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# RationalWiki:Technical support/Archive7

This is an archive page, last updated 10 December 2012. Please do not make edits to this page.
Archives for this talk page: <1>, <2>, <3>, <4>, <5>, <6>, <8>, <9>, <10>, <11>, <12>, <13>, <14>, <15>, <16>, <17>, <18>, <19>, (back)

## URL workaround for watchlist button

My mobile browser won't let me click on the "add/remove from watchlist" star. Is there a url &action= workaround for this? Or possibly an alternative method? Radioactive afikomen Please ignore all my awful pre-2014 comments. 10:15, 13 September 2012 (UTC)

&action=watch? sterilesporadic heavy hitter 11:04, 13 September 2012 (UTC)
and action=unwatch. -- Nx / talk 11:35, 13 September 2012 (UTC)
Thanks, both of you! It doesn't work if I tack it on to a .org/wiki/Article_name url, but it does with the .org/w/index.php?title=Article_name urls. But no on ever said workarounds were elegant -__- Radioactive afikomen Please ignore all my awful pre-2014 comments. 07:46, 16 September 2012 (UTC)

Is there an easy way to prevent usernames containing problematic characters from being registered?

A vandal registered the annoyingly long username, "The God-fearing Christian 1% must crush the inferior, sick, starving, morally bankrupt pagans of the 99%." This was eventually rectified, but until then the wiki kept giving me problems, telling me it couldn't find their user talk page (it allowed me to create the page, but gave me an error message when trying to access it) or their contributions page.

Obviously, these problems were solved when Ty renamed them, but I still find it odd that MediaWiki even allows usernames with characters that cause problems like that. Radioactive afikomen Please ignore all my awful pre-2014 comments. 02:11, 26 September 2012 (UTC)

Is it both percentage signs that are the problem, I wonder, or just the one at the end? Peter Subsisting on honey 03:54, 26 September 2012 (UTC)
% is a reserved character in URLs to, ironically, denote special characters. Hence WIGO:World is actually "RationalWiki:What_is_going_on_in_the_world%3F" with %3F standing in for the question mark. Although the URL to that user page does substitute % for %25, I imagine the error continues down into the Media Wiki back-end itself, meaning it returns an error rather than trying to direct to a page with that in. Which means you can't access any page with % in the title. sshole 10:41, 27 September 2012 (UTC)
I think its' the server not recognising it more than Media Wiki itself. This is something we should look into, especially if this whole 53%/47% and 99%/1% shit continues. bomination 10:43, 27 September 2012 (UTC)
And by "we" I mean, Trent. pathetic 10:43, 27 September 2012 (UTC)
You can get it though the "rationalwiki.org/w/index.php?title=[TITLE]" link rather than "rationalwiki.org/wiki/[TITLE]". So the error is whatever parses the latter isn't picking up %25 as a valid character and matching it with the database. That's all I can figure out. pathetic 10:46, 27 September 2012 (UTC)
When you type in a url that doesn't have index.php in it (called a short url), the server rewrites them internally and sends them to index.php. The rewrite rules RationalWiki uses are incredibly complex because we need to rewrite rationalwiki.net and rationalwiki.com into rationalwiki.org visibly while keeping the short url, (this doesn't work right, because it strips off the ? at the end, so http://rationalwiki.com/wiki/Conservapedia_talk:What_is_going_on_at_CP? is rewritten to http://rationalwiki.org/wiki/Conservapedia_talk:What_is_going_on_at_CP, and the redirect takes care of it; try it out), and then in another step, this url is internally, invisibly rewritten into rationalwiki.org/w/index.php?title=TITLE, because we want the user to see the short url in the address bar. The problem is what Armondikov said, % is a special character that's used to encode other character, and isn't encoded properly itself.
The server module that handles these rewrites, called mod_rewrite, is the most uselessly complicated piece of shit software in existence. This error is likely the result of me trying to work around its shittyness when implementing the complicated rewriting scheme described above. One solution could be to scrap the whole thing and redo it by rewriting to rationalwiki.org/w/index.php/TITLE - this is a different full url scheme than the index.php?title=TITLE scheme that was added to MediaWiki to aid in rewriting and to make default urls without rewriting set up look a bit better - it's handled entirely by mediawiki, not mod_rewrite, so it's a bit easier to set up, but it has its own problems too. -- Nx / talk 08:28, 28 September 2012 (UTC)
I fucking hate computers. gnostic 10:00, 28 September 2012 (UTC)

## Bot flag for User:ZooBot

Please.--ZooGuard (talk) 12:05, 1 October 2012 (UTC)

Done. ТyBother me 12:17, 1 October 2012 (UTC)

## Is Capturebot working yet?

Just wondering - David Gerard (talk) 10:05, 29 September 2012 (UTC)

Does anyone know what exactly is the problem? Incompatibility with the latest version of the MediaWiki API? Is there any way to see any error messages, or it requires server access?
I've had another look at User:Capturebot2. It seems that we have the source code and it runs on Python and Qt. I know a guy who works with Qt and I can ask him for help. Though I doubt that the problem is in the Qt part.--ZooGuard (talk) 10:13, 29 September 2012 (UTC)
Since it happened after the upgrade, the problem is almost certainly that the pywikipediabot version capturebot is using is outdated and incompatible. Though Pibot works, and if I remember correctly, Capturebot still responds to status commands, so it's just a problem with file uploads. -- Nx / talk 10:31, 29 September 2012 (UTC)
Pibot died on the 10th of August (a little after the upgrade) and hasn't been seen since. Peter Subsisting on honey 23:30, 3 October 2012 (UTC)
Who can I thank for pushing the button? Peter Subsisting on honey 23:45, 3 October 2012 (UTC)
So, I've decided to take a look: User:ZooBot. The first bug I found: the regexp looking for capture links in check() assumes that between the name of the "a" tag and the "href" attribute there are only whitespace chars. Our current version of MW puts there the "rel" and "class" attributes. Someone who knows more about regexps than me should have a look. I made a crude fix that seems to find the links, but the web2png script exploded. Now I have to look at that.--ZooGuard (talk) 12:53, 29 September 2012 (UTC)
I still can't make the webkit2png script work (using the code from User:Capturebot2/webkit2png.py). I don't know if the problem is in it or in my setup. The original error ("exploded") was a stupid syntax error that was trivial to fix. But there seems to be a problem in render(), and I don't know enough about Python/Qt to identify it.
So, someone please patch the regexp first and see if this fixes Capturebot.--ZooGuard (talk) 16:56, 29 September 2012 (UTC)

Pywikipedia has been updated, bots are running, file uploads are failing. Don't know why, looked into it, don't have time for much anymore. Is the code published somewhere? Other people can give it a shot using their own bot acocunts. Tmtoulouse (talk) 18:57, 29 September 2012 (UTC)

Acocunts? Генгисevolving 19:00, 29 September 2012 (UTC)
I just did that (User:ZooBot). Reade my posts above, there are links to the code. The Capturebot code is working (reports status), but due to some changes, it no longer can recognize <capture> tags. Proposed fix: open capturebot2.py and replace this line:
regexp = re.compile(']*>(?:[^<]|<[^/]|</[^a]|])*<a\s*href="[^"]*"\s*class="new"\s*title="(?:Image:|File:)([^&"]*).png', re.UNICODE)

with this:

regexp = re.compile(']*\s*href="([^"]*)"[^>]*>(?:[^<]|<[^/]|</[^a]|])*<a\s*href="[^"]*"\s*class="new"\s*title="(?:Image:|File:)([^&"]*).png', re.UNICODE)

