model for each domain.

## Input and Output ### Input The input directory should contain domain files. For each domain, there should be 2 files (can be opened by text editors):

1. domain.docs: each line (representing a document) contains a list of word ids. Here, a document is a sentence in a review after preprocessing.
2. domain.vocab: mapping from word id (starting from 0) to word, separated by ":".

Output

The output directory contains topic model results for each learning iteration (different from Gibbs sampling iteration, see the paper for details). LearningIteration 0 is always LDA, i.e., without any knowledge. LearningIteration i with i > 0 is the LTM model. The knowledge used for LearningIteration i is extracted from LearningIteration i - 1, except LearningIteration 0 which is LDA.

Under each learning iteration folder and sub-folder "DomainModels", there are a list of domain folders where each domain folder contains topic model results for each domain. Under each domain folder, there are 8 files (can be opened by text editors):

1. domain.docs: each line (representing a document) contains a list of word ids.
2. domain.dtopicdist: topic-word distribution.
3. domain.knowl: record the knowledge (for LTM only).
4. domain.param: parameter settings.
5. domain.tassign: topic assignment for each word in each document.
6. domain.twdist: topic-word distribution
7. domain.twords: top words under each topic. The columns are separated by '\t' where each column corresponds to each topic.
8. domain.vocab: mapping from word id (starting from 0) to word.

## Efficiency The program and parameters are set to achieve the best performance in terms of topic coherence quality, instead of efficiency. There are several ways to improve efficiency (from the simplest to the hardest).

1. Increase the number of threads in the program (specified by -nthreads in file "global/CmdOption.java"). The topic models are execuated in parallel in each domain using multithreading.
2. Reduce the frequency of updating knowledge in Gibbs sampling (i.e., knowledgeUpdatelag in the file "model/ModelParameters.java"). The default setting is 1, meaning the knowledge is updated in each Gibbs sampling iteration. Setting this value to any number from 10 to 50 will greatly reduce the execution time while slightly deteriorating the topic quality.
3. Use a better implementation for Apriori algorithm or use faster frequent itemset algorithm such as FP-growth.

## Contact Information * Author: Zhiyuan (Brett) Chen * Affiliation: University of Illinois at Chicago * Research Area: Text Mining, Machine Learning, Statistical Natural Language Processing, and Data Mining * Email: [email protected] * Homepage: http://www.cs.uic.edu/~zchen/