Overview
The CMake tool is used to build ECMWF software. The build process takes place in two stages. First, standard build files are created from configuration files using the CMake tool; Then the platform's native build tools (e.g. Makefiles) are used for the actual building.
Each project has a CMakeLists.txt file in every directory that controls the build process. The CMakeLists.txt file has one or more commands in the form COMMAND (args...), with COMMAND representing the name of each command and args the list of arguments, each separated by white space.
Prerequisite
To install any ECMWF software package, the CMake tool needs to be installed on your system. On most systems this can be done through the standard package manager to install software. For further information to install CMake see
http://www.cmake.org/cmake/help/install.html
Directories
During a build with CMake there are three different directories involved: The source dir, the build dir and the install dir.
Source directory: (ex: tar zvxf Magics2.22.0.tar.gz in /tmp/.../src)
The source dir is where the project's sources are stored. In This the directory to which you extract the project's source archive. The source dir also contains the files which describe the build to CMake.
Build directory: (Ex: /tmp/.../build/magics)
This directory is where all compiler outputs are stored, which includes both object files as well as final executables and libraries. CMake also stores several files of its own here, including its cache. The location of the build dir is entirely up to you.
Install director: (Ex: /usr/local/magics)
Traditionally Unix builds are finished with a call of 'make install' which copies all relevant files from the built project you need for your everyday use to a clean place. Basically it separates all necessary files from the "garbage" which is output in the build directory. The location of the install directory is governed by the CMake cache variable CMAKE_INSTALL_PREFIX. Of course, installation is entirely optional and only takes place if you build the install target.
Generating the Makefiles with CMake
After changing into the build Magics directory, the user has to run CMake with his own options. The command gives feedback on what requirements are fulfilled and what software is still required. Table 1 gives an overview of the different options of configure. The default (without any options) will compile a share library only and install it in /usr/local/.
cmake options | doc | default | ECMWF Scpecific |
|---|---|---|---|
| CMAKE_INSTALL_PREFIX | where you want to install your Magics library | /usr/local | |
| CMAKE_BUILD_TYPE | to select the type of compilation:
| ? | Debug |
| CMAKE_CXX_FLAGS | More flags for the C++ compiler |
The C, C++ and Fortran compilers are chosen by CMake. This can be overwritten by setting the environment variables CC, CXX and F77, before the call of cmake, to set the preferred compiler. Further the variable CMAKE_CXX_FLAGS can be used to set compiler flags for optimisation or debugging. For example, it is recommended to use CMAKE_CXX_FLAGS="-O2 -mtune=native" or any other optimisation to compile Magics.
Package dependent options for CMake
All ECMWF packages should use the same options. Here is the list of available options:
Name | Default | eckit | grib_api | odb_api | magics | ... | Comment |
|---|---|---|---|---|---|---|---|
| ENABLE_NETCDF | AUTO | ✓ | ✓ | ||||
| ENABLE_HDF | AUTO | ✓ | ✓ | ||||
| ENABLE_JPEG | AUTO | ✓ | Enable JPEG2000 support. This option should look for Jasper or OpenJPG. | ||||
| ENABLE_PYTHON | AUTO | ✓ | ✓ | ✓ | Offers the Python interface to the package. | ||
| ENABLE_FORTRAN | AUTO | ✓ | ✓ | ✓ | Offers the Fortran interface to the package. | ||
| ENABLE_METVIEW | OFF | ✓ | This one should go. | ||||
| ENABLE_CAIRO | AUTO | ✓ | This should be rename ENABLE_RASTER or something like that. | ||||
| ENABLE_GRIB | AUTO | ✓ | ✓ | ||||
| ENABLE_BUFR | AUTO | ✓ | |||||
| GRIB_API_PATH | Where to find grib_api for non-standard installations. | ||||||
| ODB_API_PATH | Where to find odb_api for non standard installations. | ||||||
| NETCDF_PATH | Where to find Netcdf for non standard installations. |
The user will specify ON or OFF. If the user does not specify the option, and the default is AUTO, then cmake should try to enable it if possible, otherwise the feature is turned off. If the user explicitly specifies ON, an the feature cannot be enabled because some libraries are missing, the cmake must fail. cmake will report which options are ON and which are OFF. Please note that only features are enabled with flags, therefore, there should not be a ENABLE_BOOST flag.
Quick installation guide
This is an example list of commands needed to install Magics. It is assumed “>” is the shell prompt. The Magics version number may vary.
>mkdir magics
> mkdir build
>tar -xzf Magics++-2.22.0.tar.gz
>cd build
>cmake –DCMAKE_INSTALL_PREFIX. =/path/to/where/you/install/Magics++-2.22.0
checking build system type... i686-suse-linux
...
> make
> make install
> make test