Symbolic Partial-Order Execution for Testing Multi-Threaded Programs

We describe a technique for systematic testing of multi-threaded programs. We combine Quasi-Optimal Partial-Order Reduction, a state-of-the-art technique that tackles path explosion due to interleaving non-determinism, with symbolic execution to handle data non-determinism. Our technique iteratively and exhaustively finds all executions of the program. It represents program executions using partial orders and finds the next execution using an underlying unfolding semantics. We avoid the exploration of redundant program traces using cutoff events. We implemented our technique as an extension of KLEE and evaluated it on a set of large multi-threaded C programs. Our experiments found several previously undiscovered bugs and undefined behaviors in memcached and GNU sort, showing that the new method is capable of finding bugs in industrial-size benchmarks.Comment: Extended version of a paper presented at CAV'2

Global equality of resources and the problem of valuation

The principle that every individual on the planet has a claim to an equal share of Earth’s natural resources has an intuitive attraction. Yet the Principle of Natural Resource Equality is not without its problems. This article focuses on the problem of valuation. Unless and until its adherents are able to develop an adequate theoretical mechanism for determining the comparative value of two or more bundles of natural resources the principle lacks applicability and persuasive force. Three adequacy constraints on such a mechanism are presented and then applied to a theorisation of the Principle of Natural Resource Equality that I have already expounded elsewhere: Global Equality of Resources. In each case I try to argue that Global Equality of Resources could satisfy the adequacy constraint, provided that both this theory and the relevant constraint are properly understood

Managing adult hatchery summer steelhead for a recreational fishery with reduced hatchery and wild interactions

Hatcheries whose purpose is to provide for a recreational fishery must minimize impacts on wild fishes. Management to reduce hatchery and wild interactions is especially important on river systems that contain Endangered Species Act (ESA) listed species. I examined adult hatchery summer steelhead, Oncorhynchus mykiss, behavior, current management and a potential future management practice in a river with both introduced and ESA listed steelhead. I used radio telemetry to determine hatchery summer steelhead activity, behavior, and examine management tactics in the Clackamas River, Oregon. I evaluated the movement and distribution of radio-tagged fish between July 2007 through January 2008 using a combination of fixed and mobile radio-tracking. In addition, I used electromyogram (EMG) transmitters to record activity and behavior while the fish were holding in their natal river. An EMG-tagged fish was caught on hook and line during tracking and is the first known instance of estimated activity levels during capture. I evaluated the fish recycling program on the Clackamas River. Recycling involves the transport and release of adult steelhead back downstream following their collection at the hatchery to increase angler success. I estimated that up to 41% of recycled fish were caught in the recreational fishery. However, the majority of fish (44 -67%) were unaccounted for after release and may negatively affect wild populations. The Oregon Department of Fish and Wildlife is investigating the feasibility of sterilizing returning adult hatchery steelhead to reduce hatchery and wild interactions and increase recreational fishing opportunity. To evaluate the effect of sterilization on adult fish behavior, I gonadectomized and radio-tagged 40 hatchery summer steelhead and monitored their behavior and contribution to the fishery compared to sham-operated fish. Gonadectomized fish remained in the river, were distributed downstream of control fish, and were caught in the recreational fishery. Based on my results, I conclude that sterilization may be a useful technique to improve angler opportunity while minimizing the impact to wild fish. Behavior and activity of hatchery fish and their responses to management procedures should be closely monitored to better manage hatchery fisheries

IMPLEMENTATION OF A QUASI-OPTICAL FREE-SPACE S-PARAMETERS MEASUREMENT SYSTEM

A quasi-optical (QO) free-space test bench, based on two dual reflector Compact Test Range (CTR) systems, has been developed to characterise the RF properties of materials and QO components used in mm-wave astronomical instrumentation. While this facility has been designed to operate for several spectral bandwidths, in the first instance measurements have been performed in the W-band (75-110 GHz). We present the modelled and measured performance of the test bench and the procedure for calibrating and measuring samples under test. First measured results of the field across a 10 cm quiet zone indicate a maximum intensity variation of -4.5 dB and a maximum phase variation of 7°. Measurements of the cross-polarisation indicate higher levels than were predicted. A free-space calibration method has been developed based on the use of 3 calibration standards (Thru-Reflect-Line). Initial measurements of the reflectivity and transmittance for a range of materials have been performed, allowing the deduction of the refractive index