Constructive approaches to Program Induction

Search is a key technique in artificial intelligence, machine learning and Program Induction. No matter how efficient a search procedure, there exist spaces that are too large to search effectively and they include the search space of programs. In this dissertation we show that in the context of logic-program induction (Inductive Logic Programming, or ILP) it is not necessary to search for a correct program, because if one exists, there also exists a unique object that is the most general correct program, and that can be constructed directly, without a search, in polynomial time and from a polynomial number of examples. The existence of this unique object, that we term the Top Program because of its maximal generality, does not so much solve the problem of searching a large program search space, as it completely sidesteps it, thus improving the efficiency of the learning task by orders of magnitude commensurate with the complexity of a program space search. The existence of a unique Top Program and the ability to construct it given finite resources relies on the imposition, on the language of hypotheses, from which programs are constructed, of a strong inductive bias with relevance to the learning task. In common practice, in machine learning, Program Induction and ILP, such relevant inductive bias is selected, or created, manually, by the human user of a learning system, with intuition or knowledge of the problem domain, and in the form of various kinds of program templates. In this dissertation we show that by abandoning the reliance on such extra-logical devices as program templates, and instead defining inductive bias exclusively as First- and Higher-Order Logic formulae, it is possible to learn inductive bias itself from examples, automatically, and efficiently, by Higher-Order Top Program construction. In Chapter 4 we describe the Top Program in the context of the Meta-Interpretive Learning approach to ILP (MIL) and describe an algorithm for its construction, the Top Program Construction algorithm (TPC). We prove the efficiency and accuracy of TPC and describe its implementation in a new MIL system called Louise. We support theoretical results with experiments comparing Louise to the state-of-the-art, search-based MIL system, Metagol, and find that Louise improves Metagol’s efficiency and accuracy. In Chapter 5 we re-frame MIL as specialisation of metarules, Second-Order clauses used as inductive bias in MIL, and prove that problem-specific metarules can be derived by specialisation of maximally general metarules, by MIL. We describe a sub-system of Louise, called TOIL, that learns new metarules by MIL and demonstrate empirically that the metarules learned by TOIL match those selected manually, while maintaining the accuracy and efficiency of learning. iOpen Acces

Louise: A Meta-Interpretive Learner for Efficient Multi-clause Learning of Large Programs

We present Louise, a new Meta-Interpretive Learner that performs efficient multi-clause learning, implemented in Prolog. Louise is efficient enough to learn programs that are too large to be learned with the current state-of-the-art MIL system, Metagol. Louise learns by first constructing the most general program in the hypothesis space of a MIL problem and then reducing this "Top program" by Plotkin's program reduction algorithm. In this extended abstract we describe Louise's learning approach and experimentally demonstrate that Louise can learn programs that are too large to be learned by our implementation of Metagol, Thelma

Excellent treatment outcomes in children treated for tuberculosis under routine operational conditions in Cape Town, South Africa

Background Tuberculosis (TB) remains a leading cause of death in children globally. While recognised that HIV infection increases the risk of developing TB, our understanding of the impact of HIV on risk of mortality for children treated for TB is limited. We aimed to identify predictors of mortality in children treated for drug- susceptible TB. Methods A retrospective analysis of all children (<15 years) routinely treated between 2005 and 2012 for drug-susceptible TB in Cape Town was conducted using the programmatic electronic TB treatment database. Survival analysis using cox regression was used to estimate hazard ratios for death. Logistic regression was used to estimate the odds of unfavourable outcomes. Results Of 29,519 children treated for and notified with TB over the study period, <1% died during TB treatment and 89.5% were cured or completed treatment. The proportion of children with known HIV status increased from 13% in 2005 to 95% in 2012. Children under 2 years had an increased hazard of death (aHR: 3.13; 95%CI:1.78 5.52) and greater odds of unfavourable outcome (aOR: 1.44; 95%CI:1.24-1.66) compared to children 10-15 years. HIVpositive children had increased mortality compared to HIV-negative children (aHR: 6.85; 95%CI:4.60-10.19) and increased odds of unfavourable outcome (aOR: 2.01; 95%CI:1.81-2.23). Later year of TB treatment was a protective predictor for both mortality and unfavourable outcome

Baja SAE Semi-Active Suspension

This Final Design Review (FDR) Report outlines the senior design project of the Baja SAE Semi-Active Suspension group, which includes mechanical and electrical engineering students at California Polytechnic State University San Luis Obispo. This document compiles the Baja SAE Semi-Active Suspension senior project team’s research and development of a semi-active suspension system for the Cal Poly Racing Baja SAE racecar. The goal is to design a system that adjusts the damping constant of the racecar’s spring-damper suspension while the vehicle is being driven in order to improve vehicle dynamics and driver comfort. None of the semi-active dampers that exist on the market were built for a Baja SAE-type application. Initial technical and existing product research found that magnetorheological fluid, electrorheological fluid, and mechanical valving are the main three ways to vary damping rate in a given damper. Interviews with industry professionals and controlled convergence analysis of these damping adjustment methods lead the team to develop a concept design that focuses on adjusting high-speed compression damping using a mechanical actuator which is controlled by an electronic control loop. Further research and exposure to the off-road suspension industry encouraged the team to narrow the focus of the project to utilize an existing valve actuator and develop the control algorithm to retrofit the valve for the Baja application. The team’s scope focused on developing an electronic interface and test bench setup to test the first iteration of the semi-active damper off-car. The team’s results and recommendations for future projects are detailed in the results and conclusion sections respectively, and they serve as a starting point for the next senior project group that will continue the project’s development for on-car applications

Preliminary results of carbon degassing in the tectonically active areas of Balkan Peninsula

The deeply derived CO2 from tectonically active areas is contributing in a significant proportion, still unquantified in detail, to CO2 Earth degassing. Several studies highlighted how in these tectonically active areas most of the CO2 is dissolved in the groundwaters circulating in the large regional aquifers hosted by the permeable formations of the active orogens. Quantifying the amount of deep CO2 dissolved into groundwater can represent a powerful tool for regional investigations, because springs are representative of their catchment area that can extend from tens to hundreds of square kilometers. In the framework of a Deep Carbon Observatory supported project, we investigated for the first time, the geogenic carbon emission from the Balkan Peninsula (southeastern Europe). This area is known for its high carbon Earth degassing (both CO2 and CH4), but lacks the necessary data for quantification and for determining the origin of carbon (especially for what regards the isotopic composition of dissolved carbon). We investigated thermal manifestations (thermal springs and drillings), CO2 emission (including dry and wet moffetas), thermal wells containing CH4 and karst springs from tectonically active areas. During the field investigation, we visited Romania (Mangalia and Tyulenevo coastal area (Romania and Bulgaria), Apuseni Mountains, Ciuc Basin and Herculane Graben), Slovenia, Central Serbia, Macedonia and Croatia visiting and collecting more than 350 sites. Water samples were collected for water chemistry, water stable isotopes, carbon13 from TDIC, dissolved H2S, dissolved gas composition, carbon13 from CO2 and CH4 from dissolved gases, and for dissolved noble gases (He, Ne, Ar). For those sites were also free gas was present, the team collected free gas samples for compositional, isotopic and noble gas analyses. The availability of this data is the first attempt in quantifying the carbon flux with real data from this tectonically active area