Mis-threaded messages
Jim Elbrecht
Has anyone else noticed messages with different subject lines being
buried in a thread? This could be my very old copy of FA-- or it
could be Worldnet's server-farm-- but it seems to be happening with
increasing frequency.
I've noticed it in three different newsgroups at least. The latest
is a thread in alt.war.civil-usa . I had locked a message with the
Subject;"Did the Civil War Really Happen? (A Survey)"
someone started a new thread called;"What Did You Get for
Christmas?"
and that subject line doesn't show. If I search for 'Christmas'- it
finds that thread, however. The person who started the second thread
is very unlikely to have hit 'post follow-up' and changed the subject
line-- and the places it has happened elsewhere are similar.
I see the latest Free Agent cures some problems caused be multiple
news-servers---- is this one of them? (I really hate touching
anything that is otherwise doing everything I want it to.<g>)
thanks,
jim
pls.se...@my.sig
>The person who started the second thread
>is very unlikely to have hit 'post follow-up' and changed the subject
>line-
Just open the headers and check.
>is this one of them?
You should definitely upgrade; doing so is completely painless and IMO
well worth the almost trivial effort (although it won't help with this
quirk).
The problem you report (the apparent 'threading' of two messages with
different subjects, neither of which has a References: header) is the
result of the hashing mechanism used by all versions of [Free] Agent
to 'match' headers for threading purposes.
BTW: a detailed analysis of the probability that unrelated subjects
would 'collide' in this way was published some time ago in this group.
If the term 'birthday paradox' means something to you, you may enjoy
reading the messages found by searching this group on Deja News (URL
below) for
hash & collision
and then viewing the related threads.
If you are interested (and find that there are too many gaps in the
archive to follow the discussion), repost; someone may have 'private'
copies of the missing articles available.
--
JimB [mailto:JLBr...@worldnet.att.net.gov] The best .gov is no .gov.
Checked [Free] Agent help and need the FAQs? http://sd.znet.com/~lance/
Want an answer fast? http://www.dejanews.com/home_sf.shtml
Internet beginner? http://www.netstrider.com/tutorials/internet/index.html
What about binaries? http://pages.prodigy.net/michael_santovec/decode.htm
Jim Elbrecht
Jim wrote;
> The problem you report (the apparent 'threading' of two messages with
> different subjects, neither of which has a References: header) is the
> result of the hashing mechanism used by all versions of [Free] Agent
> to 'match' headers for threading purposes.
If I registered, would Agent *not* do this? It might give me the
last good reason I need to send Forte $30.<g> I hate skipping over a
thread for a week before I realize it's really a new thread.
> BTW: a detailed analysis of the probability that unrelated subjects
> would 'collide' in this way was published some time ago in this group.
> If the term 'birthday paradox' means something to you, you may enjoy
You've got a good memory-- that was last June. I read enough on
Deja News to know that I have no idea what you folks were discussing.
I just drive this thing-- I hate to work on it.
In spite of that-- when I decide whether to register or just
upgrade, I guess I'll have to download something.<g>
Thanks-- It's been a long time since I've followed this group
regularly, but there seem to be the same quick and efficient answers
here that there were a couple years ago.
jim
pls.se...@my.sig
>would Agent *not* do this?
No.
As I said, all versions of [Free] Agent are identical in this respect.
pls.se...@my.sig
On Fri, 26 Dec 1997 19:34:12 GMT, she...@fun.horX.de (Sherlog) wrote:
[Welcome back, stranger!]
>Select the
>offending message and hit 'H' to show the headers:
Er, that's ALT+A;H in his version.
>You can double-click the
>last message id in the References: line to have Agent call up that message.
Or he could if he had $29 Agent.
>Free Agent has that option
Yes, at
Options | Preferences | Navigation
in his version.
>It is not very likely that you can observe it in practice unless you
>habitually keep 5000..10000 articles or more in your newsgroups, and even
>then you are quite unlikely to /notice/ unless you have a program that
>scans the database and alerts you to the fact.
So much for
> Subject: JEHAD - Threading observation - Attn: Sherlog
> From: pls.se...@my.sig
> Date: 1997/05/27
> Message-ID: <339856f9...@netnews.worldnet.att.net>
(available on Deja News, URL below).
Jim Elbrecht
she...@fun.horX.de (Sherlog) wrote;
> :
> : and that subject line doesn't show. If I search for 'Christmas'- it
> : finds that thread, however. The person who started the second thread
> : is very unlikely to have hit 'post follow-up' and changed the subject
> Unlikely as it may seem this is /precisely/ what has happened. Select the
> offending message and hit 'H' to show the headers:
Thanks for dropping back in. Sure enough-- the other occurence that
I saved reveals the same thing-- I got so confused trying to follow
'the birthday paradox' & 'hash collision' that I forgot to go
check.<g>
> You can have Agent start a new thread when the follow-up subject changes by
> checking the option
>
> [x] Start a New thread when follow-up subject changes
Thanks for the fix.
> It is not very likely that you can observe it in practice unless you
> habitually keep 5000..10000 articles or more in your newsgroups, and even
> then you are quite unlikely to /notice/ unless you have a program that
> scans the database and alerts you to the fact.
Just out of curiosity--- does that mean 5000-10000 articles total--
or in one particular group. If it's the former, then it's probably
time for me to do some housecleaning.
thanks again to both you and Jim,
jim
pls.se...@my.sig
>does that mean 5000-10000 articles total--
>or in one particular group.
For threading, the relevant datum is the number of articles in the
group. Remember, however, that it is a matter of probabilities; one
pair of subjects seen to collide in this group were posted within a
few days of each other (which means that the event could have been
observed in a database of only a few hundred messages). In fact, some
users may have received both as new messages in the same download; for
them, a database of zero messages would have sufficed.
Sherlog's analysis
> 0.0001 0.001 0.01 0.1 0.5 0.9 0.99 0.999 0.9999
>----------------------------------------------------------------------------------
> 67108786: 117 367 1162 3761 9646 17580 24861 30448 35157
can be interpreted in a number of ways.
For example, there is (roughly speaking) a 1% chance of a collision in
a sample of 1162 headers with distinct subjects. Each header download
is an experiment; after a surprisingly small number of repetitions, it
would be amazing if a collision did _not_ occur (although whether you
[or anyone] would happen to notice it is another matter).
pls.se...@my.sig
On Sat, 27 Dec 1997 09:50:31 GMT,
m.p...@NOSPAMPLEASEWEREBRITISHcableinet.co.uk (Malcolm Pack) wrote:
>Also Sprach Sherlog:
>
>Massage: <bmfh$8832274...@J.E.H.A.D>
>Froom: she...@fun.horX.de (Sherlog)
>On: Fri, 26 Dec 1997 19:34:12 GMT
>______________________________
>
>> (Gravity sucks.)
>
>I'm sure the feeling *ought* to be mutual...
Relatively speaking, it generally is...
Jerry Bloomfield
On Fri, 26 Dec 1997 11:20:15 GMT,
in message <6803s0$2...@bgtnsc02.worldnet.att.net>
pls.se...@my.sig wrote:
>On Fri, 26 Dec 1997 03:37:50 GMT, elbr...@worldnet.att.net (Jim
>Elbrecht) wrote:
>
>>would Agent *not* do this?
>No.
>As I said, all versions of [Free] Agent are identical in this respect.
Yes, this is true. I found one of these recently in my Agent
database for this very newsgroup. I had accidentally configured a
kill filter to Keep the messages as well as marking them read. I was
surprised to suddenly see that old thread re-appear with new messages.
I was even more surprised when the new messages had no relationships
to the old messages...