enerators using +,- or xor. I would suggest
   combining SWB with KISS, MWC, SHR3, or CONG.
   KISS+SWB has period &gt;2^7700 and is highly
   recommended.
   Subtract-with-borrow has the same local behaviour
   as lagged Fibonacci using +,-,xor---the borrow
   merely provides a much longer period.
   SWB fails the birthday spacings test, as do all
   lagged Fibonacci and other generators that merely
   combine two previous values by means of =,- or xor.
   Those failures are for a particular case: m=512
  