Detection and optimization of suspension-free logic programs

AbstractIn recent years, language mechanisms to suspend, or delay, the execution of goals until certain variables become bound have become increasingly popular in logic programming languages. While convenient, such mechanisms can make control flow within a program difficult to predict at compile time, and therefore render many traditional compiler optimizations inapplicable. Unfortunately, this performance cost is also incurred by programs that do not use any delay primitives. In this paper, we describe a simple dataflow analysis for detecting computations where suspension effects can be ignored, and discuss several low-level optimizations that rely on this information. Our algorithm has been implemented in the jc system. Optimizations based on information it produces result in significant performance improvements, demonstrating speed comparable to or exceeding that of optimized C programs

Geographies of generosity: beyond the 'moral turn'

This paper questions Geographers debates about 'caring at a distance' and the 'geographies of responsibility', focussing on the treatment of the theme of partiality in ethics and justice. Debates in Geography often present partial commitments as morally or politically problematic on the grounds that they prioritize self-interest, exclusionary, and geographically restricted ways of relating to others. We outline how debates about caring at a distance and the geographies of responsibility frame partiality as a problem to be overcome. We argue that Geography's engagements with moral philosophy are premised on faulty assumptions about the sorts of influences people are liable to act upon (one's that privilege causal knowledge as the primary motivating force), and also flawed assumptions about the sorts of problems that academic reasoning about normative issues is meant to address (the assumption that people are too egoistical and not altruistic enough). We use the theme of generosity as an entry point to argue that partiality and finitude might be the conditions for any ethical–political project that de-centres the motivation of practical action away from the sovereign self towards responsive and attentive relations of encounter with the needs of others. Understanding generosity as a modality of power suggests a revised programme for geographical investigations of the intersection between ethics, morality and politics: one which looks at how opportunities to address normative demands in multiple registers are organized and transformed; at the ways in which dispositions to respond and to be receptive to others are worked up; and how opportunities for acting responsively on these dispositions are organized

Critical realism and economic anthropology

This paper discusses basic critical realism within the context of economic anthropology and develops an approach to studying material relations between people. A diachronic form of analysis, following the work of Bhaskar and Archer, is described as a practical means of analysing property rights. This new approach emphasises epistemic relativism and ontological realism in order to compare disparate forms of human interaction across cultures. The aim of doing this is to develop a philosophical framework that allows for the comparison of economic practices without resorting to judgemental relativism. The implications are significant for institutional economics and anthropology alike, particularly for researchers examining multiple overlapping practices such as market and gift exchange

Effects of Anacetrapib in Patients with Atherosclerotic Vascular Disease

BACKGROUND: Patients with atherosclerotic vascular disease remain at high risk for cardiovascular events despite effective statin-based treatment of low-density lipoprotein (LDL) cholesterol levels. The inhibition of cholesteryl ester transfer protein (CETP) by anacetrapib reduces LDL cholesterol levels and increases high-density lipoprotein (HDL) cholesterol levels. However, trials of other CETP inhibitors have shown neutral or adverse effects on cardiovascular outcomes. METHODS: We conducted a randomized, double-blind, placebo-controlled trial involving 30,449 adults with atherosclerotic vascular disease who were receiving intensive atorvastatin therapy and who had a mean LDL cholesterol level of 61 mg per deciliter (1.58 mmol per liter), a mean non-HDL cholesterol level of 92 mg per deciliter (2.38 mmol per liter), and a mean HDL cholesterol level of 40 mg per deciliter (1.03 mmol per liter). The patients were assigned to receive either 100 mg of anacetrapib once daily (15,225 patients) or matching placebo (15,224 patients). The primary outcome was the first major coronary event, a composite of coronary death, myocardial infarction, or coronary revascularization. RESULTS: During the median follow-up period of 4.1 years, the primary outcome occurred in significantly fewer patients in the anacetrapib group than in the placebo group (1640 of 15,225 patients [10.8%] vs. 1803 of 15,224 patients [11.8%]; rate ratio, 0.91; 95% confidence interval, 0.85 to 0.97; P=0.004). The relative difference in risk was similar across multiple prespecified subgroups. At the trial midpoint, the mean level of HDL cholesterol was higher by 43 mg per deciliter (1.12 mmol per liter) in the anacetrapib group than in the placebo group (a relative difference of 104%), and the mean level of non-HDL cholesterol was lower by 17 mg per deciliter (0.44 mmol per liter), a relative difference of -18%. There were no significant between-group differences in the risk of death, cancer, or other serious adverse events. CONCLUSIONS: Among patients with atherosclerotic vascular disease who were receiving intensive statin therapy, the use of anacetrapib resulted in a lower incidence of major coronary events than the use of placebo. (Funded by Merck and others; Current Controlled Trials number, ISRCTN48678192 ; ClinicalTrials.gov number, NCT01252953 ; and EudraCT number, 2010-023467-18 .)

An efficient and portable implementation of a concurrent constraint language

This dissertation describes a sequential implementation of a concurrent constraint programing language called Janus. The language implemented is somewhat different from the original Janus; it is a flat guarded language with assignment, similar to Strand and to FGHC. This implementation, called jc (Janus Compiler) compiles Janus source code to C, and then calls a C compiler to compile the C code. This technique gives us most of the performance benefits of compiling to machine code, but also has the portability of an interpreter. There are some special problems involved in the implementation of a language like Janus. First, Janus data is dynamically typed. Therefore each data value must carry type information and in principle every operation must check this type information in order to operate correctly. Second, procedure calls are much more common in Janus than in most other languages since every conditional and every loop must be coded as a call to a procedure. Third, Janus has the ability to suspend if a variable is evaluated before it is assigned a value. The jc implementation addresses these problems with a set of novel design decisions and optimization techniques. It was our goal to ensure, as far as possible, that programs that do not make essential use of the special features of Janus should not pay the performance penalty of having those features available. In particular, a program that is a fairly direct translation of a C program to Janus should execute about as fact as the original C program did

jc: An Efficient and Portable Sequential Implementation of Janus

Janus is a language designed for distributed constraint programming [12]. This paper describes jc, an efficient and portable sequential implementation of Janus, which compiles Janus programs down to C code. Careful attention to the C code generated, together with some simple local optimizations, allows the system to have fairly good performance despite the lack (at this time) of global flow analysis and optimization