oct-fftw.cc

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////////////////////////////////////////////////////////////////////////
//
// Copyright (C) 2001-2022 The Octave Project Developers
//
// See the file COPYRIGHT.md in the top-level directory of this
// distribution or <https://octave.org/copyright/>.
//
// This file is part of Octave.
//
// Octave is free software: you can redistribute it and/or modify it
// under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
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// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Octave; see the file COPYING.  If not, see
// <https://www.gnu.org/licenses/>.
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////////////////////////////////////////////////////////////////////////
 
#if defined (HAVE_CONFIG_H)
#  include "config.h"
#endif
 
#if defined (HAVE_FFTW3_H)
#  include <fftw3.h>
#endif
 
#include "lo-error.h"
#include "oct-fftw.h"
#include "oct-locbuf.h"
#include "quit.h"
#include "singleton-cleanup.h"
 
#if defined (HAVE_FFTW3_THREADS) || defined (HAVE_FFTW3F_THREADS)
#  include "nproc-wrapper.h"
#endif
 
namespace octave
{
#if defined (HAVE_FFTW)
 
  fftw_planner *fftw_planner::s_instance = nullptr;
 
  // Helper class to create and cache FFTW plans for both 1D and
  // 2D.  This implementation defaults to using FFTW_ESTIMATE to create
  // the plans, which in theory is suboptimal, but provides quite
  // reasonable performance in practice.
 
  // Also note that if FFTW_ESTIMATE is not used then the planner in FFTW3
  // will destroy the input and output arrays.  We must, therefore, create a
  // temporary input array with the same size and 16-byte alignment as
  // the original array when using a different planner strategy.
  // Note that we also use any wisdom that is available, either in a
  // FFTW3 system wide file or as supplied by the user.
 
  // FIXME: if we can ensure 16 byte alignment in Array<T>
  // (<T> *data) the FFTW3 can use SIMD instructions for further
  // acceleration.
 
  // Note that it is profitable to store the FFTW3 plans, for small FFTs.
 
  fftw_planner::fftw_planner (void)
    : m_meth (ESTIMATE), m_rplan (nullptr), m_rd (0), m_rs (0), m_rr (0),
      m_rh (0), m_rn (), m_rsimd_align (false), m_nthreads (1)
  {
    m_plan[0] = m_plan[1] = nullptr;
    m_d[0] = m_d[1] = m_s[0] = m_s[1] = m_r[0] = m_r[1] = m_h[0] = m_h[1] = 0;
    m_simd_align[0] = m_simd_align[1] = false;
    m_inplace[0] = m_inplace[1] = false;
    m_n[0] = m_n[1] = dim_vector ();
 
#if defined (HAVE_FFTW3_THREADS)
    int init_ret = fftw_init_threads ();
    if (! init_ret)
      (*current_liboctave_error_handler) ("Error initializing FFTW threads");
 
    // Use number of processors available to the current process
    // This can be later changed with fftw ("threads", nthreads).
    m_nthreads =
      octave_num_processors_wrapper (OCTAVE_NPROC_CURRENT_OVERRIDABLE);
 
    fftw_plan_with_nthreads (m_nthreads);
#endif
 
    // If we have a system wide wisdom file, import it.
    fftw_import_system_wisdom ();
  }
 
  fftw_planner::~fftw_planner (void)
  {
    fftw_plan *plan_p;
 
    plan_p = reinterpret_cast<fftw_plan *> (&m_rplan);
    if (*plan_p)
      fftw_destroy_plan (*plan_p);
 
    plan_p = reinterpret_cast<fftw_plan *> (&m_plan[0]);
    if (*plan_p)
      fftw_destroy_plan (*plan_p);
 
    plan_p = reinterpret_cast<fftw_plan *> (&m_plan[1]);
    if (*plan_p)
      fftw_destroy_plan (*plan_p);
  }
 
  bool
  fftw_planner::instance_ok (void)
  {
    bool retval = true;
 
    if (! s_instance)
      {
        s_instance = new fftw_planner ();
        singleton_cleanup_list::add (cleanup_instance);
      }
 
    return retval;
  }
 
  void
  fftw_planner::threads (int nt)
  {
#if defined (HAVE_FFTW3_THREADS)
    if (instance_ok () && nt != threads ())
      {
        s_instance->m_nthreads = nt;
        fftw_plan_with_nthreads (nt);
        // Clear the current plans.
        s_instance->m_rplan = nullptr;
        s_instance->m_plan[0] = s_instance->m_plan[1] = nullptr;
      }
#else
    octave_unused_parameter (nt);
 
    (*current_liboctave_warning_handler)
      ("unable to change number of threads without FFTW thread support");
#endif
  }
 
