fft.c

OPIE/Qtopia的测试工具

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void  BenchFFT( void )
{
  int         i;
  int         k;
  FFT         fft;

  fft.N = OBJ_DATA_COUNT;
  fft.r = OBJ_DATA_SISU;
  fft.result_A = SpectA;
  fft.result_B = SpectB;

  for ( i= 0 ; i < FFT_TEST_COUNT ; i++ )
  {
      for( k= 0 ; k < fft.N ; k++ )
      {
          fft.result_A[k] = TestData[i+k];
      }
      digital_fft( &fft );
  }
  return;
}



void  digital_fft( FFT* fft )
{
  int           col;                // ≈误∽戎规
  int           g;                  // グル〖プ戎规
  int           i;                  // グル〖プで乖う剩燎捐换搀眶
  int           group_count;        // 部グル〖プ赂哼するか
  int           group_item;         // グル〖プ柒にいくつの妥燎が赂哼するか
  int           mul_count;          // 剩燎捐换搀眶
  int           pair_plus;          // バタフライ遍换で滇めたデ〖タの滦になる戎规に颅す猛
  int           pair1;              // バタフライ遍换で滇める１つ誊の戎规
  int           pair2;              // バタフライ遍换で滇める２つ誊の戎规
  int           j;
  int           k;
  int           w;                  // ビットを瓤啪した冯蔡
  int           bit;
  int           mask;
  int           set;
  double        radian;
  double        rad;
  double        wk_cos;
  double        wk_sin;
  double        wk_A;
  double        wk_B;

  // ---------------------------------------------- デ〖タ介袋肋年
  for ( i= 0 ; i < fft->N ; i++ )
  {
      fft->result_B[i] = 0;
  }

  group_count = 1;
  mul_count   = fft->N / 2;
  pair_plus   = fft->N / 2;
  radian      = 2 * M_PI / fft->N;
  // --------------------------------------------- ｒ搀≈误∽纷换を乖う
  for ( col= 0 ; col < fft->r ; col++ )
  {
      rad = 0.0;
      // ----------------------------------------- グル〖プで乖う剩燎捐换搀眶
      for ( i= 0 ; i < mul_count ; i++ )
      {
          wk_cos = cos( rad );
          wk_sin = sin( rad );
          rad   += radian;

          group_item = mul_count + mul_count;
          pair1 = i;

          // ------------------------------------ グル〖プの眶尸乖う
          for ( g= 0 ; g < group_count ; g++ )
          {
              // -------------------------------- ≈误∽纷换の滦になるもう１つの戎规を滇める
              pair2 = pair1 + pair_plus;

              wk_A  = fft->result_A[pair1] - fft->result_A[pair2];
              wk_B  = fft->result_B[pair1] - fft->result_B[pair2];
              fft->result_A[pair1] = fft->result_A[pair1] + fft->result_A[pair2];
              fft->result_B[pair1] = fft->result_B[pair1] + fft->result_B[pair2];
              fft->result_A[pair2] = wk_cos * wk_A + wk_sin * wk_B;
              fft->result_B[pair2] = wk_cos * wk_B - wk_sin * wk_A;

              // -------------------------------- 肌のグル〖プの黎片疤弥の戎规をセット
              pair1 += group_item;
          }
      }
      group_count += group_count;               // グル〖プ眶は≈误∽髓に２擒に笼えていく
      mul_count   /= 2;                         // グル〖プで乖う剩燎捐换搀眶は≈误∽髓に１】２になる
      pair_plus   /= 2;                         // 滦になるデ〖タの疤弥は≈误∽髓に１】２になる
      radian      += radian;
  }

  // --------------------------------------------- デ〖タのビット界を傅に提す
  for ( i= 0 ; i < fft->N - 1 ; i++ )
  {
      mask = 1;                   // チェックするビット
      set  = 1 << ( fft->r-1 );   // ( fft->r-1 ) 尸焊へシフト
      w    = 0;

      for ( j= 0, k= fft->r ; k > 0 ; j++, k-- )
      {
          bit = i & mask;
          if ( bit )
              w |= set;
          mask <<= 1;
          set  >>= 1;
      }
      if ( w <= i )                             // update 1994.04.02 链デ〖タをリバ〖スしていたため傅に提っていた
          continue;

      wk_A = fft->result_A[i];
      wk_B = fft->result_B[i];
      fft->result_A[i] = fft->result_A[w];
      fft->result_A[w] = wk_A;
      fft->result_B[i] = fft->result_B[w];
      fft->result_B[w] = wk_B;
  }
}