METIS MESH Files

These are some examples of "mesh" files used by the METIS program. METIS can read a mesh file, and partition the elements in a balanced way so that each partition has about the same number of elements, while minimizing the number of cases in which elements from different parts of the partition share an edge or face. This process is designed with the idea that the mesh represents a computation that is to be divided up among various processors, with the stipulation that the amount of interprocessor communication must be limited.

METIS MESH File Characteristics:

• ASCII
• a mesh of N elements is stored in a file of N+1 lines;
• the first line lists the number of elements, and a code that indicates the type of element;
  1. 2D triangles;
  2. 3D tetrahedrons;
  3. 3D hexahedrons ("bricks" with 6 sides and 8 vertices);
  4. 2D quadrilaterals;
• each subsequent line lists the vertices of one element;
• for triangular and tetrahedral elements, the vertices may be listed in any order; quadrilateral and hexahedral elements require that the vertices be listed in a particular order;
• comment lines begin with a "%" sign;

Reference:

1. metis.pdf,
   George Karypis and Vipin Kumar,
   METIS, a Software Package for Partitioning Unstructured Graphs and Computing Fill-Reduced Orderings of Sparse Matrices;
2. George Karypis and Vipin Kumar,
   A fast and high quality multilevel scheme for partitioning irregular graphs,
   SIAM Journal on Scientific Computing,
   Volume 20, Number 1, 1998, pages 359-392;
3. http://www.cs.umn.edu/~metis,
   The METIS home page;

Programs and routines to read a METIS MESH file:

• io.c contains the routines needed to read a METIS mesh file.

Programs to process a METIS MESH file:

• partdmesh can partition the elements of a mesh defined by a METIS MESH file, using the dual graph.
• partnmesh can partition the elements of a mesh defined by a METIS MESH file, using the nodal graph.

Programs to convert a METIS MESH file to another format:

• MESH2DUAL is an executable C program which reads a METIS MESH file and writes out a METIS GRAPH file of the dual graph.
• MESH2NODAL is an executable C program which reads a METIS MESH file and writes out a METIS GRAPH file of the nodal graph.
• NEIGHBORS_TO_METIS_GRAPH is a program which reads a data file containing adjacency information for a mesh of tetrahedral elements, and writes out a METIS GRAPH file.

Sample METIS MESH Files:

• metis.mesh, a mesh of the a region that looks like the word "METIS";
• tri.mesh, a tiny example mesh of a 2D region, using triangular elements;
• tet.mesh, a tiny example mesh of a 3D region, using tetrahedral elements;
• quad.mesh, a tiny example mesh of a 2D region, using quadrilateral elements;
• hex.mesh, a tiny example mesh of a 3D region, using hexahedral (brick) elements;

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