NPEFix: Automatic Runtime Repair of Null Pointer Exceptions in Java

Null pointer exceptions, also known as null dereferences are the number one exceptions in the field. In this paper, we propose 9 alternative execution semantics when a null pointer exception is about to happen. We implement those alternative execution strategies using code transformation in a tool called NPEfix. We evaluate our prototype implementation on 11 field null dereference bugs and 519 seeded failures and show that NPEfix is able to repair at runtime 10/11 and 318/519 failures

Causal Repair of Learning-enabled Cyber-physical Systems

Models of actual causality leverage domain knowledge to generate convincing diagnoses of events that caused an outcome. It is promising to apply these models to diagnose and repair run-time property violations in cyber-physical systems (CPS) with learning-enabled components (LEC). However, given the high diversity and complexity of LECs, it is challenging to encode domain knowledge (e.g., the CPS dynamics) in a scalable actual causality model that could generate useful repair suggestions. In this paper, we focus causal diagnosis on the input/output behaviors of LECs. Specifically, we aim to identify which subset of I/O behaviors of the LEC is an actual cause for a property violation. An important by-product is a counterfactual version of the LEC that repairs the run-time property by fixing the identified problematic behaviors. Based on this insights, we design a two-step diagnostic pipeline: (1) construct and Halpern-Pearl causality model that reflects the dependency of property outcome on the component's I/O behaviors, and (2) perform a search for an actual cause and corresponding repair on the model. We prove that our pipeline has the following guarantee: if an actual cause is found, the system is guaranteed to be repaired; otherwise, we have high probabilistic confidence that the LEC under analysis did not cause the property violation. We demonstrate that our approach successfully repairs learned controllers on a standard OpenAI Gym benchmark

Rewriting Human History and Empowering Indigenous Communities with Genome Editing Tools.

Appropriate empirical-based evidence and detailed theoretical considerations should be used for evolutionary explanations of phenotypic variation observed in the field of human population genetics (especially Indigenous populations). Investigators within the population genetics community frequently overlook the importance of these criteria when associating observed phenotypic variation with evolutionary explanations. A functional investigation of population-specific variation using cutting-edge genome editing tools has the potential to empower the population genetics community by holding "just-so" evolutionary explanations accountable. Here, we detail currently available precision genome editing tools and methods, with a particular emphasis on base editing, that can be applied to functionally investigate population-specific point mutations. We use the recent identification of thrifty mutations in the CREBRF gene as an example of the current dire need for an alliance between the fields of population genetics and genome editing

Who participates : the supply of volunteer labor and the distribution of government programs in rural Peru

Numerous analysts have linked volunteering and participation to positive economic and political outcomes. The author uses the 1994 Peru Living Standards Measurement Survey to analyze volunteering patterns in rural Peru. He finds that volunteers in rural Peru have a high opportunity cost of time. They are more educated and more likely to hold a job. Other household characteristics, such as gender, marital status, length of residence, and ethnicity, are also important predictors of the probability of volunteering. Controlling for household characteristics, communities differ widely in aggregate volunteer levels. These differences seem unrelated to differences in patterns of government expenditures. Volunteering may have important benefits in building social capital and encouraging greater ownership of development projects. For example, many public programs in rural Peru and elsewhere ask that the intended beneficiaries"participate"as a means of building trust and social capital, increasing the sustainability of investments and helping self-target investments to the poor. But the author finds that encouraging participation by potential beneficiaries is unlikely to be an effective form of self-targeting, since people with a higher opportunity cost of time volunteer more. Moreover, social programs that require participation may have difficulty reaching some vulnerable groups, such as women and the illiterate.Health Economics&Finance,Labor Policies,Decentralization,Public Health Promotion,Environmental Economics&Policies,Environmental Economics&Policies,Housing&Human Habitats,Health Monitoring&Evaluation,Health Economics&Finance,Poverty Assessment

A means to an industrialisation end? Demand side management in Nigeria

Electricity is essential for economic development and industrialisation processes. Balancing demand and supply is a recurrent problem in the Nigerian electricity market. The aim of this work is to assess the technical and economic potential of Demand Side Management (DSM) in Nigeria given different future levels of industrialisation. The paper places industrialisation at the centrefold of the appraisal of DSM potential in Nigeria. It does so by designing industrialisation scenarios and consequently deriving different DSM penetration levels using a cost-optimisation model. Findings show that under the high industrialisation scenario by the year 2050 DSM could bring about 7 billion USD in cumulative savings thanks to deferred investment in new generation and full deployment of standby assets along with interruptible programmes for larger industrial users. The paper concludes by providing policy recommendations regarding financial mechanisms to increase DSM deployment in Nigeria. The focus on DSM serves to shift the policy debate on electricity in Nigeria from a static state versus market narrative on supply to an engagement with the agency and influence on industrial end-users

On Multiple Semantics for Declarative Database Repairs

We study the problem of database repairs through a rule-based framework that we refer to as Delta Rules. Delta Rules are highly expressive and allow specifying complex, cross-relations repair logic associated with Denial Constraints, Causal Rules, and allowing to capture Database Triggers of interest. We show that there are no one-size-fits-all semantics for repairs in this inclusive setting, and we consequently introduce multiple alternative semantics, presenting the case for using each of them. We then study the relationships between the semantics in terms of their output and the complexity of computation. Our results formally establish the tradeoff between the permissiveness of the semantics and its computational complexity. We demonstrate the usefulness of the framework in capturing multiple data repair scenarios for an Academic Search database and the TPC-H databases, showing how using different semantics affects the repair in terms of size and runtime, and examining the relationships between the repairs. We also compare our approach with SQL triggers and a state-of-the-art data repair system

Roll out the red carpet and they will come : investment promotion and FDI inflows

As red tape in host countries and information asymmetries constitute a significant obstacle to investment flows across international borders, an important policy question is: what can aspiring FDI destinations do to reduce such barriers? This study uses newly collected data on 124 countries to examine the effects of investment promotion on inflows of US FDI. We test whether sectors explicitly targeted by investment promotion agencies in their efforts to attract FDI receive more investment in the post-targeting period, relative to the pre-targeting period and non-targeted sectors. The results of our analysis are consistent with investment promotion leading to higher FDI flows to countries in which red tape and information asymmetries are likely to be severe. The data suggest that investment promotion works in developing countries but not in industrialized economies

A novel process-linked assembly failure model for adhesively bonded composite structures

The globally growing market for polymer composites and their increasing use within aircraft structures has necessitated reliable bonding of composite laminates to prevent structural failure. However, knowledge behind the interaction between curing process parameters and the failure of polymer composite bonded joints is not keeping pace with the market. A novel nonlinear correlation analysis has been employed and applied to experimental data, to attentively quantify the effect of curing parameters on the failure of bonded composite assemblies. The materials (adherends and adhesive) and the bonding processes were selected from those used in assembly of composite aircraft structures