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Date:      Mon, 07 Oct 1996 14:50:59 -0600
From:      Warner Losh <imp@village.org>
To:        "=?KOI8-R?Q?=E1=CE=C4=D2=C5=CA_=FE=C5=D2=CE=CF=D7?=" (Andrey A. Chernov) <ache@nagual.ru>
Cc:        hackers@FreeBSD.org
Subject:   Re: rand() and srand() 
Message-ID:  <199610072050.OAA09190@rover.village.org>
In-Reply-To: Your message of "Tue, 08 Oct 1996 00:15:20 %2B0400." <199610072015.AAA00446@nagual.ru> 
References:  <199610072015.AAA00446@nagual.ru>  

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In message <199610072015.AAA00446@nagual.ru> "=?KOI8-R?Q?=E1=CE=C4=D2=C5=CA_=FE=C5=D2=CE=CF=D7?=" writes:
: NOBODY HERE WANTS TO BREAK THE "SAME SEEDING" in rand() or random()!
: TERRY'S IDEA OF "SAME SEEDING" IS HIS OWN TOY WHICH HAVE NOTHIG
: COMMON WITH STANDARD "SAME SEEDING" IDEA.

If I understand what you are proposing, you are breaking the same
seeding in one case.

run program X with seed S get random number sequence R1.
upgrade to new rev of FreeBSD
run program X with seed S get random number sequence R2.

which seems wrong to me and needs to be very loudly documented if that
is the case.  This obsoletes people's numerical research and a warning
is needed.  Look at the flack Intel got over the division bug.  Not
because it would happen so rarely, but the numerical types went non-
linear because literally thousands of hours of results were
invalidated and had to be done again.  If this is well documented,
including a blurb in the BUGS section of the man page, then it may be
acceptible.

It is a big issue that people know these things have changed.  It is
quite important to a small segment of the population.  However, it is
reasonable to expect them to cope with the change once they are
informed of it.  There are many workarounds for this issue.

<non-technical>
Finally, Terry's "Toy" as you call it is a legitimate use of the
system.  Many people are using the system in a similar manner.  You
might not like Terry or his Toys, but that is no excuse to yell at me
*ME* about raising the same point he does.  In fact, since this is a
public forum, that is no excuse for a character attack on Terry (or
anyone else).  Please keep this discussion technical.  If you can't do
that, please don't post to hackers.
</non-technical>

Warner



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