Transfer Learning to overcome catastrophic forgetting

In machine learning deep convolutional networks (deep learning) are very successful for solving particular problems [1] – at least when having many training samples. Great success has been made recently, e.g. in automatic game playing by AlphaGo (see the nature news here).  As fantastic these approaches are, it should be mentioned that deep learning has still serious limitations: they are black-box approaches, where it is currently difficult to explain how and why a result was achieved – see our recent work on glass-box approach [2], consequently lacking transparency and trust – issues which will become increasingly important in our data-centric world; they are demanding huge computational resources, and need enormous amounts of training data (often thousands, sometimes even millions of training samples) and standard approaches are poor at representing uncertainties which calls for Bayesian deep learning approaches [3]. Most of all, deep learning approaches are affected by an effect we call “catastrophic forgetting”.

What is catastrophic forgetting? One of the critical steps towards general artificial intelligence (human-level AI) is the ability to continually learn – similarly as we humans do: ongoing and continuous being capable of learning a new task B without forgetting how to perform an old task A. This seemingly trivial characteristic is not trivial for machine learning generally and deep learning specifically: McCloskey & Cohen already in 1989 [4] showed that neural networks have difficulties with this kind of transfer learning and coined the term catastrophic forgetting – and transfer learning is one attempt to overcoming it. Transfer learning is the ability to learn tasks permanently. Humans can do that very good – even very little children (refer to the work of Alison Gopnik, e.g. [5],  and at the bottom of this post). The synaptic consolidation in human brains may enable continual learning by reducing the plasticity of synapses that are vital to previously learned tasks ([6] and see a recent work on intelligent synapses for multi-task and transfer learning [7]). Based on these ideas the Google Deepmind Group around Demis Hassabis implemented a cool algorithm that performs a similar operation in artificial neural networks by constraining important parameters to stay close to their old values in their work on overcoming catastrophic forgetting in neural networks  (arXiv:1612.00796), [8]. As we know, a deep neural network consists of multiple layers of linear projections followed by element-wise non-linearities. Learning a task consists basically of adjusting the set of weights and biases θ of the linear projections, consequently, many configurations of θ will result in the same performance which is relevant for the so-called elastic weight consolidation (EWC): over-parametrization makes it likely that there is a solution for task B, θ ∗ B , that is close to the previously found solution for task A, θ ∗ A . While learning task B, EWC therefore protects the performance in task A by constraining the parameters to stay in a region of low error for task A centered around θ ∗ A. This constraint has been implemented as a quadratic penalty, and can therefore be imagined as a mechanical spring anchoring the parameters to the previous solution, hence the name elastic. In order to justify this choice of constraint and to define which weights are most important for a task, it is useful to consider neural network training from a probabilistic perspective. From this point of view, optimizing the parameters is tantamount to finding their most probable values given some data D. Interestingly, this can be computed as conditional probability p(θ|D) from the prior probability of the parameters p(θ) and the probability of the data p(D|θ) by: log p(θ|D) = log p(D|θ) + log p(θ) − log p(D).

Here exists and constantly emerge a lot of open and important research avenues which challenge the international machine learning community (see e.g. [9]).  The most interesting is what we don’t know yet – and the breaktrough machine learning approaches have not yet invented.

Andrew Y. Ng at the last NIPS 2016 conferene in Barcelona hold a tutorial where he emphasized the importance of transfer learning research and that “transfer learning will be the next driver of machine learning success” …
There is a wonderful post by Sebastian Ruder, see: http://knowledgeofficer.com/knowledge/46-transfer-learning-machine-learning-s-next-frontier

[1]          Yann Lecun, Yoshua Bengio & Geoffrey Hinton 2015. Deep learning. Nature, 521, (7553), 436-444, doi:10.1038/nature14539.

[2]          Andreas Holzinger, Markus Plass, Katharina Holzinger, Gloria Cerasela Crisan, Camelia-M. Pintea & Vasile Palade 2017. A glass-box interactive machine learning approach for solving NP-hard problems with the human-in-the-loop. arXiv:1708.01104.

