Fast Bayesian Deep Learning

Over recent years, Deep Learning has been demonstrated to offer impressive performance across a range of application domains. In part, this is because of its ability to exploit modern many-cored processors (e.g., GPUs).

At its heart, Deep Learning makes use of stochastic gradient ascent, an approach that is known to struggle in the context of both local maxima and (the more numerous) saddle-points, degrading performance possible using a fixed dataset. Techniques have been developed that replace the stochastic gradient ascent with numerical Bayesian methods typified by Markov chain Monte Carlo (MCMC). Unfortunately, while such use of MCMC makes it theoretically possible to always find the global maximum, MCMC is so slow that this is hard to achieve in practice. This has restricted the extent to which MCMC has been used in the context of Deep Learning.

Recent work by the University of Liverpool has developed a variant of the Sequential Monte Carlo (SMC) sampler, as a generic alternative to MCMC. SMC samplers appear to offer the same global optimisation capability as MCMC but with substantially reduced computational cost. This comes about, in part, because SMC samplers are inherently parallel, making it possible to exploit, for example, GPUs.
Deep Learning achieves parallelism by distributing the processing across the data. SMC samplers achieve parallelism by distributing the consideration of the many hypotheses that the data could imply to be true. This studentship will begin by investigating the extent to which a combination of Deep Learning and SMC samplers can be parallelised by simultaneously considering parallelism across the data and the hypotheses. The studentship will then go on to undertake research that is only possible as a result of the existence of fast Bayesian Deep Learning (e.g., related to robust outlier detection).

This CDT's focus on using "Future Computing Systems" to move "Towards a Data-driven Future" resonates strongly with two themes of non-academic organisation. In both themes, albeit for slightly different reasons, commodity data science is insufficient and there is a hunger both for the future leaders that this CDT will produce and the high-performance solutions that the students will develop.

The first theme is associated with defence and security. In this context, operational performance is of paramount importance. Government organisations (e.g., Dstl, GCHQ and the NCA) will benefit from our graduates' ability to configure many-core hardware to maximise the ability to extract value from the available data. The CDT's projects and graduates will achieve societal impact by enabling these government organisations to better protect the world's population from threats posed by, for example, international terrorism and organised crime.

There is then a supply chain of industrial organisations that deliver to government organisations (both in the UK and overseas). These industrial organisations (e.g., Cubica, Denbridge Marine, FeatureSpace, Leonardo, MBDA, Ordnance Survey, QinetiQ, RiskAware, Sintela, THALES (Aveillant) and Vision4ce) operate in a globally competitive marketplace where operational performance is a key driver. The skilled graduates that this CDT will provide (and the projects that will comprise the students' PhDs) are critical to these organisations' ability to develop and deliver high-performance products and services. We therefore anticipate economic impact to result from this CDT.

The second theme is associated with high-value and high-volume manufacturing. In these contexts, profit margins are very sensitive to operational costs. For example, a change to the configuration of a production line for an aerosol manufactured by Unilever might "only" cut costs by 1p for each aerosol, but when multiplied by half a billion aerosols each year, the impact on profit can be significant. In this context, industry (e.g., Renishaw, Rolls Royce, Schlumberger, ShopDirect and Unilever) is therefore motivated to optimise operational costs by learning from historic data. This CDT's graduates (and their projects) will help these organisations to perform such data-driven optimisation and thereby enable the CDT to achieve further economic impact.

Other organisations (e.g., IBM) provide hardware, software and advice to those operating in these themes. The CDT's graduates will ensure these organisations can be globally competitive.

The specific organisations mentioned above are the CDT's current partners. These organisations have all agreed to co-fund studentships. That commitment indicates that, in the short term, they are likely to be the focus for the CDT's impact. However, other organisations are likely to benefit in the future. While two (Lockheed Martin and Arup) have articulated their support in letters that are attached to this proposal, we anticipate impact via a larger portfolio of organisations (e.g., via studentships but also via those organisations recruiting the CDT's graduates either immediately after the CDT or later in the students' careers). Those organisations are likely to include those inhabiting the two themes described above, but also others. For example, an entrepreneurial CDT student might identify a niche in another market sector where Distributed Algorithms can deliver substantial commercial or societal gains. Predicting where such niches might be is challenging, though it seems likely that sectors that are yet to fully embrace Data Science while also involving significant turn-over are those that will have the most to gain: we hypothesise that niches might be identified in health and actuarial science, for example.

As well as training the CDT students to be the leaders of tomorrow in Distributed Algorithms, we will also achieve impact by training the CDT's industrial supervisors.