#define CHECK_SIMD_ALIGNMENT(x)                         \
  (((reinterpret_cast<std::ptrdiff_t> (x)) & 0xF) == 0)
 
  void *
  fftw_planner::do_create_plan (int dir, const int rank,
                                const dim_vector& dims,
                                octave_idx_type howmany,
                                octave_idx_type stride,
                                octave_idx_type dist,
                                const Complex *in, Complex *out)
  {
    int which = (dir == FFTW_FORWARD) ? 0 : 1;
    fftw_plan *cur_plan_p = reinterpret_cast<fftw_plan *> (&m_plan[which]);
    bool create_new_plan = false;
    bool ioalign = CHECK_SIMD_ALIGNMENT (in) && CHECK_SIMD_ALIGNMENT (out);
    bool ioinplace = (in == out);
 
    // Don't create a new plan if we have a non SIMD plan already but
    // can do SIMD.  This prevents endlessly recreating plans if we
    // change the alignment.
 
    if (m_plan[which] == nullptr || m_d[which] != dist || m_s[which] != stride
        || m_r[which] != rank || m_h[which] != howmany
        || ioinplace != m_inplace[which]
        || ((ioalign != m_simd_align[which]) ? ! ioalign : false))
      create_new_plan = true;
    else
      {
        // We still might not have the same shape of array.
 
        for (int i = 0; i < rank; i++)
          if (dims(i) != m_n[which](i))
            {
              create_new_plan = true;
              break;
            }
      }
 
    if (create_new_plan)
      {
        m_d[which] = dist;
        m_s[which] = stride;
        m_r[which] = rank;
        m_h[which] = howmany;
        m_simd_align[which] = ioalign;
        m_inplace[which] = ioinplace;
        m_n[which] = dims;
 
        // Note reversal of dimensions for column major storage in FFTW.
        octave_idx_type nn = 1;
        OCTAVE_LOCAL_BUFFER (int, tmp, rank);
 
        for (int i = 0, j = rank-1; i < rank; i++, j--)
          {
            tmp[i] = dims(j);
            nn *= dims(j);
          }
 
        int plan_flags = 0;
        bool plan_destroys_in = true;
 
        switch (m_meth)
          {
          case UNKNOWN:
          case ESTIMATE:
            plan_flags |= FFTW_ESTIMATE;
            plan_destroys_in = false;
            break;
          case MEASURE:
            plan_flags |= FFTW_MEASURE;
            break;
          case PATIENT:
            plan_flags |= FFTW_PATIENT;
            break;
          case EXHAUSTIVE:
            plan_flags |= FFTW_EXHAUSTIVE;
            break;
          case HYBRID:
            if (nn < 8193)
              plan_flags |= FFTW_MEASURE;
            else
              {
                plan_flags |= FFTW_ESTIMATE;
                plan_destroys_in = false;
              }
            break;
          }
 
        if (ioalign)
          plan_flags &= ~FFTW_UNALIGNED;
        else
          plan_flags |= FFTW_UNALIGNED;
 
        if (*cur_plan_p)
          fftw_destroy_plan (*cur_plan_p);
 
        if (plan_destroys_in)
          {
            // Create matrix with the same size and 16-byte alignment as input
            OCTAVE_LOCAL_BUFFER (Complex, itmp, nn * howmany + 32);
            itmp = reinterpret_cast<Complex *>
                   (((reinterpret_cast<std::ptrdiff_t> (itmp) + 15) & ~ 0xF) +
                    ((reinterpret_cast<std::ptrdiff_t> (in)) & 0xF));
 
            *cur_plan_p
              = fftw_plan_many_dft (rank, tmp, howmany,
                                    reinterpret_cast<fftw_complex *> (itmp),
                                    nullptr, stride, dist,
                                    reinterpret_cast<fftw_complex *> (out),
                                    nullptr, stride, dist, dir, plan_flags);
          }
        else
          {
            *cur_plan_p
              = fftw_plan_many_dft (rank, tmp, howmany,
                                    reinterpret_cast<fftw_complex *> (const_cast<Complex *> (in)),
                                    nullptr, stride, dist,
                                    reinterpret_cast<fftw_complex *> (out),
                                    nullptr, stride, dist, dir, plan_flags);
          }
 
        if (*cur_plan_p == nullptr)
          (*current_liboctave_error_handler) ("Error creating FFTW plan");
      }
 
    return *cur_plan_p;
  }
 
  void *
  fftw_planner::do_create_plan (const int rank, const dim_vector& dims,
                                octave_idx_type howmany,
                                octave_idx_type stride,
                                octave_idx_type dist,
                                const double *in, Complex *out)
  {
    fftw_plan *cur_plan_p = reinterpret_cast<fftw_plan *> (&m_rplan);
    bool create_new_plan = false;
    bool ioalign = CHECK_SIMD_ALIGNMENT (in) && CHECK_SIMD_ALIGNMENT (out);
 
    // Don't create a new plan if we have a non SIMD plan already but
    // can do SIMD.  This prevents endlessly recreating plans if we
    // change the alignment.
 