[3]          Alex Kendall & Yarin Gal 2017. What Uncertainties Do We Need in Bayesian Deep Learning for Computer Vision? arXiv:1703.04977.

[4]          Michael Mccloskey & Neal J Cohen 1989. Catastrophic interference in connectionist networks: The sequential learning problem. In: Bower, G. H. (ed.) The Psychology of Learning and Motivation, Volume 24. San Diego (CA): Academic Press, pp. 109-164.

[5]          Alison Gopnik, Clark Glymour, David M Sobel, Laura E Schulz, Tamar Kushnir & David Danks 2004. A theory of causal learning in children: causal maps and Bayes nets. Psychological review, 111, (1), 3.

[6]          Stefano Fusi, Patrick J Drew & Larry F Abbott 2005. Cascade models of synaptically stored memories. Neuron, 45, (4), 599-611.

[7]          Friedemann Zenke, Ben Poole & Surya Ganguli. Continual Learning Through Synaptic Intelligence.  International Conference on Machine Learning, 2017. 3987-3995.

[8]          James Kirkpatrick, Razvan Pascanu, Neil Rabinowitz, Joel Veness, Guillaume Desjardins, Andrei A. Rusu, Kieran Milan, John Quan, Tiago Ramalho, Agnieszka Grabska-Barwinska, Demis Hassabis, Claudia Clopath, Dharshan Kumaran & Raia Hadsell 2017. Overcoming catastrophic forgetting in neural networks. Proceedings of the National Academy of Sciences, 114, (13), 3521-3526, doi:10.1073/pnas.1611835114.

[9]          Ian J Goodfellow, Mehdi Mirza, Da Xiao, Aaron Courville & Yoshua Bengio 2015. An empirical investigation of catastrophic forgeting in gradient-based neural networks. arXiv:1312.6211v3.

 

 

Machine learning researchers should watch the videos by Alison Gopnik, e.g.:

Federated Collaborative Machine Learning

The Google Research Group [1] is always doing awesome stuff, the most recent one is on Federated Learning [2], which enables e.g. smart phones (of course any computational device, and maybe later all internet-of-things, intelligent sensors in either smart hospitals or in smart factories etc.) to collaboratively learn a shared representation model, whilst keeping all the training data on the local devices, decoupling the ability to do machine learning from the need to store the data centralized in the cloud. This goes beyond the use of local models that make predictions on mobile devices (like the Mobile Vision API and On-Device Smart Reply) by bringing model training to the device as well – which is great. The problem with standard approaches is that you always need centralized training data – either on your USB-stick, as the medical doctors do, or in a sophisticated centralized data center.

The basic idea is that the mobile device downloads the current modela and subsequently improves it by learning from data on the respective device, and then summarizes the changes as a small focused update. The remarkable detail is that only this update to the model is sent to the cloud (yes, here privacy, data protection safety and security is challenged see e.g. [3] – but this is much easier to do with this small data – as when you would do it with the raw data – think for example on patient data), where it is immediately averaged with other devicer updates to improve the shared model. All the training data remains on the local devices, and no individual updates are stored in the cloud.

The Google Group recently solved a lot of algorithmic and technical challenges. In a typical machine learning system, an optimization algorithm e.g. Stochastic Gradient Descent (SGD) [4] runs on a large dataset partitioned homogeneously across servers in the cloud. Such highly iterative algorithms require low-latency, high-throughput connections to the training data. But in the Federated Learning setting, the data is distributed across millions of devices in a highly uneven fashion. In addition, these devices have significantly higher-latency, lower-throughput connections and are only intermittently available for training.

This calls for a lot of further investigations with interactive Machine Learning (iML) bringing the human-into-the loop, i.e. making use of human cognitive abilities. This can be of particular interest to solve problems, where learning algorithms suffer due to insufficient training samples (rare events, single events), where we deal with complex data and/or computationally hard problems. For example, “doctors-in-the-loop” can help with their long-term experience and heursitic knowledge to solve problems which otherwise would remain NP-hard [5, 6]. A further step is with many humans-in-the-loop: Such collaborative interactive Machine Learning (ciML) can help in many application areas and domains, e.g. in in health informatics (smart hospital) or in industrial applications (smart factory) [7].

