text: /*
  
  This file is part of FFTS -- The Fastest Fourier Transform in the South
  
  Copyright (c) 2012, Anthony M. Blake <amb@anthonix.com>
  Copyright (c) 2012, The University of Waikato
  
  All rights reserved.
  
  Redistribution and use in source and binary forms, with or without
  modification, are permitted provided that the following conditions are met:
  * Redistributions of source code must retain the above copyright
  notice, this list of conditions and the following disclaimer.
  * Redistributions in binary form must reproduce the above copyright
  notice, this list of conditions and the following disclaimer in the
  documentation and/or other materials provided with the distribution.
  * Neither the name of the organization nor the
  names of its contributors may be used to endorse or promote products
  derived from this software without specific prior written permission.
  
  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
  ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  DISCLAIMED. IN NO EVENT SHALL ANTHONY M. BLAKE BE LIABLE FOR ANY
  DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
  SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  
  */
  
  #include "ffts.h"
  
  #include "ffts_internal.h"
  #include "ffts_chirp_z.h"
  #include "ffts_static.h"
  #include "ffts_trig.h"
  #include "macros.h"
  #include "patterns.h"
  
  #ifndef DYNAMIC_DISABLED
  #include "codegen.h"
  #endif
  
  #if _WIN32
  #include <windows.h>
  #else
  #if __APPLE__
  #include <libkern/OSCacheControl.h>
  #endif
  
  #if HAVE_SYS_MMAN_H
  #include <sys/mman.h>
  #endif
  #endif
  
  #if defined(HAVE_NEON)
  static const FFTS_ALIGN(64) float w_data[16] = {
       0.70710678118654757273731092936941f,
       0.70710678118654746171500846685376f,
      -0.70710678118654757273731092936941f,
      -0.70710678118654746171500846685376f,
       1.0f,
       0.70710678118654757273731092936941f,
      -0.0f,
      -0.70710678118654746171500846685376f,
       0.70710678118654757273731092936941f,
       0.70710678118654746171500846685376f,
       0.70710678118654757273731092936941f,
       0.70710678118654746171500846685376f,
       1.0f,
       0.70710678118654757273731092936941f,
       0.0f,
       0.70710678118654746171500846685376f
  };
  #endif
  
  static FFTS_INLINE int
  ffts_allow_execute(void *start, size_t len)
  {
      int result;
  
  #ifdef _WIN32
      DWORD old_protect;
      result = !VirtualProtect(start, len, PAGE_EXECUTE_READ, &old_protect);
  #else
      result = mprotect(start, len, PROT_READ | PROT_EXEC);
  #endif
  
      return result;
  }
  
  static FFTS_INLINE int
  ffts_deny_execute(void *start, size_t len)
  {
      int result;
  
  #ifdef _WIN32
      DWORD old_protect;
      result = (int) VirtualProtect(start, len, PAGE_READWRITE, &old_protect);
  #else
      result = mprotect(start, len, PROT_READ | PROT_WRITE);
  #endif
  
      return result;
  }
  
  static FFTS_INLINE int
  ffts_flush_instruction_cache(void *start, size_t length)
  {
  #ifdef _WIN32
      return !FlushInstructionCache(GetCurrentProcess(), start, length);
  #else
  #ifdef __APPLE__
      sys_icache_invalidate(start, length);
  #elif __ANDROID__
      cacheflush((long) start, (long) start + length, 0);
  #elif __linux__
  #if GCC_VERSION_AT_LEAST(4,3)
      __builtin___clear_cache(start, (char*) start + length);
  #elif __GNUC__
      __clear_cache((long) start, (long) start + length);
  #endif
  #endif
      return 0;
  #endif
  }
  
  static FFTS_INLINE void*
  ffts_vmem_alloc(size_t length)
  {
  #if __APPLE__
      return mmap(NULL, length, PROT_READ | PROT_WRITE, MAP_ANON | MAP_SHARED, -1, 0);
  #elif _WIN32
      return VirtualAlloc(NULL, length, MEM_COMMIT | MEM_RESERVE, PAGE_READWRITE);
  #else
  #ifndef MAP_ANONYMOUS
  #define MAP_ANONYMOUS 0x20
  #endif
  
      return mmap(NULL, length, PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_SHARED, -1, 0);
  #endif
  }
  
  static FFTS_INLINE void
  ffts_vmem_free(void *addr, size_t length)
  {
  #ifdef _WIN32
      (void) length;
      VirtualFree(addr, 0, MEM_RELEASE);
  #else
      munmap(addr, length);
  #endif
  }
  
