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PALM preprocessor options / define strings

PALM uses so-called preprocessor define strings for conditional compilation of the code. These compile switches are mainly used for activating calls to external libraries like MPI or NetCDF. Additionally, some preprocessor options are used to replace specific character strings. Define strings and other preprocessor options need to be given in the configuration file .palm.config.<host_identifier> in the line starting with %cpp_options.

The following list gives a complete overview of the define strings used in the PALM code, and of additional preprocessor options that are used to replace strings in the FORTRAN code.

Define strings

The define strings are used to activate specific parts of the code. For activation, compiler option -Dactivation_string has to be used. All activation strings used in PALM start with two underscores, e.g. __parallel. Be aware to add respective include- and library-paths to the compiler options with respect to the specific define strings that has been set, e.g. if you have set -D__netcdf you need to provide the path to the NetCDF library.

activation_string	meaning
__cuda_fft	Enables usage of the NVIDIA CUDA specific FFT library in case PALM runs on GPUs using OpenACC
__fftw	Enables usage of the FFTW library.
__intel_compiler	May be used in case of the Intel FORTRAN compiler to guarantee correct formatting of the progress bar, which is output to the terminal in case of interactive PALM runs.
__nec	Enables usage of specific NEC FFT. This additionally requires to set the initialization parameter fft_method = 'system-specific'.
__netcdf	Enables NetCDF I/O. If this activation string is not set, PALM does not read or write any NetCDF data. ASCII I/O files are not affected. You may omit -D__netcdf in order to test PALM without having a NetCDF library available on your system.
__netcdf4	Enables to use the NetCDF4/HDF5 data format. -D__netcdf has to be set too. See initialization parameter netcdf_data_format about how to choose the NetCDF data format.
__netcdf4_parallel	Enables to use NetCDF4/HDF5 parallel I/O. -D__netcdf and -D__netcdf4 have to be set too. See initialization parameter netcdf_data_format about how to choose the NetCDF data format.
__parallel	Enables usage of MPI. If you do not set -D__parallel, PALM runs in non-parallel mode on a single core.
__rrtmg	Enables usage of the Rapid Radiation Transfer Model library. See doc/tec/radiation for further details.
__single_precision	Attention: This is a test feature. Enables 32bit working precision for all REALs. Based on r4015, single precision works for the PALM core (cyclic horizontal boundaries, no additinal modules switched on) with FFT- and MG-pressure solvers. Other setups have not been tested so far.

Other preprocessor options

Preprocessor options are used for string replacement. By default, two options are required to compile the PALM code:

option	meaning
-DMPI_REAL=MPI_DOUBLE_PRECISION	Replaces strings MPI_REAL by MPI_DOUBLE_PRECISION wherever they appear in the code.
-DMPI_2REAL=MPI_2DOUBLE_PRECISION	Replaces strings MPI_2REAL by MPI_2DOUBLE_PRECISION wherever they appear in the code.

These preprocessor options are required, because by default the precision of REAL quantities in PALM is set to 64bit. You may define 32bit as the working precision (see routine palm/trunk/SOURCE/mod_kinds.f90@3151#L69​) by setting the preprocessor option -D__single_precision. In such a case, you must omit the above preprocessor options.