On Sun, 2013-02-17 at 12:38 -0500, Neal Becker wrote: > The 1st example says: > >>> import pyfftw > >>> import numpy > >>> a = pyfftw.n_byte_align_empty(128, 16, 'complex128') > >>> a[:] = numpy.random.randn(128) + 1j*numpy.random.randn(128) > >>> b = pyfftw.interfaces.numpy_fft.fft(a) > > I don't see why I need to specify the alignment. The fftw library has > a > function to allocate aligned arrays that are allocated optimally. Why > doesn't > pyfft.n_byte_align_empty just align things correctly without me having > to tell > it the alignment?
No very good reason. When I started it was simply easier to have numpy handle the memory management, which is what is still used, and that precluded using FFTW's memory manager. It was all written when FFTW didn't support AVX and so basically 16-byte alignment was all that was needed. Extending to support 32-byte alignment was done in this framework because I deemed there were more important things to work on. It is possible to achieve the same result by replacing the alignment argument with pyfft.simd_alignment, which acquires the optimum alignment by inspecting the CPU (on x86/amd64). This isn't obvious from the tutorial, which is a deficiency borne of limited time. Why didn't I write a function that does that for you? I'm sure I had a good reason at the time ;) Consider this a 0.9.1 feature (i'll add an issue now). hen _______________________________________________ NumPy-Discussion mailing list NumPy-Discussion@scipy.org http://mail.scipy.org/mailman/listinfo/numpy-discussion