Of course, make sure it has the original indentation level.--ZooGuard (talk) 19:19, 29 September 2012 (UTC)

Just as I found the fix, Conservapedia seems to have died (can't access it from my browser either). I've updated User:Capturebot2/webkit2png.py. -- Nx / talk 22:36, 29 September 2012 (UTC)

Also, the regexp fix ZooGuard found, User:Capturebot2/capturebot2.py. -- Nx / talk 22:37, 29 September 2012 (UTC)
Thank you very much for your work on this! - David Gerard (talk) 10:09, 30 September 2012 (UTC)

Any update on the bot status?--ZooGuard (talk) 14:46, 2 October 2012 (UTC)

I sent you an e-mail offering to setup access to the bot account using your RW e-mail link, otherwise it has to fit into my schedule. Tmtoulouse (talk) 14:54, 2 October 2012 (UTC)
I'm really sorry for being pushy. Thank you for your time. As for the email, my Inbox is a mess. :(--ZooGuard (talk) 09:08, 5 October 2012 (UTC)
Don't have to apologize, but there are several complicating factors to just pasting in something and calling it a day. First, as the only person actually doing tech support on our servers I have to take the time to make sure I have at least a working understanding of what the problem was and the fix, and second even after replacing the code the bot was crashing. This was an issue with the setup, but one that required actually sitting down and debugging for a chunk of time to figure out/fix. If you are interested in directly supporting some of this stuff server side I will be posting more info soon about trying to recruit some sys admins. Tmtoulouse (talk) 14:42, 5 October 2012 (UTC)

## Search broken again?

Free text search, at least. "Lisle" and "Lightner" come up with nothing. "Jason Lisle" comes up with " There were no results matching the query. There is a page named "Jason Lisle" on this wiki." - David Gerard (talk) 22:30, 3 October 2012 (UTC)

Seems to be fixed now.--ZooGuard (talk) 09:12, 5 October 2012 (UTC)

## Something is broken

On the Category:Logic page beneath High Priority Articles there is a line which reads Extension:DynamicPageList (DPL), version 1.8.9 : <dpl_log_16>. I have a sneaking suspicion that this is not what was intended. ГенгисOur ignorance is God; what we know is science. 15:47, 4 October 2012 (UTC)

Probably means that there are no "high priority articles" in the category "logic". The DPL code for that only uses the manual maintenance category Category:High priority, not the rate/priority template as that's a separate system that only lists talk pages. postate 15:52, 4 October 2012 (UTC)

## Oct 06: Customisations failing

Not sure what this lot was, but it's all extra customisations, JS, CSS, etc. hiccupping around the same time, so I'm grouping it together - David Gerard (talk) 22:48, 12 October 2012 (UTC)

The links to "to do" and "new pages" have vanished from the watchlist; the "click here to format this for the voting extension" bit has disappeared from "to do" - David Gerard (talk) 22:06, 5 October 2012 (UTC)

### Blocks and Deletions

So Blocks have, for most of the day, been on standard wiki lengths and reasons (and blocked users can't unblock themselves), and I think the deletion reasons are the same. Whats with?--Mikal Harass Follow 00:17, 6 October 2012 (UTC)

You also can't block yourself (atleast when i tried) and I can't get the IP block on me to end for other accounts -.- --Mikal Harass Follow 00:23, 6 October 2012 (UTC)
Given that most of the customization seems broken, it's very likely a server issue. ТyBother me 00:50, 6 October 2012 (UTC)

### CSS on the main page is screwed up

What I said. 00:51, 6 October 2012 (UTC)

### Yellow floaty box fail

Comme ca.
The yellow floaty box thing that shows up when you mousehover over a blue link is borked. It looks like the picture (not just in RC but ordinary pages too). SophieWilder 11:38, 6 October 2012 (UTC)

## Vandal brake

Displays <ipbanononly> next to one of the checkboxes -- Nx / talk 19:32, 15 October 2012 (UTC)

Also, <ipblocklist-username> on Special:VandalBin -- Nx / talk 19:33, 15 October 2012 (UTC)
AIUI VandalBrake was never quite brought up to 1.19-ness. Trent? - David Gerard (talk) 22:12, 16 October 2012 (UTC)

## Messing around with shit

Having just been rooted on RW, I'm wandering around contemplating the wonders of the server, which is sort of like a cartoon steam engine that's flexing back and forth, making foreboding noises and belching clouds of black smoke. I've done the following: 0. added a shitload of stuff to the Munin monitoring graphs so I know wtf is going on 1. upped memcached from 64MB to 128MB (looking at Munin, I'm not sure it'll do a lot, might try APC too if needed) 2. switched off KeepAlive in Apache (which promptly saved us 400MB) and the biggie, 3. enabled HTML page caching for anonymous users, which should greatly help with the intermittent Reddit-dottings and doesn't break the hit counts at the bottom of the pages. Let's see how things go - David Gerard (talk) 22:45, 12 October 2012 (UTC)

We in fact have APC. And its cache hit rate is 99.8%, which can reasonably be described as "optimal" - David Gerard (talk) 23:21, 12 October 2012 (UTC)
Also just wound PHP-in-Apache allowed memory from 256MB (ridiculous) to 64MB. This shouldn't break anything in MediaWiki (could wind it back to 32MB in theory), and just put free memory over a gig. But let us know if weird shit starts happening on complicated pages - David Gerard (talk) 23:34, 12 October 2012 (UTC)

So basically it is like the TARDIS? Cobbled together from stolen spare parts, and mostly invisible to the user? ħuman 00:21, 15 October 2012 (UTC)

Not as photogenic. I've just switched KeepAlive back on with a short timeout (2 sec) and only 10 reqs per thread, which should be enough to load CSS/JS/images. We got hit by something a bit under an hour ago that sent the server into swap, in which state it was pretty much unresponsive; I'll see if this will help with that - David Gerard (talk) 22:11, 16 October 2012 (UTC)

Just asked mediawiki-l for general help. The response from seasoned MediaWiki devs is heartwarming - David Gerard (talk) 23:50, 17 October 2012 (UTC)

Try replying to a thread. The loader gif for the toolbar keeps spinning. The request actually completes successfully, so the problem is probably in the javascript. -- Nx / talk 13:50, 13 October 2012 (UTC)

