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CMake compilation must be done is in a separate build directory to both the source and the install directory.
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mkdir bld
mkdir grib-api
cd bld
export CC=gcc
export FC=gfortran
cmake ../grib_api-1.14.0-Source \
-DCMAKE_INSTALL_PREFIX="../grib-api" \
-DENABLE_NETCDF=ON \
-DENABLE_JPG=OFF \
-DENABLE_PNG=OFF \
-DENABLE_PYTHON=ON \
-DENABLE_FORTRAN=ON \
-DENABLE_GRIB_OMP_THREADS=ON \
-DBUILD_SHARED_LIBS=OFF |
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| These lines set the choice of compiler. CMake is often able to determine the available compilers for itself. However, in cases where multiple compilers are available, or where compiler wrappers are used (as on HPC systems), it's preferable to set these explicitly by use of environment variables. These lines can often be omitted. |
CMAKE_INSTALL_PREFIX="../grib_api" | This specifies the location where the 'make install' command will place the grib-api installation. |
ENABLE_NETCDF=ON | Enabling netcdf ensures the grib_to_netcdf command can be used. |
ENABLE_JPG=OFFENABLE_PNG=OFF | As OpenIFS models do not deal with any image based GRIB data these options can be disabled, unless you have other grib data containing images that you need to work with. |
ENABLE_PYTHON=ON | Some of the utilities that come with the OpenIFS models model make use of the python interface to grib_api, e.g. the tools to create and manipulate the model data. For this option to work, ensure that a python installation is available. This option is not needed for the single column nor offline surface models currently. |
ENABLE_FORTRAN=ON | This enables the Fortran interface to grib_api and should always be on. |
ENABLE_GRIB_OMP_THREADS=ON | Not essential but recommended. This ensures grib_api is compiled to be 'thread-safe'supports OpenMP threads. Note this is not the same as the option ENABLE_GRIB_THREADS which is for Posix threading and not used by the OpenIFS model. Although OpenIFS models do not currently use multiple threaded calls to grib-api, future versions may do so this option is recommended. |
BUILD_SHARED_LIBS=OFF | grib_api can be built with both 'shared' and 'static' libraries for linking. Normally static libraries are sufficient. Note that some IBM users may experience problems if shared libraries are built. |
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| Info |
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This command will cause cmake to run its system discovery if this is the first time the command has been used. On some systems, this may take time to complete. |
Configuring
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using autotools
Grib_api compilation can be made using the GNU configure tool. This will be familiar to many who have previously installed software.
The configure command is probably the easiest method as it does not rely on having the CMake package installed, though note it is deprecated in favour of using cmake (see below).
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A description of what these options are for:
--prefix | This specifies where you want the grib_api files to be installed. In example here, the source code is in $HOME/ecmwf/grib_api_1.14.0-Source and the compiled grib_api libraries will go in directory $HOME/ecmwf/grib_api. You are free to choose any installation directory but it's recommended to keep the installed binaries & libraries in a separate directory to the source code, in case different compiler versions are needed. On a shared high performance computer facility, the install path would most likely be somewhere central. If nothing is specified for --prefix, by default grib_api will install in /usr/local. |
--disable-jpeg | OpenIFS models do not need to support JPEG and PNG for data compression. This removes the need to link against the Jasper library (libjasper.a). |
--enable-pthread | This option ensures that grib_api is thread-safe and is a recommended option. |
--enable-python | This option is not essential but |
| desirable. It enables the python interface and is required as some utilities make use of the grib-api python interface. If the make fails because of a missing numpy header file |
| we recommend installing numpy. Although you could add the --disable-numpy option |
| , if this option does not work, some of the tools provided with OpenIFS models may not work. |
Other options
--help option to configure can be used to see what other options are possible, also see the grib_api website for more detailed documentation.
--enable-vector option should be used on vector based computers (e.g. NEC). Grib_api will then use a more efficient packing/unpacking method suitable for vector hardware. n.b. there is a bug in the 1.9.18 release that if the --disable-vector option is used, this has the reverse effect of enabling the vector code. See grib_api issue GRIB-269 for more details.--disable-numpy option should be used if python is enabled but configure can't find the NumPy package.
Shared and static libraries
grib_api will build both shared and static libraries by default. Shared libraries may need to be built if the python interface is used, depending on your installation.
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