Re: CEERAN0 API

["Simon Coulter" <shc@xxxxxxxxxxxxxxxxx>]


Hello Mike,

Its time to read Chapter 3 of Knuth's second volume.  Neither CEERAN0 nor the 
C-language 
rand() function generate truly 'random' numbers.  They generate psuedo-random 
numbers 
which are generated deterministically i.e., there is a direct relationship 
between one 
number and the previous number (and indeed the seed value).  The numbers are 
not actually 
random, they just appear to be random.  If you start with the same seed you 
will get the 
same sequence of numbers.

I believe both the above functions use different methods for generating the 
numbers, 
however they are uniformly distributed and may be considered statistically 
random.  Note 
that rand() returns integers in the range 0 to RAND_MAX (32767) while CEERAN0 
returns 
real numbers in the range 0 to 1.

You may be able to achieve your goal by changing the seed value on successive 
iterations.  
The seed could also be random number.  CEERAN0 allows you to use the current 
GMT as the 
seed by specifying a seed of zero -- you will need to set the seed to zero on 
each 
iteration since CEERAN0 updates the seed variable in preparation for the next 
call.

If neither of these functions are unsuitable for your purposes then you'll need 
to create 
your own generator but note the following quote from Knuth "... random numbers 
should not 
be generated with a method chosen at random ..."

Finally, something slightly more interesting than the free-format drivel!

Regards,
Simon Coulter.

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