Reliable scalable symbolic computation: The design of SymGridPar2

Symbolic computation is an important area of both Mathematics and Computer Science, with many large computations that would benefit from parallel execution. Symbolic computations are, however, challenging to parallelise as they have complex data and control structures, and both dynamic and highly irregular parallelism. The SymGridPar framework (SGP) has been developed to address these challenges on small-scale parallel architectures. However the multicore revolution means that the number of cores and the number of failures are growing exponentially, and that the communication topology is becoming increasingly complex. Hence an improved parallel symbolic computation framework is required. This paper presents the design and initial evaluation of SymGridPar2 (SGP2), a successor to SymGridPar that is designed to provide scalability onto 10^5 cores, and hence also provide fault tolerance. We present the SGP2 design goals, principles and architecture. We describe how scalability is achieved using layering and by allowing the programmer to control task placement. We outline how fault tolerance is provided by supervising remote computations, and outline higher-level fault tolerance abstractions. We describe the SGP2 implementation status and development plans. We report the scalability and efficiency, including weak scaling to about 32,000 cores, and investigate the overheads of tolerating faults for simple symbolic computations

The Scalable Commutativity Rule: Designing Scalable Software for Multicore Processors

What fundamental opportunities for scalability are latent in interfaces, such as system call APIs? Can scalability opportunities be identified even before any implementation exists, simply by considering interface specifications? To answer these questions this paper introduces the following rule: Whenever interface operations commute, they can be implemented in a way that scales. This rule aids developers in building more scalable software starting from interface design and carrying on through implementation, testing, and evaluation. To help developers apply the rule, a new tool named Commuter accepts high-level interface models and generates tests of operations that commute and hence could scale. Using these tests, Commuter can evaluate the scalability of an implementation. We apply Commuter to 18 POSIX calls and use the results to guide the implementation of a new research operating system kernel called sv6. Linux scales for 68% of the 13,664 tests generated by Commuter for these calls, and Commuter finds many problems that have been observed to limit application scalability. sv6 scales for 99% of the tests.Engineering and Applied Science

The rush for the rare : reptiles and amphibians in the European pet trade

The exotic pet trade has been identified as a main threat to many reptile and amphibian species, especially for optically attractive species or those with special biological features. The international exotic pet trade is largely unregulated and in large parts still heavily depends on wild-caught specimens. Rarity sells, and species that are new to science or new on the pet market are highly sought-after and may fetch record prices. The European Union is a main hub and destination for both legally and illegally sourced wildlife. In the German town Hamm, one of the largest reptile trade shows in the world takes place four times a year, attracting traders and clients from across Europe and beyond. Based on ten case studies, our article illustrates marketing mechanisms and trade dynamics for reptiles and amphibians, which have only recently been described by science. The paper also highlights the problems of insufficient international legislation to prevent over-exploitation of such species or even those which are nationally protected in their country of origin, and presents solutions

SVD-DIP: Overcoming the Overfitting Problem in DIP-based CT Reconstruction

The deep image prior (DIP) is a well-established unsupervised deep learning method for image reconstruction; yet it is far from being flawless. The DIP overfits to noise if not early stopped, or optimized via a regularized objective. We build on the regularized fine-tuning of a pretrained DIP, by adopting a novel strategy that restricts the learning to the adaptation of singular values. The proposed SVD-DIP uses ad hoc convolutional layers whose pretrained parameters are decomposed via the singular value decomposition. Optimizing the DIP then solely consists in the fine-tuning of the singular values, while keeping the left and right singular vectors fixed. We thoroughly validate the proposed method on real-measured $\mu$CT data of a lotus root as well as two medical datasets (LoDoPaB and Mayo). We report significantly improved stability of the DIP optimization, by overcoming the overfitting to noise

FINJ: A Fault Injection Tool for HPC Systems

We present FINJ, a high-level fault injection tool for High-Performance Computing (HPC) systems, with a focus on the management of complex experiments. FINJ provides support for custom workloads and allows generation of anomalous conditions through the use of fault-triggering executable programs. FINJ can also be integrated seamlessly with most other lower-level fault injection tools, allowing users to create and monitor a variety of highly-complex and diverse fault conditions in HPC systems that would be difficult to recreate in practice. FINJ is suitable for experiments involving many, potentially interacting nodes, making it a very versatile design and evaluation tool.Comment: To be presented at the 11th Resilience Workshop in the 2018 Euro-Par conferenc

The Rush for the Rare: Reptiles and Amphibians in the European Pet Trade

Direct exploitation is one of the five main reasons for the loss of biodiversity, and collections for the international pet trade are an ongoing threat for many reptiles and amphibians. The European Union and in particular Germany have a central role as a hub and destination for exotic pets from all over the world. Rare species of reptiles and amphibians especially are in the focus of collectors. Rarity on the market may be either caused by rarity of a species in the wild or by a limited availability for sale, e.g., due to national protection measures in the range state or remote localities. The present study identified 43 species that are not listed by the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) and were only recently described, but have already entered the European pet trade. Ten of these species were selected as case studies, representing species from different geographic regions and illustrating the marketing mechanisms. Many such species that are new to science are neither assessed by the International Union for Conservation of Nature (IUCN) Red List of Threatened Species nor are they covered by international legislation, even though in several countries, where such internationally sought-after species are caught, national protection measures are in place. This paper analyses the challenges and opportunities for the protection of potentially threatened and newly described reptile and amphibian species against over-exploitation for the pet trade

The Rush for the Rare: Reptiles and Amphibians in the European Pet Trade

Direct exploitation is one of the five main reasons for the loss of biodiversity, and collections for the international pet trade are an ongoing threat for many reptiles and amphibians. The European Union and in particular Germany have a central role as a hub and destination for exotic pets from all over the world. Rare species of reptiles and amphibians especially are in the focus of collectors. Rarity on the market may be either caused by rarity of a species in the wild or by a limited availability for sale, e.g., due to national protection measures in the range state or remote localities. The present study identified 43 species that are not listed by the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) and were only recently described, but have already entered the European pet trade. Ten of these species were selected as case studies, representing species from different geographic regions and illustrating the marketing mechanisms. Many such species that are new to science are neither assessed by the International Union for Conservation of Nature (IUCN) Red List of Threatened Species nor are they covered by international legislation, even though in several countries, where such internationally sought-after species are caught, national protection measures are in place. This paper analyses the challenges and opportunities for the protection of potentially threatened and newly described reptile and amphibian species against over-exploitation for the pet trade.</jats:p