That's been happening to me for weeks, so I assumed it was an inherent problem with LQT. Radioactive afikomen Please ignore all my awful pre-2014 comments. 20:42, 13 October 2012 (UTC)
Yeah, the upgrade broke it. -- Nx / talk 20:47, 13 October 2012 (UTC)
LQT is officially unmaintained. We basically get to keep both pieces - David Gerard (talk) 21:16, 13 October 2012 (UTC)
Nx or anyone - do we have a list of what's broken with LQT? I may ask on mediawiki-l and mwusers.com in case anyone else has successfully hacked the damn thing into limping along - David Gerard (talk) 21:43, 13 October 2012 (UTC)
That, and css and js loading too late, so before the page fully loads, it looks like shit. I just checked, and there's a half-finished LQT 3.0 in git, but I don't know how broken that is, and I don't know if there's a conversion script for the new db schema (probably not). -- Nx / talk 21:46, 13 October 2012 (UTC)
Or if this one will ever be finished either. Personally I'd look for a conversion script to turn LQT pages into wikitext - David Gerard (talk) 21:49, 13 October 2012 (UTC)
@Nx: Is that what makes it look like this? (Chatting via LQT is even more difficult than editing MW is normally on my phone. That should not be possible, but it is.) Radioactive afikomen Please ignore all my awful pre-2014 comments. 22:11, 13 October 2012 (UTC)
Yeah, that's it. -- Nx / talk 22:14, 13 October 2012 (UTC)

David, LQT is not completely dead, it's on life support. The problem is, our version had a few patches, and I don't know where those are (probably somewhere in ~nx) or if Trent upgraded LQT and discarded my patches or what. -- Nx / talk 22:27, 13 October 2012 (UTC)

Krinkle (MW dev) recommends making sure we get the latest [1]. I'm disinclined to mess with it until I have time to set up rationalbeta.com to be as exactly like rationalwiki.org as possible (libphp rather than cgi, for a start) and then make sure nothing breaks. The idea is not to break the rest of the site by messing with LQT on live. (Mostly I'm waiting for the next Reddit-dotting to see if the minimal messing about I've done so far will hold up.)
Hmm, is your patched version likely to still be on rationalbeta? - David Gerard (talk) 23:00, 13 October 2012 (UTC)
Probably not. Is the lqt extension dir still on svn? you could do an svn diff I guess...
How much disk space does RationalBeta have? Would it be possible to copy the entire database over to beta verbatim? -- Nx / talk 23:09, 13 October 2012 (UTC)
The master branch has LQT2.0, LQT3.0 is in the lqt-updates branch. -- Nx / talk 23:32, 13 October 2012 (UTC)
We're not critically short on disk - 94GB used, 71GB free. It's on the to-do list - David Gerard (talk) 23:35, 13 October 2012 (UTC)
In order to dump the database for back up we have to have atleast the size of the DB free. Tmtoulouse (talk) 23:37, 13 October 2012 (UTC)
Isn't RationalBeta on a different server?
Back to the topic at hand, I just checked out MW1.21 alpha and latest LQT and guess what, toolbar doesn't load.... -- Nx / talk 23:40, 13 October 2012 (UTC)
No everything has been consolidated to one server, with the bots running on my personal cloud. Tmtoulouse (talk) 23:50, 13 October 2012 (UTC)
Ok, figured it out, LQT has a hardcoded dependency for WikiEditor (the shiny new edit toolbar), and if it's not present, this happens. RW has WikiEditor installed, but either it or LQT or both are out of date. -- Nx / talk 00:02, 14 October 2012 (UTC)
Meanwhile, LQT3.0 is in a completely unfinished and broken state, enabling it means losing all content on LQT talk pages, and I don't think there's a conversion script. -- Nx / talk 00:22, 14 October 2012 (UTC)
My psychic powers tell me it'll never be finished either, given LQT2 is in production on WMF wikis despite its experimental status - David Gerard (talk) 00:31, 14 October 2012 (UTC)
That sounds promising! - David Gerard (talk) 00:31, 14 October 2012 (UTC)
I'll see what scurvy tricks I can come up with. Things to take slowly and get right - David Gerard (talk) 00:31, 14 October 2012 (UTC)
Don't try to use LQT style indentation with wikitext, it doesn't work without visual guides. -- Nx / talk 00:53, 14 October 2012 (UTC)
WHEN I WAS A LAD WE JUST COUNTED THE COLONS. Kids these days - David Gerard (talk) 08:55, 14 October 2012 (UTC)
LQT is a festering boil on the buttocks of the wiki-world; the sooner it is lanced and the resultant oozing pus is cleansed away, the better. Doctor Dark (talk) 04:36, 15 October 2012 (UTC)
Your sentiment is 100% accurate and we're stuck with the damn thing - David Gerard (talk) 05:53, 15 October 2012 (UTC)
It was an ambitious attempt to make commenting in MediaWiki not suck. Too ambitious perhaps. It's still better than MW talk pages. -- Nx / talk 06:06, 15 October 2012 (UTC)

### LQT patches

One of the patches I made was to prevent someone from editing the sig of a comment without editing the comment text. This was a hack, but it was necessary, because I thought it was possible to edit a sig irreversibly and without any trace. Turns out I was wrong, it does show up in a page's history, though it's not obvious at all, the entry says comment text edited, and it links to a diff that doesn't show anything, because there was no change to the text, only the sig, which is stored separately. It also doesn't show up in Recent Changes, so it's a great vandal target, my patch at least fixed that. I just tested, and it seems the patch is gone. -- Nx / talk 00:58, 14 October 2012 (UTC)

Tchaaa! Is there a submitted bug for this? - David Gerard (talk) 11:00, 14 October 2012 (UTC)
Yeah, 36096. -- Nx / talk 18:00, 14 October 2012 (UTC)
David, please clone the master branch of LQT (keep a backup of the current extension we're using just in case), it should fix the immediate issues, and I'd also like to know if it's compatible with MW19 -- Nx / talk 06:06, 15 October 2012 (UTC)
Done. Using the handy test thread, it appears worse. (The version installed was the one that was supposed to go with 1.19.) Reverting. I think LQT brokenness is presently not easily fixable, given the updated maintenance version works worse than the one we have already. The devs' reply is "works for us, must be you" - David Gerard (talk) 21:10, 16 October 2012 (UTC)
Try git master. -- Nx / talk 04:59, 17 October 2012 (UTC)
That was what I did try (if the above wasn't clear). The one that supposedly goes with 1.19 was what was there before, now it's back to that - David Gerard (talk) 08:00, 17 October 2012 (UTC)
Ah, I misunderstood you. What was broken with git master? -- Nx / talk 08:04, 17 October 2012 (UTC)
Multiple spinners, CSS loaded even more unreliably (in a minute's thumping it) - David Gerard (talk) 10:01, 17 October 2012 (UTC)

