Latest posts of: Mr Z

I just have one minor change to propose, for the Difficulty calculation that's currently shown here: https://en.bitcoin.it/wiki/Difficulty#How_is_difficulty_calculated.3F_What_is_the_difference_between_bdiff_and_pdiff.3F

You can compute the difficulty in a much simpler manner, at least in C and C++.

Code:

#include <cmath>

double difficulty(const unsigned bits) {
  const unsigned exponent_diff  = 8 * (0x1D - ((bits >> 24) & 0xFF));
  const double significand = bits & 0xFFFFFF;
  return std::ldexp(0x00FFFF / significand, exponent_diff);
}

In C, just change cmath to math.h and std::ldexp to ldexp.

The ldexp() function lets you scale by a power of two almost for free, by directly adjusting the exponent on the floating point number. Thus, the difficulty calculation gets reduced to a couple integer arithmetic steps, single floating point divide, and a single scale-by-power-of-2.

This should be quite a bit faster than what's currently on the Wiki, and it's far more direct. No need for multiple floating point multiplies or an expensive floating point exponentiation.