Building from source on Unix-based operating systems#

This section provides a guide through the build of CHarm and/or PyHarm from source on Unix-based operating systems, particularly Linux and macOS. First discussed are the steps to compile CHarm (the C library) and then follow instructions on how to (optionally) build PyHarm (the Python wrapper).

CHarm (the C library)#


  • C compiler supporting C99. GCC is recommended (available by default on most Linux distributions). Other compilers that are known to successfully compile CHarm are listed in the Tested platforms chapter.

    To compile in quadruple precision, GCC is mandatory (v4.6 or later) and no other compiler is allowed.

  • Make to build the library (available by default on most Linux distributions).

  • pkg-config for managing library compile and link flags (available by default on most Linux distributions).

  • FFTW for discrete fast Fourier transforms.

Installation on Linux#

At first, we will install FFTW and then we will proceed with the installation of CHarm.

FFTW installation#

FFTW can either be installed via you package manager or built from the source.

  • Using your package manager

    • Debian-based distributions:

      sudo apt install libfftw3-dev
    • Arch Linux: You may want to install, for instance, fftw-mpi using your package manager.

    After the installation, make sure the following libraries were successfully installed, depending on whether you want to use CHarm in single/double/quadruple precision and with OpenMP enabled/disabled:

    • for single precision version of CHarm with OpenMP disabled,

    • for single precision version of CHarm with OpenMP enabled,

    • for double precision version of CHarm with OpenMP disabled,

    • for double precision version of CHarm with OpenMP enabled,

    • for quadruple precision version of CHarm with OpenMP disabled,

    • for quadruple precision version of CHarm with OpenMP enabled.

  • Compilation from source

    Please read the manual on the homepage of FFTW on how to install the library. Example FFTW installation could be:

    ./configure --enable-openmp --enable-shared
    make check
    sudo make install

    Do not forget to add the --enable-shared flag to compile FFTW also as a shared library (mandatory to install CHarm). To install CHarm in single or quadruple precision, add also the --enable-single or --enable-quad-precision flag, respectively, when calling the configure script. If you do not want to parallelize FFTW, you may omit the --enable-openmp flag.

Default CHarm installation#

If you

  • want to install CHarm to /usr/local,

  • have installed FFTW (version 3.X.X) to the default path available to the compiler,

  • want a double precision version of CHarm,

  • do not want OpenMP parallelization,

  • do not want to enable SIMD CPU instructions, and

  • have root privileges,

you may simply execute the following commands:

make check
sudo make install

Briefly, ./configure checks the availability of all components necessary to build CHarm and prepares makefiles and a few other files. make compiles the library. make check compiles and executes a test program. make install installs the library.

Customized CHarm installation#

The installation process can be tailored by appending one or more of the following flags to the ./configure call.

  • --enable-single-precision or --enable-double-precision or --enable-quad-precision to compile CHarm in single, double or quadruple precision, respectively (float, double and __float128 data types for floating point numbers, respectively). If not specified, double precision is used as default.

  • --enable-openmp to enable OpenMP parallelization (no parallelization by default).

    The number of threads can be set either in your code by omp_set_num_threads(N) or by using the OMP_NUM_THREADS environment variable.

  • --enable-avx or --enable-avx2 or --enable-avx-512 to enable AVX, AVX2 or AVX-512 CPU instructions, respectively (all disabled by default).

    AVX, AVX2 and AVX-512 are SIMD instructions introduced by Intel in 2011, 2013 and 2017, respectively. The most critical number crunching parts of CHarm are hand-written to take advantage of these instructions in order to significantly improve the performance. As a general rule, it is strongly recommended to enable the latest set of AVX instructions that are supported by your processor. On many Linux distributions, you can find all the supported CPU instructions by executing lscpu. On the hardware level, SIMD instructions are not supported in quadruple precision, thus can be enabled only when compiling in single or double precision.

  • --prefix=/your/custom/path to specify a custom installation path for CHarm (default is --prefix=/usr/local).

  • LDFLAGS=-L/your/path/to/FFTW/lib to specify a custom path to your FFTW libs (empty by default, that is, default is to assume that FFTW is accessible to the compiler).

    You only need to specify the path to the FFTW library; the lib files themselves are linked automatically.

  • CPPFLAGS=-I/your/path/to/FFTW/include to specify a custom path to your FFTW header file (empty by default, that is, default is to assume that FFTW is accessible to the compiler).

  • --disable-shared to not compile CHarm as a shared library.

  • Other useful variables:

    • CC selects other than your system’s default C compiler, e.g. CC=clang for Clang, and

    • CFLAGS defines user-defined compiler flags, e.g., CFLAGS="-O3 -ffast-math" (GCC).

  • To get a summary of all the supported flags, execute ./configure --help.

