Description

   The erand48 function generates pseudorandom numbers using the
   linear congruential algorithm and 48-bit integer arithmetic.

   It returns nonnegative, double-precision, floating-point values
   uniformly distributed over the range of y values, such that 0.0
   <= y < 1.0.

   The erand48 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 erand48 function requires that the calling program pass an
   array as the xsubi argument. For the first call, the array must
   be initialized to the 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, the erand48 function 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.