EAS3

EAS3 ( input-output system 3) is a software toolkit for binary reading and writing structured data, including information geometry and to analyze stored data. It serves to binary floating point data in IEEE format exchange between different computers to edit this data, if appropriate or convert to other formats. It is generally suitable for storing structured data and, in particular in the direct digital simulation (DNS ) is used.

Program package

The software package consists of libraries for use in -house and from a stand-alone command line program and runs on all POSIX systems. It is written in Fortran and C. The libraries contain several numerical algorithms and routines for reading and writing in binary format EAS3. The read-write routines are provided as Fortran and C subroutines. When numerical methods are among others the Fast Fourier Transform ( FFT), which implements Thomas algorithm for solving tridiagonal systems of equations or interpolation routines. The libraries are also suitable for use in vector machines.

History

EAS3 was developed at the University of Stuttgart, Institute of Aerodynamics and Gas Dynamics (IAG ). The previous versions (EAS and EAS2 ) Go back to the end of the 1980s, as the computer capacity allowed first large spatial nonlinear direct numerical simulations. With the emerging amounts of data, there was the problem of effectively handling and evaluation. Since the release of EAS3 in 1999, the package of employees of the participating institutions is continuously developed.

The current version number of the software package is 1.6.7 from April 2009. Paragraph 3 in the name of the software package does not refer to the version number, but on the step of storing three-dimensional data fields ( plus parameters and time step ) as opposed to its predecessor EAS2 in which individual spanwise modes still had to be stored in separate files.

File Format

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Task of EAS3 file format is to store floating-point numbers in binary in IEEE format and exchange between different computer architectures (little / big -endian). In this case, the data is organized as a parameter. A parameter is a textured one, two or three dimensional array of floating point data. Several of these parameters can be combined into a time step in turn. Thus, it is possible to store five-dimensional data fields. The geometry information to the respective directions are in the label of the file. The label may also include additional information in custom fields. The data can be written in either single-precision ( 32-bit), double -precision (64 -bit) or quadruple -precision ( 128-bit). The file size is only limited by the file system, the computer architecture and the fact that the field size must be 64 -bit integer representing.

Functionality

The actual EAS3 program has a command line interface, EAS3 files can be edited or converted to the. The supported commands range from basic operations, such as basic arithmetic operations on file operations to complex operations such as deriving Fourier transforms or interpolation. Specific commands for flow data are also implemented, such as the calculation of the lambda2 vortex criterion. The output in other file formats is supported. Since the commands are read from standard input to EAS3 is also suitable for use in scripts to automate processes.

Overview of key features:

• File management: rearranging, concatenation, cut
• Conversion into other data formats (ASCII, Covise, Tecplot )
• Mathematical operations: basic arithmetic, logarithms, etc.
• Deriving and integrating
• Interpolate
• Data reduction: Averaging, RMS values ​​, etc.
• Fourier transformations: single / double, real / complex
• DNS - Specific: Eddy criterion, coordinate rotation

Installation

The sources can be obtained directly from the CVS repository or as a zipped tar file. For various Rechnerarchtiketuren Makefiles are included. This includes the possibility of cross-compiling, as is customary, for example, for supercomputers with front-end machine. Since there can be problems when linking created with different Fortran compilers, object files, a ready-made binary package (RPM. Deb ) has so far decided not to offer.

Pros and Cons

Benefits

For the programmer, the main advantage is a simple Implementiereung of read - write access to large binary data sets. So is ensured by the library that the data are always written in big- endian format. The resulting platform independence of the files makes it easy to exchange between different computer architectures. This is particularly important when using supercomputers important. For the user, it is advantageous that various methods are provided for data analysis, which may also be processed automatically by means of scripts.

Disadvantages

A disadvantage is the specialization in structured grids for some users. So far, only Cartesian grids or a representation in the spectral domain are implemented. Records, for example, are given in cylindrical coordinates, though can be saved, but you can see the existing analysis routines do not or only partially apply it. Since the visualization programs commonly used to support the EAS3 format directly, it is usually necessary to convert the records in the file format of the program. The EAS3 program there is only text-based, a graphical user interface does not exist. Although the auto-complete in the EAS3 console is a relief to the interactive work, but one has to rely on a detailed help on the site.

License

The complete EAS3 package is under the MIT license and is thus freely available. Due to the less strict license conditions compared to the GNU General Public License to use the routines provided not obliged to publish its own source code.

Use

EAS3 is used among others by the following institutions:

• Transition group at the Institute of Aerodynamics and Gas Dynamics (IAG ), University of Stuttgart
• Computational Fluid Dynamics Laboratory at the University of Arizona
• Institute of Fluid Dynamics, Swiss Federal Institute of Technology Zurich
• Institute of Aerodynamics at the Technical University Munich ( group high-speed aerodynamics)

Related data formats

Other data formats for storing binary data sets are:

• CFD General Notation System ( CGNS )
• Common Data Format (CDF ) of the NASA
• Covise data format
• NetCDF, based on (CDF )
• Tecplot binary data