Read the original article, posted on April, 6, 2017,  here:
https://research.googleblog.com/2017/04/federated-learning-collaborative.html

[1] https://research.googleblog.com

[2] NIPS Workshop on Private Multi-Party Machine Learning, Barcelona, December, 9, 2016, https://pmpml.github.io/PMPML16/

[3] Bonawitz, K., Ivanov, V., Kreuter, B., Marcedone, A., Mcmahan, H. B., Patel, S., Ramage, D., Segal, A. & Seth, K. 2016. Practical Secure Aggregation for Federated Learning on User-Held Data. arXiv preprint arXiv:1611.04482.

[4] Bottou, L. 2010. Large-scale machine learning with stochastic gradient descent. Proceedings of COMPSTAT’2010. Springer, pp. 177-186. doi:10.1007/978-3-7908-2604-3_16  (N.B.: 836 citations as of 08.04.2017)

[5] Holzinger, A. 2016. Interactive Machine Learning for Health Informatics: When do we need the human-in-the-loop? Brain Informatics, 3, (2), 119-131, doi:10.1007/s40708-016-0042-6

[6] Holzinger, A., Plass, M., Holzinger, K., Crisan, G., Pintea, C. & Palade, V. 2016. Towards interactive Machine Learning (iML): Applying Ant Colony Algorithms to solve the Traveling Salesman Problem with the Human-in-the-Loop approach. In: Springer Lecture Notes in Computer Science LNCS 9817. Heidelberg, Berlin, New York: Springer, pp. 81-95, [pdf]

[7] Robert, S., Büttner, S., Röcker, C. & Holzinger, A. 2016. Reasoning Under Uncertainty: Towards Collaborative Interactive Machine Learning. In: Machine Learning for Health Informatics: Lecture Notes in Artifical Intelligence LNAI 9605. Springer, pp. 357-376, [pdf]

Image source: https://research.googleblog.com/2017/04/federated-learning-collaborative.html

 

3,2 Trillion USD on health per year

The U.S. spends more on health care than any other country

Dieleman et al. (2016) just (Dec, 27, 2016) published a paper [1] which discusses data from the National Health Expenditure Accounts to estimate US spending on personal health care and public health, according to condition, age and sex group, and type of care. This paper was mentioned in the Washington Post by Carolyn Y. Johnson on December 27 at 11:00 AM

Here a link to the original paper:

[1] Dieleman JL, Baral R, Birger M, Bui AL, Bulchis A, Chapin A, Hamavid H, Horst C, Johnson EK, Joseph J, Lavado R, Lomsadze L, Reynolds A, Squires E, Campbell M, DeCenso B, Dicker D, Flaxman AD, Gabert R, Highfill T, Naghavi M, Nightingale N, Templin T, Tobias MI, Vos T, Murray CJL. US Spending on Personal Health Care and Public Health, 1996-2013. JAMA. 2016;316(24):2627-2646. doi:10.1001/jama.2016.16885

Here the article (shortened) from the Washington Post:

American health-care spending, measured in trillions of dollars, boggles the mind. Last year, we spent $3.2 trillion on health care  a number so large that it can be difficult to grasp its scale.

A new study published in the Journal of the American Medical Association reveals what patients and their insurers are spending that money on, breaking it down by 155 diseases, patient age and category — such as pharmaceuticals or hospitalizations. Among its findings:

  • Chronic — and often preventable — diseases are a huge driver of personal health spending. The three most expensive diseases in 2013: diabetes ($101 billion), the most common form of heart disease ($88 billion) and back and neck pain ($88 billion).
  • Yearly spending increases aren’t uniform: Over a nearly two-decade period, diabetes and low back and neck pain grew at more than 6 percent per year — much faster than overall spending. Meanwhile, heart disease spending grew at 0.2 percent.
  • Medical spending increases with age — with the exception of newborns. About 38 percent of personal health spending in 2013 was for people over age 65. Annual spending for girls between 1 and 4 years old averaged $2,000 per person; older women 70 to 74 years old averaged $16,000.

