On Counterexample Guided Quantifier Instantiation for Synthesis in CVC4

We introduce the first program synthesis engine implemented inside an SMT solver. We present an approach that extracts solution functions from unsatisfiability proofs of the negated form of synthesis conjectures. We also discuss novel counterexample-guided techniques for quantifier instantiation that we use to make finding such proofs practically feasible. A particularly important class of specifications are single-invocation properties, for which we present a dedicated algorithm. To support syntax restrictions on generated solutions, our approach can transform a solution found without restrictions into the desired syntactic form. As an alternative, we show how to use evaluation function axioms to embed syntactic restrictions into constraints over algebraic datatypes, and then use an algebraic datatype decision procedure to drive synthesis. Our experimental evaluation on syntax-guided synthesis benchmarks shows that our implementation in the CVC4 SMT solver is competitive with state-of-the-art tools for synthesis

Is there an optimal diet for weight management and metabolic health?

Individuals can lose body weight and improve health status on a wide range of energy (calorie) restricted dietary interventions. In this paper, we have reviewed the effectiveness of the most commonly utilized diets, including low-fat, low-carbohydrate and Mediterranean approaches in addition to commercial slimming programmes, meal replacements and newly-popularized intermittent fasting diets. We also consider the role of artificial sweeteners in weight management. Low-fat diets tend to improve LDL-cholesterol most, whilst lower-carbohydrate diets may preferentially improve triglycerides and HDL-cholesterol, however differences between diets are marginal. Weight loss improves almost all obesity related co-morbidities and metabolic markers, regardless of the macronutrient composition of the diet, but individuals do vary in preferences and ability to adhere to different diets. Optimizing adherence is the most important factor for weight loss success, and this is enhanced by regular professional contact and supportive behavioral change programs. Maintaining weight losses in the long-term remains the biggest challenge, and is undermined by an ‘obesogenic’ environment and biological adaptations that accompany weight loss

Efficient color code decoders in d≥2d\geq 2 dimensions from toric code decoders

We introduce an efficient decoder of the color code in $d\geq 2$ dimensions, the Restriction Decoder, which uses any $d$-dimensional toric code decoder combined with a local lifting procedure to find a recovery operation. We prove that the Restriction Decoder successfully corrects errors in the color code if and only if the corresponding toric code decoding succeeds. We also numerically estimate the Restriction Decoder threshold for the color code in two and three dimensions against the bit-filp and phase-flip noise with perfect syndrome extraction. We report that the 2D color code threshold $p_{\textrm{2D}} \approx 10.2\%$ on the square-octagon lattice is on a par with the toric code threshold on the square lattice.Comment: 28 pages, 8 figure

Collusion in the Indian Tea Industry in the Great Depression : An Analysis of Panel Data

This paper analyzes the effectiveness of the control schemes in the Indian tea industry during the Great Depression, whereby producers attempted to collude by reducing output. Analysis of data from a panel of plantations shows that collusion was effective. We suggest that the system of management of plantations by "managing agents" enhanced the degree of monopoly in the industry, thereby facilitating collusion. The social cohesiveness of expatriate business may have also contributed to the enforcement of collusion.

The Rise in Absenteeism: Disentangling the Impacts of Cohort, Age and Time

We examine the remarkable rise in absenteeism among Norwegian employees since the early 1990's, with particular emphasis on disentangling the roles of cohort, age, and time. Based on a fixed effects model, we show that individual age-adjusted absence propensities have risen even more than aggregate absence rates from 1993 to 2005, debunking the popular hypothesis that the rise in absenteeism resulted from the inclusion of new cohorts – with weaker work-norms – into the workforce. We also reject the idea that the rise in absenteeism resulted from more successful integration of workers with poor health; on the contrary, a massive rise in disability rolls during the 1990’s suggest that poor-health workers have left the labor market in unprecedented numbers.sickness absence, endogenous selection, multicollinearity, fixed effects logit