## Hiccups in the last coupla hours

The server went into swap and thrashed itself to death (not apparently due to lots of hits, it just did it by itself); I restarted Apache, that didn't quite do it, Trent restarted the box itself and it fsck'ed (that's Unix for chkdsk). Everything should be back. This sort of thing is the problem we have, which is underresourcing. Going from the 4GB Linode to the 8GB Linode is the bit that would cost us another $200/mo; Trent's researched this and says this is about the going rate for non-crappy hosting. Expect this to happen from time to time as the box occasionally shudders and farts. (Lucene doesn't help, 'cos it's a fat bastard, but it's also the only search that's any good.) I will be researching and writing a plaintive message to mediawiki-l asking what gaffer-tape we might try in the meantime - David Gerard (talk) 19:48, 17 October 2012 (UTC) Actually, sphinx is also very good. There's just the issue of updating the search index (unlike lucene, sphinx needs a complete rebuild of the index every time, but that's offset by the vastly superior rebuilding speed, and the incremental updates feature). There's also a realtime index feature, which doesn't require rebuilding and is always up-to-date, but it is less efficient, especially as the index grows, and it lacks some search features. There's an MW extension for easy integration into MediaWiki. -- Nx / talk 21:05, 17 October 2012 (UTC) ## User name character limit Could we please have a character limit for user names? When a user name troll or just a random idiot show up with a screed within a name it can really muck up recent changes, especially if they decide to edit. inb4 cries of fascism and sarcastic requests for "nite moad"--"Shut up, Brx." 22:29, 17 October 2012 (UTC) What would a reasonable limit even look like? OnTheInternetNobodyKnowsYou'reAGod's own username is 34 characters long. Radioactive afikomen Please ignore all my awful pre-2014 comments. 23:49, 17 October 2012 (UTC) I don't know. I am just trying to open dialogue on what I feel is a minor problem that could use fixing. How about a non-retroactive ban on all user names longer than 25 characters? 40 characters?--"Shut up, Brx." 02:00, 18 October 2012 (UTC) If the only problem is aesthetic then there is no problem. Acei9 02:14, 18 October 2012 (UTC) Pretty much what ace said. Our username friend is sporadic with account creation and most others are rare occasions of trolling and unless that changes theres not really much other need. --Mikal Harass Follow 02:31, 18 October 2012 (UTC) The problem is that it's retroactive, users who have a name longer than the limit won't be allowed to log in. -- Nx / talk 04:50, 18 October 2012 (UTC) What? And kill great legacies such as this: User:Mynameisexcessivelylongbutidon'tcarebecauseiamatrollvandalandsockoficewedge,sometimesallthreeatthesametime, actuallyimadethisaccounttotestcharacterlimitsbutwhatever ? I won't stand for it! Radioactive afikomen Please ignore all my awful pre-2014 comments. 05:05, 18 October 2012 (UTC) ## Blank watchlist (from Saloon Bar) This evening when I click my Watchlist tab all I ever get is a totally blank page -- not even a RW logo or error message. Anybody else, or do computers hate me again? Doctor Dark (talk) 01:16, 13 October 2012 (UTC) How many pages do you think you have on your watchlist?--"Shut up, Brx." 01:56, 13 October 2012 (UTC) If it had anything to do with size, Human would've mentioned something. He has practically half the site on his watchlist. Radioactive afikomen Please ignore all my awful pre-2014 comments. 02:06, 13 October 2012 (UTC) My guess is it could be related to the changes in memory allocation, drop this not over at tech support. Tmtoulouse (talk) 02:54, 13 October 2012 (UTC) Actually, that's alarmingly plausible. Might be memory, might be timeout. Could everyone please try their watchlist? If you get a blank page, how long did it take to return a blank page? - David Gerard (talk) 08:26, 13 October 2012 (UTC) Blank page loads promptly, and done. Same thing as yesterday evening. I only watch pages I happen to have edited, no idea how many. Sprocket J Cogswell (talk) 13:00, 13 October 2012 (UTC) More than 5000 pages on my watchlist, loads after a second or two. -- Nx / talk 13:16, 13 October 2012 (UTC) Hmm, that's disconcerting. Like many here I suspect, my watchlist is the page I usually come to RW on. Mine says at the top "360 pages on your watchlist, not counting talk pages." Of course, you can't see that ... (Tech detail: the confusing thing is the Apache logs don't show any "200 0" for Special:Watchlist, at all. So either it's serving something that renders as a blank page, or something before Apache, which should be nothing whatsoever, is showing a blank page. I see a few "200 0" for other pages. A bit over 1% of connections give a 408 request timeout, for example - but the request timeout is 300 seconds, which is quite huge enough.) One thing that would really help: to know the IP you're coming from and the approximate time, so I can look in the logs and see what's up. If anyone's getting a blank watchlist, please check your IP and email it to me at dgerard@gmail.com with the time, and I'll see if I can spot it in the logs - David Gerard (talk) 13:31, 13 October 2012 (UTC) Nothing in the php error log? It might be something else. -- Nx / talk 13:44, 13 October 2012 (UTC) Nothing obvious, though if I get timed error reports I'll look there too. I see 22 memory exhaustion errors in 859,000 server hits in yesterday's log, which is not awful - David Gerard (talk) 14:06, 13 October 2012 (UTC) I tried Susan's old DPL-heavy user page after you lowered the memory limit, and it worked, Best of CP also works,, can't think of anything else that would be memory intensive right now. -- Nx / talk 14:10, 13 October 2012 (UTC) Make a test account and copy the rows from the watchlist table where user id is Sprocket's. Then test. Also, Btw, do you know on which pages those 22 memory exhaustion errors were? -- Nx / talk 14:25, 13 October 2012 (UTC) I'll try the copy-watchlist trick in an idle moment. Dunno what pages, the error log just lists the actual MediaWiki PHP files that errored. S'pose I could correlate with Apache logs, but I'm putting off cleaning the house as it is. Ah, the joy of a new pet (RW) - David Gerard (talk) 14:44, 13 October 2012 (UTC) Well, you could do something like this, don't know if it'll conflict with anything MediaWiki does, but if you put it into localsettings, it'll probably be earlier than anything MW is trying to do and will get overwritten when needed. -- Nx / talk 14:56, 13 October 2012 (UTC) That is a fantastic idea and I just put it into place - David Gerard (talk) 17:34, 13 October 2012 (UTC) 0 reports since I posted the above. Is this still happening? Please work with me here if it is - David Gerard (talk) 17:12, 13 October 2012 (UTC) Still happening for me. Sprocket J Cogswell (talk) 17:22, 13 October 2012 (UTC) Aha, data! Now to dive in ... - David Gerard (talk) 17:33, 13 October 2012 (UTC) ps: if it was in the last few minutes, that was me fecking about to try to log URIs per above - David Gerard (talk) 17:34, 13 October 2012 (UTC) Still blank as of a few seconds ago... Sprocket J Cogswell (talk) 17:37, 13 October 2012 (UTC) Me too. In response to some earlier questions (1) my watch list is not huge, maybe a few dozen pages (though of course I can't see it now..) and (2) the blank page returns within 5-10 seconds. Doctor Dark (talk) 17:53, 13 October 2012 (UTC) BLOODY ARGH nothing in the logs. I'll thump it again after dinner - David Gerard (talk) 18:03, 13 October 2012 (UTC) Doctor Dark, please go to Special:EditWatchlist/raw, and if it loads, copy and paste the list somewhere, e.g. a subpage of your userpage. I'd like to try your watchlist, to see if it'll happen to me as well. -- Nx / talk 18:34, 13 October 2012 (UTC) ### Copied watchlist I copied Doctor Dark's watchlist over to one of my other accounts and it loads for me. Tmtoulouse (talk) 20:02, 13 October 2012 (UTC) Doctor Dark do you use any gadgets or other java script? Does it error on any browser/computer you use if you have tried more than one? Tmtoulouse (talk) 20:04, 13 October 2012 (UTC) Ooh yes, the "other browser" test. Mind you, the user-agents showing the 500 error on Special:Watchlist are pretty diverse in browser and OS - David Gerard (talk) 20:09, 13 October 2012 (UTC) My guess is that it isn't a browser per say, but wondering about addons/gadgets/apps etc. Tmtoulouse (talk) 20:12, 13 October 2012 (UTC) If it's a 500 error, then there should be something in the php error log. -- Nx / talk 20:13, 13 October 2012 (UTC) Edit: LQT hooks into the watchlist to display that "there are new messages" notice, perhaps that's the culprit? -- Nx / talk 20:14, 13 October 2012 (UTC) Plausible - LQT throws a few warnings - David Gerard (talk) 20:56, 13 October 2012 (UTC) What are they? -- Nx / talk 20:58, 13 October 2012 (UTC) Here's the last few days' worth. Jeez, fat bugger with memory. By the way - I think those timestamps are UTC, not EDT (the Apache logs are EDT) - David Gerard (talk) 21:19, 13 October 2012 (UTC) [11-Oct-2012 02:13:43] PHP Notice: Undefined variable: _SESSION in /home/rationalwiki/public_html/w/extensions/LiquidThreads/classes/View.php on line 363/ [11-Oct-2012 02:33:57] PHP Fatal error: Call to a member function getTitle() on a non-object in /home/rationalwiki/public_html/w/extensions/LiquidThreads/classes/View.php on line 87/ [12-Oct-2012 17:24:15] PHP Fatal error: Call to a member function getPrefixedText() on a non-object in /home/rationalwiki/public_html/w/extensions/LiquidThreads/api/ApiFeedLQTThreads.php on line 117/ [12-Oct-2012 23:57:24] PHP Fatal error: Call to a member function getPrefixedText() on a non-object in /home/rationalwiki/public_html/w/extensions/LiquidThreads/api/ApiFeedLQTThreads.php on line 122/ [12-Oct-2012 23:58:19] PHP Fatal error: Call to a member function getPrefixedText() on a non-object in /home/rationalwiki/public_html/w/extensions/LiquidThreads/api/ApiFeedLQTThreads.php on line 122/ [13-Oct-2012 00:10:27] PHP Fatal error: Call to a member function getTitle() on a non-object in /home/rationalwiki/public_html/w/extensions/LiquidThreads/classes/View.php on line 87/ [13-Oct-2012 01:44:51] PHP Fatal error: Allowed memory size of 67108864 bytes exhausted (tried to allocate 82 bytes) in /home/rationalwiki/public_html/w/extensions/LiquidThreads/classes/Thread.php on line 487/ [13-Oct-2012 01:44:59] PHP Fatal error: Allowed memory size of 67108864 bytes exhausted (tried to allocate 83 bytes) in /home/rationalwiki/public_html/w/extensions/LiquidThreads/classes/Thread.php on line 505/ [13-Oct-2012 05:25:52] PHP Fatal error: Call to a member function getPrefixedText() on a non-object in /home/rationalwiki/public_html/w/extensions/LiquidThreads/api/ApiFeedLQTThreads.php on line 122/ [13-Oct-2012 05:40:22] PHP Fatal error: Call to a member function getPrefixedText() on a non-object in /home/rationalwiki/public_html/w/extensions/LiquidThreads/api/ApiFeedLQTThreads.php on line 122/ [13-Oct-2012 06:01:42] PHP Fatal error: Call to a member function getTitle() on a non-object in /home/rationalwiki/public_html/w/extensions/LiquidThreads/classes/View.php on line 87/ [13-Oct-2012 12:07:58] PHP Fatal error: Call to a member function getTitle() on a non-object in /home/rationalwiki/public_html/w/extensions/LiquidThreads/classes/View.php on line 87/ [13-Oct-2012 12:59:21] PHP Fatal error: Allowed memory size of 67108864 bytes exhausted (tried to allocate 88 bytes) in /home/rationalwiki/public_html/w/extensions/LiquidThreads/classes/Thread.php on line 487/ [13-Oct-2012 17:20:44] PHP Fatal error: Allowed memory size of 67108864 bytes exhausted (tried to allocate 32768 bytes) in /home/rationalwiki/public_html/w/extensions/LiquidThreads/classes/Threads.php on line 81/ [13-Oct-2012 18:08:25] PHP Fatal error: Call to a member function getTitle() on a non-object in /home/rationalwiki/public_html/w/extensions/LiquidThreads/classes/View.php on line 87/ Doesn't look like there's anything watchlist related in there. LQT modifies the db query so that pages in the thread namespace are left out of the watchlist. If we can get someone who's having the problem to try it before and after, it might be worth trying with this line commented out temporarily in LiquidThreads.php: $wgHooks['SpecialWatchlistQuery'][] = 'LqtHooks::beforeWatchlist';

