building

Linux, Unix-like systems
Packaging systems
- spack
- easybuild
Darwin (Mac-OS)
- Known issues
Windows (cross-compiled)
Tuning

Linux, Unix-like systems

Version	Build
v2106	Build
v2012	Build
v2006	Build
v1912	Build
v1906	Build
older	obsolete

Packaging systems

System	Links	Status	Notes
spack	package openfoam	Actively maintained by OpenCFD	notes
EasyBuild	package OpenFOAM	Maintained independently, with input from OpenCFD
debian, RPM	See precompiled	Actively maintained by OpenCFD

spack

The installation of OpenFOAM with spack will generally require the latest (development version) of spack. If this is available, you can install OpenFOAM in various configurations and dependencies, but typically can simply install directly:

$ spack install openfoam

easybuild

The installation of OpenFOAM with easybuild will generally require the latest (development version) of easybuild.

Darwin (Mac-OS)

The support for Darwin is complete, but less well tested than Linux.

The Darwin build (and operation) requires a case-sensitive file system, which is often created as a disk image and mounted (for older systems).
Compilation uses the system clang compiler.

Known issues

CGAL

ThirdParty CGAL will normally need to be compiled without mpfr/gmp. This should be done manually prior to building OpenFOAM or other ThirdParty. For example,
```
cd $WM_THIRD_PARTY_DIR
./makeCGAL gmp-none mpfr-none
```
The wmake/rules/darwin64Clang/CGAL file has been adjusted to eliminate references to gmp/mpfr libraries.

Windows (cross-compiled)

Windows 64bit binaries can be generated on 64bit Linux by cross-compilation.

Tuning

Different configurations

Sometimes it is useful to switch between entire sets of configuration preferences without re-editing the files each time. This is the purpose of the FOAM_CONFIG_ETC variable. It specifies an absolute path, or a path relative to the project directory where various configuration files can be found. These are selected in preference to the normal shipped configuration files.

This allows swapping in a set of different preferences without modifying the regular settings. See cross-compilation for an example of its use.

Processor-specific handling

Processor-specific builds are typically handled by creating a new compilation option. For example, to create Broadwell-specific options:

    $ cd wmake/rules/linux64Gcc
    $ cp c++Opt c++OptBdw

edit this file and then use WM_COMPILE_OPTION=OptBdw in the prefs.sh before re-sourcing the OpenFOAM environment.

Since OpenFOAM is purely C++ code, there is no need to apply special processor-specific optimizations for C code (the regular -O2 optimization is fine) since these components only appear as part of the wmake build toolchain itself.

Different compiler versions

By default, OpenFOAM handles newer/older non-system compilers as ThirdParty installations and uses the combination of WM_COMPILER and WM_COMPILER_TYPE to select them. In some cases, however, it can be much more convenient for the user to install prebuilt compiler binaries as system compilers (e.g., using deb or rpm packages). This poses a slight problem since the OpenFOAM build rules normally use the main compiler name (gcc, clang etc) without any additional version information, but the various system compilers are frequently installed with versioned names such as gcc-8, clang-10 etc.

Here is a simple way to solve this, using clang-10 on openSUSE for the example:

Install the desired system compiler. In this case clang-10 from tools:compiler which installs /usr/bin/clang-10 and /usr/bin/clang++-10.
Next override the OpenFOAM compiler calls, but without blindly rewriting everything.

We create a new directory for our special rules:
```
mkdir wmake/rules/linux64Clang100
```
Inside this directory, we add an general rules file (wmake/rules/linux64Clang100/general) with the following contents:
```
# Override compiler calls for llvm-10

cc  = clang-10
CC  = clang++-10 -std=c++11
```
Or if this shall be restricted to system compilers only:
```
# Override system compiler calls for llvm-10
ifeq (system,$(WM_COMPILER_TYPE))
    cc  = clang-10
    CC  = clang++-10 -std=c++11
endif
```
The final step is to select this compiler definition with the following combination:
```
# Preferences for system Clang100

export WM_COMPILER=Clang100
export WM_COMPILER_TYPE=system
```
If this change represents your standard default compiler definition, then place the information into the etc/prefs.sh file (see the etc/bashrc file for some details) and re-source your OpenFOAM environment.

If you would like to selectively enable this compiler definition, a common means is to place the same definition information into a user configuration file (for example, ~/.OpenFOAM/clang100) and then specify that configuration when sourcing your OpenFOAM environment. For example,
```
source /path/to/OpenFOAM-version/etc/bashrc  clang100
```
The bashrc will locate and use the configuration file, after which the compiler will be properly selected. To verify that this is indeed the case:
```
wmake -show-cxx
```
should display the selected compiler. You may also wish to verify its path:
```
wmake -show-path-cxx
```
For older versions, which $(wmake -show-cxx) instead.