  FFTS_API void
  ffts_execute(ffts_plan_t *p, const void *in, void *out)
  {
      /* TODO: Define NEEDS_ALIGNED properly instead */
  #if defined(HAVE_SSE) || defined(HAVE_NEON)
      if (((uintptr_t) in % 16) != 0) {
          LOG("ffts_execute: input buffer needs to be aligned to a 128bit boundary\n");
      }
  
      if (((uintptr_t) out % 16) != 0) {
          LOG("ffts_execute: output buffer needs to be aligned to a 128bit boundary\n");
      }
  #endif
  
      p->transform(p, (const float*) in, (float*) out);
  }
  
  FFTS_API void
  ffts_free(ffts_plan_t *p)
  {
      if (p) {
          p->destroy(p);
      }
  }
  
  static void
  ffts_free_1d(ffts_plan_t *p)
  {
  #if !defined(DYNAMIC_DISABLED)
      if (p->transform_base) {
          ffts_deny_execute(p->transform_base, p->transform_size);
          ffts_vmem_free(p->transform_base, p->transform_size);
      }
  #endif
  
      if (p->ws_is) {
          free(p->ws_is);
      }
  
      if (p->ws) {
          ffts_aligned_free(p->ws);
      }
  
      if (p->is) {
          free(p->is);
      }
  
      if (p->offsets) {
          free(p->offsets);
      }
  
      free(p);
  }
  
  static int
  ffts_generate_luts(ffts_plan_t *p, size_t N, size_t leaf_N, int sign)
  {
      V4SF MULI_SIGN;
      size_t n_luts;
      ffts_cpx_32f *w;
      ffts_cpx_32f *tmp;
      size_t i, j, m, n;
      int stride;
  
      if (sign < 0) {
          MULI_SIGN = V4SF_LIT4(-0.0f, 0.0f, -0.0f, 0.0f);
      } else {
          MULI_SIGN = V4SF_LIT4(0.0f, -0.0f, 0.0f, -0.0f);
      }
  
      /* LUTS */
      n_luts = ffts_ctzl(N / leaf_N);
      if (n_luts >= 32) {
          n_luts = 0;
      }
  
      if (n_luts) {
          size_t lut_size;
  
  #if defined(__arm__) && !defined(HAVE_NEON)
          lut_size = leaf_N * (((1 << n_luts) - 2) * 3 + 1) * sizeof(ffts_cpx_32f) / 2;
  #else
          lut_size = leaf_N * (((1 << n_luts) - 2) * 3 + 1) * sizeof(ffts_cpx_32f);
  #endif
  
          p->ws = ffts_aligned_malloc(lut_size);
          if (!p->ws) {
              goto cleanup;
          }
  
          p->ws_is = (size_t*) malloc(n_luts * sizeof(*p->ws_is));
          if (!p->ws_is) {
              goto cleanup;
          }
      }
  
      w = p->ws;
      n = leaf_N * 2;
  
  #ifdef HAVE_NEON
      V4SF neg = (sign < 0) ? V4SF_LIT4(0.0f, 0.0f, 0.0f, 0.0f) : V4SF_LIT4(-0.0f, -0.0f, -0.0f, -0.0f);
  #endif
  
      /* calculate factors */
      m = leaf_N << (n_luts - 2);
      tmp = ffts_aligned_malloc(m * sizeof(ffts_cpx_32f));
  
      ffts_generate_cosine_sine_pow2_32f(tmp, m);
  
      /* generate lookup tables */
      stride = 1 << (n_luts - 1);
      for (i = 0; i < n_luts; i++) {
          p->ws_is[i] = w - (ffts_cpx_32f*) p->ws;
  
          if (!i) {
              ffts_cpx_32f *w0 = ffts_aligned_malloc(n/4 * sizeof(ffts_cpx_32f));
              float *fw0 = (float*) w0;
              float *fw = (float*) w;
  
              for (j = 0; j < n/4; j++) {
                  w0[j][0] = tmp[j * stride][0];
                  w0[j][1] = tmp[j * stride][1];
              }
  
