An Extensible Timing Infrastructure for Adaptive Large-scale Applications

Real-time access to accurate and reliable timing information is necessary to profile scientific applications, and crucial as simulations become increasingly complex, adaptive, and large-scale. The Cactus Framework provides flexible and extensible capabilities for timing information through a well designed infrastructure and timing API. Applications built with Cactus automatically gain access to built-in timers, such as gettimeofday and getrusage, system-specific hardware clocks, and high-level interfaces such as PAPI. We describe the Cactus timer interface, its motivation, and its implementation. We then demonstrate how this timing information can be used by an example scientific application to profile itself, and to dynamically adapt itself to a changing environment at run time

GridRun: A lightweight packaging and execution environment for compact, multi-architecture binaries

Abstrac

A Nursery-Based Cooking Skills Programme with Parents and Children Reduced Food Fussiness and Increased Willingness to Try Vegetables: A Quasi-Experimental Study

Children’s fussy eating is associated with a reduced vegetable intake. This quasi-experimental study evaluated “Big Chef Little Chef” (BCLC), a nursery-based cooking skills programme aimed at reducing food fussiness and increasing willingness to try green vegetables by incorporating repeated exposure and sensory learning. Parent and child (3–5 years) dyads attended BCLC for four/1.5 h weekly sessions. A comparison group was recruited after BCLC completion and attended a single education session at week 1. A questionnaire measured food fussiness at week 1 and week 4. At week 4, all children were offered six green vegetables (raw and cooked) and an average score (1 = did not try; 2 = tried it/ate some; 3 = ate it all) was calculated for willingness to try vegetables. In total, 121 dyads (intervention: n = 64; comparison: n = 57) participated. The food fussiness score (1 min–5 max) in the intervention group decreased significantly from 3.0 to 2.6 (p < 0.01) between time points, while there was no change in the comparison group (3.1 (week 1) and 3.0 (week 4)). The intervention group was more willing to try green vegetables with significantly higher (p < 0.001) median scores for raw and cooked vegetables (2.5 for both) compared with the comparison group (2.0 and 1.7, respectively). The BCLC reduced food fussiness and increased willingness to try green vegetables

GRB Light Curves in the Relativistic Turbulence Model

Randomly oriented relativistic emitters in a relativistically expanding shell provides an alternative to internal shocks as a mechanism for producing GRBs' variable light curves with efficient conversion of energy to radiation. In this model the relativistic outflow is broken into small emitters moving relativistically in the outflow's rest frame. Variability arises because an observer sees an emitter only when its velocity points towards him so that only a small fraction of the emitters are seen by a given observer. Models with significant relativistic random motions require converting and maintaining a large fraction of the overall energy into these motions. While it is not clear how this is achieved, we explore here, using two toy models, the constraints on parameters required to produce light curves comparable to the observations. We find that a tight relation between the size of the emitters and the bulk and random Lorentz factors is needed and that the random Lorentz factor determines the variability. While both models successfully produce the observed variability there are several inconsistencies with other properties of the light curves. Most of which, but not all, might be resolved if the central engine is active for a long time producing a number of shells, resembling to some extent the internal shocks model.Comment: Significantly revised with a discussion of additional models. Accepted for publication in APJ

Three-dimensional general relativistic hydrodynamics II: long-term dynamics of single relativistic stars

This is the second in a series of papers on the construction and validation of a three-dimensional code for the solution of the coupled system of the Einstein equations and of the general relativistic hydrodynamic equations, and on the application of this code to problems in general relativistic astrophysics. In particular, we report on the accuracy of our code in the long-term dynamical evolution of relativistic stars and on some new physics results obtained in the process of code testing. The tests involve single non-rotating stars in stable equilibrium, non-rotating stars undergoing radial and quadrupolar oscillations, non-rotating stars on the unstable branch of the equilibrium configurations migrating to the stable branch, non-rotating stars undergoing gravitational collapse to a black hole, and rapidly rotating stars in stable equilibrium and undergoing quasi-radial oscillations. The numerical evolutions have been carried out in full general relativity using different types of polytropic equations of state using either the rest-mass density only, or the rest-mass density and the internal energy as independent variables. New variants of the spacetime evolution and new high resolution shock capturing (HRSC) treatments based on Riemann solvers and slope limiters have been implemented and the results compared with those obtained from previous methods. Finally, we have obtained the first eigenfrequencies of rotating stars in full general relativity and rapid rotation. A long standing problem, such frequencies have not been obtained by other methods. Overall, and to the best of our knowledge, the results presented in this paper represent the most accurate long-term three-dimensional evolutions of relativistic stars available to date.Comment: 19 pages, 17 figure