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Prerequisites

You should have completed: the install grib_api and downloaded and unpacked the OpenIFS data files and OpenIFS source code.

Set your environment

OpenIFS uses software called 'FCM' to handle the compilation of the code. FCM is distributed in the tarball downloaded from the ftp site.

Before trying to compile, make sure the FCM directory is added to your PATH environment variable so the fcm command can be found (if you already have fcm available on your system, we still recommend using the distributed version):

 

e.g. assuming OpenIFS is unpacked in $HOME/ecmwf/oifs
export PATH=$PATH:$HOME/ecmwf/oifs/fcm/bin

 

On this page

Build configuration

This is a brief introduction on compiling the OpenIFS model. For a more detailed description of the build system for OpenIFS and the different ways to configure it, see HowTo customize the OpenIFS build.

Before compiling the model, the build configuration must first be set by several environment variables:

OIFS_COMP - This sets the choice of compiler. The default is 'gnu' which means the gfortran/gcc compilers will be used.

OIFS_BUILD - This sets the type of build.

These environment variables directly correspond to the names of the FCM configuration files in the make/cfg/ directory in the source. Please see this directory for the choices provided.

Build types: OIFS_BUILD sets the type of build and there will be one FCM configuration file for each type. Build types provided are:

  • opt - Recommended optimized compile settings for this compiler. Tested to provide best performance for this platform & compiler.
  • noopt - Debugging options. No optimization set for all of the code. Suitable for use with a debugger. OpenMP is disabled.
  • nansC - Debugging options with extra checks. Array bound checking enabled and variables initialized to NAN (not-a-number). Use of a variable set to NaN will trigger a floating point exception. This option is useful for debugging purposes but will run the slowest.

e.g.

export OIFS_COMP=intel
export OIFS_BUILD=opt

means using the Intel ifort compiler and the model will be compiled with full optimization compiler settings. So the FCM build system will expect to find a file:

make/cfg/intel-opt.cfg

Setting:

export OIFS_COMP=xlf
export OIFS_BUILD=noopt

means FCM will expect to find a file:

make/cfg/xlf-noopt.cfg

suitable for building on IBM Power6 architecture using the XLF/XLCC compilers using non-optimized settings.

If using GNU on a Mac, please see MacOS X known issues.

Building for other systems/environments

As the environment variables refer to the corresponding filename in the make/cfg  directory it is straightforward to create a build configuration for other environments. Take a copy of an existing file and modify it as necessary. It's also possible to alter compile options by the use of additional environment variables (see below). Which approach you use depends on your personal preference. Be aware however that the optimization compiler flags in the provided configuration files are the recommended ones. It is impossible to test all combinations of compiler flags so the model may become unstable or performance may reduce if higher optimizations are tried.

Setting the location of libraries

The model requires a number of libraries (see 5.2 Prerequisites) to compile. As well as the GRIB_API library, the LAPACK & BLAS numerical libraries are required. An MPI library is also required but this is assumed to be provided by compiler wrappers provided by the MPI implementation (e.g. the command mpif90 rather than gfortran).

To set the location of the GRIB_API & LAPACK libraries, two other environment variables need to be defined as the defaults in the FCM configuration files will most likely not be appropriate.

OIFS_GRIB_API_DIR - Defines the location of the grib_api library. If you followed the example in '5.3 Install GRIB library for OpenIFS' it will be installed in $HOME/ecmwf/grib_api_gcc.

OIFS_LAPACK_LIB - Defines the location of the directory containing the liblapack.a and libblas.a files. This varies from system to system but typically /usr/local/lib.

If you do not have LAPACK installed on your system or find it does not work, OpenIFS comes with all the necessary LAPACK code to run. It is disabled by default, contact openifs-support@ecmwf.int for instructions on how to enable it.

e.g.

export OIFS_GRIB_API_DIR=$HOME/ecmwf/grib_api_gcc
export OIFS_LAPACK_LIB="-L/usr/local/lib -llapack -lblas"

Or if you prefer you can either edit the default value in the appropriate FCM configuration file in make/cfg directory or make a copy of the supplied configuration file (.cfg) and use that.

Compiling OpenIFS

Once the environment variables are set, OpenIFS can be compiled (make sure you have edited your PATH environment variable to add the FCM installation /bin directory). Assuming you are in the directory where the OpenIFS source code was unpacked:

cd make
fcm make -f oifs.cfg

The command 'fcm make' starts the compilation. The -f option specifies the location of the master configuration file for OpenIFS. For more information about fcm command options, try: fcm --help .

This generates output similar to:

[init] make                # 2012-12-20 19:59:59Z
[init] make config-parse   # 2012-12-20 19:59:59Z
[info] config-file=...../make/oifs.cfg
[info] config-file= - ...../make/cfg/gnu-opt.cfg
[done] make config-parse   # 0.3s
[init] make dest-init      # 2012-12-20 19:59:59Z
[info] mode=new
[done] make dest-init      # 0.3s
[init] make build          # 2012-12-20 20:00:00Z
[info] sources: total=2194, analysed=2194, elapsed-time=11.7s, total-time=32.2s
[info] target-tree-analysis: elapsed-time=9.8s
[info] compile   targets: modified=2073, unchanged=0, total-time=1095.5s
[info] compile+  targets: modified=628, unchanged=0, total-time=1.6s
[info] ext-iface targets: modified=1247, unchanged=0, total-time=21.9s
[info] install   targets: modified=120, unchanged=0, total-time=0.3s
[info] link      targets: modified=1, unchanged=0, total-time=18.3s
[info] TOTAL     targets: modified=4069, unchanged=0, elapsed-time=316.3s
[done] make build          # 329.1s
[done] make                # 329.8s

Verbose compilation

The default output of FCM is quite terse. To get more verbose output use the '-v' option. Also if you have a multicore machine you can use the -j option to specify additional processes to build in parallel.

e.g.

fcm make -v -j 4 -f oifs.cfg

will produce a more detailed report and use 4 processes to analyse and build the model code in parallel.

Successful compilation

After a successful compilation, the OpenIFS executable, master.exe, can be found in the 'make/gnu-opt/oifs/bin' subdirectory:

% ls
cfg  gnu-opt
% ls gnu-opt/oifs
bin   include   o
% ls gnu-opt/oifs/bin
master.exe

The 'gnu-opt' subdirectory is generated by FCM using the values of the OIFS_COMP & OIFS_BUILD environment variables. The oifs/include directory contains all the files referenced in the code by a '#include' statement. This includes the Fortran interface block files which are auto-generated by FCM and end in .intfb.h. The oifs/o directory contains all the compiled object files. The OpenIFS build does not place any additional files in the src directory (known as building 'out of source').

Compilation problems

If you get the message:

fcm make -f oifs.cfg
/bin/ksh: fcm: not found [No such file or directory]

you need to add the 'bin' directory of the FCM installation to your PATH environment variable. FCM is supplied with OpenIFS and is in the directory 'fcm'.

 


 

 

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