Review of solar energetic particle models

Solar Energetic Particle (SEP) events are interesting from a scientific perspective as they are the product of a broad set of physical processes from the corona out through the extent of the heliosphere, and provide insight into processes of particle acceleration and transport that are widely applicable in astrophysics. From the operations perspective, SEP events pose a radiation hazard for aviation, electronics in space, and human space exploration, in particular for missions outside of the Earth’s protective magnetosphere including to the Moon and Mars. Thus, it is critical to improve the scientific understanding of SEP events and use this understanding to develop and improve SEP forecasting capabilities to support operations. Many SEP models exist or are in development using a wide variety of approaches and with differing goals. These include computationally intensive physics-based models, fast and light empirical models, machine learning-based models, and mixed-model approaches. The aim of this paper is to summarize all of the SEP models currently developed in the scientific community, including a description of model approach, inputs and outputs, free parameters, and any published validations or comparisons with data.</p

Lc/Dc: Lockless Containers And Data Concurrency A Novel Nonblocking Container Library For Multicore Applications

Exploiting the parallelism in multiprocessor systems is a major challenge in modern computer science. Multicore programming demands a change in the way we design and use fundamental data structures. The standard collection of data structures and algorithms in CCC11 is the sequential standard template library (STL). In this paper, we present their vision for the theory and practice for the design and implementation of a collection of highly concurrent fundamental data structures for multiprocessor application development with associated programming interface and advanced optimization support. Specifically, the proposed approach will provide a familiar, easy-to-use, and composable interface, similar to that of CCC STL. Each container type will be enhanced with internal support for nonblocking synchronization of its data access, thereby providing better safety and performance than traditional blocking synchronization by: 1) eliminating hazards such as deadlock, livelock, and priority inversion and 2) by being highly scalable in supporting large numbers of threads. The new library, lockless containers/data concurrency, will provide algorithms for handling fundamental computations in multithreaded contexts, and will incorporate these into libraries with familiar look and feel. The proposed approach will provide an immense boost in performance and software reuse, consequently productivity, for developers of scientific and systems applications, which are predominantly in C/CCC. STL is widely used and a concurrent replacement library will have an immediate practical relevance and a significant impact on a variety of parallel programming domains including simulation, massive data mining, computational biology, financial engineering, and embedded control systems. As a proof-of-concept, this paper discusses the first design and implementation of a waitfree hash table. © 2013 IEEE

Concurrent lock-free unbounded priority queue with mutable priorities

The priority queue with DeleteMin and Insert operations is a classical interface for ordering items associated with priorities. Some important algorithms, such as Dijkstra’s single-source-shortest-path, Adaptive Huffman Trees, etc. also require changing the priorities of items in the runtime. Existing lock-free priority queues do not directly support the dynamic mutation of the priorities. This paper presents the first concurrent lock-free unbounded binary heap that implements a priority queue with mutable priorities. The operations are provably linearizable. We also designed an optimized version of the algorithm by combining the concurrent operations that substantially improves the performance. For experimental evaluation, we implemented the algorithm in both C/C++ and Java. A number of micro-benchmarks show that our algorithm performs well in comparison to existing implementations