  #if defined(__arm__)
  #ifdef HAVE_NEON
              for (j = 0; j < n/4; j += 4) {
                  V4SF2 temp0 = V4SF2_LD(fw0 + j*2);
                  temp0.val[1] = V4SF_XOR(temp0.val[1], neg);
                  V4SF2_STORE_SPR(fw + j*2, temp0);
              }
  #else
              for (j = 0; j < n/4; j++) {
                  fw[j*2+0] = fw0[j*2+0];
                  fw[j*2+1] = (sign < 0) ? fw0[j*2+1] : -fw0[j*2+1];
              }
  #endif
              w += n/4;
  #else
              for (j = 0; j < n/4; j += 2) {
                  V4SF re, im, temp0;
                  temp0 = V4SF_LD(fw0 + j*2);
                  re = V4SF_DUPLICATE_RE(temp0);
                  im = V4SF_DUPLICATE_IM(temp0);
                  im = V4SF_XOR(im, MULI_SIGN);
                  V4SF_ST(fw + j*4 + 0, re);
                  V4SF_ST(fw + j*4 + 4, im);
              }
  
              w += n/4 * 2;
  #endif
  
              ffts_aligned_free(w0);
          } else {
              ffts_cpx_32f *w0 = (ffts_cpx_32f*) ffts_aligned_malloc(n/8 * sizeof(ffts_cpx_32f));
              ffts_cpx_32f *w1 = (ffts_cpx_32f*) ffts_aligned_malloc(n/8 * sizeof(ffts_cpx_32f));
              ffts_cpx_32f *w2 = (ffts_cpx_32f*) ffts_aligned_malloc(n/8 * sizeof(ffts_cpx_32f));
  
              float *fw0 = (float*) w0;
              float *fw1 = (float*) w1;
              float *fw2 = (float*) w2;
  
              float *fw = (float *)w;
  
              for (j = 0; j < n/8; j++) {
                  w0[j][0] = tmp[2 * j * stride][0];
                  w0[j][1] = tmp[2 * j * stride][1];
  
                  w1[j][0] = tmp[j * stride][0];
                  w1[j][1] = tmp[j * stride][1];
  
                  w2[j][0] = tmp[(j + (n/8)) * stride][0];
                  w2[j][1] = tmp[(j + (n/8)) * stride][1];
              }
  
  #if defined(__arm__)
  #ifdef HAVE_NEON
              for (j = 0; j < n/8; j += 4) {
                  V4SF2 temp0, temp1, temp2;
  
                  temp0 = V4SF2_LD(fw0 + j*2);
                  temp0.val[1] = V4SF_XOR(temp0.val[1], neg);
                  V4SF2_STORE_SPR(fw + j*2*3, temp0);
                  
                  temp1 = V4SF2_LD(fw1 + j*2);
                  temp1.val[1] = V4SF_XOR(temp1.val[1], neg);
                  V4SF2_STORE_SPR(fw + j*2*3 + 8,  temp1);
                  
                  temp2 = V4SF2_LD(fw2 + j*2);
                  temp2.val[1] = V4SF_XOR(temp2.val[1], neg);
                  V4SF2_STORE_SPR(fw + j*2*3 + 16, temp2);
              }
  #else
              for (j = 0; j < n/8; j++) {
                  fw[j*6+0] = fw0[j*2+0];
                  fw[j*6+1] = (sign < 0) ? fw0[j*2+1] : -fw0[j*2+1];
                  fw[j*6+2] = fw1[j*2+0];
                  fw[j*6+3] = (sign < 0) ? fw1[j*2+1] : -fw1[j*2+1];
                  fw[j*6+4] = fw2[j*2+0];
                  fw[j*6+5] = (sign < 0) ? fw2[j*2+1] : -fw2[j*2+1];
              }
  #endif
              w += n/8 * 3;
  #else
              for (j = 0; j < n/8; j += 2) {
                  V4SF temp0, temp1, temp2, re, im;
  
                  temp0 = V4SF_LD(fw0 + j*2);
                  re = V4SF_DUPLICATE_RE(temp0);
                  im = V4SF_DUPLICATE_IM(temp0);
                  im = V4SF_XOR(im, MULI_SIGN);
                  V4SF_ST(fw + j*2*6+0, re);
                  V4SF_ST(fw + j*2*6+4, im);
  
