Subj : parity checksum algorithm
To   : comp.programming
From : Paminu
Date : Wed Oct 05 2005 10:59 am

I am interested in getting some help with the "even parity check" algorithm.
I used google to find this:

unsigned parity(unsigned arg)
{
  unsigned a = arg;

  a ^= a >> 16;
  a ^= a >> 8;
  a ^= a >> 4;
  a ^= a >> 2;
  a ^= a >> 1;

  return a & 1;
} 

Who have invented this algorithm?

Is it possible to find an explanation somewhere because I see that it works
but would never myself have come up with it. Therefore I would like to know
the theory behind it.

.