Method CountBits2

avida-core/source/tools/cBitArray.cc:104–116

This technique is another way of counting bits; It does a bunch of clever bit tricks to do it in parallel in each int.

// This technique is another way of counting bits; It does a bunch of
// clever bit tricks to do it in parallel in each int.
int cRawBitArray::CountBits2(const int num_bits) const
{
  const int num_fields = GetNumFields(num_bits);
  int bit_count = 0;
  
  for (int i = 0; i < num_fields; i++) {
    const int  v = bit_fields[i];
    unsigned int const t1 = v - ((v >> 1) & 0x55555555);
    unsigned int const t2 = (t1 & 0x33333333) + ((t1 >> 2) & 0x33333333);
    bit_count += ((t2 + (t2 >> 4) & 0xF0F0F0F) * 0x1010101) >> 24;
  }
  return bit_count;
}

int cRawBitArray::FindBit1(const int num_bits, const int start_pos) const
{