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Plans for complex-data DFTs (see 2d MPI example) are created by: cannam@95: cannam@95:
fftw_plan fftw_mpi_plan_dft_1d(ptrdiff_t n0, fftw_complex *in, fftw_complex *out, cannam@95: MPI_Comm comm, int sign, unsigned flags); cannam@95: fftw_plan fftw_mpi_plan_dft_2d(ptrdiff_t n0, ptrdiff_t n1, cannam@95: fftw_complex *in, fftw_complex *out, cannam@95: MPI_Comm comm, int sign, unsigned flags); cannam@95: fftw_plan fftw_mpi_plan_dft_3d(ptrdiff_t n0, ptrdiff_t n1, ptrdiff_t n2, cannam@95: fftw_complex *in, fftw_complex *out, cannam@95: MPI_Comm comm, int sign, unsigned flags); cannam@95: fftw_plan fftw_mpi_plan_dft(int rnk, const ptrdiff_t *n, cannam@95: fftw_complex *in, fftw_complex *out, cannam@95: MPI_Comm comm, int sign, unsigned flags); cannam@95: fftw_plan fftw_mpi_plan_many_dft(int rnk, const ptrdiff_t *n, cannam@95: ptrdiff_t howmany, ptrdiff_t block, ptrdiff_t tblock, cannam@95: fftw_complex *in, fftw_complex *out, cannam@95: MPI_Comm comm, int sign, unsigned flags); cannam@95:cannam@95:
These are similar to their serial counterparts (see Complex DFTs)
cannam@95: in specifying the dimensions, sign, and flags of the transform. The
cannam@95: comm argument gives an MPI communicator that specifies the set
cannam@95: of processes to participate in the transform; plan creation is a
cannam@95: collective function that must be called for all processes in the
cannam@95: communicator. The in and out pointers refer only to a
cannam@95: portion of the overall transform data (see MPI Data Distribution)
cannam@95: as specified by the ‘local_size’ functions in the previous
cannam@95: section. Unless flags contains FFTW_ESTIMATE, these
cannam@95: arrays are overwritten during plan creation as for the serial
cannam@95: interface. For multi-dimensional transforms, any dimensions >
cannam@95: 1 are supported; for one-dimensional transforms, only composite
cannam@95: (non-prime) n0 are currently supported (unlike the serial
cannam@95: FFTW). Requesting an unsupported transform size will yield a
cannam@95: NULL plan. (As in the serial interface, highly composite sizes
cannam@95: generally yield the best performance.)
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The advanced-interface fftw_mpi_plan_many_dft additionally
cannam@95: allows you to specify the block sizes for the first dimension
cannam@95: (block) of the n0 × n1 × n2 × … × nd-1 input data and the first dimension
cannam@95: (tblock) of the n1 × n0 × n2 ×…× nd-1 transposed data (at intermediate
cannam@95: steps of the transform, and for the output if
cannam@95: FFTW_TRANSPOSED_OUT is specified in flags). These must
cannam@95: be the same block sizes as were passed to the corresponding
cannam@95: ‘local_size’ function; you can pass FFTW_MPI_DEFAULT_BLOCK
cannam@95: to use FFTW's default block size as in the basic interface. Also, the
cannam@95: howmany parameter specifies that the transform is of contiguous
cannam@95: howmany-tuples rather than individual complex numbers; this
cannam@95: corresponds to the same parameter in the serial advanced interface
cannam@95: (see Advanced Complex DFTs) with stride = howmany and
cannam@95: dist = 1.
