NEIGHBORS_TO_METIS_GRAPH
Reformat Tet Mesh Neighbor File

NEIGHBORS_TO_METIS_GRAPH is a FORTRAN90 program, using double precision arithmetic, which reads a file describing the graph-theoretic adjacency structure of the tetrahedral elements in a mesh ("tet mesh") and writes out a similar file that is suitable for input to the mesh partitioning program METIS.

Since we know we are dealing with a tet mesh, each "node" of the adjacency graph has four potential edges. If a potential edge is not used (in other words, if a face is a boundary face), then by convention we write out a "-1" for the neighbor value. Otherwise, the adjacency information lists the index of the tetrahedral element that is a neighbor on that face of the tetrahedron.

Converting to a METIS GRAPH format is trivial. We include an initial line that lists the number of "nodes" (elements) and "edges" (interfaces between pairs of elements), followed by, for each node (element), a list of the adjacent nodes (a list of the adjacent elements, omitting the "-1" values). A cross-eyed schoolboy sitting on a tack would be able to carry out this task!

Usage:

neighbors_to_metis_graph neighbor_file metis_graph_file

reads the data in neighbor_file, rearranges it to suit METIS, and writes out the modified data to metis_graph_file

Related Programs:

GRAPHCHK is an executable C program which can read a METIS GRAPH file and verify that it has the proper format.

KMETIS is an executable C program, using METIS, which can partition the nodes of a graph.

METIS is a C library of routines for partitioning the nodes of a graph or the elements of a mesh or reordering the variables in a sparse matrix.

METIS_GRAPH is a data directory contains an explanation and some examples of the graph file format used by METIS.

OEMETIS is an executable C program which reads the adjacency graph of a sparse matrix, stored in METIS GRAPH format, and produces a reordering of the nodes to minimize fill.

ONMETIS is an executable C program which reads the adjacency graph of a sparse matrix, stored in METIS GRAPH format, and produces a reordering of the nodes to minimize fill.

PMETIS is an executable C program, using METIS, which can partition the nodes of a graph.

TET_MESH_NEIGHBORS is an executable FORTRAN90 program which reads information describing a tet mesh, and writes out the corresponding tet mesh neighbor file.

Reference:

1. metis.pdf,
   George Karypis, Vipin Kumar,
   METIS, a Software Package for Partitioning Unstructured Graphs and Computing Fill-Reduced Orderings of Sparse Matrices;

Source Code:

• neighbors_to_metis_graph.f90, the source code.
• neighbors_to_metis_graph.csh, commands to compile the source code.

Examples and Tests:

• cube_tetra.neighbors, a sample tet mesh neighbor file that can be used as input to the program.
• cube_tetra.metis_graph, the modified tet mesh neighbor file created by the program, suitable for input to METIS.

List of Routines:

• MAIN is the main program for NEIGHBORS_TO_METIS_GRAPH.
• CH_CAP capitalizes a single character.
• CH_EQI is a case insensitive comparison of two characters for equality.
• CH_TO_DIGIT returns the integer value of a base 10 digit.
• DTABLE_DATA_READ reads data from a double precision table file.
• DTABLE_HEADER_READ reads the header from a double precision table file.
• FILE_COLUMN_COUNT counts the number of columns in the first line of a file.
• FILE_NAME_EXT_GET determines the "extension" of a file name.
• FILE_NAME_EXT_SWAP replaces the current "extension" of a file name.
• FILE_ROW_COUNT counts the number of row records in a file.
• GET_UNIT returns a free FORTRAN unit number.
• I4COL_COMPARE compares columns I and J of a integer array.
• I4COL_SORT_A ascending sorts an integer array of columns.
• I4COL_SWAP swaps columns J1 and J2 of a integer array of column data.
• I4I4I4_SORT_A ascending sorts a triple of integers.
• I4MAT_TRANSPOSE_PRINT prints an I4MAT, transposed.
• I4MAT_TRANSPOSE_PRINT_SOME prints some of the transpose of an I4MAT.
• ITABLE_DATA_READ reads data from an integer table file.
• ITABLE_DATA_WRITE writes data to an integer table file.
• ITABLE_HEADER_READ reads the header from an integer table file.
• ITABLE_HEADER_WRITE writes the header to an integer table file.
• METIS_GRAPH_WRITE writes the METIS graph file.
• R8MAT_TRANSPOSE_PRINT prints an R8MAT, transposed.
• R8MAT_TRANSPOSE_PRINT_SOME prints some of an R8MAT, transposed.
• S_BLANK_DELETE removes blanks from a string, left justifying the remainder.
• S_INDEX_LAST_C finds the LAST occurrence of a given character.
• S_TO_I4 reads an integer value from a string.
• S_TO_I4VEC reads an I4VEC from a string.
• S_TO_R8 reads an R8 from a string.
• S_TO_R8VEC reads an R8VEC from a string.
• S_WORD_COUNT counts the number of "words" in a string.
• SORT_HEAP_EXTERNAL externally sorts a list of items into ascending order.
• TIMESTAMP prints the current YMDHMS date as a time stamp.
• TIMESTRING writes the current YMDHMS date into a string.

You can go up one level to the FORTRAN90 source codes.