-- Nx / talk 21:30, 13 October 2012 (UTC)
Never mind, didn't see the comments below. -- Nx / talk 21:31, 13 October 2012 (UTC)
I think I'm not going to mess with it on a live wiki when I can't duplicate it myself and revert bad changes in seconds, but that would be the next thing if it happens again - David Gerard (talk) 21:41, 13 October 2012 (UTC)

### Upping memory

I've just turned PHP-in-Apache's memory up from 64MB to 96MB. (And there goes our memory headroom *sob*) Doctor Dark, Sprocket, please try again - David Gerard (talk) 21:19, 13 October 2012 (UTC)

Now I see a watchlist. FWIW, I try to stay away from LQT, because either this Firefox thingy takes its own sweet time parsing it, or somewhat's hosed at server side? I don't know. DIfferent issue. Sprocket J Cogswell (talk) 21:23, 13 October 2012 (UTC)
Yeah, it's broken since the upgrade. -- Nx / talk 21:33, 13 October 2012 (UTC)
It works! Sorry for the delay in replying. Doctor Dark (talk) 21:30, 13 October 2012 (UTC)

Human reports a broken watchlist. FUCK. At least I have an IP and time, will try to track down what's going on later - David Gerard (talk) 10:23, 14 October 2012 (UTC)

[14-Oct-2012 01:05:50] PHP Fatal error: Allowed memory size of 100663296 bytes exhausted (tried to allocate 32 bytes) in /home/rationalwiki/public_html/w/includes/GlobalFunctions.php on line 317 COCK COCK COCK FUCKSOCKS WANKBISCUIT I've upped memory allocation to 112M, will up to 128M if that doesn't fix Human's watchlist (which is probably, indeed, pathological) - David Gerard (talk) 21:45, 14 October 2012 (UTC)
I was going to mention that I was having watchlist problems again earlier today, but I don't want to be responsible for paying David's diazepam bill. Doctor Dark (talk) 22:21, 14 October 2012 (UTC)
Seven seconds to a blank screen (page source is also completely blank). ħuman 00:19, 15 October 2012 (UTC)
Didn't Trent clear your watchlist last time? -- Nx / talk 04:09, 15 October 2012 (UTC)

Upped it to 128MB. Chad on mediawiki-l notes that MW is, in point of fact, a fat bastard. PLEASE DO TRY AGAIN, GENTLEPERSONS. (And supply time of blank pages.) - David Gerard (talk) 05:53, 15 October 2012 (UTC)

None in the 14 hours since I did that, so that's nice. I have a stomach bug so will not be attempting anything fancy with a root prompt for now - David Gerard (talk) 18:11, 15 October 2012 (UTC)

Human was still getting a blank page, so I've upped it to 140MB - David Gerard (talk) 22:18, 16 October 2012 (UTC)

And again (and I can see the memory exhaustion in the PHP error log), so upped it to 160MB - David Gerard (talk) 10:00, 18 October 2012 (UTC)

