Evaluating the performance of parallel subsurface simulators: An illustrative example with PFLOTRAN.

[1] To better inform the subsurface scientist on the expected performance of parallel simulators, this work investigates performance of the reactive multiphase flow and multicomponent biogeochemical transport code PFLOTRAN as it is applied to several realistic modeling scenarios run on the Jaguar supercomputer. After a brief introduction to the code's parallel layout and code design, PFLOTRAN's parallel performance (measured through strong and weak scalability analyses) is evaluated in the context of conceptual model layout, software and algorithmic design, and known hardware limitations. PFLOTRAN scales well (with regard to strong scaling) for three realistic problem scenarios: (1) in situ leaching of copper from a mineral ore deposit within a 5-spot flow regime, (2) transient flow and solute transport within a regional doublet, and (3) a real-world problem involving uranium surface complexation within a heterogeneous and extremely dynamic variably saturated flow field. Weak scalability is discussed in detail for the regional doublet problem, and several difficulties with its interpretation are noted.

Information, choice, and reactions to stress: a field experiment in a blood bank with laboratory analogue.

Two experiments examined the effects of various operations of personal control on reactions to stress. The first study incorporated two features into the blood drawing procedure at a blood bank: providing donors with accurate information and allowing donors to choose the arm to be used. Measurement of nurses' actions to prevent donors from fainting and self-reports of discomfort revealed that the combination of choice and information was somewhat effective in reducing distress. However, providing either information or choice alone was more effective. In a second laboratory study using a cold pressor stimulus as stressor, subjects given a choice (the option to terminate the aversive stimulus and choice of hand used) showed a reduction of aftereffects on a measure of attention to detail. Subjects given information but not choice also showed this reduction. Combining information and choice was no different from either treatment alone. Taken together, the results of both studies indicate that moderate levels of choice and information are optimal for coping with stress. An explanation was suggested based on a contextually determined relationship amomg choice, information, and perceived control.