CMake, CTest, and ecbuild

The JEDI manufacturing system (build, test and package) is based on the CMake tool suite. CMake is open source and it’s purpose is to facilitate the creation of make files that can be used to compile, test and install your software. For example, you can tell CMake that you need the netcdf and openmpi libraries, and it will automatically find those on your machine and place necessary paths, in the make files it generates, for compiling and linking your source code. CMake is in widespread use and the CMake website includes documentation and tutorials to help you get started.

CTest is the part of CMake that handles testing your code. CTest allows for an easy way to run your newly built programs with various argument and option settings, and then check the results against expected output. This system is well suited for short, fast running tests that tend to be in the unit level testing category. We may need to go beyond CTest to address our large scale system testing that is geared more toward performance benchmarking and verifying functionality on HPC systems.

Ecbuild is a set of CMake macros provided by the ECMWF that assist with the specification of the manufacturing processes. Along with ecbuild we are using additional ECMWF libraries:

  • eckit is a C++ library that provides utilities including logging, MPI, configuration file (JSON, YAML) parsing and math functions.

  • fckit is a Fortran tool kit that provides similar utilities as eckit, plus helper functions to convert strings and arrays between Fortran and C/C++, and extending the unit test framework to Fortran.

  • atlas is library for numerical weather prediction and climate modelling. Atlas is predominantly C++ code, with main features available to Fortran codes through a F2003 interface. Note that atlas is called ecmwf-atlas in spack, because spack already contains the Atlas Linear Algebra Software.

CMake and CTest

The CMake developers provide a single package for CMake and CTest. Documentation and downloads are available at the CMake website.

Installing CMake and CTest

This step is only necessary if you are working outside preconfigured JEDI environments or containers, and when not following the spack-stack instructions to set up your environment.

For the Mac, use homebrew to install CMake.

brew install cmake

For Windows and Linux systems, see the CMake downloads website for packages and instructions.

Using CMake and CTest

At the heart of CMake are the CMakeLists.txt files. These files are where the specification takes place for all manufacturing processes. This specification may include items such as where the source code lives, dependencies for that source code, what libraries to link in, configuration of tests and the selection of programs and scripts for installation. Here is a CMake tutorial that is helpful for getting an idea of what goes into a CMakeLists.txt file.

Once the CMakeLists.txt for a project are created, all one does to build, test and install your software is:

cmake <dir_where_toplevel_CMakeLists.txt_file>   # generate the make files

make              # compile everything
ctest             # run the tests
make install      # install the programs and scripts

In the example above, the <dir_where_toplevel_CMakeLists.txt_file> argument to cmake is the Linux path to wherever the top level CMakeLists.txt file exists (only the directory part of the path). This path can be relative or absolute. Here are some examples for running cmake:

cmake .      # top level CMakeLists.txt is in the current directory

cmake ..     # top level CMakeLists.txt is one up from the current directory

cmake $HOME/projects/my-project   # top level CMakeLists.txt file lives
                                  # in $HOME/project/my-project

Output from the cmake command is captured in the following files:

./CMakeFiles/CMakeOutput.log   # messages from cmake
./CMakeFiles/CMakeError.log    # errors and warnings from cmake

The ctest command without arguments will run the entire set of tests. In the case that you want to run a specific test or you want more information on tests that failed, you can run individual tests using ctest as shown below.

ctest -R test_ufo_radiosonde  # this runs just the one test

ctest -R test_ufo_*           # file globbing and regular expression can be
                              # applied to select a subset of tests to run

ctest -V -R test_ufo_radiosonde   # -V increases the verbosity of output


Many unit tests use MPI, which can require additional MPI configuration. For example, using OpenMPI on the Mac typically requires the following to enable oversubscribing (which means running more MPI processes than available cores). Note that extra MPI processes beyond the number of cores on a system do not actually run in parallel, but that’s okay with short, fast-running programs such as unit tests.

To enable oversubscribing on the Mac with OpenMPI:

  1. Create the file: $HOME/.openmpi/mca-params.conf

  2. Place the following in the mca-params.conf file

# This Mac has 2 cores. Enable oversubscribe so that more than 2 MPI
# processes can be run on this system.
rmaps_base_oversubscribe = 1

Test output is captured in the files:

./Testing/Temporary/LastTest.log          # output from the last invocation of ctest
./Testing/Temporary/LastTestsFailed.log   # names of the tests that failed during
                                          # the last invocation of ctest


It is highly recommended that you build your code in a directory that is separate from the directory where the source code lives. CMake does not restrict you to do this, but doing so will keep the source directories free from all of the clutter that the build process produces such as object files, the generated make files, and additional CMake configuration and log files. If you build in a separate directory, one simple remove command will clean up the entire build area (without danger of removing source files) and keep the source git repository clear of extra files that you do not want to check into the repository.

