Description

   The jrand48 function generates pseudorandom numbers using the
   linear congruential algorithm and 48-bit integer arithmetic.

   The function returns signed long integers uniformly distributed
   over the range of y values, such that -231 
   The function works by generating a sequence of 48-bit integer
   values, Xi, according to the linear congruential formula:

          Xn+1 = (aXn+c)mod m        n >= 0

   The argument m equals 248, so 48-bit integer arithmetic is

   performed. Unless you invoke the lcong48 function, the multiplier
   value a and the addend value c are:

         a = 5DEECE66D16 = 2736731631558

         c = B16 = 138

   The jrand48 function requires that the calling program pass an
   array as the xsubi argument, which for the first call must be
   initialized to the initial value of the pseudorandom-number
   sequence. Unlike the drand48 function, it is not necessary to
   call an initialization function prior to the first call.

   By using different arguments, jrand48 allows separate modules
   of a large program to generate several independent sequences of
   pseudorandom numbers. For example, the sequence of numbers that
   one module generates does not depend upon how many times the
   function is called by other modules.