$\Omega_h$ - Parallel adaptive simplex meshes

WHY WOULD I USE OMEGA_H ?

  You are doing something with tetrahedral or triangle meshes,
  probably solving PDEs on them, probably on HPC hardware.
  You would like a library and/or programs which handle
  mesh parallelization, topology, and adaptivity.

WHAT CAN IT DO ?

  Omega_h can do the following:
    - Accept meshes from mesh generators including
      Gmsh (http://gmsh.info/),
      TetGen (http://wias-berlin.de/software/tetgen/),
      and Triangle (http://www.cs.cmu.edu/~quake/triangle.html)
    - Associate and maintain simulation data with the mesh
    - Store meshes in a partitioned, lossless, flexible format
      based on VTK's UnstructuredGrid format.
    - Derive topological information about a given mesh
      (vertices-to-vertices, derive element boundaries...)
    - Partition a mesh with an arbitrary number of halo/ghost layers
    - Maintain a partitioned data structure and take care
      of scalably exchanging information among the partitions
    - Adapt a partitioned mesh using edge splits, collapses,
      and swaps to maintain a conformal representation,
      all the while transferring simulation data.
    - Do all of the above using either OpenMP or CUDA within
      each of the MPI ranks.

HOW DO I INSTALL IT ?

  Omega_h supports the usual procedure:

    ./configure && make && make install

  However, our configure is not yet very smart, so
  you may have to be quite specific about some things.
  Run this to determine the available options:

    ./configure --help

  Running our configure script produces a config.mk
  file, and an equally valid way to compile omega_h
  is to write your own config.mk file.
  Several examples are included in the source,
  look for *_config.mk.

HOW DO I USE IT ?

  Omega_h creates two things:
    - A library libomega_h and a corresponding API in omega_h.h
      The API functions are C functions.
    - A series of programs that help accomplish basic operations.

  The source tree contains the same layout as you
  would expect to see in the installation PREFIX,
  i.e. running `make' produces bin/, lib/, include/, etc.
  In that sense, one can easily use the source directory
  as the PREFIX in most cases, but we support `make install'
  for copying files into a separate PREFIX.

  The API is documented as man pages.
  If omega_h is not installed in a system directory,
  set your environment:
    export MANPATH=$MANPATH:$PREFIX/share/man

WHAT DO THE PROGRAMS DO ?

  warp.exe - runs an example mesh motion + adaptivity example in 2D,
             outputs files warp_000N.vtu
  warp_3d.exe - similar to warp.exe, runs a 3D example

  box.exe - generates a uniform mesh of an N-dimensional box
            (square, cube, line)
  from_gmsh.exe - converts a Gmsh .msh file into a .vtu file.
  node_ele.exe - converts .node and .ele files into a .vtu file
                 (this is the format output by TetGen and Triangle)
  vtkdiff.exe - compares two .vtu files with floating point
                tolerance, modeled after the exodiff program.
  partition.exe - partitions a single .vtu file into multiple
                  .vtu files and a .pvtu file.
  ghost.exe - adds ghost/halo layers to a partitioned mesh.
  vtk_ascii.exe - converts a .vtu file to its equivalent in
                  plain ASCII form, with human-readable arrays.
  subdim.exe - extracts boundary entities as their own mesh,
               for example the edges of a tetrahedral mesh.
               useful for advanced rendering / debugging.

WHAT IS THE FILE FORMAT ?

  Omega_h uses a superset of the VTK UnstructuredGrid format
  (http://www.vtk.org/wp-content/uploads/2015/04/file-formats.pdf).
  It consists of .vtu files for each mesh partition, and a
  .pvtu file that describes the partitions, in case there
  is more than one.
  Each of these files can be opened directly by
  Paraview (http://www.paraview.org/), and also by VisIt
  (https://wci.llnl.gov/simulation/computer-codes/visit).

  The format encodes binary information as ASCII using base64.
  It also uses XML headers at the top level for metadata,
  so for the most part it is quite human readable and can
  be opened in a text editor.