Method update

src/arithmeticmodel.cpp:139–181

}

void ArithmeticModel::update()
{
  // halve counts when a threshold is reached
  if ((total_count += update_cycle) > DM__MaxCount)
  {
    total_count = 0;
    for (U32 n = 0; n < symbols; n++)
    {
      total_count += (symbol_count[n] = (symbol_count[n] + 1) >> 1);
    }
  }
  
  // compute cumulative distribution, decoder table
  U32 k, sum = 0, s = 0;
  U32 scale = 0x80000000U / total_count;

  if (compress || (table_size == 0))
  {
    for (k = 0; k < symbols; k++)
    {
      distribution[k] = (scale * sum) >> (31 - DM__LengthShift);
      sum += symbol_count[k];
    }
  }
  else
  {
    for (k = 0; k < symbols; k++)
    {
      distribution[k] = (scale * sum) >> (31 - DM__LengthShift);
      sum += symbol_count[k];
      U32 w = distribution[k] >> table_shift;
      while (s < w) decoder_table[++s] = k - 1;
    }
    decoder_table[0] = 0;
    while (s <= table_size) decoder_table[++s] = symbols - 1;
  }
  
  // set frequency of model updates
  update_cycle = (5 * update_cycle) >> 2;
  U32 max_cycle = (symbols + 6) << 3;
  if (update_cycle > max_cycle) update_cycle = max_cycle;
  symbols_until_update = update_cycle;
}

ArithmeticBitModel::ArithmeticBitModel()
{