                  temp1 = V4SF_LD(fw1 + j*2);
                  re = V4SF_DUPLICATE_RE(temp1);
                  im = V4SF_DUPLICATE_IM(temp1);
                  im = V4SF_XOR(im, MULI_SIGN);
                  V4SF_ST(fw + j*2*6+8 , re);
                  V4SF_ST(fw + j*2*6+12, im);
  
                  temp2 = V4SF_LD(fw2 + j*2);
                  re = V4SF_DUPLICATE_RE(temp2);
                  im = V4SF_DUPLICATE_IM(temp2);
                  im = V4SF_XOR(im, MULI_SIGN);
                  V4SF_ST(fw + j*2*6+16, re);
                  V4SF_ST(fw + j*2*6+20, im);
              }
  
              w += n/8 * 3 * 2;
  #endif
  
              ffts_aligned_free(w0);
              ffts_aligned_free(w1);
              ffts_aligned_free(w2);
          }
  
          n *= 2;
          stride >>= 1;
      }
  
  #if defined(HAVE_NEON)
      if (sign < 0) {
          p->oe_ws = (void*)(w_data + 4);
          p->ee_ws = (void*)(w_data);
          p->eo_ws = (void*)(w_data + 4);
      } else {
          p->oe_ws = (void*)(w_data + 12);
          p->ee_ws = (void*)(w_data + 8);
          p->eo_ws = (void*)(w_data + 12);
      }
  #endif
  
      ffts_aligned_free(tmp);
  
      p->lastlut = w;
      p->n_luts = n_luts;
      return 0;
  
  cleanup:
      return -1;
  }
  
  #ifdef FFTS_DOUBLE
  static int
  ffts_generate_luts_64f(ffts_plan_t *p, size_t N, size_t leaf_N, int sign)
  {
      V4DF MULI_SIGN;
      size_t n_luts;
      ffts_cpx_64f *w;
      ffts_cpx_64f *tmp;
      size_t i, j, m, n;
      int stride;
  
      if (sign < 0) {
          MULI_SIGN = V4DF_LIT4(-0.0, 0.0, -0.0, 0.0);
      } else {
          MULI_SIGN = V4DF_LIT4(0.0, -0.0, 0.0, -0.0);
      }
  
      /* LUTS */
      n_luts = ffts_ctzl(N / leaf_N);
      if (n_luts >= 32) {
          n_luts = 0;
      }
  
      if (n_luts) {
          size_t lut_size;
  
          lut_size = leaf_N * (((1 << n_luts) - 2) * 3 + 1) * sizeof(ffts_cpx_64f);
  
          p->ws = ffts_aligned_malloc(lut_size);
          if (!p->ws) {
              goto cleanup;
          }
  
          p->ws_is = (size_t*) malloc(n_luts * sizeof(*p->ws_is));
          if (!p->ws_is) {
              goto cleanup;
          }
      }
  
      w = p->ws;
      n = leaf_N * 2;
  
      /* calculate factors */
      m = leaf_N << (n_luts - 2);
      tmp = ffts_aligned_malloc(m * sizeof(ffts_cpx_64f));
  
      ffts_generate_cosine_sine_pow2_64f(tmp, m);
  
      /* generate lookup tables */
      stride = 1 << (n_luts - 1);
      for (i = 0; i < n_luts; i++) {
          p->ws_is[i] = w - (ffts_cpx_64f*) p->ws;
  
          if (!i) {
              ffts_cpx_64f *w0 = ffts_aligned_malloc(n/4 * sizeof(ffts_cpx_64f));
              double *fw0 = (double*) w0;
              double *fw = (double*) w;
  
              for (j = 0; j < n/4; j++) {
                  w0[j][0] = tmp[j * stride][0];
                  w0[j][1] = tmp[j * stride][1];
              }
  
              for (j = 0; j < n/4; j += 2) {
                  V4DF re, im, temp0;
                  temp0 = V4DF_LD(fw0 + j*2);
                  re = V4DF_DUPLICATE_RE(temp0);
                  im = V4DF_DUPLICATE_IM(temp0);
                  im = V4DF_XOR(im, MULI_SIGN);
                  V4DF_ST(fw + j*4 + 0, re);
                  V4DF_ST(fw + j*4 + 4, im);
              }
  