    if (m_rplan == nullptr || m_rd != dist || m_rs != stride || m_rr != rank
        || m_rh != howmany || ((ioalign != m_rsimd_align) ? ! ioalign : false))
      create_new_plan = true;
    else
      {
        // We still might not have the same shape of array.
 
        for (int i = 0; i < rank; i++)
          if (dims(i) != m_rn(i))
            {
              create_new_plan = true;
              break;
            }
      }
 
    if (create_new_plan)
      {
        m_rd = dist;
        m_rs = stride;
        m_rr = rank;
        m_rh = howmany;
        m_rsimd_align = ioalign;
        m_rn = dims;
 
        // Note reversal of dimensions for column major storage in FFTW.
        octave_idx_type nn = 1;
        OCTAVE_LOCAL_BUFFER (int, tmp, rank);
 
        for (int i = 0, j = rank-1; i < rank; i++, j--)
          {
            tmp[i] = dims(j);
            nn *= dims(j);
          }
 
        int plan_flags = 0;
        bool plan_destroys_in = true;
 
        switch (m_meth)
          {
          case UNKNOWN:
          case ESTIMATE:
            plan_flags |= FFTW_ESTIMATE;
            plan_destroys_in = false;
            break;
          case MEASURE:
            plan_flags |= FFTW_MEASURE;
            break;
          case PATIENT:
            plan_flags |= FFTW_PATIENT;
            break;
          case EXHAUSTIVE:
            plan_flags |= FFTW_EXHAUSTIVE;
            break;
          case HYBRID:
            if (nn < 8193)
              plan_flags |= FFTW_MEASURE;
            else
              {
                plan_flags |= FFTW_ESTIMATE;
                plan_destroys_in = false;
              }
            break;
          }
 
        if (ioalign)
          plan_flags &= ~FFTW_UNALIGNED;
        else
          plan_flags |= FFTW_UNALIGNED;
 
        if (*cur_plan_p)
          fftw_destroy_plan (*cur_plan_p);
 
        if (plan_destroys_in)
          {
            // Create matrix with the same size and 16-byte alignment as input
            OCTAVE_LOCAL_BUFFER (double, itmp, nn + 32);
            itmp = reinterpret_cast<double *>
                   (((reinterpret_cast<std::ptrdiff_t> (itmp) + 15) & ~ 0xF) +
                    ((reinterpret_cast<std::ptrdiff_t> (in)) & 0xF));
 
            *cur_plan_p
              = fftw_plan_many_dft_r2c (rank, tmp, howmany, itmp,
                                        nullptr, stride, dist,
                                        reinterpret_cast<fftw_complex *> (out),
                                        nullptr, stride, dist, plan_flags);
          }
        else
          {
            *cur_plan_p
              = fftw_plan_many_dft_r2c (rank, tmp, howmany,
                                        (const_cast<double *> (in)),
                                        nullptr, stride, dist,
                                        reinterpret_cast<fftw_complex *> (out),
                                        nullptr, stride, dist, plan_flags);
          }
 
        if (*cur_plan_p == nullptr)
          (*current_liboctave_error_handler) ("Error creating FFTW plan");
      }
 
    return *cur_plan_p;
  }
 
  fftw_planner::FftwMethod
  fftw_planner::do_method (void)
  {
    return m_meth;
  }
 
  fftw_planner::FftwMethod
  fftw_planner::do_method (FftwMethod _meth)
  {
    FftwMethod ret = m_meth;
    if (_meth == ESTIMATE || _meth == MEASURE
        || _meth == PATIENT || _meth == EXHAUSTIVE
        || _meth == HYBRID)
      {
        if (m_meth != _meth)
          {
            m_meth = _meth;
            if (m_rplan)
              fftw_destroy_plan (reinterpret_cast<fftw_plan> (m_rplan));
            if (m_plan[0])
              fftw_destroy_plan (reinterpret_cast<fftw_plan> (m_plan[0]));
            if (m_plan[1])
              fftw_destroy_plan (reinterpret_cast<fftw_plan> (m_plan[1]));
            m_rplan = m_plan[0] = m_plan[1] = nullptr;
          }
      }
    else
      ret = UNKNOWN;
    return ret;
  }
 
  float_fftw_planner *float_fftw_planner::s_instance = nullptr;
 
  float_fftw_planner::float_fftw_planner (void)
    : m_meth (ESTIMATE), m_rplan (nullptr), m_rd (0), m_rs (0), m_rr (0),
      m_rh (0), m_rn (), m_rsimd_align (false), m_nthreads (1)
  {
    m_plan[0] = m_plan[1] = nullptr;
    m_d[0] = m_d[1] = m_s[0] = m_s[1] = m_r[0] = m_r[1] = m_h[0] = m_h[1] = 0;
    m_simd_align[0] = m_simd_align[1] = false;
    m_inplace[0] = m_inplace[1] = false;
    m_n[0] = m_n[1] = dim_vector ();
 
