Installation

The easiest way to install is to use pip,

$ pip install .

Note that Ramos requires Python 3, so you need to use a pip command that is tied to Python 3. On some systems, this may be called pip3.

$ pip3 install .

Pip is often not installed by default, and may be found in a distribution package named something like python-pip or python3-pip.

The above commands install gmesh system-wide and may require sudo. To install locally, use

$ pip3 install −−user .

The ramos script will then be installed to a directory such as ~/.local/bin. To run gmesh, make sure that this is in your PATH, e.g. put

export PATH=$HOME/.local/bin:$PATH

in your shell startup file.

Dependencies

pip automatically installs the hard dependencies (such as numpy), however some of the ramos commands require optional dependencies to be installed. If you need any of them, please install them manually, and please do ensure that you get the Python 3 versions.

File types

• The Python HDF5 bindings are required for reading HDF5 files. E.g. in Ubuntu, try the python3-h5py package.
• The Python vtk bindings are required for reading and writing VTK files.

Usage

Data sources

Ramos can handle a variety of data sets, but the most mature support is for VTK files, where the data is in two dimensions (triangular or quadrilateral meshes) or three dimensions (tetrahedral or hexahedral meshes). Mixed meshes are fine.

VTK data sets are commonly found in a structure such as this:

folder/filename-0.vtk
folder/filename-1.vtk
folder/filename-2.vtk
...

Or this:

folder/<time1>/<fieldname1>.vtk
folder/<time1>/<fieldname2>.vtk
...
folder/<time2>/<fieldname1>.vtk
folder/<time2>/<fieldname2>.vtk
...

To ensure that Ramos can understand your data source, execute the command

ramos summary <folder>

and inspect the output, especially make sure that all steps are accounted for and that all fields you expect to be found are found.

Note: By and large, all Ramos operations will write new data in the same format as the source data.

Mesh interpolation

For reduction to work, all source data must coexist on the same mesh. This is not necessarily guaranteed across multiple steps and data sources. For this, Ramos supplies the interpolate command.

ramos interpolate -o <output> <input>

This interpolates all data sets from the input source on the same mesh and writes the data to output. The mesh chosen is the first one in the input source (from the first timestep). You can optionally specify which mesh to use with

ramos interpolate -o <output> -t <target> <input>

After this, it's probably a good idea to do

ramos summary <output>

to ensure that everything worked as planned.

Reduction

To perform reduction on a data set, use the reduce command.

ramos reduce -f <fieldname> -e <error> --min-modes <nmodes> -o <output> <inputs...>

Specify the field name you want to reduce over, and optionally the error threshold you are interested in. In some cases it may be useful to specify a minimum number of modes to output as well.

The modes will be written to the output data target as separate timesteps. A csv file will also be produced with the system spectrum, in four columns:

• index
• eigenvalue
• normalized tail sum of eigenvalues
• square root of normalized tail sum of eigenvalues (i.e. expected error)