Concurrent Access Algorithms for Different Data Structures: A Research Review

Algorithms for concurrent data structure have gained attention in recent years as multi-core processors have become ubiquitous. Several features of shared-memory multiprocessors make concurrent data structures significantly more difficult to design and to verify as correct than their sequential counterparts. The primary source of this additional difficulty is concurrency. This paper provides an overview of the some concurrent access algorithms for different data structures

Fuelwood harvesting and selection in Valley Thicket, South Africa

The Thicket Biome is the second smallest biome in South Africa, and is renowned for its high biodiversity. Yet, less than 5% of the biome is in formal conservation areas. Much of the currently intact thicket outside protected areas is threatened by land transformation to commercial agriculture or heavy use by rural communities. There is limited understanding of the ecological structure and function of thicket communities and their response to these human pressures. This paper reports on a study to characterize the woody communities in Valley Thicket and Thornveld surrounding a rural village. We also examined the demand and selection for specific woody species. There was a marked selection for key species for different uses, including fuelwood, construction timber, and cultural stacks. There was also strong selection for specific size classes of stem, especially those between 16–45 cm circumference. The density, biomass and species richness of woody species was reduced close to the village, and increased with distance away from human settlement. A similar trend was found for the basal area of preferred species, but not for the basal area of all species. The strong selectivity for both species and size class means that the anthropogenic impacts are not uniform within the woody strata, leading to marked changes in community structure and floristics at a local scale

Brief announcement: 2D-stack - A scalable lock-free stack design that continuously relaxes semantics for better performance

We briefly describe an efficient lock-free concurrent stack design with tunable and tenable relaxed semantics to allow for better performance. The design is tunable and allow for a continuous monotonic trade of weaker semantics for better throughput performance. Concurrent stacks have an inherent scalability bottleneck due to their single access point for both their operations. Elimination and semantics relaxation have been proposed in the literature to address this problem. Semantics relaxation has the potential to reach monotonically very high throughput by continuously trading relaxation for throughput. Previous solutions could not fully leverage this potential. We suggest a new two dimensional design that can achieve this by exploiting disjoint access parallelism in one dimension and locality in the other within tight accuracy bounds. The behaviour of the algorithm is tightly bound. We compare experimentally to previous work, with respect to throughput and relaxed behaviour observed, on different relaxation and concurrency settings. The experimental evaluation shows that our algorithm significantly outperform all other algorithms in terms of performance, also maintain better accuracy in contrast to other designs with relaxed semantics

Monotonically relaxing concurrent data-structure semantics for performance: An efficient 2D design framework

There has been a significant amount of work in the literature proposing semantic relaxation of concurrent data structures for improving scalability and performance. By relaxing the semantics of a data structure, a bigger design space, that allows weaker synchronization and more useful parallelism, is unveiled. Investigating new data structure designs, capable of trading semantics for achieving better performance in a monotonic way, is a major challenge in the area. We algorithmically address this challenge in this paper. We present an efficient, lock-free, concurrent data structure design framework for out-of-order semantic relaxation. Our framework introduces a new two dimensional algorithmic design, that uses multiple instances of a given data structure. The first dimension of our design is the number of data structure instances operations are spread to, in order to benefit from parallelism through disjoint memory access. The second dimension is the number of consecutive operations that try to use the same data structure instance in order to benefit from data locality. Our design can flexibly explore this two-dimensional space to achieve the property of monotonically relaxing concurrent data structure semantics for achieving better throughput performance within a tight deterministic relaxation bound, as we prove in the paper. We show how our framework can instantiate lock-free out-of-order queues, stacks, counters and dequeues. We provide implementations of these relaxed data structures and evaluate their performance and behaviour on two parallel architectures. Experimental evaluation shows that our two-dimensional data structures significantly outperform the respected previous proposed ones with respect to scalability and throughput performance. Moreover, their throughput increases monotonically as relaxation increases

Fine-tuning the performance of ddRAD-seq in the peach genome

The advance of Next Generation Sequencing (NGS) technologies allows high-throughput genotyping at a reasonable cost, although, in the case of peach, this technology has been scarcely developed. To date, only a standard Genotyping by Sequencing approach (GBS), based on a single restriction with ApeKI to reduce genome complexity, has been applied in peach. In this work, we assessed the performance of the double-digest RADseq approach (ddRADseq), by testing 6 double restrictions with the restriction profile generated with ApeKI. The enzyme pair PstI/MboI retained the highest number of loci in concordance with the in silico analysis. Under this condition, the analysis of a diverse germplasm collection (191 peach genotypes) yielded 200,759,000 paired-end (2 × 250 bp) reads that allowed the identification of 113,411 SNP, 13,661 InDel and 2133 SSR. We take advantage of a wide sample set to describe technical scope of the platform. The novel platform presented here represents a useful tool for genomic-based breeding for peach.EEA San PedroFil: Aballay, Maximiliano Martín. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria San Pedro; Argentina.Fil: Aballay, Maximiliano Martín. Consejo Nacional de Investigaciones Científica y Técnicas; ArgentinaFil: Aguirre, Natalia Cristina. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Biotecnología; Argentina.Fil: Aguirre, Natalia Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Agrobiotecnología y Biología Molecular; Argentina.Fil: Filippi, Carla Valeria. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Biotecnología; ArgentinaFil: Filippi, Carla Valeria. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Agrobiotecnología y Biología Molecular; ArgentinaFil: Valentini, Gabriel Hugo. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria San Pedro; ArgentinaFil: Sánchez, Gerardo. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria San Pedro; Argentin

Concurrent Access Algorithms for Different Data Structures: A Research Review

Algorithms refers to a finite set of steps, which when followed solves a number of problems and algorithams for concurrent data structure have gained attention in recent years as multi-core processors have become ubiquitous. Several features of shared-memory multiprocessors make concurrent data structures significantly more difficult to design and to verify as correct than their sequential counterparts. The primary source of this additional difficulty is concurrency. This paper provides an overview of the some concurrent access algorithms for different data structures. Keywords: concurrency, lock-free, non-blocking, mem-ory management, compares and swap, eliminatio

2D-Stack: A scalable lock-free stack design that continuously relaxes semantics for better performance

In this report, we propose an efficient lock-free concurrent stack design with tunable and tenable relaxed semantics to allow for better performance. The design is materialized by a shared memory distributed stack design that allow for a continuous monotonic trade of weaker semantics for better throughput performance. Concurrent stacks have an inherent scalability bottleneck due to their single access point for both push and pop operations.Elimination and semantics relaxation have been proposed in the literature to address this problem. Semantic relaxation has the potential and flexibility to reach monotonically very high throughput. Previous solutions could not fully leverage this potential. We propose a new two-dimensional design that can achieve this by exploiting disjoint access parallelism in one dimension and locality in the other. This is achieved through distributing the stack in form of sub-stacks that are accessed independently in parallel. Load balancing is used to keep a balanced number of operations on individual sub-stacks. We also provide tight relaxation bounds for the behaviour of our algorithm. We compare experimentally to previous work, with respect to throughput and relaxed behaviour observed, on different relaxation and concurrency settings. The results show that our algorithm signicantly outperform all other algorithms in terms of performance, while maintaining better quality in contrast to other designs with relaxed semantics