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The flags can be any of those for the serial FFTW
cannam@95: (see Planner Flags), and in addition may include one or more of
cannam@95: the following MPI-specific flags, which improve performance at the
cannam@95: cost of changing the output or input data formats.
cannam@95:
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FFTW_MPI_SCRAMBLED_OUT, FFTW_MPI_SCRAMBLED_IN: valid for
cannam@95: 1d transforms only, these flags indicate that the output/input of the
cannam@95: transform are in an undocumented “scrambled” order. A forward
cannam@95: FFTW_MPI_SCRAMBLED_OUT transform can be inverted by a backward
cannam@95: FFTW_MPI_SCRAMBLED_IN (times the usual 1/N normalization).
cannam@95: See One-dimensional distributions.
cannam@95:
cannam@95: FFTW_MPI_TRANSPOSED_OUT, FFTW_MPI_TRANSPOSED_IN: valid
cannam@95: for multidimensional (rnk > 1) transforms only, these flags
cannam@95: specify that the output or input of an n0 × n1 × n2 × … × nd-1 transform is
cannam@95: transposed to n1 × n0 × n2 ×…× nd-1. See Transposed distributions.
cannam@95:
cannam@95: Plans for real-input/output (r2c/c2r) DFTs (see Multi-dimensional MPI DFTs of Real Data) are created by: cannam@95: cannam@95:
fftw_plan fftw_mpi_plan_dft_r2c_2d(ptrdiff_t n0, ptrdiff_t n1, cannam@95: double *in, fftw_complex *out, cannam@95: MPI_Comm comm, unsigned flags); cannam@95: fftw_plan fftw_mpi_plan_dft_r2c_2d(ptrdiff_t n0, ptrdiff_t n1, cannam@95: double *in, fftw_complex *out, cannam@95: MPI_Comm comm, unsigned flags); cannam@95: fftw_plan fftw_mpi_plan_dft_r2c_3d(ptrdiff_t n0, ptrdiff_t n1, ptrdiff_t n2, cannam@95: double *in, fftw_complex *out, cannam@95: MPI_Comm comm, unsigned flags); cannam@95: fftw_plan fftw_mpi_plan_dft_r2c(int rnk, const ptrdiff_t *n, cannam@95: double *in, fftw_complex *out, cannam@95: MPI_Comm comm, unsigned flags); cannam@95: fftw_plan fftw_mpi_plan_dft_c2r_2d(ptrdiff_t n0, ptrdiff_t n1, cannam@95: fftw_complex *in, double *out, cannam@95: MPI_Comm comm, unsigned flags); cannam@95: fftw_plan fftw_mpi_plan_dft_c2r_2d(ptrdiff_t n0, ptrdiff_t n1, cannam@95: fftw_complex *in, double *out, cannam@95: MPI_Comm comm, unsigned flags); cannam@95: fftw_plan fftw_mpi_plan_dft_c2r_3d(ptrdiff_t n0, ptrdiff_t n1, ptrdiff_t n2, cannam@95: fftw_complex *in, double *out, cannam@95: MPI_Comm comm, unsigned flags); cannam@95: fftw_plan fftw_mpi_plan_dft_c2r(int rnk, const ptrdiff_t *n, cannam@95: fftw_complex *in, double *out, cannam@95: MPI_Comm comm, unsigned flags); cannam@95:cannam@95:
Similar to the serial interface (see Real-data DFTs), these cannam@95: transform logically n0 × n1 × n2 × … × nd-1 real data to/from n0 × n1 × n2 × … × (nd-1/2 + 1) complex cannam@95: data, representing the non-redundant half of the conjugate-symmetry cannam@95: output of a real-input DFT (see Multi-dimensional Transforms). cannam@95: However, the real array must be stored within a padded n0 × n1 × n2 × … × [2 (nd-1/2 + 1)] cannam@95: cannam@95:
array (much like the in-place serial r2c transforms, but here for
cannam@95: out-of-place transforms as well). Currently, only multi-dimensional
cannam@95: (rnk > 1) r2c/c2r transforms are supported (requesting a plan
cannam@95: for rnk = 1 will yield NULL). As explained above
cannam@95: (see Multi-dimensional MPI DFTs of Real Data), the data
cannam@95: distribution of both the real and complex arrays is given by the
cannam@95: ‘local_size’ function called for the dimensions of the
cannam@95: complex array. Similar to the other planning functions, the
cannam@95: input and output arrays are overwritten when the plan is created
cannam@95: except in FFTW_ESTIMATE mode.
