Re: [ros-dev] ping Alex regarding log2() for scheduler

[Rick Parrish]

Couldn't you just take the binary log and round down? Okay ... just kidding.

Seriously, I think Mark had the right idea ... if you use a smaller 
table. This is similar to some ECC code I use for counting the number of 
1's in a word. Removing the while() loop is left "as an exercise for the 
reader" ...

static const unsigned char list[16] = {0, 1, 2, 2, 3, 3, 3, 3, 4, 4, 4, 
4, 4, 4, 4, 4};

// 0 = no bits set, 1 = 1st bit set, etc.
unsigned char highest_bit(int iWord)
{
  unsigned char iResult = 0;
  unsigned char iPass = 0;
  while (iWord != 0)
  {
    iResult = list[iWord & 0xF];
    iWord >>= 4;
    if (iWord) iPass += 4;
  }
  return iResult + iPass;
}

-rick