This paper introduces FlowVR, a middleware dedicated to virtual reality applications distributed on clusters or grid environments. FlowVR supports coupling of heterogeneous parallel codes and is component oriented to favor code reuse. While classical communication paradigms focus on either a synchronous approach (FIFO channels) or an asynchronous one (sampling), FlowVR enables a large range of intermediate policies to better balance the application performance between levels of details, latencies and refresh rates.

International audienceCombining molecular dynamics simulations with user interaction would have various applications in both education and research. By enabling interactivity the scientist will be able to visualize the experiment in real time and drive the simulation to a desired state more easily. However, interacting with systems of interesting size requires significant computing resources due to the complexity of the simulation. In this paper, we propose an approach to combine a classical parallel molecular dynamics simulator, Gromacs, to a 3D virtual reality environment allowing to steer the simulation through external user forces applied with an haptic device to a selection of atoms. We specifically focused on minimizing the intrusion in the simulator code, on efficient parallel data extraction and filtering to transfer only the necessary data to the visualization environment, and on a controlled asynchronism between various components to improve interactivity. We managed to steer molecular systems of 1.7 M atoms at about 25 Hz using 384 CPU cores. This framework allowed us to study a concrete scientific problem by testing one hypothesis of the transport of an iron complex from the exterior of the bacteria to the periplasmic space through the FepA membrane protein

The amount of data generated by molecular dynamics simulations of large molecular assemblies and the sheer size and complexity of the systems studied call for new ways to analyse, steer and interact with such calculations. Traditionally, the analysis is performed off-line once the huge amount of simulation results have been saved to disks, thereby stressing the supercomputer I/O systems, and making it increasingly difficult to handle post-processing and analysis from the scientist's office. The ExaViz framework is an alternative approach developed to couple the simulation with analysis tools to process the data as close as possible to their source of creation, saving a reduced, more manageable and pre-processed data set to disk. ExaViz supports a large variety of analysis and steering scenarios. Our framework can be used for live sessions (simulations short enough to be fully followed by the user) as well as batch sessions (long-time batch executions). During interactive sessions, at runtime, the user can display plots from analysis, visualise the molecular system and steer the simulation with a haptic device. We also emphasise how a CAVE-like immersive environment could be used to leverage such simulations, offering a large display surface to view and intuitively navigate the molecular system.

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