Optimisation of patch distribution strategies for AMR applications

As core counts increase in the world's most powerful supercomputers, applications are becoming limited not only by computational power, but also by data availability. In the race to exascale, efficient and effective communication policies are key to achieving optimal application performance. Applications using adaptive mesh refinement (AMR) trade off communication for computational load balancing, to enable the focused computation of specific areas of interest. This class of application is particularly susceptible to the communication performance of the underlying architectures, and are inherently difficult to scale efficiently. In this paper we present a study of the effect of patch distribution strategies on the scalability of an AMR code. We demonstrate the significance of patch placement on communication overheads, and by balancing the computation and communication costs of patches, we develop a scheme to optimise performance of a specific, industry-strength, benchmark application

Hierarchical analysis of molecular spectra

A novel representation of molecular spectra in terms of hierarchical trees has proven to be an important aid for the study of many significant problems in gas-phase chemical dynamics. Trees are generated from molecular spectra by monitoring the changes that occur in a spectrum as resolution is changed in a continuous manner. A tree defines a genealogy among all lines of a spectrum. This allows for a detailed understanding of the assignment of features of a spectrum that may be difficult to obtain any other way as well as an understanding of intramolecular energy transfer time scales, mechanisms, and pathways. The methodology has been applied to several problems: transition state spectroscopy, intramolecular energy transfer in highly excited molecules, high-resolution overtone spectroscopy, and the nature of the classical-quantum correspondence when there is classical chaos (``quantum chaos``)

Archaeology and Cosmopolitanism in Early Historic and Medieval Sri Lanka

Whilst the Early Historic and Medieval periods of Sri Lanka are often presented as a golden age of Sinhalese and Buddhist achievement, there is also substantial evidence for a multiplicity of communities residing within the island during that time. This is unsurprising, given the island’s location on trade routes spanning the Indian Ocean, linking its communities with East Africa, the Middle East, South-east Asia and China. The physical evidence of this trade is clear from excavations within the island's ancient capital Anuradhapura and its major port, Mantai, with their assemblages of fine Chinese ceramics, glazed and bitumen-coated vessels from Mesopotamia, and semi-precious stones from Afghanistan (Carswell et al. 2013; Coningham 2006). The spread of Buddhism into the island also forged strong regional links with communities in northern India but, at the same time contributed to increasing differentiation between communities in the south of the Subcontinent. Indeed, tensions were also evident within and between the island’s Buddhist sects, which led to conflict on a number of occasions. Archaeological research in the hinterland around Anuradhapura has also identified a variety of competing, yet complementary ritual foci, indicating that whilst Buddhism may have been regarded as the official religion of the island, other traditions and belief systems were strong and pervasive (Coningham & Gunawardhana 2013). These divisions may have often been superficial or have had ‘fuzzy’ boundaries in the past, yet they have been used to legitimate colonial and post-colonial religious and political inequalities. Despite these uncertainties, Sri Lanka's place at the heart of international trade routes, linking East and West is undisputable, creating an island of diverse communities and traditions, and prospering in the process

Environmental isotopes investigation in groundwater of Challaghatta valley, Bangalore: A case study

Radiogenic isotopes (3H and 14C) and stable isotope (18O) together with TDS, EC and salinity of water were used to discriminate qualitative and quantitative groundwater age, probable recharge time, flow respectively in groundwater of Challaghatta valley, Bangalore. The variations between TDS and EC values of sewage, corporation water, bore and open wells with concomitant variations in salinity confirmed an immerse relationship with the depth of wells, Also, the source of recharge and contamination of groundwater as sewage. However, lighter ä18O bearing water more commonly occurred at higher elevations and heavier at lower elevations in the entire valley presenting a clear enrichment in ä18O probably due to evaporation and confirming major source of surface water as South - West monsoon. The groundwater samples in valley contained higher 3H except five samples (OW21, OW24, BW5, BW20 and BW24), suggesting recent recharge and categorized as modern age water. Further, from the results of 14C it is inferred that some groundwater samples in Challaghatta valley belongs to old water regime with pmC values ranging between 58 and 112

Free expansion of Bose-Einstein condensates with quantized vortices

The expansion of Bose-Einstein condensates with quantized vortices is studied by solving numerically the time-dependent Gross-Pitaevskii equation at zero temperature. For a condensate initially trapped in a spherical harmonic potential, we confirm previous results obtained by means of variational methods showing that, after releasing the trap, the vortex core expands faster than the radius of the atomic cloud. This could make the detection of vortices feasible, by observing the depletion of the density along the axis of rotation. We find that this effect is significantly enhanced in the case of anisotropic disc-shaped traps. The results obtained as a function of the anisotropy of the initial configuration are compared with the analytic solution for a noninteracting gas in 3D as well as with the scaling law predicted for an interacting gas in 2D.Comment: 5 pages, 6 postscript figure

Thermodynamics of an interacting trapped Bose-Einstein gas in the classical field approximation

We present a convenient technique describing the condensate in dynamical equilibrium with the thermal cloud, at temperatures close to the critical one. We show that the whole isolated system may be viewed as a single classical field undergoing nonlinear dynamics leading to a steady state. In our procedure it is the observation process and the finite detection time that allow for splitting the system into the condensate and the thermal cloud.Comment: 4 pages, 4 eps figures, final versio

Long-Wavelength Instability in Surface-Tension-Driven Benard Convection

Laboratory studies reveal a deformational instability that leads to a drained region (dry spot) in an initially flat liquid layer (with a free upper surface) heated uniformly from below. This long-wavelength instability supplants hexagonal convection cells as the primary instability in viscous liquid layers that are sufficiently thin or are in microgravity. The instability occurs at a temperature gradient 34% smaller than predicted by linear stability theory. Numerical simulations show a drained region qualitatively similar to that seen in the experiment.Comment: 4 pages. The RevTeX file has a macro allowing various styles. The appropriate style is "mypprint" which is the defaul