              w += n/4 * 2;
              ffts_aligned_free(w0);
          } else {
              ffts_cpx_64f *w0 = (ffts_cpx_64f*) ffts_aligned_malloc(n/8 * sizeof(ffts_cpx_64f));
              ffts_cpx_64f *w1 = (ffts_cpx_64f*) ffts_aligned_malloc(n/8 * sizeof(ffts_cpx_64f));
              ffts_cpx_64f *w2 = (ffts_cpx_64f*) ffts_aligned_malloc(n/8 * sizeof(ffts_cpx_64f));
  
              double *fw0 = (double*) w0;
              double *fw1 = (double*) w1;
              double *fw2 = (double*) w2;
  
              double *fw = (double*)w;
  
              for (j = 0; j < n/8; j++) {
                  w0[j][0] = tmp[2 * j * stride][0];
                  w0[j][1] = tmp[2 * j * stride][1];
  
                  w1[j][0] = tmp[j * stride][0];
                  w1[j][1] = tmp[j * stride][1];
  
                  w2[j][0] = tmp[(j + (n/8)) * stride][0];
                  w2[j][1] = tmp[(j + (n/8)) * stride][1];
              }
  
              for (j = 0; j < n/8; j += 2) {
                  V4DF temp0, temp1, temp2, re, im;
  
                  temp0 = V4DF_LD(fw0 + j*2);
                  re = V4DF_DUPLICATE_RE(temp0);
                  im = V4DF_DUPLICATE_IM(temp0);
                  im = V4DF_XOR(im, MULI_SIGN);
                  V4DF_ST(fw + j*2*6+0, re);
                  V4DF_ST(fw + j*2*6+4, im);
  
                  temp1 = V4DF_LD(fw1 + j*2);
                  re = V4DF_DUPLICATE_RE(temp1);
                  im = V4DF_DUPLICATE_IM(temp1);
                  im = V4DF_XOR(im, MULI_SIGN);
                  V4DF_ST(fw + j*2*6+8 , re);
                  V4DF_ST(fw + j*2*6+12, im);
  
                  temp2 = V4DF_LD(fw2 + j*2);
                  re = V4DF_DUPLICATE_RE(temp2);
                  im = V4DF_DUPLICATE_IM(temp2);
                  im = V4DF_XOR(im, MULI_SIGN);
                  V4DF_ST(fw + j*2*6+16, re);
                  V4DF_ST(fw + j*2*6+20, im);
              }
  
              w += n/8 * 3 * 2;
              ffts_aligned_free(w0);
              ffts_aligned_free(w1);
              ffts_aligned_free(w2);
          }
  
          n *= 2;
          stride >>= 1;
      }
  
      ffts_aligned_free(tmp);
  
      p->lastlut = w;
      p->n_luts = n_luts;
      return 0;
  
  cleanup:
      return -1;
  }
  #endif
  
  FFTS_API ffts_plan_t*
  ffts_init_1d(size_t N, int sign)
  {
      const size_t leaf_N = 8;
      ffts_plan_t *p;
  
      if (N < 2) {
          LOG("FFT size must be greater than 1");
          return NULL;
      }
  
      /* check if size is not a power of two */
      if (N & (N - 1)) {
          return ffts_chirp_z_init(N, sign);
      }
  
      p = (ffts_plan_t*) calloc(1, sizeof(*p));
      if (!p) {
          return NULL;
      }
  
      p->destroy = ffts_free_1d;
      p->N = N;
  
      if (N >= 32) {
          /* generate lookup tables */
          if (ffts_generate_luts(p, N, leaf_N, sign)) {
              goto cleanup;
          }
  
          p->offsets = ffts_init_offsets(N, leaf_N);
          if (!p->offsets) {
              goto cleanup;
          }
  
          p->is = ffts_init_is(N, leaf_N, 1);
          if (!p->is) {
              goto cleanup;
          }
  
          p->i0 = N/leaf_N/3 + 1;
          p->i1 = p->i2 = N/leaf_N/3;
          if ((N/leaf_N) % 3 > 1) {
              p->i1++;
          }
  
  #if !defined(HAVE_VFP) || defined(DYNAMIC_DISABLED)
          p->i0 /= 2;
          p->i1 /= 2;
  #endif
  