CMake provides many controls which are enabled through specifying the -D command line option. See the CMake variables documentation for details. This list is extensive, and probably the most relevant is CMAKE_INSTALL_PREFIX, which is used to specify where the programs and scripts are to be installed. By default, this is /usr/local. However, if you don’t have write permission to /usr/local, then you will need this control to be able to do the install step. Let’s say that you want to install in your home directory in the path $HOME/tools. Then run cmake as follows:

cmake -DCMAKE_INSTALL_PREFIX=$HOME/tools $HOME/projects/my-project

Another set of useful controls are those for setting which compilers will be used for building your project. CMake will search your system in common directories (/bin, /usr/bin, /usr/local/bin, etc.) for compilers and libraries needed by your project. It’s common for several versions of compilers to exist on a given machine and it’s not always clear which one CMake will choose. These controls can be used to force CMake to use the versions you want.

cmake -DCMAKE_C_COMPILER=/usr/local/bin/gcc            $HOME/projects/my_project # C code
cmake -DCMAKE_CXX_COMPILER=/usr/local/bin/g++          $HOME/projects/my_project # C++ code
cmake -DCMAKE_Fortran_COMPILER=/usr/local/bin/gfortran $HOME/projects/my_project # Fortran code

# Note that combinations of these can be issued with one CMake command if you
# have a mix of source code languages. Say you've got C, C++ and Fortran.
      -DCMAKE_Fortran_COMPILER=$CMP_ROOT/gfortran $HOME/projects/my_project

CMake also has tools that are useful for debugging. In particular, the --trace and --debug-output options show every line of every script file that is executed while cmake is running.


ecbuild and other ECMWF libraries can be installed with spack-stack or manually by using cmake and providing the necessary dependencies. Note that the much simpler and supported method is to let spack-stack handle the software dependencies.

Ecbuild does enforce the restriction recommended above on building your project outside of the source directories.

Installing ecbuild

As before, the steps shown in this section are only necessary if you are working outside preconfigured JEDI environments or containers, and when not following the recommendation to use spack-stack v1.7.0 to set up your environment.

For all systems, you need to have CMake, eigen3 installed before installing ecbuild. To install these on the Mac:

brew install cmake              # as shown above
brew install eigen              # this will install eigen3

JEDI projects use Boost header-only libraries and building Boost is not required.

For Windows and Linux systems, see the CMake downloads website, Eigen website and Boost website for packages and instructions.

Since ecbuild is actually a collection of CMake macros there is no compiling required, thus no need to run make nor ctest. In the following example, the ecbuild clone is going to be placed in $HOME/projects and the build directory will be $HOME/projects/ecbuild/build.

# create the ecbuild clone and make sure you are on the master branch
cd $HOME/projects
git clone

cd ecbuild
git checkout 2.9.4 # check out the most recent release

# create the build directory
mkdir build
cd build

# install ecbuild
cmake ..        # This assumes that you have write permission in /usr/local
sudo make install

# if you don't have permission to write into /usr/local
make install

Once ecbuild is installed, it can be used to build and install the eckit and fckit libraries. Currently, it is recommended to only install eckit, since fckit is generally built along with the JEDI code. This is done because the JEDI team often make changes to fckit and we generally work from our own fork.

For the following code example, assume that the clones are placed in $HOME/projects and the build directories are subdirectories of the clones called “build”.

# create the eckit clone
cd $HOME/projects
git clone

cd eckit
git checkout 0.23.0 # check out the most recent public release

# create the build directory
mkdir build
cd build

# build, test, install eckit
# Note the use of ecbuild in place of cmake
# If no write permission in /usr/local, add -DCMAKE_INSTALL_PREFIX=$HOME/tools
# to the ecbuild command and omit the :code:`sudo` in the :code:`make install`.
ecbuild ..
sudo make install

Using ecbuild

The ecbuild installation provides a command called ecbuild which is a direct replacement for the cmake command. Ecbuild simply loads its set of macros and then passes all appropriate arguments and options on through to a call to cmake. For example, you can use the option -DCMAKE_INSTALL_PREFIX with ecbuild and this gets passed through to cmake.