#if defined (HAVE_FFTW3F_THREADS)
    int init_ret = fftwf_init_threads ();
    if (! init_ret)
      (*current_liboctave_error_handler) ("Error initializing FFTW3F threads");
 
    // Use number of processors available to the current process
    // This can be later changed with fftw ("threads", nthreads).
    m_nthreads =
      octave_num_processors_wrapper (OCTAVE_NPROC_CURRENT_OVERRIDABLE);
 
    fftwf_plan_with_nthreads (m_nthreads);
#endif
 
    // If we have a system wide wisdom file, import it.
    fftwf_import_system_wisdom ();
  }
 
  float_fftw_planner::~float_fftw_planner (void)
  {
    fftwf_plan *plan_p;
 
    plan_p = reinterpret_cast<fftwf_plan *> (&m_rplan);
    if (*plan_p)
      fftwf_destroy_plan (*plan_p);
 
    plan_p = reinterpret_cast<fftwf_plan *> (&m_plan[0]);
    if (*plan_p)
      fftwf_destroy_plan (*plan_p);
 
    plan_p = reinterpret_cast<fftwf_plan *> (&m_plan[1]);
    if (*plan_p)
      fftwf_destroy_plan (*plan_p);
  }
 
  bool
  float_fftw_planner::instance_ok (void)
  {
    bool retval = true;
 
    if (! s_instance)
      {
        s_instance = new float_fftw_planner ();
        singleton_cleanup_list::add (cleanup_instance);
      }
 
    return retval;
  }
 
  void
  float_fftw_planner::threads (int nt)
  {
#if defined (HAVE_FFTW3F_THREADS)
    if (instance_ok () && nt != threads ())
      {
        s_instance->m_nthreads = nt;
        fftwf_plan_with_nthreads (nt);
        // Clear the current plans.
        s_instance->m_rplan = nullptr;
        s_instance->m_plan[0] = s_instance->m_plan[1] = nullptr;
      }
#else
    octave_unused_parameter (nt);
 
    (*current_liboctave_warning_handler)
      ("unable to change number of threads without FFTW thread support");
#endif
  }
 
  void *
  float_fftw_planner::do_create_plan (int dir, const int rank,
                                      const dim_vector& dims,
                                      octave_idx_type howmany,
                                      octave_idx_type stride,
                                      octave_idx_type dist,
                                      const FloatComplex *in,
                                      FloatComplex *out)
  {
    int which = (dir == FFTW_FORWARD) ? 0 : 1;
    fftwf_plan *cur_plan_p = reinterpret_cast<fftwf_plan *> (&m_plan[which]);
    bool create_new_plan = false;
    bool ioalign = CHECK_SIMD_ALIGNMENT (in) && CHECK_SIMD_ALIGNMENT (out);
    bool ioinplace = (in == out);
 
    // Don't create a new plan if we have a non SIMD plan already but
    // can do SIMD.  This prevents endlessly recreating plans if we
    // change the alignment.
 
    if (m_plan[which] == nullptr || m_d[which] != dist || m_s[which] != stride
        || m_r[which] != rank || m_h[which] != howmany
        || ioinplace != m_inplace[which]
        || ((ioalign != m_simd_align[which]) ? ! ioalign : false))
      create_new_plan = true;
    else
      {
        // We still might not have the same shape of array.
 
        for (int i = 0; i < rank; i++)
          if (dims(i) != m_n[which](i))
            {
              create_new_plan = true;
              break;
            }
      }
 
    if (create_new_plan)
      {
        m_d[which] = dist;
        m_s[which] = stride;
        m_r[which] = rank;
        m_h[which] = howmany;
        m_simd_align[which] = ioalign;
        m_inplace[which] = ioinplace;
        m_n[which] = dims;
 
        // Note reversal of dimensions for column major storage in FFTW.
        octave_idx_type nn = 1;
        OCTAVE_LOCAL_BUFFER (int, tmp, rank);
 
        for (int i = 0, j = rank-1; i < rank; i++, j--)
          {
            tmp[i] = dims(j);
            nn *= dims(j);
          }
 
        int plan_flags = 0;
        bool plan_destroys_in = true;
 
        switch (m_meth)
          {
          case UNKNOWN:
          case ESTIMATE:
            plan_flags |= FFTW_ESTIMATE;
            plan_destroys_in = false;
            break;
          case MEASURE:
            plan_flags |= FFTW_MEASURE;
            break;
          case PATIENT:
            plan_flags |= FFTW_PATIENT;
            break;
          case EXHAUSTIVE:
            plan_flags |= FFTW_EXHAUSTIVE;
            break;
          case HYBRID:
            if (nn < 8193)
              plan_flags |= FFTW_MEASURE;
            else
              {
                plan_flags |= FFTW_ESTIMATE;
                plan_destroys_in = false;
              }
            break;
          }
 
        if (ioalign)
          plan_flags &= ~FFTW_UNALIGNED;
        else
          plan_flags |= FFTW_UNALIGNED;
 
        if (*cur_plan_p)
          fftwf_destroy_plan (*cur_plan_p);
 
        if (plan_destroys_in)
          {
            // Create matrix with the same size and 16-byte alignment as input
            OCTAVE_LOCAL_BUFFER (FloatComplex, itmp, nn * howmany + 32);
            itmp = reinterpret_cast<FloatComplex *>
                   (((reinterpret_cast<std::ptrdiff_t> (itmp) + 15) & ~ 0xF) +
                    ((reinterpret_cast<std::ptrdiff_t> (in)) & 0xF));
 