## WIGO: CP talk's edit screen templates re: capturebot

If you begin to edit WIGO:CP Talk, the notice on how to insert Capturebot's tags is followed by "(And then manually screenshot it yourself, as Capturebot is presently down.)". Capturebot is back. Someone should probably remove the instruction to bypass using Capturebot and screencap manually since that's not necessary anymore. I had a dig through the templates list to try and fix it myself, but then I realized that a Wiki template that lives inside of the edit box (i.e., on normal pages) is not going to be able to affect the edit page's UI. I'm guessing it's something in MediaWiki. Ochotonaprincepsnot a pokémon 09:01, 18 October 2012 (UTC)

For future reference. -- Nx / talk 09:48, 18 October 2012 (UTC)
I had no idea that was there. Well, that's my something learned for the day, time to go play video games until my thumbs can't move. Thanks for the tip, Nx. Ochotonaprincepsnot a pokémon 11:26, 19 October 2012 (UTC)

## Ru

Now ru.rationalwiki.org redirects to rationalwiki.org . Does somebody know what the problem?--Mr. B 22:07, 18 October 2012 (UTC)

We are working on some infrastructure changes to better handle traffic spikes, the likely culprit here, keep reporting any problems you have and will try and get them solved asap. Tmtoulouse (talk) 00:41, 19 October 2012 (UTC)
Ok.--Mr. B 10:38, 19 October 2012 (UTC)
One more question. What the approximate time estimation of repairing?--Mr. B 21:51, 19 October 2012 (UTC)
It should be fixed as far as I know, its a DNS propagation so maybe hasn't reached you yet. Anyone else not able to access it? Tmtoulouse (talk) 21:59, 19 October 2012 (UTC)
Mmm... The site is not available from Firefox, and IS availadle from IE. Thank you. Now, I see that the problem is with my own PC.--Mr. B 22:36, 19 October 2012 (UTC)
Clear your cache. Tmtoulouse (talk) 22:37, 19 October 2012 (UTC)

### Rationalwiki.com

Dead in the water. I actually enter the .com domain more often than .org. Osaka Sun (talk) 04:32, 19 October 2012 (UTC)

fixed? 50.130.133.249 (talk) 04:37, 19 October 2012 (UTC)
Yes. Thanks Trent BoN. Osaka Sun (talk) 04:49, 19 October 2012 (UTC)

## WIGO voting not working?

Anyone else seeing problems with the WIGO voting? I couldn't get it to count my up-vote on the (CP) drunk driving entry, and when I tried changing it to a down-vote, it removed someone's up-vote and replaced it with my down, as though I had previously voted on that entry even though I know I hadn't. Wehpudicabok (talk) 06:39, 21 October 2012 (UTC)

Humm, this might be tech support. I was wondering how the WIGO extension would work through the new Squid proxy and was satisfied when I verified I could up/down things. Is this a consistent failure for you or a hiccup? - David Gerard (talk) 09:22, 21 October 2012 (UTC)
For me, the drunk driving WIGO on CP is showing +2 atm. If I click "up", nothing happens; if I click "down", it goes to zero. I haven't voted on it before. The one below was showing 77; when I click up it goes to 79 then back down to 77. This seems to be the rule - either nothing happens or it changes by 2. rpeh •TCE 09:40, 21 October 2012 (UTC)
It changes by 2 because it thinks you have already voted and that you are therefore changing your vote, there's obviously something wrong though because I clicked the latest WIGOWorld up (also standing at 2) and nothing happened while the down arrow went to 0. ГенгисYou have the right to be offended; and I have the right to offend you. 10:37, 21 October 2012 (UTC)
I know that's what it usually means, but I definitely hadn't voted on that one. rpeh •TCE 10:46, 21 October 2012 (UTC)
It doesn't change, it refreshed the value from the server. So if someone votes up at the same time as you vote down, you won't see a change. -- Nx / talk 11:15, 21 October 2012 (UTC)
Well I'd hate to get too technical with you Nx but if someone votes down surely the up/meh/down bar would change, even if the balance doesn't. ГенгисRationalWiki GOLD member 11:27, 21 October 2012 (UTC)
That's true, but do people notice that? And if someone votes up and you vote down, and assuming there are no neutral votes, it won't change, because the ration doesn't change. -- Nx / talk 11:35, 21 October 2012 (UTC)
I voted on the most recent WIGO World for which there were just 2 ups votes and the bar was all green. It didn't change to 3 when I pressed the up but it went down to 0 and equal red/green split when I pressed the down. ГенгисOur ignorance is God; what we know is science. 11:39, 21 October 2012 (UTC)
3 down votes came in between the time you opened the page (it's possible that the new caching interferes with that, giving you an older version of the page, though it shouldn't if you're logged in) and voted? -- Nx / talk 11:40, 21 October 2012 (UTC)
It happens with several different votes. One on the economy had 1-1-1, I gave it a red and there was no change but when I voted meh it went to 2 orange and 0 red, another vote down on one that was big up registered immediately. I am wondering if the cache is holding the most recent and ignoring an incoming of the same type and only acting on it if it is completely different. ГенгисGum disease 11:52, 21 October 2012 (UTC)
How do test votes go on older WIGO items, not recent ones? I'm seeing what might be others voting at the same time on recent ones, but older ones seem to be behaving as expected - David Gerard (talk) 11:53, 21 October 2012 (UTC)
One from mid-September that was 100% positive increased OK. But if you've been messing around with backroom stuff maybe there was nothing in the cache for that. ГенгисYou have the right to be offended; and I have the right to offend you. 12:06, 21 October 2012 (UTC)

For WIGO addicts like myslelf, this is getting excruciatingly annoying. Osaka Sun (talk) 19:15, 21 October 2012 (UTC)

David, I think I know why this is happening. WIGO uses IPs to uniquely identify users. I just tried voting on a few WIGO:CP entries, and it appears as if I had already voted. My guess is that it's getting the proxy's IP, not the user's IP, The code uses getenv ("REMOTE_ADDR"), which isn't correct behind a proxy (I don't know why it works sometimes though, probably bypassing the proxy if it's not in the cache or something). I'll take a look at some core mediawiki code for the correct code to use. -- Nx / talk 19:29, 21 October 2012 (UTC)

My guess is that its pulling the IP address from the squid not the user. Tmtoulouse (talk) 19:27, 21 October 2012 (UTC)

