Image Processing Reference
In-Depth Information
User
Interface
Application
Communication
User
Data
Collection
Visualization
Interpretation
Simulation
Data
Distribution
Input Handling
Manipulation
Fig. 31.7
Computational steering loop. Users are able to steer a running simulation by communi-
cating with the simulation through a user interface
simulation variables during a simulation run can increase the scientist's understand-
ing of the modeled physics and decreases the number of iterations required in order
to successfully perform a simulation. Due to this importance, computational steer-
ing, the process of influencing a running numerical simulation, has applied since the
early times of numerical simulations.
Figure
31.7
depicts the computational steering process according to Muelder
et al. [
36
]. Information about a running simulation needs to be communicated to
a user interface (online monitoring). The user interprets the visual feedback to deter-
mine potential manipulations. These manipulations then have to be distributed to the
simulation nodes for execution. Based on these functionalities of a computational
steering process the following issues are identified:
•
Instrumentation: The definition of interfaces between the simulation and the steer-
ing framework as well as the required adaption inside the simulation.
•
Re-usability: A steering framework should support various types of simulation
solvers. This involves dealing with different data layouts and generic graphical
user interfaces.
•
Data Exchange: Data collection and distribution is essential for various tasks. E.g.
simulation data needs read and write access by the user interface.
Due to the fact that visualization is a key component for computational steering, it
is not surprising that many computational steering approaches are based on enhanced
visualization toolkits. Therefore, VisIt and ParaView, the two main open-source visu-
alization systems, provide a computational steering solution.
VisIt is a parallel high-performance visualization environment providing efficient
visual analysis of scientific data. libsim [
9
] is a lightweight library that offers an
API in order to connect simulations to the VisIt environment. However, this API has
a complex instrumentation and requires many code changes. Furthermore, data is
required to be converted into VisIt's native data structures. ParaView, on the other
hand, did not originally support computational steering. Nevertheless, Biddiscombe
et al. [
3
] extended ParaView with a plugin and a IO library which enables computa-
tional steering. They make use of a virtual file driver which emulates conventional
disc storage and distributes data via message passing. This ParaView plugin, called
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