Building FleCSI

FleCSI can be configured to run with different distributed-memory runtimes, including Legion, and MPI. FleCSI also has support for various fine-grained, node-level runtimes, including OpenMP, Kokkos, and the C++17 extensions for parallelism. Full documentation of FleCSI requires both Sphinx and Doxygen. These configuration options are listed to convey to the reader that the FleCSI build system has several paths that can be taken to tailor FleCSI to a given system and architecture.

Requirements & Prerequisites

The following list of requirements provides a complete set of build options, but is not necessary for a particular build:

  • C++17 compliant compiler
    At the current time, FleCSI has been tested with GNU, Clang, and Intel C++ compilers.

  • MPI
    If Legion support is enabled, the MPI implementation must have support for MPI_THREAD_MULTIPLE.

  • Legion
    We are currently using the most up-to-date version of the master branch.

  • GASNet
    GASNet is only required if Legion support is enabled.

  • CMake
    We currently require CMake version 3.12 or greater.

  • Boost
    We require program_options and stacktrace.

  • Doxygen
    Doxygen is only required to build the interface documentation.

  • Sphinx
    Sphinx is only required to build the web-based documentation. We are currently using Sphinx 1.1.0. We also require the Sphinx RTD Theme (using version 0.4.2). These can be installed on most Linux systems using pip.

  • Python
    We currently require Python 2.7 or greater.


The preferred method for installing FleCSI is to use the spack package:

$ spack install flecsi
$ spack load -r flecsi

FleCSI supports several different versions and variants, e.g.:

$ spack install flecsi@1.0 +legion +graphviz

For a complete list of versions and variants, type:

$ spack info flecsi

Currently, FleCSI depends on the following spack packages:

$ spack install cmake
$ spack install boost@1.68.0
$ spack install parmetis
$ spack install hdf5
$ spack install kokkos
$ spack install legion@ctrl-rep


Users of spack can safely ignore the remaining sections on this page. Loading the flecsi spack package will properly configure your environment.

FleCSI Third Party Libraries Project


The FleCSI superbuild project is deprecated in favor of Spack, and will eventually be removed.

To facilitate FleCSI adoption by a broad set of users, we have provided a superbuild project that can build many of the libraries and tools required to build and use FleCSI. The FleCSI Third Party Libraries (TPL) project is available from github at Note that a suitable version of MPI is required for the superbuild.


Users should note that, while this approach is easier, it may not provide as robust a solution as individually building each dependency, and that care should be taken before installing these libraries on a production system to avoid possible conflicts or duplication. Production deployments of some of these tools may have architecture or system specific needs that will not be met by our superbuild. Users who are working with development branches of FleCSI are encouraged to build each package separately.

Build instructions for the TPLs:

$ git clone --recursive
$ cd flecsi-third-party
$ mkdir build
$ cd build
$ cmake -DCMAKE_INSTALL_PREFIX=/path/to/install/directory ..
$ make
$ make install

It is recommended that users remove the install directory before updating or re-compiling the TPLs to insure a clean build.

Build Environment

FleCSI uses CMake as part of its build system. A convenient mechanism for identifying directory paths that should be searched by CMake’s find_package function is to set the CMAKE_PREFIX_PATH environment variable. If you are using the FleCSI TPLs discussed above, you can set CMAKE_PREFIX_PATH to include the path to your TPL installation directory and FleCSI will automatically find all of its dependencies:

$ export CMAKE_PREFIX_PATH=/path/to/install/directory (bash)

Getting The Code

Clone the FleCSI git repository, and create an out-of-source build area (FleCSI prohibits in-source builds):

$ git clone --recursive
$ cd flecsi
$ mkdir build
$ cd build

Note: FleCSI developers, i.e., those who have permission to create new branches and pull requests, should clone the source code using their github account and the *git* user:

$ git clone --recursive
$ cd flecsi
$ mkdir build
$ cd build

Configuration & Build

Configuration of FleCSI requires the selection of the backend runtimes that will be used by the FleCSI programming model abstraction to invoke tasks and kernels. There are currently two supported distributed-memory runtimes, a serial runtime, and one supported node-level runtime:

  • Distributed-Memory
    Legion or MPI

  • Serial [supported thorugh MPI runtime]
    The serial build is no longer supported. Users wishing to emulate this build mode should select the MPI runtime and run executables with a single-rank.

  • Node-Level

Example configuration: MPI


Example configuration: MPI + OpenMP


Example configuration: Legion

$ cmake -DFLECSI_RUNTIME_MODEL=legion ..

After configuration is complete, just use make to build:

$ make -j 16

Installation uses the normal make install, and will install FleCSI in the directory specified by CMAKE_INSTALL_PREFIX:

$ make install

Building the Unit Tests

To build FleCSI unit test suite, enable the option for the FleCSI logging utility (flog). By default, this will also enable the unit tests.

$ cmake .. -DENABLE_FLOG

After building FleCSI, you can run the unit tests like:

$ make test

Building the Documentation

FleCSI uses Doxygen for its API reference, and Sphinx for user and developer documentation.

Doxygen can be installed with most Linux package managers. To install Sphinx, you can install pip3, and use it to install Sphinx, recommonmark, and sphinx_rtd_theme. Your package manager should also have pip3, e.g., on Ubuntu, you can install all of these requirements like:

$ sudo apt install doxygen
$ sudo apt install python3-pip
$ sudo apt install python3-breathe
$ pip3 install Sphinx
$ pip3 install recommonmark
$ pip3 install sphinx_rtd_theme

To enable Doxygen and Sphinx, these options need to be enabled in CMake:


Once you have properly configured FleCSI, you can build the documentation like:

$ make doxygen
$ make sphinx

Both of these targets will be built in your build directory under doc, e.g., the main Doxygen index.html page will be located at ‘doc/doxygen/html/index.html’. Similarly, the Sphinx main index.html page will be located at ‘doc/sphinx/index.html’. You can open these in your browser with file:///path/to/your/build/directory/doc/doxygen/html/index.html, and file:///path/to/your/build/directory/doc/sphinx/index.html.