FEM_IO
Read or Write a Finite Element Model

FEM_IO is a C++ library which reads or writes FEM files, which describe the nodes, elements, and function values associated with a finite element method (FEM) model;

The finite element model is assumed to include three items:

• Node coordinates;
• Elements defined by a sequence of node indices;
• Node data;

Licensing:

The computer code and data files described and made available on this web page are distributed under the GNU LGPL license.

Languages:

FEM_IO is available in a C version and a C++ version and a FORTRAN77 version and a FORTRAN90 version and a MATLAB version.

Related Data and Programs:

FEM_DISPLAY, a MATLAB program which reads the FEM model of a 2D mesh, consisting of polygonal elements of any uniform order, and displays an image of the elements and nodes, with optional numbering.

FEM_TO_GMSH, a C++ program which reads FEM files definining a 1D, 2D or 3D mesh, namely a file of node coordinates and a file of elements defined by node indices, and creates a Gmsh mesh file.

FEM_TO_MEDIT, a C++ program which reads a pair of FEM files defining node coordinates and elements, and creates a corresponding MEDIT mesh file.

FEM_TO_TRIANGLE, a C++ program which reads FEM files defining a 2D mesh of triangles, namely a file of node coordinates and a file of elements defined by node indices, and creates a corresponding pair of node and element files for use by Jonathan Shewchuk's triangle program.

FEM_TO_XML, a C++ program which reads FEM files defining a 1D, 2D or 3D mesh, namely a file of node coordinates and a file of elements defined by node indices, and creates a corresponding XML file for input to DOLFIN or FENICS.

FEM1D, a data directory which contains examples of 1D FEM files, three text files that describe a 1D finite element model;

FEM2D, a data directory which contains examples of 2D FEM files, three text files that describe a 2D finite element geometry;

FEM2D_PACK, a C++ library which is useful for 2D finite element calculations.

FEM3D, a data directory which contains examples of 3D FEM files, three text files that describe a 3D finite element geometry;

GMSH_TO_FEM, a C++ program which reads a mesh data file created by the GMSH program and writes a pair of node and element files that correspond to the FEM format.

MEDIT_IO, a C++ library which can read or write MEDIT mesh files, which can be used to define the geometry of a finite element mesh in 2D or 3D, using triangles, quadrilaterals, tetrahedrons or hexahedrons.

MEDIT_TO_FEM, a C++ program which reads a mesh file created by the MEDIT program and writes a corresponding pair of node and element files that correspond to the FEM format.

TABLE_IO, a C++ library which can read and write TABLE files.

TRIANGLE_TO_FEM, a C++ program which reads the NODE and ELE files created by triangle() to describe a triangular mesh, and writes a corresponding pair of node and element files in the 2D FEM format.

Reference:

1. Hans Rudolf Schwarz,
   Finite Element Methods,
   Academic Press, 1988,
   ISBN: 0126330107,
   LC: TA347.F5.S3313..
2. Gilbert Strang, George Fix,
   An Analysis of the Finite Element Method,
   Cambridge, 1973,
   ISBN: 096140888X,
   LC: TA335.S77.
3. Olgierd Zienkiewicz,
   The Finite Element Method,
   Sixth Edition,
   Butterworth-Heinemann, 2005,
   ISBN: 0750663200,
   LC: TA640.2.Z54
4. Daniel Zwillinger, editor,
   CRC Standard Mathematical Tables and Formulae,
   30th Edition,
   CRC Press, 1996,
   ISBN: 0-8493-2479-3.

Source Code:

• fem_io.cpp, the source code.
• fem_io.hpp, the include file.
• fem_io.sh, commands to compile the source code.

Examples and Tests:

FEM_IO_PRB is a test program which tests the routines that read and write finite element data.

• fem_io_prb.cpp is the source code of the tests.
• fem_io_prb.sh runs all the tests.
• fem_io_prb_output.txt the output file.

ELL is an example of a 2D finite element model in which a scalar value is stored.

• ell_nodes.txt
• ell_elements.txt
• ell_values.txt

P01 is a 3D rectangular channel, with dimensions 1x1x3, using 584 nodes and 2568 elements. This data was created by DISTMESH.

• p01_nodes.txt
• p01_elements.txt
• p01_values.txt

TINY is a "tiny" example of a 2D finite element model in which a vector value is stored. This data was written by the FEM_WRITE routine.

• tiny_nodes.txt
• tiny_elements.txt
• tiny_values.txt

List of Routines:

• CH_CAP capitalizes a single character.
• CH_EQI is true if two characters are equal, disregarding case.
• CH_TO_DIGIT returns the integer value of a base 10 digit.
• FEM_DATA_READ reads data from a set of FEM files.
• FEM_HEADER_PRINT prints the header to set of FEM files.
• FEM_HEADER_READ reads the sizes of arrays in a set of FEM files.
• FEM_WRITE writes data files associated with a finite element solution.
• FILE_COLUMN_COUNT counts the number of columns in the first line of a file.
• FILE_ROW_COUNT counts the number of row records in a file.
• I4_MAX returns the maximum of two integers.
• I4_MIN returns the smaller of two integers.
• I4MAT_TRANSPOSE_PRINT prints an I4MAT, transposed.
• I4MAT_TRANSPOSE_PRINT_SOME prints some of an I4MAT, transposed.
• 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 of an integer TABLE file.
• R8_EPSILON returns the roundoff unit for R8's.
• R8MAT_TRANSPOSE_PRINT prints an R8MAT, transposed.
• R8MAT_TRANSPOSE_PRINT_SOME prints some of an R8MAT, transposed.
• R8TABLE_DATA_READ reads the data from an R8TABLE file.
• R8TABLE_DATA_WRITE writes data to an R8TABLE file.
• R8TABLE_HEADER_READ reads the header from an R8TABLE file.
• R8TABLE_HEADER_WRITE writes the header of an R8TABLE file.
• S_BLANK_DELETE removes blanks from a string, left justifying the remainder.
• S_LEN_TRIM returns the length of a string to the last nonblank.
• S_TO_I4 reads an I4 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 a real vector from a string.
• S_WORD_COUNT counts the number of "words" in a string.
• TIMESTAMP prints the current YMDHMS date as a time stamp.
• TIMESTRING returns the current YMDHMS date as a string.

You can go up one level to the C++ source codes.