cannam@95:
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As for the complex DFTs above, there is an advance interface that
cannam@95: allows you to manually specify block sizes and to transform contiguous
cannam@95: howmany-tuples of real/complex numbers:
cannam@95:
cannam@95:
fftw_plan fftw_mpi_plan_many_dft_r2c cannam@95: (int rnk, const ptrdiff_t *n, ptrdiff_t howmany, cannam@95: ptrdiff_t iblock, ptrdiff_t oblock, cannam@95: double *in, fftw_complex *out, cannam@95: MPI_Comm comm, unsigned flags); cannam@95: fftw_plan fftw_mpi_plan_many_dft_c2r cannam@95: (int rnk, const ptrdiff_t *n, ptrdiff_t howmany, cannam@95: ptrdiff_t iblock, ptrdiff_t oblock, cannam@95: fftw_complex *in, double *out, cannam@95: MPI_Comm comm, unsigned flags); cannam@95:cannam@95:
There are corresponding plan-creation routines for r2r
cannam@95: transforms (see More DFTs of Real Data), currently supporting
cannam@95: multidimensional (rnk > 1) transforms only (rnk = 1 will
cannam@95: yield a NULL plan):
cannam@95:
cannam@95:
fftw_plan fftw_mpi_plan_r2r_2d(ptrdiff_t n0, ptrdiff_t n1, cannam@95: double *in, double *out, cannam@95: MPI_Comm comm, cannam@95: fftw_r2r_kind kind0, fftw_r2r_kind kind1, cannam@95: unsigned flags); cannam@95: fftw_plan fftw_mpi_plan_r2r_3d(ptrdiff_t n0, ptrdiff_t n1, ptrdiff_t n2, cannam@95: double *in, double *out, cannam@95: MPI_Comm comm, cannam@95: fftw_r2r_kind kind0, fftw_r2r_kind kind1, fftw_r2r_kind kind2, cannam@95: unsigned flags); cannam@95: fftw_plan fftw_mpi_plan_r2r(int rnk, const ptrdiff_t *n, cannam@95: double *in, double *out, cannam@95: MPI_Comm comm, const fftw_r2r_kind *kind, cannam@95: unsigned flags); cannam@95: fftw_plan fftw_mpi_plan_many_r2r(int rnk, const ptrdiff_t *n, cannam@95: ptrdiff_t iblock, ptrdiff_t oblock, cannam@95: double *in, double *out, cannam@95: MPI_Comm comm, const fftw_r2r_kind *kind, cannam@95: unsigned flags); cannam@95:cannam@95:
The parameters are much the same as for the complex DFTs above, except
cannam@95: that the arrays are of real numbers (and hence the outputs of the
cannam@95: ‘local_size’ data-distribution functions should be interpreted as
cannam@95: counts of real rather than complex numbers). Also, the kind
cannam@95: parameters specify the r2r kinds along each dimension as for the
cannam@95: serial interface (see Real-to-Real Transform Kinds). See Other Multi-dimensional Real-data MPI Transforms.
cannam@95:
cannam@95:
cannam@95: FFTW also provides routines to plan a transpose of a distributed
cannam@95: n0 by n1 array of real numbers, or an array of
cannam@95: howmany-tuples of real numbers with specified block sizes
cannam@95: (see FFTW MPI Transposes):
cannam@95:
cannam@95:
fftw_plan fftw_mpi_plan_transpose(ptrdiff_t n0, ptrdiff_t n1, cannam@95: double *in, double *out, cannam@95: MPI_Comm comm, unsigned flags); cannam@95: fftw_plan fftw_mpi_plan_many_transpose cannam@95: (ptrdiff_t n0, ptrdiff_t n1, ptrdiff_t howmany, cannam@95: ptrdiff_t block0, ptrdiff_t block1, cannam@95: double *in, double *out, MPI_Comm comm, unsigned flags); cannam@95:cannam@95:
These plans are used with the fftw_mpi_execute_r2r new-array
cannam@95: execute function (see Using MPI Plans), since they count as (rank
cannam@95: zero) r2r plans from FFTW's perspective.
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