An example installation

  • with a custom CHarm installation directory,

  • with a custom FFTW installation directory,

  • in quadruple precision,

  • with OpenMP parallelization enabled, and

  • with SIMD instructions disabled

looks like:

./configure --prefix=/opt/charm --enable-openmp --enable-quad-precision \
     LDFLAGS=-L/opt/fftwq-3.3.9/lib \
make check
sudo make install

Installation on macOS#

At first, we will install FFTW and then we will proceed with the installation of CHarm.

FFTW installation#

FFTW can either be installed via you package manager or built from the source, preferably with GCC. The latter is strongly recommended on macOS.

  • Using your package manager

    You can use one of the following commands, depending on the package manager you use:

    sudo port install fftw-3
    brew install fftw

    This, however, most likely does not install FFTW in quadruple precision and/or with OpenMP support. You may therefore be able to compile CHarm only in single or double precision with OpenMP disabled.

  • Compilation from source

    It is recommended to compile FFTW using GCC. If you do not have GCC installed yet, you may execute one of the following commands:

    sudo port install gcc10
    brew install gcc@10

    Now, you should be ready to build FFTW by following the instructions in the FFTW installation chapter (Linux, compilation from source). There is, however, one important additional remark. When calling the FFTW’s ./configure script, specify also your GCC compiler, including its version number, e.g.:

    ./configure --enable-openmp CC=gcc-10

    Without the CC flag, Clang will most likely be used which may cause an installation failure when using the --enable-openmp and/or --enable-quad-precision flag(s). It may not be sufficient to add CC=gcc (GCC version number omitted), as this will still likely call Clang.

CHarm installation#

Having installed FFTW, you may proceed with the same instructions as given in the Default CHarm installation and Customized CHarm installation chapters for Linux. Similarly as when installing FFTW, it is recommended to use the GCC compiler via the CC variable when calling the ./configure script from the CHarm installation.

A few installation notes#

  • The output lib names depend on the precision used to compile CHarm:

    • libcharmf – single precision,

    • libcharm – double precision,

    • libcharmq – quadruple precision.

  • You may install CHarm in single, double and quadruple precision to the same installation path. You don’t have to worry about overwriting the header and lib files.


Execute sudo make uninstall.

PyHarm (the Python wrapper)#

Before reading this chapter, make sure you know how to compile CHarm. Otherwise, you won’t be able to build PyHarm.


Additional prerequisites when compared with requirements:

  • Python interpreter 3.6 or newer,

  • Python module pip,

  • Python module numpy (reasonably old version),

  • Python module ctypes (reasonably old version).

Building PyHarm#

Installation of PyHarm is disabled by default. To enable it, you have to add the --enable-python flag to the configure call in addition to the flags discussed in the CHarm (the C library) chapter.

The following flags may be used in addition to --enable-python.

  • The PYTHON variable specifies the Python interpreter you want to use. For instance, PYTHON=python3.9 will ensure that the build is done with/for Python version 3.9. Use the appropriate version (depends on your machine).

  • By default, PyHarm is built to the ${prefix}/lib directory. The path in ${prefix} is taken from the --prefix flag (see CHarm (the C library)). The default installation path can be replaced by a custom one using the --with-python_prefix flag, for instance, --with-python_prefix=/home/isaac/pyharm.

    Using the correct path in --with-python_prefix is crucial for Python to find PyHarm. Otherwise, when calling

    >>> import pyharm

    from within the Python shell or a Python script, ModuleNotFoundError will be thrown.

    There are several strategies to choose the installation path.

    • If you are not really confident with all this, create and activate a Python virtual environment:

      python3 -m venv /path/to/your/virtual/environment/
      source /path/to/your/virtual/environment/bin/activate

      Then use --with-python_prefix=/path/to/your/virtual/environment when calling the configure script. After executing make and make install, you are ready to import PyHarm in a Python shell or a Python script:

      >>> import pyharm
    • If you want to install PyHarm as a user, find the lib path of your Python user packages, for instance,

      python3 -m site --user-site

      The output might like /home/isaac/.local/lib/python3.9/site-packages, depending on the version of your Python and on your OS. Based on this path, you can specify your installation path; in this case it is --with-python_prefix=/home/isaac/.local. Note that the lib/python3.9/site-packages directories have to be omitted, as they are added to the installation path automatically.

    • If you want to install PyHarm next to your system Python packages, you must specify neither --prefix nor --with-python_prefix.

    Note that if you use a custom path in --prefix but do not specify --with-python_prefix, you will most likely not be able to (easily) import PyHarm.

Example installation#

A typical installation of PyHarm to a Python virtual environment looks like this:

python3 -m venv /tmp/python-venv
source /tmp/python-venv/bin/activate
./configure --prefix=/tmp/charm --enable-openmp \
   LDFLAGS=-L/opt/fftw-3.3.9/lib CPPFLAGS=-I/opt/fftw-3.3.9/include \
   --enable-python PYTHON=python3.9 --with-python_prefix=/tmp/python-venv
make check
make install

Then, open Python:


From within Python, you can now work with PyHarm:

>>> import pyharm as ph
>>> ph.misc.print_info()
>>> quit()

Deactivate the virtual environment from the shell:



See Uninstallation.