  #ifdef DYNAMIC_DISABLED
          if (sign < 0) {
              p->transform = ffts_static_transform_f_32f;
          } else {
              p->transform = ffts_static_transform_i_32f;
          }
  #else
          /* determinate transform size */
  #if defined(__arm__)
          if (N < 8192) {
              p->transform_size = 8192;
          } else {
              p->transform_size = N;
          }
  #else
          if (N < 2048) {
              p->transform_size = 16384;
          } else {
              p->transform_size = 16384 + 2*N/8 * ffts_ctzl(N);
          }
  #endif
  
          /* allocate code/function buffer */
          p->transform_base = ffts_vmem_alloc(p->transform_size);
          if (!p->transform_base) {
              goto cleanup;
          }
  
          /* generate code */
          p->transform = ffts_generate_func_code(p, N, leaf_N, sign);
          if (!p->transform) {
              goto cleanup;
          }
  
          /* enable execution with read access for the block */
          if (ffts_allow_execute(p->transform_base, p->transform_size)) {
              goto cleanup;
          }
  
          /* flush from the instruction cache */
          if (ffts_flush_instruction_cache(p->transform_base, p->transform_size)) {
              goto cleanup;
          }
  #endif
      } else {
          switch (N) {
          case 2:
              p->transform = &ffts_small_2_32f;
              break;
          case 4:
              if (sign == -1) {
                  p->transform = &ffts_small_forward4_32f;
              } else if (sign == 1) {
                  p->transform = &ffts_small_backward4_32f;
              }
              break;
          case 8:
              if (sign == -1) {
                  p->transform = &ffts_small_forward8_32f;
              } else if (sign == 1) {
                  p->transform = &ffts_small_backward8_32f;
              }
              break;
          case 16:
          default:
              if (sign == -1) {
                  p->transform = &ffts_small_forward16_32f;
              } else {
                  p->transform = &ffts_small_backward16_32f;
              }
              break;
          }
      }
  
      return p;
  
  cleanup:
      ffts_free_1d(p);
      return NULL;
  }
  
  #ifdef FFTS_DOUBLE
  FFTS_API ffts_plan_t*
  ffts_init_1d_64f(size_t N, int sign)
  {
      const size_t leaf_N = 8;
      ffts_plan_t *p;
  
      if (N < 2) {
          LOG("FFT size must be greater than 1");
          return NULL;
      }
  
      p = (ffts_plan_t*) calloc(1, sizeof(*p));
      if (!p) {
          return NULL;
      }
  
      p->destroy = ffts_free_1d;
      p->N = N;
  
      if (N >= 32) {
          /* generate lookup tables */
          if (ffts_generate_luts_64f(p, N, leaf_N, sign)) {
              goto cleanup;
          }
  
          p->offsets = ffts_init_offsets(N, leaf_N);
          if (!p->offsets) {
              goto cleanup;
          }
  
          p->is = ffts_init_is(N, leaf_N, 1);
          if (!p->is) {
              goto cleanup;
          }
  
          p->i0 = N/leaf_N/3 + 1;
          p->i1 = p->i2 = N/leaf_N/3;
          if ((N/leaf_N) % 3 > 1) {
              p->i1++;
          }
  
          p->i0 /= 2;
          p->i1 /= 2;
  
          if (sign < 0) {
              p->transform = ffts_static_transform_f_64f;
          } else {
              p->transform = ffts_static_transform_i_64f;
          }
      } else {
          switch (N) {
          case 2:
              p->transform = &ffts_small_2_64f;
              break;
          case 4:
              if (sign == -1) {
                  p->transform = &ffts_small_forward4_64f;
              } else if (sign == 1) {
                  p->transform = &ffts_small_backward4_64f;
              }
              break;
          case 8:
              if (sign == -1) {
                  p->transform = &ffts_small_forward8_64f;
              } else if (sign == 1) {
                  p->transform = &ffts_small_backward8_64f;
              }
              break;
          case 16:
          default:
              if (sign == -1) {
                  p->transform = &ffts_small_forward16_64f;
              } else {
                  p->transform = &ffts_small_backward16_64f;
              }
              break;
          }
      }
  
      return p;
  
  cleanup:
      ffts_free_1d(p);
      return NULL;
  }
  #else
  FFTS_API ffts_plan_t*
  ffts_init_1d_64f(size_t N, int sign)
  {
      /* disabled */
      return NULL;
  }
  #endif