Here the link to the original article:
https://www.washingtonpost.com/news/wonk/wp/2016/12/27/the-u-s-spends-more-on-health-care-than-any-other-country-heres-what-were-buying/?tid=pm_business_pop&utm_term=.71fc517cdc11

machine learning for health informatics

LNAI 9605 Machine Learning for Health Informatics available

NEW – just appeared – NEW

Holzinger, A. (ed.) 2016. Machine Learning for Health Informatics: State-of-the-Art and Future Challenges. Cham: Springer International Publishing, doi:10.1007/978-3-319-50478-0

[book homepage]

Machine learning (ML) is the fastest growing field in computer science, and Health Informatics (HI) is amongst the greatest application challenges, providing future benefits in improved medical diagnoses, disease analyses, and pharmaceutical development. However, successful ML for HI needs a concerted effort, fostering integrative research between experts ranging from diverse disciplines from data science to visualization.

Tackling complex challenges needs both disciplinary excellence and cross-disciplinary networking without any boundaries. Following the HCI-KDD approach, in combining the best of two worlds, it is aimed to support human intelligence with machine intelligence.

This state-of-the-art survey is an output of the international HCI-KDD expert network and features 22 carefully selected and peer-reviewed chapters on hot topics in machine learning for health informatics; they discuss open problems and future challenges in order to stimulate further research and international progress in this field.

Machine Learning with Fun

Google Research hosts a number of very interesting so-called A.I. experiments, which let you play with machine learning algorithms in a very amusing way, e.g. Quick Draw, where a neural network learns to recognize hand drawn sketches (called doodles), see:

https://quickdraw.withgoogle.com

which is part of the A.I. Experiments platform:

https://aiexperiments.withgoogle.com

and here the explanatory video:
https://www.youtube.com/watch?v=oOwfiYnRi5c

 

Visualization of High Dimensional Data

Google is doing experiments with visualization of high dimenisonal data. This experiment helps visualize what’s happening in machine learning. It allows coders to see and explore their high-dimensional data. The goal is to eventually make this an open-source tool within TensorFlow, so that any coder can use these visualization techniques to explore their data.
Built by Daniel Smilkov, Fernanda Viégas, Martin Wattenberg, and the Big Picture team at Google:
This work is based on a method developed by Laurens van der Maaten & Geoffrey Hinton in 2008:
Maaten, L. V. D. & Hinton, G. 2008. Visualizing data using t-SNE. Journal of Machine Learning Research, 9, 11, 2579-2605, http://www.jmlr.org/papers/v9/vandermaaten08a.html
t-Distributed Stochastic Neighbor Embedding (t-SNE, spoken: Disney) is a (prize-winning) nonlinear technique for dimensionality reduction that is particularly well suited for the visualization of high-dimensional data sets into R2 or R3. The technique can be implemented via Barnes-Hut approximations, allowing it to be applied on large real-world datasets (“big data”).
For details please refer directly to:
Compare this method to our own work on subspace clustering:

Obama on humans-in-the-loop

How artificial intelligence will affect jobs

In an discussion on how artificial intelligence will affect jobs, by President Barack OBAMA, the Wired Editor Scott DADICH, and MIT Media Lab Director Joi ITO,  the president demonstrates good understanding of the field and indicates the importance of the humans-in-the-loop, despite all progress of fully automatic approaches.

 

Wired is a monthly tech magazine which reports since 1993 on how emerging technologies may affect culture, politics, economics. Very interesting to note is that Wired is known for coning the popular terms “long tail” and “crowdsourcing”.

