Use of Graph Networks in Machine Learning

Deep learning has achieved a big success in the past few years, but its interpretive power is limited. They work largely because of the abundance of data. On the other hand, traditional machine learning algorithms are much better in interpretive power, but manual feature engineering costs a lot, due to the lack of data in earlier era. In light of this, a group of scientists initiated the work of graph networks, aiming at devising new artificial intelligence algorithms that exploits the advantages of two worlds, while still holding the principle of combinatorial generalization in constructing methods by using known building blocks to build new methods. Graph is good at interpretation as it is good for relational representation.

The use of graph networks is more than the graph convolutional neural networks (GCN) in the previous two blog entries. (part I and part II) However, to achieve relational inductive biases, an entity (an element with attributes), a relation, (a property between entities) and a rule. (a function that maps entities and relations to other entities and relations) This can be realized using graph, which is a mathematical structure that contains nodes and edges (that connect nodes.) To generalize the use of graph networks in various machine learning and deep learning methods, they reviewed the graph block, which is basically a function, or a mapping, from a graph to another graph, as shown in the algorithm below:

GBBlock

Works of graph networks are not non-existent; the authors listed previous works that can be seen as graph networks, for example:

  • Message-passing neural network (MPNN) (2017);
  • Non-local neural networks (NLNN) (2018).

The use of graph networks, I believe, is the next trend. There have been works regarding the graph-powered machine learning. (see Google AI blog, GraphAware Slideshare) I recently started an open-source project, a Python package called graphflow, to explore various algorithms using graphs, including PageRank, HITS, resistance, and non-linear resistance.

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Quantum Chemistry Simulation on Quantum Computers

Quantum computation was proposed initially partly to simulate the physical universe because of the likeness of the nature and quantum systems. Some experimental simulations of Hawking radiation or Kibble-Zurek mechanisms were carried out in condensed matter systems, but they are simply too expensive to carry out. However, some scientists performed simulations on molecular systems using a quantum computer with an array of superconducting qubits. They performed the electronic structure calculation, as reported in “Scalable Quantum Simulation of Molecular Energies,” published in Physical Review X. Later, Google’s Quantum AI Team, Microsoft’s QuArC Team, and Caltech reports their work on simulating electronic structure using a quantum computer, that reduces running time but increases accuracies. Their work was reported in “Low-Depth Quantum Simulation of Materials,” also published in Physical Review X. The same team, adding a Harvard’s group, further studied the application of these molecular systems lined up as a linear array to design algorithms in quantum computers. It is reported in “Quantum Simulation of Electronic Structure with Linear Depth and Connectivity,” published in Physical Review Letters.

These people published an open-source software package, a Python library, called OpenFermion. It facilitates simulation of quantum algorithms in fermionic systems.

For a completeness, a few years ago, another group of scientists published a Python package, QuTiP, that helps simulating the open quantum systems.

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Short Text Mining using Advanced Keras Layers and Maxent: shorttext 0.4.1

On 07/28/2017, shorttext published its release 0.4.1, with a few important updates. To install it, type the following in the OS X / Linux command line:

>>> pip install -U shorttext

The documentation in PythonHosted.org has been abandoned. It has been migrated to readthedocs.org. (URL: http://shorttext.readthedocs.io/ or http:// shorttext.rtfd.io)

Exploiting the Word-Embedding Layer

This update is mainly due to an important update in gensim, motivated by earlier shorttext‘s effort in integrating scikit-learn and keras. And gensim also provides a keras layer, on the same footing as other neural networks, activation function, or dropout layers, for Word2Vec models. Because shorttext has been making use of keras layers for categorization, such advance in gensim in fact makes it a natural step to add an embedding layer of all neural networks provided in shorttext. How to do it? (See shorttext tutorial for “Deep Neural Networks with Word Embedding.”)

import shorttext
wvmodel = shorttext.utils.load_word2vec_model('/path/to/GoogleNews-vectors-negative300.bin.gz')   # load the pre-trained Word2Vec model
trainclassdict = shorttext.data.subjectkeywords()   # load an example data set

 

