for (int i = 0; i < attr_piwt.LENGTH; i++) {
  attr_piwt.fv[i] = arm::q_to_float(attr_piwt.v[i], 27 - attr_piwt.GAIN);
}
int32_t rnd = attr_seed;
rnd = rnd * 1664525 + 1013904223;
rnd = rnd * 1664525 + 1013904223;
rnd = rnd * 1664525 + 1013904223;
for (int pass = 0; pass < attr_iterations; pass++) {
  float u = 0;
  float v[16];
  for (int i = 0; i < 16; i++)
    v[i] = 0;
  rnd = rnd * 1664525 + 1013904223;
  int order = ((rnd >> 24) & 0x7) + 7;
  rnd = rnd * 1664525 + 1013904223;
  bool dir = true;
  rnd = rnd * 1664525 + 1013904223;
  float g = 0.782f + 0.2f * arm::q_to_float(rnd, 31);

  if (dir) {
    rnd = rnd * 1664525 + 1013904223;
    float g = 0.782f + 0.2f * arm::q_to_float(rnd, 31);
    for (int warmup = 0; warmup < 1024 / attr_piwt.LENGTH; warmup++) {
      for (int i = attr_piwt.LENGTH - 1; i >= 0; i--) {
        u = attr_piwt.fv[i] + g * v[order];
        for (int j = order; j > 0; j--)
          v[j] = v[j - 1];
        v[0] = u;
      }
    }
    for (int i = attr_piwt.LENGTH - 1; i >= 0; i--) {
      u = attr_piwt.fv[i] + g * v[order];
      attr_piwt.fv[i] = v[order] - g * u;
      for (int j = order; j > 0; j--)
        v[j] = v[j - 1];
      v[0] = u;
    }
  }
}
attr_piwt.prepare();