More information see:

https://www.wired.com

 

 

 

 

Google releases their Syntactic Parser Open Source

Google researchers spend a lot of time thinking about how computer systems can read and understand human language in order to process it in intelligent ways. On May, 12, 2016 Slav Petrov (expertise) based in New York and leading the machine learning for natural language group (Slav Petrov Page), announced that they released SyntaxNet as an open-source neural network framework implemented in TensorFlow that provides a new foundation for Natural Language Understanding (NLU) . The release includes all code needed to train new SyntaxNet models on own data, as well as Parsey McParseface, an English parser that the Googlers have trained and that can be used to analyze English text. Parsey McParseface is built on powerful machine learning algorithms that learn to analyze the linguistic structure of language, and that can explain the functional role of each word in a given sentence.

Read more:
http://googleresearch.blogspot.co.at/2016/05/announcing-syntaxnet-worlds-most.html

Literature:

Andor, D., Alberti, C., Weiss, D., Severyn, A., Presta, A., Ganchev, K., Petrov, S. & Collins, M. 2016. Globally normalized transition-based neural networks. arXiv preprint arXiv:1603.06042.

Petrov, S., Mcdonald, R. & Hall, K. 2016. Multi-source transfer of delexicalized dependency parsers. US Patent 9,305,544.

Weiss, D., Alberti, C., Collins, M. & Petrov, S. 2015. Structured Training for Neural Network Transition-Based Parsing. arXiv:1506.06158.

Vinyals, O., Kaiser, Ł., Koo, T., Petrov, S., Sutskever, I. & Hinton, G. Grammar as a foreign language. Advances in Neural Information Processing Systems, 2015. 2755-2763.

Human-in-the-Loop

Interactive machine learning for health informatics: when do we need the human-in-the-loop?

Machine learning (ML) is the fastest growing field in computer science, and health informatics is among the greatest challenges. The goal of ML is to develop algorithms which can learn and improve over time and can be used for predictions. Most ML researchers concentrate on automatic machine learning (aML), where great advances have been made, for example, in speech recognition, recommender systems, or autonomous vehicles. Automatic approaches greatly benefit from big data with many training sets. However, in the health domain, sometimes we are confronted with a small number of data sets or rare events, where aML-approaches suffer of insufficient training samples. Here interactive machine learning (iML) may be of help, having its roots in reinforcement learning, preference learning, and active learning. The term iML is not yet well used, so we define it as “algorithms that can interact with agents and can optimize their learning behavior through these interactions, where the agents can also be human.” This “human-in-the-loop” can be beneficial in solving computationally hard problems, e.g., subspace clustering, protein folding, or k-anonymization of health data, where human expertise can help to reduce an exponential search space through heuristic selection of samples. Therefore, what would otherwise be an NP-hard problem, reduces greatly in complexity through the input and the assistance of a human agent involved in the learning phase.

We define iML-approaches as algorithms that can interact with both computational agents and human agents *) and can optimize their learning behavior through these interactions.

*) In active learning such agents are referred to as the so-called “oracles”

From black-box to glass-box: where is the human-in-the-loop?

The first question we have to answer is: “What is the difference between the iML-approach to the aML-approach, i.e., unsupervised learning, supervised, or semi-supervised learning?”

Scenario D – see slide below – shows the iML-approach, where the human expert is seen as an agent directly involved in the actual learning phase, step-by-step influencing measures such as distance, cost functions, etc.

Obvious concerns may emerge immediately and one can argue: what about the robustness of this approach, the subjectivity, the transfer of the (human) agents; many questions remain open and are subject for future research, particularly in evaluation, replicability, robustness, etc.

Human-in-the-loop - Interactive Machine Learning

The iML-approach

Read full article here:
https://link.springer.com/article/10.1007/s40708-016-0042-6/fulltext.html
https://www.mendeley.com/catalog/interactive-machine-learning-health-informatics-we-need-humanintheloop

Yahoo Labs released largest-ever annonymized machine learning data set for researchers

In January 2016, Yahoo announce the public release of the largest-ever machine learning data set to the international research community. The data set stands at a massive ~110B events (13.5TB uncompressed) of anonymized user-news item interaction data, collected by recording the user-news item interactions of about 20M users from February 2015 to May 2015.

see: http://yahoolabs.tumblr.com/post/137281912191/yahoo-releases-the-largest-ever-machine-learning