Hm, EC was resolved automatically, give me a second to find a fix. -- Nx / talk 19:31, 21 October 2012 (UTC)
Confirmed its using proxy IP, the squid passes the user IP using | X-Forwarded-For, I will look into it too but if there is any easy command to pull that header info. Tmtoulouse (talk) 19:32, 21 October 2012 (UTC)
Ok, search for $wgWigo3ConfigStoreIPs is wigo3.php, then put global$wgRequest; before the lines that say (there should be three)
$voter =$wgWigo3ConfigStoreIPs ? getenv ("REMOTE_ADDR") : $wgUser->getName();  and replace those lines with: $voter = $wgWigo3ConfigStoreIPs ?$wgRequest->getIP() : $wgUser->getName();  That should fix it. -- Nx / talk 19:36, 21 October 2012 (UTC) Still seems to pull squid ip. Tmtoulouse (talk) 19:51, 21 October 2012 (UTC) That's the same code that's used by MediaWiki core, and it uses X-Forwarded-For (the code is a bit more advanced than that though) -- Nx / talk 19:53, 21 October 2012 (UTC) Did some quick tests, one window where I'm logged in, and an incognito window logged out, tested by voting down in one window, then up in another, and also by voting up in one, then up in the other. Sometimes it didn't work, but I can't reproduce it now. -- Nx / talk 20:10, 21 October 2012 (UTC) Purged the cache, hopefully fixed. Tmtoulouse (talk) 20:13, 21 October 2012 (UTC) Then it was the cache. It seems to be working fine now. -- Nx / talk 20:20, 21 October 2012 (UTC) BTW, all the extensions we use that you wrote - are they in github or similar, or are the copies on the server basically the copies? (That and the copy of the /w directory I just downloaded.) - David Gerard (talk) 21:42, 21 October 2012 (UTC) The latter, and even I don't have a recent copy of them. -- Nx / talk 05:27, 22 October 2012 (UTC) Heh. Drop me a line and I'll email you a zip of the ones I just grabbed, just of course ask for any others. We should put this stuff up somewhere with a mediawiki.org page, WIGO is pretty important to the site (and if it works through a Squid, then it's the sort of thing other sites would like) - David Gerard (talk) 05:36, 22 October 2012 (UTC) I've got developer access, so I'll start putting up some extensions on Git (PlaceNewSection comes to mind). For the rest, either github, or even just a simple git repo on the RW server would do. -- Nx / talk 05:39, 22 October 2012 (UTC) I'm too busy to go into detail but I just tried voting in the Saloon Bar and that still has the same problem. ГенгисOur ignorance is God; what we know is science. 00:07, 22 October 2012 (UTC) Fixed.50.130.133.249 (talk) 00:23, 22 October 2012 (UTC) ## Search Search isn't working again; only returning exact title matches. This is a recurrent problem. WēāŝēīōīďMethinks it is a Weasel 11:55, 21 October 2012 (UTC) Thought it was Lucene, restarted Lucene, it wasn't, now puzzled. Investigating - David Gerard (talk) 13:23, 21 October 2012 (UTC) Aware of this too. Tmtoulouse (talk) 19:28, 21 October 2012 (UTC) I got no frickin' clue. How did we fix this before? Or did we just wait for it to magically come good? - David Gerard (talk) 19:59, 21 October 2012 (UTC) Previous faults where lucene being killed by oom manager. Current fault has something to do with being behind proxies. Investigating. Tmtoulouse (talk) 20:13, 21 October 2012 (UTC) Should be fixed. Tmtoulouse (talk) 20:30, 21 October 2012 (UTC) \o/ Please email me what you did :-) - David Gerard (talk) 21:41, 21 October 2012 (UTC) Nice work Tmt. WeaseloidMethinks it is a Weasel 22:19, 21 October 2012 (UTC) ## Log in issue Even though I'll log in and check the "Remember my login on this browser (for a maximum of 180 days)" box, I keep getting logged out after a certain number of page views. I'm not sure if it's the site or something on my end, but was wondering if anyone had an idea or is experiencing the same thing. Sam Tally-ho! 07:41, 21 October 2012 (UTC) I will put it on the list of things to look into. Tmtoulouse (talk) 23:02, 21 October 2012 (UTC) Thanks! Sam Tally-ho! 04:04, 22 October 2012 (UTC) I have attempted a fix, let me know if it is still a problem. Tmtoulouse (talk) 17:58, 22 October 2012 (UTC) ## New error This is a new one, happened a few minutes ago. Evil fascistoh noez 19:22, 22 October 2012 (UTC) That's weird, it looks like the error is in the browser. A google search brought up this bug report. Maybe try disabling some extensions/another browser etc. -- Nx / talk 19:28, 22 October 2012 (UTC) WTF ... Mind you, Trent and I have been messing severely with the servers (servers, plural!) this evening, trying to track down weirdness a few hours ago. So if anything odd has manifested in the past coupla hours, it may well have been me - David Gerard (talk) 22:21, 22 October 2012 (UTC) ## Rename Could someone please rename me? I would like to be called "The Municipal Hero." Thank you. Good username (talk) 12:07, 23 October 2012 (UTC) Done. Evil fascistoh noez 13:49, 23 October 2012 (UTC) ## Slow and trim missing Just noting I've noticed this and am poking and prodding - David Gerard (talk) 19:08, 25 October 2012 (UTC) Ah, site crapped itself in various ways (Apache went nuts, the out-of-memory-killer came out to play and broke stuff). Trent has fixed - David Gerard (talk) 19:33, 25 October 2012 (UTC) ## Please can somebody with superpowers change my nick back? Otherwise I'll nationalise your servers. --PsyGremlinParlez! 13:23, 2 November 2012 (UTC) Done. Evil fascistoh noez 13:35, 2 November 2012 (UTC) Ta muchly! --PsyGremlin話しなさい 13:52, 2 November 2012 (UTC) ## Tiny text ## Disappearing Edits I am having edits disappearing from recent changes (which is why the other day/night I accused Nx of some tech wizardry in blocking me because the block-log kept disappearing on me), not only that talkpage edits don't appear when not logged in then appear when again hen I log in. Weird. Would you like me to screen shot it? Acei9 05:34, 25 October 2012 (UTC) "... talkpage edits don't appear when not logged in then appear when again hen I log in." That's because of squid caching - if you are not logged in, you are getting a cached version of the page. I don't know about the Recent Changes issue.--ZooGuard (talk) 06:09, 25 October 2012 (UTC) I must have slept through the last wiki-fu class, squid caching? Acei9 06:26, 25 October 2012 (UTC) Anonymous users get a cached version of the page, which might be out of date. But what you describe shouldn't be happening. What can happen is that when you're logged out, the most recent changes don't appear on the list. -- Nx / talk 06:32, 25 October 2012 (UTC) Just tested that too, and it isn't happening for me. -- Nx / talk 06:33, 25 October 2012 (UTC) Anonymous users get a cached version of the page Why? When I get this weirdness again I'll take some screen shots. Acei9 06:34, 25 October 2012 (UTC) If you read some of the posts above you might see that David Gerard has been given the keys to the toy cupboard and he's been messing around with back room stuff to improve the site's traffic handling. As far as I undersand it, part of this has been the installation of Squid which caches pages so that the server is not being continually hit with new requests. This helps smooth the burden and means we aren't being forced to upgrade our hosting package which obviously costs money. (Hope I've got this right.) ГенгисRationalWiki GOLD member 06:58, 25 October 2012 (UTC) Pretty much. Trent put it into place because he had important Ph.D work to procrastinate on and I was sick for a week. RWF is paying slightly more money (three extra small nodes) and the wiki has sped the fuck up. Modulo a few hiccups, as detailed above. The cached page, served to anons, shouldn't be terribly older than the uncached version logged-in users get, but it would explain the behaviour Ace is seeing. Nx doesn't use tech wizardry powers any more, it's all me and Trent now, with Nx merely providing enormously helpful information on where the bodies were buried - David Gerard (talk) 07:24, 25 October 2012 (UTC) Thank you gentlemen, I shall cease worrying and go back to my ruminations and recriminations. Acei9 07:34, 25 October 2012 (UTC) Well if you are still getting problems like you described we should try and track it down. Screen shots are helpful, but keep us informed. Tmtoulouse (talk) 16:13, 25 October 2012 (UTC) Any sign of this weirdness still? - David Gerard (talk) 21:49, 4 November 2012 (UTC) ## {{talkpage}} Something appears to be wrong with this template's "create an archive" function. When I try to use it on Essay_talk:AD's_Beliefs, it just puts me on a page with "Bad Title."--talk 04:41, 26 October 2012 (UTC) I'll take a look, probably a bit later. -- Nx / talk 04:53, 26 October 2012 (UTC) Thank you!--talk 05:04, 26 October 2012 (UTC) Fixed. -- Nx / talk 05:16, 30 October 2012 (UTC) Did you ever know that you're my hero? You're everything I wish I could be. I could fly higher than an eagle, for you are the wind beneath my wings. Thanks!--talk 22:08, 4 November 2012 (UTC) ## Math tag There is a little question. How to enable a math tag?--Mr. B 23:19, 29 October 2012 (UTC) Should be easy enough, the math tag works on English RW, it just hasn't been installed on ru.rw. I'll try it tomorrow night (it's bedtime right now) - David Gerard (talk) 23:48, 29 October 2012 (UTC) Thank you!--Mr. B 01:09, 30 October 2012 (UTC) I still haven't done this. I'll let you know when I do - David Gerard (talk) 17:33, 1 November 2012 (UTC) I've enabled the extension and put in the config identically to en.rw. I have no idea if it works, please test and let me know - David Gerard (talk) 23:20, 1 November 2012 (UTC) Of course, there's the small detail that it doesn't work on en.rw, e.g. $U_e = \int {\frac{E A_0 \Delta L} {L_0}}\, d\Delta L = \frac {E A_0} {L_0} \int { \Delta L }\, d\Delta L = \frac {E A_0 {\Delta L}^2} {2 L_0}$ gives Failed to parse (unknown error): U_e = \int {\frac{E A_0 \Delta L} {L_0}}\, d\Delta L = \frac {E A_0} {L_0} \int { \Delta L }\, d\Delta L = \frac {E A_0 {\Delta L}^2} {2 L_0}. This has several corrective approaches, I'll apply some and see how we go - David Gerard (talk) 16:41, 2 November 2012 (UTC) Now working (set$wgTexvc to the binary, not the path):