            *cur_plan_p
              = fftwf_plan_many_dft (rank, tmp, howmany,
                                     reinterpret_cast<fftwf_complex *> (itmp),
                                     nullptr, stride, dist,
                                     reinterpret_cast<fftwf_complex *> (out),
                                     nullptr, stride, dist, dir, plan_flags);
          }
        else
          {
            *cur_plan_p
              = fftwf_plan_many_dft (rank, tmp, howmany,
                                     reinterpret_cast<fftwf_complex *> (const_cast<FloatComplex *> (in)),
                                     nullptr, stride, dist,
                                     reinterpret_cast<fftwf_complex *> (out),
                                     nullptr, stride, dist, dir, plan_flags);
          }
 
        if (*cur_plan_p == nullptr)
          (*current_liboctave_error_handler) ("Error creating FFTW plan");
      }
 
    return *cur_plan_p;
  }
 
  void *
  float_fftw_planner::do_create_plan (const int rank, const dim_vector& dims,
                                      octave_idx_type howmany,
                                      octave_idx_type stride,
                                      octave_idx_type dist,
                                      const float *in, FloatComplex *out)
  {
    fftwf_plan *cur_plan_p = reinterpret_cast<fftwf_plan *> (&m_rplan);
    bool create_new_plan = false;
    bool ioalign = CHECK_SIMD_ALIGNMENT (in) && CHECK_SIMD_ALIGNMENT (out);
 
    // Don't create a new plan if we have a non SIMD plan already but
    // can do SIMD.  This prevents endlessly recreating plans if we
    // change the alignment.
 
    if (m_rplan == nullptr || m_rd != dist || m_rs != stride || m_rr != rank
        || m_rh != howmany || ((ioalign != m_rsimd_align) ? ! ioalign : false))
      create_new_plan = true;
    else
      {
        // We still might not have the same shape of array.
 
        for (int i = 0; i < rank; i++)
          if (dims(i) != m_rn(i))
            {
              create_new_plan = true;
              break;
            }
      }
 
    if (create_new_plan)
      {
        m_rd = dist;
        m_rs = stride;
        m_rr = rank;
        m_rh = howmany;
        m_rsimd_align = ioalign;
        m_rn = dims;
 
        // Note reversal of dimensions for column major storage in FFTW.
        octave_idx_type nn = 1;
        OCTAVE_LOCAL_BUFFER (int, tmp, rank);
 
        for (int i = 0, j = rank-1; i < rank; i++, j--)
          {
            tmp[i] = dims(j);
            nn *= dims(j);
          }
 
        int plan_flags = 0;
        bool plan_destroys_in = true;
 
        switch (m_meth)
          {
          case UNKNOWN:
          case ESTIMATE:
            plan_flags |= FFTW_ESTIMATE;
            plan_destroys_in = false;
            break;
          case MEASURE:
            plan_flags |= FFTW_MEASURE;
            break;
          case PATIENT:
            plan_flags |= FFTW_PATIENT;
            break;
          case EXHAUSTIVE:
            plan_flags |= FFTW_EXHAUSTIVE;
            break;
          case HYBRID:
            if (nn < 8193)
              plan_flags |= FFTW_MEASURE;
            else
              {
                plan_flags |= FFTW_ESTIMATE;
                plan_destroys_in = false;
              }
            break;
          }
 
        if (ioalign)
          plan_flags &= ~FFTW_UNALIGNED;
        else
          plan_flags |= FFTW_UNALIGNED;
 
        if (*cur_plan_p)
          fftwf_destroy_plan (*cur_plan_p);
 
        if (plan_destroys_in)
          {
            // Create matrix with the same size and 16-byte alignment as input
            OCTAVE_LOCAL_BUFFER (float, itmp, nn + 32);
            itmp = reinterpret_cast<float *>
                   (((reinterpret_cast<std::ptrdiff_t> (itmp) + 15) & ~ 0xF) +
                    ((reinterpret_cast<std::ptrdiff_t> (in)) & 0xF));
 
