Re: Generating normally distributed randoms in CL

* (Raymond Toy (RT/EUS)) <sxd1w1b9l7y.fsf@xxxxxxxxxxxxxxx> :
Wrote on Wed, 30 Jul 2008 16:21:37 -0400:

| Madhu> I suggest that there is another reason to use a well known
| Madhu> implementation.
|
| Madhu> For serious simulations you want to publish repeatable results,
| Madhu> _independent_ of the Common Lisp implementation you use---In
| Madhu> that case your simulation program cannot depend on a package
| Madhu> which calls CL:RANDOM [as different implementations will
| Madhu> produce different sequences of numbers]. It is preferable to
| Madhu> use FFI to a "Standard" C implementation, like the "RANLIB.C"
| Madhu> package from NETLIB,
|
| I would suggest that if your simulation results depended on the
| sequence of random numbers, then your simulation is broken.

No that is not what I'm suggesting.

The point I'm making is about getting the exact same simulation result
(after seeding the rng identically) on different runs of the
application. [This is often required to verify your simulation is NOT
broken in some ways]

If you switch lisp implementation you get a different number from your
program because you are switching the rng. The suggestion to use a well
known RNG was to get identical results regardless of the lisp
implementation.

Am I missing something?

| Well, assuming that the simulation wasn't about the rng, and assuming
| the random number generator itself is not broken. :-)

--
Madhu




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