Whoops, that earlier email was meant to go to the list as well. Let's
get it back on track.
Martin Jansche wrote:
> On 11/12/06, Joseph Wakeling <[EMAIL PROTECTED]> wrote:
>
>> Can you advise on appropriately seeding the rng's for different threads,
>> so as to avoid problems of correlation?
>
> What I usually do is to have a "master seed" that's used to generate
> the seeds for the individual threads. Most of the time I just do that
> by incrementing the seed: if the first thread is seeded with 42, the
> second thread gets 43, etc. Pathological cases aside, that should be
> enough to ensure that the rng's are uncorrelated with high
> probability.
OK. Sounds good, and allows you to keep the simplicity of having one
"real" seed that can be re-used.
> What you don't want to do is seed the rng's with random
> integers obtained from the same type of rng, because often enough the
> seed is the first value (or the value before the first one) you get
> from an rng. If you did that, you'd guarantee that the threads are
> correlated.
This is what I thought, and wanted to avoid. ;-)
> If you want to seed the threads quasi-randomly, you could
> use a very simple rng for that, e.g. a linear congruential rng since
> there are relatively few threads, as long as you use a different type
> of rng in the threads to do the real work.
Sounds like a good possibility, too.
I usually take the present time as the seed, unless I specifically want
to enter one by hand: could I just take several times? (I admit that's
probably not a good idea on a system where taking the time takes all of
a fraction of a second:-).
> Hope this helps,
Very much. Thank you!
-- Joe
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