RANDOM_WRITE:
  FORTRAN90 version
 
  This program makes a file of random integers 
  for input to the DIEHARD tests.
 
  Select a sequence from this list:
 
  1.  A multiply-with-carry (MWC) generator
      x(n) = a * x(n-1) + carry mod 2^32
  2.  A MWC generator on pairs of 16 bits
  3.  The "Mother of all random number generators"
  4.  The KISS generator
  5.  The simple but very good generator COMBO
  6.  The lagged Fibonacci-MWC combination ULTRA
  7.  A combination MWC/subtract-with-borrow 
      (SWB) generator, period ~ 10^364
  8.  An extended congruential generator
  9.  The Super-Duper generator
 10.  A subtract-with-borrow generator
 11.  Any specified congruential generator
 12.  The 31-bit generator ran2 from Numerical Recipes
 13.  Any specified shift-register generator,
      31 or 32 bits
 14.  The system generator in Sun Fortran f77
 15.  Any lagged-Fibonacci generator,  
      x(n) = x(n-r) op x(n-s)
 16.  An inverse congruential generator
 
 
RANDOM_WRITE:
  Enter your choice, 1 to 16:
 
This program creates a binary file containing 11+ 
megabytes of 32-bit integers from a multiply-with-carry
generator
  x(n)=a*x(n-1)+carry mod 2^32
You choose the multiplier from a list.   The period 
of the generator will be a*2^31-1.  This class of 
generators is particularly well suited for 
implementation in machine language, and I predict
that many system generators in the future will be 
of this class rather than the linear congruential 
generators for modulus 2^32 that are common today.
 
To illustrate how the carry works, suppose from
the current (32-bit) x and (30 bit) c, one forms 
a*x+c.  This may be done in a 64-(or double 32-) 
bit register in most modern CPU's.  Then the new 
random x is the lower 32 bits, the new carry the 
upper 32.  
 
To see how well such a simple and fast generator 
performs on tests of randomness, this program makes
a large file with the multiply-with-carry generator
implemented in 16-bit integer arithmetic.  Those 
finding it suitable may wish to make an assembler 
version for their system.
It seems to pass all tests.
 
      Select multiplier "a" from this list:
-------------------------------------------------------
 1791398085 1929682203 1683268614 1965537969 1675393560
 1967773755 1517746329 1447497129 1655692410 1606218150
 2051013963 1075433238 1557985959 1781943330 1893513180
 1631296680 2131995753 2083801278 1873196400 1554115554
-------------------------------------------------------
  (In general, for any choice of `a`, let m=a*2^32-1. 
  If both m and (m-1)/2 are prime, then the period will
  be (m-1)/2).
 
  Enter multiplier A:
  Enter a seed integer x and initial carry c:
 
  Computation is beginning.
  Please be patient!
 
  FINISHED
  The data has been written to "mwc1.32".
  2,867,200 32-bit random integers (11,468,800 bytes)
  have been written.
  The period is   0.384700E+19
 
RANDOM_WRITE:
  Normal end of execution.