Ecbuild is the workhorse for building and testing (and eventually installing) the JEDI software. Once ecbuild and associated libraries (eigen3, eckit) are installed, all subsequent manufacturing is done using the ecbuild command in place of cmake. The output from ecbuild is captured in the file:


Ecbuild has its own options which can be inspected by running ecbuild --help. Here is sample output:

>> ecbuild --help


  ecbuild [--help] [--version] [--toolchains]
  ecbuild [option...] [--] [cmake-argument...] <path-to-source>
  ecbuild [option...] [--] [cmake-argument...] <path-to-existing-build>


  ecbuild is a build system based on CMake, but providing a lot of macro's
  to make it easier to work with. Upon execution,
  the equivalent cmake command is printed.

  ecbuild/cmake must be called from an out-of-source build directory and
  forbids in-source builds.


    --help         Display this help
    --version      Display ecbuild version
    --toolchains   Display list of pre-installed toolchains (see below)

Available values for "option":

          Set which cmake binary to use. Default is 'cmake'

          Set the install path to <prefix>.
          Equivalent to cmake argument "-DCMAKE_INSTALL_PREFIX=<prefix>"

          Set the build-type to <build-type>.
          Equivalent to cmake argument "-DCMAKE_BUILD_TYPE=<build-type>"
          <build-type> can be any of:
             - debug : Lowest optimization level, useful for debugging
             - release : Highest optimization level, for best performance
             - bit : Highest optimization level while staying bit-reproducible
             - ...others depending on project

          Set the ecbuild log-level
          Equivalent to "-DECBUILD_LOG_LEVEL=<log-level>"
          <log-level> can be any of:
             - DEBUG
             - INFO
             - WARN
             - ERROR
             - CRITICAL
             - OFF
          Every choice outputs also the log-levels listed below itself

          Build static libraries.
          Equivalent to "-DBUILD_SHARED_LIBS=OFF"

    --dynamic, --shared
          Build dynamic libraries (usually the default).
          Equivalent to "-DBUILD_SHARED_LIBS=ON"

          Configuration file using CMake syntax that gets included
          Equivalent to cmake argument "-DECBUILD_CONFIG=<config-file>"

          Use a platform specific toolchain, containing settings such
          as compilation flags, locations of commonly used dependencies.
          <toolchain> can be the path to a custom toolchain file, or a
          pre-installed toolchain provided with ecbuild. For a list of
          pre-installed toolchains, run "ecbuild --toolchains".
          Equivalent to cmake argument "-DCMAKE_TOOLCHAIN_FILE=<toolchain-file>"

    --cache=<ecbuild-cache-file>    (advanced)
          A file called "ecbuild-cache.cmake" is generated during configuration.
          This file can be moved to a safe location, and specified for future
          builds to speed up checking of compiler/platform capabilities. Note
          that this is only accelerating fresh builds, as cmake internally
          caches also. Therefore this option is *not* recommended.

          Automatically download and build CMake version 3.5.2.
          Requires an internet connection and may take a while. If no prefix
          is given, install into /Users/stephenh/projects/jedi-docs/docs.

          Don't actually execute the cmake call, just print what would have
          been executed.

Available values for "cmake-argument":

    Any value that can be usually passed to cmake to (re)configure the build.
    Typically these values start with "-D".

    They can be explicitly separated from [option...] with a "--", for the case
    there is a conflicting option with the "cmake" executable, and the latter's
    option is requested.


NOTE: When reconfiguring a build, it is only necessary to change the relevant
options, as everything stays cached. For example:
  > ecbuild --prefix=PREFIX .
  > ecbuild -DENABLE_TESTS=ON .



  To compile the project with <N> threads:
    > make -j<N>

  To get verbose compilation/linking output:
    > make VERBOSE=1


  To run the project's tests
    > ctest

  Also check the ctest manual/help for more options on running tests


  To install the project in location PREFIX with
       "--prefix=PREFIX" or
    > make install



For examples on how to use ecbuild to compile JEDI bundles, see Building and Compiling JEDI (Step 3).

You can pass cmake command line options to cmake with ecbuild by proceeding them with two dashes --. For example, to use the cmake --trace option mentioned above (useful for debugging), you can enter:

ecbuild -- --trace <path_to_bundle>  # example that adds the --trace option to the cmake call

It is recommended to choose one of the JEDI repositories and look through all of the CMakeLists.txt files. This will help you get oriented in how these files are used to piece together the build, test and install flows. You will notice ecbuild macros (with names starting with “ecbuild_”) along with native cmake commands.