code: def compare(self, otherdigest, ishex=False):
          
          bits = 0
          myd = self.digest()
          if ishex:
              # convert to 32-tuple of unsighed two-byte INTs
              otherdigest = tuple([int(otherdigest[i:i+2],16) for i in range(0,63,2)])
          for i in range(32):
              bits += POPC[255 & myd[i] ^ otherdigest[i]]
          return 128 - bits
docs: Compute difference in bits between own digest and another.
             returns -127 to 128; 128 is the same, -127 is different