Re: Random Number Generators

Richard.W.Nichols@travelers.com
Wed, 16 Jun 1999 07:46:54 -0400

Its been years since I used APL, but back in the early 1980's I used to do a
class on APL where I would demonstrate the random number generator to pick lotto
numbers. I would write them down on the board after showing the APL statement
that generated them. Later in the class I would run the same APL statement,
and, magically, get the same answer. The point of the exercise was to
demonstrate that the random number generator in APL always started with the same
seed if you started in a newly opened workspace. Starting with the same seed
meant that APL would generate the same random numbers in the same order every
time. (Anyone know if this is still true?)

We warned the actuarial students taking the class to be sure to randomize the
seed, either by always saving the workspace after each simulation so that the
new seed would be saved as well, or by using the clock to randomize the seed.
We would simply pick N random numbers where N was the number of milliseconds on
the current time.

All this did nothing to fix any bias that may have been in the RNG, but it shows
that there may be other problems as well. Anyone know if you can reset the seed
in Excel?

Rich

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