How to calculate the smallest power of 2 greater than a certain value

 

For example, find the smallest power of 2 that is greater than or equal to 12, 13, 15, etc.: 16; similarly, the smallest power greater than or equal to 5, 6, and 7 is 8.

 

//v must be a 32-bit integer
int roundup_power_of_2(unsigned int v)
{
	v--;
	v |= v >> 1;
	v |= v >> 2;
	v |= v >> 4;
	v |= v >> 8;
	v |= v >> 16;
	v++;
	return v;
}

 

More bit related algorithms:

http://graphics.stanford.edu/~seander/bithacks.html#RoundUpPowerOf2