CFD Online Discussion Forums - What's the Eigen library setup for OpenFOAM?

CFD Online Discussion Forums (https://www.cfd-online.com/Forums/)

- OpenFOAM Programming & Development (https://www.cfd-online.com/Forums/openfoam-programming-development/)

- - What's the Eigen library setup for OpenFOAM? (https://www.cfd-online.com/Forums/openfoam-programming-development/253439-whats-eigen-library-setup-openfoam.html)

What's the Eigen library setup for OpenFOAM?

I want to use the Eigen header file library in an OpenFOAM preconditioner but I keep getting compiler errors telling me, that Eigen is not found.

Eigen is "installed" i.e. header files are located in the directory: /home/klaus/Programme/eigen-3.4.0/Eigen

I added the Eigen3_ROOT to the .bashrc and rebooted as shown below

Code:

# set Eigen3_ROOT

export Eigen3_ROOT=/home/klaus/Programme/eigen-3.4.0

I added

Code:

#include <Eigen/Sparse>

at the top of the source code

Online instructions tell me to add

Code:

EXTERNAL_LIBS += -lEigen3

to the Make/options file, I tried but I keep getting the same error:

Code:

MYPreconditioner.C:32:10: Fatal error: Eigen/: File or directory not found

   32 | #include <Eigen/Sparse>

| ^~~~~~~~~~~~~~

Eigen can be found at:

HTML Code:

https://eigen.tuxfamily.org/index.php?title=Main_Page

What's the setup needed to be able to use Eigen within OpenFOAM?

E.g. how to adjust the Make/options file:

Code:

EXE_INC = \

    -I$(OBJECTS_DIR) 



LIB_LIBS = \

    $(FOAM_LIBBIN)/libOSspecific.o



ifeq (libo,$(FOAM_LINK_DUMMY_PSTREAM))

    LIB_LIBS += $(FOAM_LIBBIN)/dummy/libPstream.o

else

    LIB_LIBS += -L$(FOAM_LIBBIN)/dummy -lPstream

endif



/* libz */

EXE_INC += -DHAVE_LIBZ 



LIB_LIBS += -lz





/* Project lib dependencies. Never self-link (WM_PROJECT == OpenFOAM) */

PROJECT_LIBS =

1/ Distinguish between compile and link stage.

2/ For compile stage: -I<dir> where <dir> is the directory where header files are located.

3/ For link stage: -L<dir> where <dir> is the directory where library files are located.

Quote:

Originally Posted by klausb (Post 861390)

Code:

# set Eigen3_ROOT

 export Eigen3_ROOT=/home/klaus/Programme/eigen-3.4.0

...

From my knowledge, Eigen is header-only. Please take a look at wmake/scripts/have_eigen and wmake/rules/General/eigen

Typically you would try something like
"sh wmake/scripts/have_eigen -test" from the command-line to see how things work (or not). If you take a look through the file, you will see that it also likes to find its preferences via config.sh/eigen file, where it possibly obtains an EIGEN_ARCH_PATH.

If this detection works OK, then you would add this detection in an src/OpenFOAM/Allwmake script (you need inject this yourself) and then pass through (see src/renumber/Allwmake for an example).

Of course, you could also just define it all yourself in the OpenFOAM/Make/options (might actually be easier). For example (not tested):

OpenFOAM/Make/options

Code:

EXE_INC = \

    -I$(OBJECTS_DIR) 



 ifneq (,$(Eigen3_ROOT))

    EXE_INC += -DHAVE_EIGEN -I$(Eigen3_ROOT)/include

endif

 ...

Then, similar to the HAVE_LIBZ handling, selectively include and enable in your code.

I followed the setup for an OpenFOAM solver I found online:

Add the following to the .bashrc file:

Code:

# set Eigen3_ROOT and EIGEN_LIBRARY_PATH

export Eigen3_ROOT=$HOME/Programme/eigen-3.4.0

export EIGEN_LIBRARY_PATH=$HOME/Programme/eigen-3.4.0

Include -I$(EIGEN_LIBRARY_PATH) into the Make/options file as shown below

Code:

EXE_INC = \

    -I$(OBJECTS_DIR) \

    -I$(EIGEN_LIBRARY_PATH)