In mathematics, the logarithm with the base of 2 (log2n), also known as binary logarithm, is to obtain the exponent that n must be raised to the power of 2.
That is, for any real number x,
For example: log2 1 = 0，log2 2 = 1，log2 4 = 2，log2 8 = 3, log2 16 = 4, log2 32 = 5