Re: ceerano and the seed

["Raquel & Peter Lunde" <lunde@xxxxxxxxxxxx>]

Vernon,

See inline comments...

Peter.

----- Original Message -----
From: "Vernon Hamberg" <vhamberg@attbi.com>
To: <midrange-l@midrange.com>
Sent: Tuesday, September 17, 2002 8:45 AM
Subject: Re: ceerano and the seed


> Peter
>
> Would it make sense to treat a user-supplied seed the same way, since it
is
> limited to a 4-byte signed integer?

Hopefully the user is better at picking a prime number than the computer.

> BTW, what does the expression "multiplicative congruential" mean? The
first
> word is simple enough. Are all forms of this kind of generator essentially
> the same, just different constants? I've seen things on the net about
> 2^31-1 and 2^61-1 (or something like that)

Multiplicative because each seed is a linear function of the previous seed
(with the overflow thrown away).
Congruential because the random number is determined by taking the modulus
(2 ^ 31) - 1 of the of the new seed.
Or something like that.
Multiplicative Congruential is just one type of random number generator.
There are many types.

> I seem to recall problems with skewed distributions when generating
> integers between 2 values. Does this "bucketizing" diminish the quality of
> the distribution? The random number generator actually returns values
> between 0 and 1.

I think the bucketizing is the result of a poor seed.  Bucketizing would
certainly diminish the quality of the distribution.