# Cygwin Build for Windows

### Overview

Cygwin provides a unix-like environment on a Windows machine, and emulates some of the functionality of a linux distribution. Downloads and more information on Cygwin is available at http://www.cygwin.com/. To compile and run SU2 in Cygwin on a Windows machine, you will need to configure Cygwin with the appropriate packages (listed below), and then continue from within Cygwin as though you were using a linux machine. In summary, the steps are:

2. Install Cygwin, selecting the packages necessary to compile the source code.
4. Install SU2 according to the directions for the linux installation.

### Notes on installing Cygwin for first-time or beginner Cygwin users

• It is often recommended to install in a directory rather than the default C:\ location.
• The Cygwin shell will only be able to access folders that are within the cygwin\ directory; you will need to install and run SU2 inside the cygwin directory.

### Cygwin packages

At the package selection step, search for the following terms and select the associated packages to install. This list is a work-in-progress, and further packages may be required or desired.

#### Basic

• g++, gcc compiler
• python: install the packages under the python sub-heading
• cpp: all debug, pre-processor, regular expression packages.

### Example SU2 installation on WINDOWS 10 using 64-bit Cygwin

The CYGWIN bash shell is used for all steps on the command line. It is automatically available after the first installation step (typically to be launched via the CYGWIN desktop icon).

1. Install CYGWIN (64-bit version) and development packages

setup-x86_64.exe

Inside the Cygwin Setup GUI use C:\cygwin64 for both Root Directory and Local Package Directory. Chose a Download Site close to you (also http mirrors often work better). Continue to complete the bare minimum installation. This will end with a desktop icon named Cygwin64 Terminal. Double-click this to open the shell and launch further commands from there.

For detailed informations on how to install CYGWIN and selected packages see CYGWIN Installation.

• Install development tools (dependencies on these packages will be automatically selected by CYGWIN)

NOTE: A single command installing all required packages in one is given below this list

1. General build environment tools
• autoconf
• autoconf2.5
• autogen
• automake
• automake1.15
• libtool
• make
2. Compilers
• gcc-g++
• mingw64-x86_64-gcc-core
• mingw64-x86_64-gcc-g++
3. Python
• python37
• python37-devel
• python3-configobj
4. OpenMPI
• libopenmpi-devel
• openmpi
5. Miscellaneous
• vim (or any other editor in order to be able to edit files)
• rsh
• zlib-devel
• All-in-one installation of packages (after the initial minimum installation):

NOTE: Prepend path to setup-x86_64.exe (depending where it has been downloaded)

  setup-x86_64.exe -q -P autoconf,autoconf2.5,autogen,automake,automake1.15,libtool,make,gcc-g++,mingw64-x86_64-gcc-core,mingw64-x86_64-gcc-g++,python37,python37-devel,python3-configobj,libopenmpi-devel,openmpi,vim,rsh,wget,zlib-devel

2. Configure CYGWINs default mount point (optional, but following steps use a syntax relying on this)

mount -c / -o binary,noacl,posix=0
mount -m > /etc/fstab

3. Configure OpenMPI

Because in OpenMPI the C++ interface was removed, the option -lmpi_cxx has to be removed from the linker defaults. We need to check if this option is contained in the wrapper control file. This depends on the installed OpenMPI libraries.

Assuming the 64-bit CYGWIN is installed in C:\cygwin64 and /etc/fstab has been modified as in the previous step:

cat /c/cygwin64/usr/share/openmpi/mpic++-wrapper-data.txt | grep lmpi_cxx


If the option is set, then the following lines would be the result of the above grepcommand:

libs=-lmpi_cxx -lmpi
libs_static=-lmpi_cxx -lmpi -lopen-rte -lopen-pal -lm -lgdi3


NOTE: If -lmpi_cxx was not found, skip the next step

If this is the case, edit mpic++-wrapper-data.txt and remove the -lmpi_cxx options so that the respective lines look like this:

libs=-lmpi
libs_static=-lmpi -lopen-rte -lopen-pal -lm -lgdi3

4. Set the Python version for the installation process (for permanent setting add this line to ~/.profile)

export PYTHON=/usr/bin/python3.7

5. Get the SU2 source code:

 wget https://github.com/su2code/SU2/archive/v6.2.0.tar.gz

• Extract files and change into the folder where the files were extracted to:

 tar -xzvf v6.2.0.tar.gz
cd SU2-6.2.0


NOTE: This is later the folder where the SU2_HOME variable points to

6. Run the utility for autoconf/automake toolchain setup:

./bootstrap

7. Set compiler flags (just to be sure not to use the debug option -g)

export CFLAGS='-O2'
export CXXFLAGS='-O2'

8. Create Makefiles:

NOTE: didn’t yet get tecio working, therefore disabled with --disable-tecio
NOTE: Removed -DHAVE_EXECINFO_H from metis cppflags (potentially could be solved via gnulib)

./configure --prefix=/home/Andreas/SU2-6.2.0 -enable-mpi --with-cc=/usr/bin/mpicc --with-cxx=/usr/bin/mpicxx --disable-tecio --with-metis-cppflags="-D_FILE_OFFSET_BITS=64 -DNDEBUG -DNDEBUG2 -DHAVE_GETLINE"


make

10. Distribute executables, etc. to their intended locations:

make install

11. Reduce size of executables significantly (strip symbols, see also CYGWIN FAQ 6.3. The SU2_CFD.exe is reduced from approx. 600MB to 15MB. Can be omitted if compiled with the -s option to gcc.

NOTE: This should NOT be necessary if compiler flags are set as shown in step 7

make install-strip

12. Cleanup the installation. This removes also the intermediate big executables from the build folders.

make clean

13. Add the $SU2_HOME and $SU2_RUN environment variables to ~/.bashrc (and source ~/.bashrc)

export SU2_RUN="path_where_you_want_the_Executables" (use same folder here as in the configure command above)
export SU2_HOME="/d/software/CFD/SU2/SU2-6.2.0"  <-- UPDATE THIS folder according to your environment
export PATH=$PATH:$SU2_RUN
export PYTHONPATH=$PYTHONPATH:$SU2_RUN

14. Test serial and parallel versions:

cd \$SU2_HOME/QuickStart


SERIAL command (due to the previous step SU2_CFD.exe should now be available in the path):

SU2_CFD.exe inv_NACA0012.cfg


PARALLEL command: Both mpirun and mpiexec do the same; mpiexec is recommended as the standard command.

mpiexec -n 4 SU2_CFD.exe inv_NACA0012.cfg


If more processes are requested than cores are available an error will be thrown:

There are not enough slots available in the system.

On WINDOWS this can be if hyperthreading is active. A system physically having 4 CPUs (cores), would show 8 CPUs in case of hyperthreading. Oversubscribe allows more processes than cores (which not necessarily is faster).

mpiexec -n 8 -oversubscribe SU2_CFD.exe inv_NACA0012.cfg