Instructions to build OpenFOAM-v7 with ARM and CRAY-MPICH compiler on Isambard

  1. Download OpenFOAM-7 and ThirdParty-7 
      BUILD_DIR=$HOME/OpenFOAM
  mkdir $BUILD_DIR
  cd $BUILD_DIR
  git clone https://github.com/OpenFOAM/OpenFOAM-7.git
  git clone https://github.com/OpenFOAM/ThirdParty-7.git

  2. Load ARM compiler1 
     # load ARM compiler if no compilers are loaded
 module load PrgEnv-allinea/6.0.5
 # or swap current cray compiler with arm compiler
 module switch PrgEnv-cray/6.0.5 PrgEnv-allinea/6.0.5
 # export compiler variables
 export CC=armclang
 export CXX=armclang++
 export FC=armflang
 export OMPI_CC=$CC
 export OMPI_CXX=$CXX
 export OMPI_FC=$FC
 # set other compiler variables 
 OF_COPT="-march=armv8.1-a -mtune=thunderx2t99 -O3 -ffp-contract=fast"
 OF_CXXOPT="$OF_COPT -std=c++11"
    
 # make modifications to the configuration files
 cd $BUILD_DIR/OpenFOAM-7
 # create necessary files with compiler options
 echo -e "WM_COMPILER=Clang \nWM_MPLIB=CRAY-MPICH \nWM_LABEL_SIZE=64" > $BUILD_DIR/OpenFOAM-7/etc/prefs.sh
 echo -e "include \$(GENERAL_RULES)/mplibMPICH" > wmake/rules/General/mplibCRAY-MPICH
 cp -r $BUILD_DIR/OpenFOAM-7/wmake/rules/linux64Clang $BUILD_DIR/OpenFOAM-7/wmake/rules/linuxAArch64Clang

  3. Download and apply patch to the configuration files 
     # Download the two patch files and apply the patch running the below commands
 wget https://dl.dropboxusercontent.com/s/gbxz7e33qpi73hm/OpenFOAM-7.patch -P $BUILD_DIR
 wget https://dl.dropboxusercontent.com/s/0t0euvwta6o4mos/ThirdParty-7.patch -P $BUILD_DIR
 (cd $BUILD_DIR/OpenFOAM-7/; patch -p1 < $BUILD_DIR/OpenFOAM-7.patch)
 (cd $BUILD_DIR/ThirdParty-7/; patch -p1 < $BUILD_DIR/ThirdParty-7.patch)

  4. Compile OpenFOAM-7 
     # source configuration file
 . etc/bashrc
 # Compile openfoam using all available processors (-j).
 ./Allwmake -j 64

    References:
    [1]: https://gitlab.com/arm-hpc/packages/wikis/packages/openfoam
    [2]: https://openfoamwiki.net/index.php/Installation/Linux/OpenFOAM-7/CentOS_SL_RHEL
    [3]: https://openfoamwiki.net/index.php/Installation/Linux/OpenFOAM-6.x/CentOS_SL_RHEL