            *cur_plan_p
              = fftwf_plan_many_dft_r2c (rank, tmp, howmany, itmp,
                                         nullptr, stride, dist,
                                         reinterpret_cast<fftwf_complex *> (out),
                                         nullptr, stride, dist, plan_flags);
          }
        else
          {
            *cur_plan_p
              = fftwf_plan_many_dft_r2c (rank, tmp, howmany,
                                         (const_cast<float *> (in)),
                                         nullptr, stride, dist,
                                         reinterpret_cast<fftwf_complex *> (out),
                                         nullptr, stride, dist, plan_flags);
          }
 
        if (*cur_plan_p == nullptr)
          (*current_liboctave_error_handler) ("Error creating FFTW plan");
      }
 
    return *cur_plan_p;
  }
 
  float_fftw_planner::FftwMethod
  float_fftw_planner::do_method (void)
  {
    return m_meth;
  }
 
  float_fftw_planner::FftwMethod
  float_fftw_planner::do_method (FftwMethod _meth)
  {
    FftwMethod ret = m_meth;
    if (_meth == ESTIMATE || _meth == MEASURE
        || _meth == PATIENT || _meth == EXHAUSTIVE
        || _meth == HYBRID)
      {
        if (m_meth != _meth)
          {
            m_meth = _meth;
            if (m_rplan)
              fftwf_destroy_plan (reinterpret_cast<fftwf_plan> (m_rplan));
            if (m_plan[0])
              fftwf_destroy_plan (reinterpret_cast<fftwf_plan> (m_plan[0]));
            if (m_plan[1])
              fftwf_destroy_plan (reinterpret_cast<fftwf_plan> (m_plan[1]));
            m_rplan = m_plan[0] = m_plan[1] = nullptr;
          }
      }
    else
      ret = UNKNOWN;
    return ret;
  }
 
  template <typename T>
  static inline void
  convert_packcomplex_1d (T *out, std::size_t nr, std::size_t nc,
                          octave_idx_type stride, octave_idx_type dist)
  {
    octave_quit ();
 
    // Fill in the missing data.
 
    for (std::size_t i = 0; i < nr; i++)
      for (std::size_t j = nc/2+1; j < nc; j++)
        out[j*stride + i*dist] = conj (out[(nc - j)*stride + i*dist]);
 
    octave_quit ();
  }
 
  template <typename T>
  static inline void
  convert_packcomplex_Nd (T *out, const dim_vector& dv)
  {
    std::size_t nc = dv(0);
    std::size_t nr = dv(1);
    std::size_t np = (dv.ndims () > 2 ? dv.numel () / nc / nr : 1);
    std::size_t nrp = nr * np;
    T *ptr1, *ptr2;
 
    octave_quit ();
 
    // Create space for the missing elements.
 
    for (std::size_t i = 0; i < nrp; i++)
      {
        ptr1 = out + i * (nc/2 + 1) + nrp*((nc-1)/2);
        ptr2 = out + i * nc;
        for (std::size_t j = 0; j < nc/2+1; j++)
          *ptr2++ = *ptr1++;
      }
 
    octave_quit ();
 
    // Fill in the missing data for the rank = 2 case directly for speed.
 
    for (std::size_t i = 0; i < np; i++)
      {
        for (std::size_t j = 1; j < nr; j++)
          for (std::size_t k = nc/2+1; k < nc; k++)
            out[k + (j + i*nr)*nc] = conj (out[nc - k + ((i+1)*nr - j)*nc]);
 
        for (std::size_t j = nc/2+1; j < nc; j++)
          out[j + i*nr*nc] = conj (out[(i*nr+1)*nc - j]);
      }
 
    octave_quit ();
 
    // Now do the permutations needed for rank > 2 cases.
 
    std::size_t jstart = dv(0) * dv(1);
    std::size_t kstep = dv(0);
    std::size_t nel = dv.numel ();
 
    for (int inner = 2; inner < dv.ndims (); inner++)
      {
        std::size_t jmax = jstart * dv(inner);
        for (std::size_t i = 0; i < nel; i+=jmax)
          for (std::size_t j = jstart, jj = jmax-jstart; j < jj;
               j+=jstart, jj-=jstart)
            for (std::size_t k = 0; k < jstart; k+= kstep)
              for (std::size_t l = nc/2+1; l < nc; l++)
                {
                  T tmp = out[i+ j + k + l];
                  out[i + j + k + l] = out[i + jj + k + l];
                  out[i + jj + k + l] = tmp;
                }
        jstart = jmax;
      }
 
    octave_quit ();
  }
 
  int
  fftw::fft (const double *in, Complex *out, std::size_t npts,
             std::size_t nsamples, octave_idx_type stride,
             octave_idx_type dist)
  {
    dist = (dist < 0 ? npts : dist);
 
    dim_vector dv (npts, 1);
    void *vplan = fftw_planner::create_plan (1, dv, nsamples,
                                             stride, dist, in, out);
    fftw_plan m_plan = reinterpret_cast<fftw_plan> (vplan);
 
    fftw_execute_dft_r2c (m_plan, (const_cast<double *>(in)),
                          reinterpret_cast<fftw_complex *> (out));
 
