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.