Usage examples

Some library examples are provided in the mmg repository, under the libexamples directory. (see the projects source tree section of the wiki for the description of the libexamples directory).

• Basic examples with automatic parsing of .mesh files are provided in the libexamples/mmg<X>/adaptation_example0/example0_a folder (<X> = <2d|3d|s> depending on the library that you want to use). Inputs/outputs are done using the API functions that read/write .mesh/.sol files.

• Basic examples with manual mesh setters and getters are provided in the libexamples/mmg<X>/adaptation_example0/example0_b folder. Inputs/outputs are done using setters and getters to transfer a mesh and a size map already stored in arrays (in the solver structures for example) to mmg entities by entities.

• Examples of Fortran calls can be found in the libexamples/mmg<X>/adaptation_example0_fortran/example0_<a|b> folders. These examples are similar to the previous ones. Usually, a Fortran subroutine similar to the C API is provided with an additional argument to store the return value of the C function. Note that if the C API takes a string as argument, the Fortran one will use another additional input argument for string length.

• An example of library call from a C++ code is provided in libexamples/mmg/adaptation_example0_cpp.

• libexamples/mmg3d/adaptation_example2 shows how to customize some of the parameters of Mmg;

• libexamples/mmg3d/IsosurfDiscretization_example0 provides examples of isovalue discretisation;

• libexamples/mmg3d/LagrangianMotion_example0 shows examples of lagrangian motion.

• Even if we try to preserve the API compatibility between mmg versions, we can have small modifications. In this case, you can use predefined macro (MMG_VERSION, MMG_VERSION_LE…) to detect the API version of Mmg in your code. An example is provided in the mmg/libexamples/mmg2d/adaptation_example0/example0_b/ directory (and its fortran version);

Since mmg3d library and API have been developped first, you will find more examples in the libexamples/mmg3d folder than in the other ones. Note that the APIs of the 3 codes works in the same way except that:

• use suitable prefixes: MMG3D_ for mmg3d, MMG2D_ for mmg2d or MMGS_ for mmgs.

• in 2D, the MMG2D_Set_vertex function takes 2D coordinates while the MMGS_Set_vertex and MMG3D_Set_vertex functions take 3D coordinates.

How to link mmg libraries

By default, the make install command installs the libraries into the /usr/local/lib directory. The header files are located into the /usr/local/include directory.

Link using CMake

Several .cmake files may be used:

• the FindMMG.cmake file to automatically find the mmg library.

• the FindMMG2D.cmake file to automatically find the mmg2d library.

• the FindMMGS.cmake file to automatically find the mmgs library.

• the FindMMG3D.cmake file to automatically find the mmg3d library.

If the package fails, try:

• setting the MMG_DIR environment variable to your mmg directory path:

  export MMG_DIR=<your_mmg_directory_path>
  

• setting the MMG_DIR CMake variable to your mmg directory path:

  SET(MMG_DIR <your_mmg_directory_path>)
  

FindMMG.cmake package

The FindMMG.cmake package defines the MMG_INCLUDE_DIRS and the MMG_LIBRARIES variables. To link a program named YOUR_TARGET with the mmg library using CMake, add the following lines in your CMakeLists.txt:

FIND_PACKAGE(MMG)
INCLUDE_DIRECTORIES(${MMG_INCLUDE_DIRS})
TARGET_LINK_LIBRARIES( ${YOUR_TARGET} ${MMG_LIBRARIES})

Do not forget to include the mmg library headers to your program:

#include "mmg/libmmg.h"

FindMMG<X>.cmake package

The FindMMG<X>.cmake packages, with <X> = <2d|3d|s>, define the MMG_INCLUDE_DIRS and the MMG_LIBRARIES variables. To link a program named YOUR_TARGET with the mmg library using CMake, add the following lines in your CMakeLists.txt:

INCLUDE(FindMMG<X>.cmake)
INCLUDE_DIRECTORIES(${MMG<X>_INCLUDE_DIRS})
TARGET_LINK_LIBRARIES( ${YOUR_TARGET} ${MMG<X>_LIBRARIES})

Do not forget to include the mmg library headers to your program:

#include "mmg/mmg<X>/libmmg<X>.h"

Link using command lines

In the following examples, it is assumed that:

• a one-file program is compiled (main.c).

• mmg libraries are installed in the <LIB_PATH> directory and the header files in the <INCLUDE_PATH> one (which is the default configuration).

• the scotch library is installed in the <SCOTCH_PATH> directory.

To compile with the mmg3d library, it is necessary to specify:

• the mmg3d include directory with the -I option.

• the mmg3d library location with the -L option.

• the mmg3d library name with the -l option.

in the following command:

gcc main.c -I<INCLUDE_PATH> -L<LIB_PATH> -L<SCOTCH_PATH> -lmmg3d -lscotch -lscotcherr -lm

Note that mmg uses the math library and may require it be to linked as well (-lm option). If mmg is built without scotch, variables related to it may be removed:

gcc main.c -I<INCLUDE_PATH> -L<LIB_PATH> -lmmg3d -lm

It may be needed to add the path toward the library directory to your LD_LIBRARY_PATH environment variable:

export LD_LIBRARY_PATH=<LIB_PATH>:$LD_LIBRARY_PATH

Finally, include the mmg3d library headers to your program:

#include "mmg/mmg3d/libmmg3d.h"

Fortran users

Depending on the extension of Fortran files and on the compiler that is used, it may be necessary to enable the preprocessing step to link with the mmg libraries.

For example, gfortran enables automatically the preprocessing for .F90 files and not for .f90 files. Thus, to compile the main.f90 file that uses the mmg API functions, add the -cpp option to gfortran:

gfortran -cpp main.f90 -lmmg3d -lscotch -lscotcherr -lm

Linking with dynamic library on macOS

To avoid trouble with the rpath under Mac OS X just add -Wl,-rpath,<LIB_PATH> to your compilation command line:

gcc main.c -I/usr/local/include/ -L/usr/local/lib -lmmg3d -lm -Wl,-rpath,<LIB_PATH>

Please refer to your compiler documentation for further information.