    // Need to create other half of the transform.
 
    convert_packcomplex_1d (out, nsamples, npts, stride, dist);
 
    return 0;
  }
 
  int
  fftw::fft (const Complex *in, Complex *out, std::size_t npts,
             std::size_t nsamples, octave_idx_type stride,
             octave_idx_type dist)
  {
    dist = (dist < 0 ? npts : dist);
 
    dim_vector dv (npts, 1);
    void *vplan = fftw_planner::create_plan (FFTW_FORWARD, 1, dv,
                                             nsamples, stride,
                                             dist, in, out);
    fftw_plan m_plan = reinterpret_cast<fftw_plan> (vplan);
 
    fftw_execute_dft (m_plan,
                      reinterpret_cast<fftw_complex *> (const_cast<Complex *>(in)),
                      reinterpret_cast<fftw_complex *> (out));
 
    return 0;
  }
 
  int
  fftw::ifft (const Complex *in, Complex *out, std::size_t npts,
              std::size_t nsamples, octave_idx_type stride,
              octave_idx_type dist)
  {
    dist = (dist < 0 ? npts : dist);
 
    dim_vector dv (npts, 1);
    void *vplan = fftw_planner::create_plan (FFTW_BACKWARD, 1, dv, nsamples,
                                             stride, dist, in, out);
    fftw_plan m_plan = reinterpret_cast<fftw_plan> (vplan);
 
    fftw_execute_dft (m_plan,
                      reinterpret_cast<fftw_complex *> (const_cast<Complex *>(in)),
                      reinterpret_cast<fftw_complex *> (out));
 
    const Complex scale = npts;
    for (std::size_t j = 0; j < nsamples; j++)
      for (std::size_t i = 0; i < npts; i++)
        out[i*stride + j*dist] /= scale;
 
    return 0;
  }
 
  int
  fftw::fftNd (const double *in, Complex *out, const int rank,
               const dim_vector& dv)
  {
    octave_idx_type dist = 1;
    for (int i = 0; i < rank; i++)
      dist *= dv(i);
 
    // Fool with the position of the start of the output matrix, so that
    // creating other half of the matrix won't cause cache problems.
 
    octave_idx_type offset = (dv.numel () / dv(0)) * ((dv(0) - 1) / 2);
 
    void *vplan = fftw_planner::create_plan (rank, dv, 1, 1, dist,
                                             in, out + offset);
    fftw_plan m_plan = reinterpret_cast<fftw_plan> (vplan);
 
    fftw_execute_dft_r2c (m_plan, (const_cast<double *>(in)),
                          reinterpret_cast<fftw_complex *> (out+ offset));
 
    // Need to create other half of the transform.
 
    convert_packcomplex_Nd (out, dv);
 
    return 0;
  }
 
  int
  fftw::fftNd (const Complex *in, Complex *out, const int rank,
               const dim_vector& dv)
  {
    octave_idx_type dist = 1;
    for (int i = 0; i < rank; i++)
      dist *= dv(i);
 
    void *vplan = fftw_planner::create_plan (FFTW_FORWARD, rank, dv,
                                             1, 1, dist, in, out);
    fftw_plan m_plan = reinterpret_cast<fftw_plan> (vplan);
 
    fftw_execute_dft (m_plan,
                      reinterpret_cast<fftw_complex *> (const_cast<Complex *>(in)),
                      reinterpret_cast<fftw_complex *> (out));
 
    return 0;
  }
 
  int
  fftw::ifftNd (const Complex *in, Complex *out, const int rank,
                const dim_vector& dv)
  {
    octave_idx_type dist = 1;
    for (int i = 0; i < rank; i++)
      dist *= dv(i);
 
    void *vplan = fftw_planner::create_plan (FFTW_BACKWARD, rank, dv,
                                             1, 1, dist, in, out);
    fftw_plan m_plan = reinterpret_cast<fftw_plan> (vplan);
 
    fftw_execute_dft (m_plan,
                      reinterpret_cast<fftw_complex *> (const_cast<Complex *>(in)),
                      reinterpret_cast<fftw_complex *> (out));
 
    const std::size_t npts = dv.numel ();
    const Complex scale = npts;
    for (std::size_t i = 0; i < npts; i++)
      out[i] /= scale;
 
    return 0;
  }
 
  int
  fftw::fft (const float *in, FloatComplex *out, std::size_t npts,
             std::size_t nsamples, octave_idx_type stride,
             octave_idx_type dist)
  {
    dist = (dist < 0 ? npts : dist);
 
    dim_vector dv (npts, 1);
    void *vplan = float_fftw_planner::create_plan (1, dv, nsamples, stride,
                                                   dist, in, out);
    fftwf_plan m_plan = reinterpret_cast<fftwf_plan> (vplan);
 
    fftwf_execute_dft_r2c (m_plan, (const_cast<float *>(in)),
                           reinterpret_cast<fftwf_complex *> (out));
 
