Re: [PATCH] random_normal function

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Paul Ramsey <pramsey(at)cleverelephant(dot)ca>
Cc: Dean Rasheed <dean(dot)a(dot)rasheed(at)gmail(dot)com>, Fabien COELHO <coelho(at)cri(dot)ensmp(dot)fr>, Michael Paquier <michael(at)paquier(dot)xyz>, Justin Pryzby <pryzby(at)telsasoft(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: [PATCH] random_normal function
Date: 2023-01-09 18:52:16
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I wrote:
> Hmm ... it occurred to me to try the same check on the existing
> random() tests (attached), and darn if they don't fail even more
> often, usually within 50K iterations. So maybe we should rethink
> that whole thing.

I pushed Paul's patch with the previously-discussed tests, but
the more I look at random.sql the less I like it. I propose
that we nuke the existing tests from orbit and replace with
something more or less as attached. This is faster than what
we have, removes the unnecessary dependency on the "onek" table,
and I believe it to be a substantially more thorough test of the
random functions' properties. (We could probably go further
than this, like trying to verify distribution properties. But
it's been too long since college statistics for me to want to
write such tests myself, and I'm not real sure we need them.)

BTW, if this does bring the probability of failure down to the
one-in-a-billion range, I think we could also nuke the whole
"ignore:" business, simplifying pg_regress and allowing the
random test to be run in parallel with others.

regards, tom lane

Attachment Content-Type Size
improve-random-tests-1.patch text/x-diff 9.0 KB

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