Chris@19: Previous: Guru Real-to-real Transforms, Chris@19: Up: Guru Interface Chris@19:
Chris@19: When compiled in 64-bit mode on a 64-bit architecture (where addresses
Chris@19: are 64 bits wide), FFTW uses 64-bit quantities internally for all
Chris@19: transform sizes, strides, and so on—you don't have to do anything
Chris@19: special to exploit this. However, in the ordinary FFTW interfaces,
Chris@19: you specify the transform size by an int quantity, which is
Chris@19: normally only 32 bits wide. This means that, even though FFTW is
Chris@19: using 64-bit sizes internally, you cannot specify a single transform
Chris@19: dimension larger than
Chris@19: 231−1numbers.
Chris@19:
Chris@19:
We expect that few users will require transforms larger than this, but,
Chris@19: for those who do, we provide a 64-bit version of the guru interface in
Chris@19: which all sizes are specified as integers of type ptrdiff_t
Chris@19: instead of int. (ptrdiff_t is a signed integer type
Chris@19: defined by the C standard to be wide enough to represent address
Chris@19: differences, and thus must be at least 64 bits wide on a 64-bit
Chris@19: machine.) We stress that there is no performance advantage to
Chris@19: using this interface—the same internal FFTW code is employed
Chris@19: regardless—and it is only necessary if you want to specify very
Chris@19: large transform sizes.
Chris@19:
Chris@19:
Chris@19:
In particular, the 64-bit guru interface is a set of planner routines
Chris@19: that are exactly the same as the guru planner routines, except that
Chris@19: they are named with ‘guru64’ instead of ‘guru’ and they take
Chris@19: arguments of type fftw_iodim64 instead of fftw_iodim.
Chris@19: For example, instead of fftw_plan_guru_dft, we have
Chris@19: fftw_plan_guru64_dft.
Chris@19:
Chris@19:
fftw_plan fftw_plan_guru64_dft( Chris@19: int rank, const fftw_iodim64 *dims, Chris@19: int howmany_rank, const fftw_iodim64 *howmany_dims, Chris@19: fftw_complex *in, fftw_complex *out, Chris@19: int sign, unsigned flags); Chris@19:Chris@19:
Chris@19: The fftw_iodim64 type is similar to fftw_iodim, with the
Chris@19: same interpretation, except that it uses type ptrdiff_t instead
Chris@19: of type int.
Chris@19:
Chris@19:
typedef struct {
Chris@19: ptrdiff_t n;
Chris@19: ptrdiff_t is;
Chris@19: ptrdiff_t os;
Chris@19: } fftw_iodim64;
Chris@19:
Chris@19: Chris@19: Every other ‘fftw_plan_guru’ function also has a Chris@19: ‘fftw_plan_guru64’ equivalent, but we do not repeat their Chris@19: documentation here since they are identical to the 32-bit versions Chris@19: except as noted above. Chris@19: Chris@19: Chris@19: Chris@19: