Compiling the library

From the src directory, simply type

% make

This should build fftMPI, so long as you have MPI installed and available in your path. The standard Makefile uses mpicxx for compiling, using whatever C++ compiler it wraps. By default, two shared library files are created, for 2d and 3d FFTs: libfft2dmpi.so and libfft3dmpi.so.

There are also a few provided Makefile.machine files that work on different supercomputers. You can use one of them or create your own edited file and invoke it as

% make -f Makefile.machine

You should only need to edit the "compiler/linker settings" section at the top of any Makefile.machine.

By default, fftMPI is built to use the provided KISS FFT library for 1d FFTs. It also computes double-precision FFTs (one complex datum = 2 64-bit floating point values). And if using an Intel compiler it uses the TBB (thread building blocks) memory allocator.

Three make variables will change those default settings. You can add one or more of them to any make command:

p=single # single-precision FFTs (double is default)
fft=fftw # options: fftw3 (same as fftw), fftw2, mkl, kiss (default)
tbb=no # do not use TBB with Intel compiler (yes is default)

Here are example make commands using these variables:

% make help # see syntax for all options % make p=single # single precision % make fft=fftw # use the FFTW3 lib for 1d FFTs % make lib # build only 2 static libs (2d and 3d) % make shlib fft=mkl # build only 2 shared libs % make all tbb=no # build both static and shared libs

The static library build will create libfft2dmpi.a and libfft3dmpi.a.

MPORTANT NOTE: You must use a value for the "p" variable that matches how your application will allocate data for its FFT grid(s). This insures the single- or double-precision data types used in both the application and within fftMPI match.

You only need to set the tbb variable to no if you get a compile-time error about being able to find the Intel TBB (thread building block) header file.

When building with a 1d FFT package other than KISS, the Makefile assumes the source directory for the package is in your path, so that it can find the appropriate include file. These files are fftw.h or sfftw.h for double/single precision for FFTW2, fftw3.h for FFTW3, and mkl_dfti.h for MKL. The KISS library kissfft.h file is included in the src dir. If the appropriate include file is not found, you will need to add a setting for its directory to FFT_INC in the Makefile, something like -I/home/me/pathforFFTW3/include.

When building fftMPI as shared libraries, the Makefile will include the library files for the 1d FFT package you have chosen in the link command.

These libraries are as follows:

FFTW2: libfftw.so
FFTW3 double precision: libfftw3.so
FFTW3 single precision: libfftw3f.so
MKL built with Intel compiler: libmkl_intel_lp64.so, libmkl_sequential.so, libmkl_core.so
MKL built with GNU compiler: libmkl_gf_lp64.so, libmkl_sequential.so, libmkl_core.so
KISS: no library file

If the build cannot find these library files in the directories specified by your LD_LIBRARY_PATH environment variable an error will result.

If the appropriate library file is not found, you will need to add a setting for the its directory to FFT_PATH in the Makefile, something like -L/home/me/pathforMKL/lib.

Note that this is not an issue when building fftMPI as static libraries. In that case you will need to insure the build of your application can find the correct 1d FFT library files; see the buildtest doc page for details.

You may wish to install both the fftMPI header files and library files in a location where the build procedure for other applications can find them, e.g. under /usr/local. This can be particulary useful for *.so shared library files, since your LD_LIBRARY_PATH environment variable is often already set to look in this location. These commands copy the 3d files; just change 3d to 2d for the 2d files.

% cd fftmpi/src
% cp fft3d.h fft3d_wrap.h remap3d_wrap.h /usr/local/include  # include files
% cp libfft3dmpi.so /usr/local/lib                           # library files

Note that you typically need super-user or sudo priveleges to copy files into /usr/local or other system dirs.