Analysis Tools

Visualization Software

Athena++ can output formatted table, VTK, and HDF5 data (see also Outputs).

The formatted table (.tab) format is intended for relatively small simulations, in particular 1D and 2D ones. This is just a simple text file which can be plotted by your favorite plotting software. For example, we recommend gnuplot as it is simple and free. The meaning of each column is described in the file header.

VTK and HDF5 are standard formats commonly used in numerical simulations. Because VTK is non-parallel IO, it is intended for relatively small 2D and 3D simulations. You can merge the VTK files using vis/vtk/join_vtk++.c, but currently this code works only for simulations without mesh refinement. For massively parallel simulations and/or simulations with mesh refinement, HDF5 is strongly recommended.

To visualize VTK or HDF5 files, there are some options publicly available, such as VisIt and ParaView. yt also supports the Athena++ HDF5 output with some minor limitations. For usage of these programs, please consult their documentation.

To read HDF5 data with VisIt or ParaView, load the corresponding .xdmf (eXtensible Data Model and Format) files, which tell the software how to read the .athdf files. All the variables are stored as scalars. For convenience, we provide typical variable expression files for VisIt in the vis/vtk directory. You can load these files from "Controls → Expressions".

For very large simulations (with thousands of MeshBlocks), VisIt can be slow to read in data. It may be helpful to first resample the HDF5 files in this case.

Python Plotting and Analysis

Several simple plotting scripts are included. These are described in Plotting Scripts. For more detailed analysis, see Reading Data into Python for how to work with Athena++ outputs in a Python script.

Reading .athdf Files

The format of .athdf files is HDF5, and can be read from your favorite programming language using the HDF5 library/package/etc. The data structure is pretty self-explanatory, and you can see it using HDFVIEW provided by the HDF Group. See also HDF5-Format.