CCFLAGS = -g -O -I/usr/local/fftw/include -DFFT_FFTW -DOMPI_SKIP_MPICXX -DOMPI_IGNORE_CXX_SEEK
What do -DFFT_FFTW -DOMPI_SKIP_MPICXX really mean? The answer is nicely given Rolf Vandevaart "Speeding Up C++ Compiles"
In a summary, from the blog
The issue is that if you are compiling C++ code, but you are not using the C++ bindings, the code can be slow to compile. The workaround is to use the -DOMPI_SKIP_MPICXX flag which tells MPI not to include the C++ header files
And here are the results. Not quite a 50% speedup, but close
