4.4. Building OpenFAST on Windows with CMake and Cygwin 64-bit¶

4.4.1. Installing prerequisites¶

Download and install Cygwin 64-bit. You will need to Run as Administrator to complete the installation process.
- Choose Install from internet
- Choose the default install location
- Choose the default package download location
- Choose Direct connection
- Choose http://www.gtlib.gatech.edu as the download site
- See next step for select packages. Alternately, you can skip this step and run setup-x86_64.exe anytime later to select and install required software.
Select packages necessary for compiling OpenFAST. Choose binary packages and not the source option.
- Choose Category view, we will be installing packages from Devel and Math
- From Devel mark the following packages for installation
  cmake
  
  cmake-doc
  
  cmake-gui
  
  cygwin-devel
  
  gcc-core
  
  gcc-fortran
  
  gcc-g++
  
  git
  
  make
  
  makedepend
- From Math mark the following packages for installation
  liblapack-devel
  
  libopenblas
- Click Next and accept all additional packages that the setup process requests to install to satisfy dependencies
It is recommended that you reboot the machine after installing Cygwin and all the necessary packages.

4.4.2. Compiling OpenFAST¶

Open Cygwin64 Terminal from the Start menu
Create a directory where you will clone OpenFAST repository (change code to your preferred name)

mkdir code
cd code

Clone the OpenFAST repository

git clone https://github.com/OpenFAST/OpenFAST.git

This will create a directory called OpenFAST within the code directory.

Create a build directory

cd OpenFAST
mkdir build
cd build

Run cmake. Note that this step is necessary only if you change compiler settings, or add new files to any of the CMakeLists.txt. Modification of .f90 files do not require you to run cmake again, just re-run make command (see next item) to recompile with latest source code modifications.

FC=gfortran cmake ../

Sample output is shown below:

$ FC=gfortran cmake ../
-- The Fortran compiler identification is GNU 5.4.0
-- The C compiler identification is GNU 5.4.0
-- Check for working Fortran compiler: /usr/bin/gfortran.exe
-- Check for working Fortran compiler: /usr/bin/gfortran.exe  -- works
-- Detecting Fortran compiler ABI info
-- Detecting Fortran compiler ABI info - done
-- Checking whether /usr/bin/gfortran.exe supports Fortran 90
-- Checking whether /usr/bin/gfortran.exe supports Fortran 90 -- yes
-- Check for working C compiler: /usr/bin/cc
-- Check for working C compiler: /usr/bin/cc -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Detecting C compile features
-- Detecting C compile features - done
-- Looking for Fortran sgemm
-- Looking for Fortran sgemm - found
-- Looking for pthread.h
-- Looking for pthread.h - found
-- Looking for pthread_create
-- Looking for pthread_create - found
-- Found Threads: TRUE
-- A library with BLAS API found.
-- A library with BLAS API found.
-- Looking for Fortran cheev
-- Looking for Fortran cheev - found
-- A library with LAPACK API found.
-- Setting system file as: src/SysGnuLinux.f90
-- Configuring done
-- Generating done
-- Build files have been written to: /home/sanantha/code/OpenFAST/build

Compile OpenFAST

make

Grab a cup of coffee as this takes a while on Cygwin. Once the compilation is completed, the OpenFAST executable is present in OpenFAST/build/glue-codes/fast/openfast.exe

Test the executable

$ glue-codes/fast/openfast.exe -h

**************************************************************************************************
FAST (v8.17.00a-bjj, 27-Aug-2016)

Copyright (C) 2016 National Renewable Energy Laboratory

This program comes with ABSOLUTELY NO WARRANTY. See the "license.txt" file distributed with this
software for details.
**************************************************************************************************

 Running FAST (v8.17.00a-bjj, 27-Aug-2016), compiled as a 64-bit application using double
 precision
 linked with NWTC Subroutine Library (v2.11.00, 12-Nov-2016)

 Syntax is:

    FAST_x64.exe [-h] <InputFile>

 where:

    -h generates this help message.
    <InputFile> is the name of the required primary input file.

 Note: values enclosed in square brackets [] are optional. Do not enter the brackets.

FAST_InitializeAll:The required input file was not specified on the command line.

FAST encountered an error during module initialization.
 Simulation error level: FATAL ERROR

 Aborting FAST.

```

4.4.3. Other tips¶

You can specify an installation location during your cmake process so that the executable, libraries, and headers (e.g., MAP and OpenFOAM headers) are installed in a common location that you can use to update your environment variables.

# 1. Create an installation location mkdir -p ~/software

# 2. Instruct CMake to use the custom install location FC=gfortran cmake
-DCMAKE\_INSTALL\_PREFIX:PATH=$HOME/software ../

# 3. Compile OpenFAST executable make

# 4. Install OpenFAST to custom install location make install \`\`\`

With this step, you can execute make install after make (see step 6 above). Now the openfast.exe and other executables (e.g., aerodyn.exe) are available in ~/software/bin/ directory.

If you desire to be able to run openfast.exe from the cmd window, then you must add the C:\cygwin64\lib\lapack and C:\cygwin64\home\<USERNAME>\software\bin to your %PATH% variable in environment setting. Replace <USERNAME> with your account name on windows system.
In addition to openfast.exe, the current CMake setup also allows the user to compile other executables or libraries without compiling the entire codebase. Use make help to see what targets are available and then do make <TARGET> to choose your desired target. For example, make aerodyn will compile only the aerodyn.exe executable and its dependencies without compiling the remaining targets.