    // Need to create other half of the transform.
 
    convert_packcomplex_1d (out, nsamples, npts, stride, dist);
 
    return 0;
  }
 
  int
  fftw::fft (const FloatComplex *in, FloatComplex *out, std::size_t npts,
             std::size_t nsamples, octave_idx_type stride,
             octave_idx_type dist)
  {
    dist = (dist < 0 ? npts : dist);
 
    dim_vector dv (npts, 1);
    void *vplan = float_fftw_planner::create_plan (FFTW_FORWARD, 1, dv,
                                                   nsamples, stride, dist,
                                                   in, out);
    fftwf_plan m_plan = reinterpret_cast<fftwf_plan> (vplan);
 
    fftwf_execute_dft (m_plan,
                       reinterpret_cast<fftwf_complex *> (const_cast<FloatComplex *>(in)),
                       reinterpret_cast<fftwf_complex *> (out));
 
    return 0;
  }
 
  int
  fftw::ifft (const FloatComplex *in, FloatComplex *out, std::size_t npts,
              std::size_t nsamples, octave_idx_type stride,
              octave_idx_type dist)
  {
    dist = (dist < 0 ? npts : dist);
 
    dim_vector dv (npts, 1);
    void *vplan = float_fftw_planner::create_plan (FFTW_BACKWARD, 1, dv,
                                                   nsamples, stride, dist,
                                                   in, out);
    fftwf_plan m_plan = reinterpret_cast<fftwf_plan> (vplan);
 
    fftwf_execute_dft (m_plan,
                       reinterpret_cast<fftwf_complex *> (const_cast<FloatComplex *>(in)),
                       reinterpret_cast<fftwf_complex *> (out));
 
    const FloatComplex scale = npts;
    for (std::size_t j = 0; j < nsamples; j++)
      for (std::size_t i = 0; i < npts; i++)
        out[i*stride + j*dist] /= scale;
 
    return 0;
  }
 
  int
  fftw::fftNd (const float *in, FloatComplex *out, const int rank,
               const dim_vector& dv)
  {
    octave_idx_type dist = 1;
    for (int i = 0; i < rank; i++)
      dist *= dv(i);
 
    // Fool with the position of the start of the output matrix, so that
    // creating other half of the matrix won't cause cache problems.
 
    octave_idx_type offset = (dv.numel () / dv(0)) * ((dv(0) - 1) / 2);
 
    void *vplan = float_fftw_planner::create_plan (rank, dv, 1, 1, dist,
                                                   in, out + offset);
    fftwf_plan m_plan = reinterpret_cast<fftwf_plan> (vplan);
 
    fftwf_execute_dft_r2c (m_plan, (const_cast<float *>(in)),
                           reinterpret_cast<fftwf_complex *> (out+ offset));
 
    // Need to create other half of the transform.
 
    convert_packcomplex_Nd (out, dv);
 
    return 0;
  }
 
  int
  fftw::fftNd (const FloatComplex *in, FloatComplex *out, const int rank,
               const dim_vector& dv)
  {
    octave_idx_type dist = 1;
    for (int i = 0; i < rank; i++)
      dist *= dv(i);
 
    void *vplan = float_fftw_planner::create_plan (FFTW_FORWARD, rank, dv,
                                                   1, 1, dist, in, out);
    fftwf_plan m_plan = reinterpret_cast<fftwf_plan> (vplan);
 
    fftwf_execute_dft (m_plan,
                       reinterpret_cast<fftwf_complex *> (const_cast<FloatComplex *>(in)),
                       reinterpret_cast<fftwf_complex *> (out));
 
    return 0;
  }
 
  int
  fftw::ifftNd (const FloatComplex *in, FloatComplex *out, const int rank,
                const dim_vector& dv)
  {
    octave_idx_type dist = 1;
    for (int i = 0; i < rank; i++)
      dist *= dv(i);
 
    void *vplan = float_fftw_planner::create_plan (FFTW_BACKWARD, rank, dv,
                                                   1, 1, dist, in, out);
    fftwf_plan m_plan = reinterpret_cast<fftwf_plan> (vplan);
 
    fftwf_execute_dft (m_plan,
                       reinterpret_cast<fftwf_complex *> (const_cast<FloatComplex *>(in)),
                       reinterpret_cast<fftwf_complex *> (out));
 
    const std::size_t npts = dv.numel ();
    const FloatComplex scale = npts;
    for (std::size_t i = 0; i < npts; i++)
      out[i] /= scale;
 
    return 0;
  }
 
#endif
 
  std::string
  fftw_version (void)
  {
#if defined (HAVE_FFTW)
    return ::fftw_version;
#else
    return "none";
#endif
  }
 
  std::string
  fftwf_version (void)
  {
#if defined (HAVE_FFTW)
    return ::fftwf_version;
#else
    return "none";
#endif
  }
}