public int Size() { int deg = 0; for ( int i = _bits.Length - 1; i >= 0; i-- ) { ulong word = _bits[i]; if ( word != 0L ) { for ( int bit = BITS - 1; bit >= 0; bit-- ) { if ( ( word & ( 1UL << bit ) ) != 0 ) { deg++; } } } } return deg; }