To train a model, you can do it the old way, or do it the new way with additional gensim function:

kmodel = shorttext.classifiers.frameworks.CNNWordEmbed(wvmodel=wvmodel, nb_labels=len(trainclassdict.keys()), vecsize=100, with_gensim=True)   # keras model, setting with_gensim=True
classifier = shorttext.classifiers.VarNNEmbeddedVecClassifier(wvmodel, with_gensim=True, vecsize=100)   # instantiate the classifier, setting with_gensim=True
classifier.train(trainclassdict, kmodel)

The parameters with_gensim in both CNNWordEmbed and VarNNEmbeddedVecClassifier are set to be False by default, because of backward compatibility. However, setting it to be True will enable it to use the new gensim Word2Vec layer.

These change in gensim and shorttext are the works mainly contributed by Chinmaya Pancholi, a very bright student at Indian Institute of Technology, Kharagpur, and a GSoC (Google Summer of Code) student in 2017. He revolutionized gensim by integrating scikit-learn and keras into gensim. He also used what he did in gensim to improve the pipelines of shorttext. He provided valuable technical suggestions. You can read his GSoC proposal, and his blog posts in RaRe Technologies, Inc. Chinmaya has been diligently mentored by Ivan Menshikh and Lev Konstantinovskiy of RaRe Technologies.

Maxent Classifier

Another important update is the adding of maximum entropy (maxent) classifier. (See the corresponding tutorial on “Maximum Entropy (MaxEnt) Classifier.”) I will devote a separate entry on the theory, but it is very easy to use it,

import shorttext
from shorttext.classifiers import MaxEntClassifier

classifier = MaxEntClassifier()

Use the NIHReports dataset as the example:

classdict = shorttext.data.nihreports()
classifier.train(classdict, nb_epochs=1000)

The classification is just like other classifiers provided by shorttext:

classifier.score('cancer immunology') # NCI tops the score
classifier.score('children health') # NIAID tops the score
classifier.score('Alzheimer disease and aging') # NIAID tops the score

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SOCcer: Computerized Coding In Epidemiology

There are many tasks that involve coding, for example, putting kids into groups according to their age, labeling the webpages about their kinds, or putting students in Hogwarts into four colleges… And researchers or lawyers need to code people, according to their filled-in information, into occupations. Melissa Friesen, an investigator in Division of Cancer Epidemiology and Genetics (DCEG), National Cancer Institute (NCI), National Institutes of Health (NIH), saw the need of large-scale coding. Many researchers are dealing with big data concerning epidemiology. She led a research project, in collaboration with Office of Intramural Research (OIR), Center for Information Technology (CIT), National Institutes of Health (NIH), to develop an artificial intelligence system to cope with the problem. This leads to a publicly available tool called SOCcer, an acronym for “Standardized Occupation Coding for Computer-assisted Epidemiological Research.” (URL: http://soccer.nci.nih.gov/soccer/)

The system was initially developed in an attempt to find the correlation between the onset of cancers and other diseases and the occupation. “The application is not intended to replace expert coders, but rather to prioritize which job descriptions would benefit most from expert review,” said Friesen in an interview. She mainly works with Daniel Russ in CIT.

SOCcer takes job title, industry codes (in terms of SIC, Standard Industrial Classification), and job duties, and gives an occupational code called SOC 2010 (Standard Occupational Classification), used by U. S. federal government agencies. The data involves short text, often messy. There are 840 codes in SOC 2010 systems. Conventional natural language processing (NLP) methods may not apply. Friesen, Russ, and Kwan-Yuet (Stephen) Ho (also in OIR, CIT; a CSRA staff) use fuzzy logic, and maximum entropy (maxent) methods, with some feature engineering, to build various classifiers. These classifiers are aggregated together, as in stacked generalization (see my previous entry), using logistic regression, to give a final score.

SOCcer has a companion software, called SOCAssign, for expert coders to prioritize the codings. It was awarded with DCEG Informatics Tool Challenge 2015. SOCcer itself was awarded in 2016. And the SOCcer team was awarded for Scientific Award of Merit by CIT/OCIO in 2016 as well (see this). Their work was published in Occup. Environ. Med.

soccer

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