$U_e = \int {\frac{E A_0 \Delta L} {L_0}}\, d\Delta L = \frac {E A_0} {L_0} \int { \Delta L }\, d\Delta L = \frac {E A_0 {\Delta L}^2} {2 L_0}$

The above works for me on ru.rw too - David Gerard (talk) 21:48, 4 November 2012 (UTC)

Thank you!--Mr. B 00:32, 5 November 2012 (UTC)

## Apache tweaks

I've set MaxClients 50 in the hope this will keep the server from completely shitting itself in busy moments. From the fact that (a) busy Apache processes seem to be quite large in top (b) the CPU goes right up in said moments (c) MySQL gets busy, I'm slightly suspecting this is not an outside traffic surge, but logged-in editors doing expensive things (e.g. centre-clicking a whole bunch of diffs in a go). Editors should be able to do this stuff, but they may have to wait in a queue for their request to be fulfilled so that the server doesn't actually collapse and need a reboot. Let me know if it gets particularly annoying - David Gerard (talk) 18:44, 30 October 2012 (UTC)

So far the server's been blissfully happy, even with occasional load peaks and with PHP back to being allowed 256MB memory (Human's pathological watchlist still runs out of memory, but at least it's not more broken than before I touched it) - David Gerard (talk) 21:52, 4 November 2012 (UTC)
And of course the bloody thing got knocked over this morning. Gah - David Gerard (talk) 14:19, 11 November 2012 (UTC)

## File templates

When I upload a file both the Info and Fair Use templates appear unformatted, displaying hexcodes instead of the CRLF and pipe characters. ГенгисOur ignorance is God; what we know is science. 10:09, 7 November 2012 (UTC)

You mean in recent changes? -- Nx / talk 10:40, 7 November 2012 (UTC)
What precisely do you do, step by step, to get this to happen? Do you have an example upload where we can see this? I'm not clear on what you're describing - David Gerard (talk) 10:41, 7 November 2012 (UTC)
Ah -- Nx / talk 10:42, 7 November 2012 (UTC)
The bug is in the fair use upload form, from RationalWiki:Upload -- Nx / talk 10:48, 7 November 2012 (UTC)
Fixed, rewrite rules are broken. -- Nx / talk 10:56, 7 November 2012 (UTC)


text:
# Find the Reference Angle -pi/40

Find the Reference Angle -pi/40
Find an angle that is positive, less than , and coterminal with .

format: plain


text:
# Differences

This shows you the differences between two versions of the page.

 phy131studiof17:lectures:phy131f15m1solutions [2017/10/05 15:39]mdawber [Question 3] phy131studiof17:lectures:phy131f15m1solutions [2017/10/05 15:49] (current)mdawber [Question 3] Both sides previous revision Previous revision 2017/10/05 15:49 mdawber [Question 3] 2017/10/05 15:39 mdawber [Question 3] 2017/08/04 13:41 external edit 2017/10/05 15:49 mdawber [Question 3] 2017/10/05 15:39 mdawber [Question 3] 2017/08/04 13:41 external edit Line 135: Line 135: $T_{long}=6.817\,\mathrm{s}$ $T_{long}=6.817\,\mathrm{s}$ + F. (5 points) If the string is cut when the masses are in the position shown in the diagram which edge of the table would the mass on the table eventually fall off (i.e. left, right, front or back?) + + Front


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#### Vol. 283, No. 1, 2016

 Recent Issues Vol. 313: 1  2 Vol. 312: 1  2 Vol. 311: 1  2 Vol. 310: 1  2 Vol. 309: 1  2 Vol. 308: 1  2 Vol. 307: 1  2 Vol. 306: 1  2 Online Archive Volume: Issue:
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Vector bundles over a real elliptic curve

### Indranil Biswas and Florent Schaffhauser

Vol. 283 (2016), No. 1, 43–62
##### Abstract

Given a geometrically irreducible smooth projective curve of genus $1$ defined over the field of real numbers, and a pair of integers $r$ and $d$, we determine the isomorphism class of the moduli space of semistable vector bundles of rank $r$ and degree $d$ on the curve. When $r$ and $d$ are coprime, we describe the topology of the real locus and give a modular interpretation of its points. We also study, for arbitrary rank and degree, the moduli space of indecomposable vector bundles of rank $r$ and degree $d$, and determine its isomorphism class as a real algebraic variety.

##### Keywords
Elliptic curves, vector bundles on curves, real algebraic varieties
##### Mathematical Subject Classification 2010
Primary: 14H52, 14H60, 14P25


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opatovaL

Answered

2021-02-25

Perform the indicated divisions of polynomials by monomials.
$\frac{12{x}^{3}-24{x}^{2}}{6{x}^{2}}$

Answer & Explanation

pierretteA

Expert

2021-02-26Added 102 answers

A polynomial is an expression of one or more algebraic terms each of which consists of a constant multiplied by one or more variables raised to a non-negative integral power.
Here the given polynomial is a binomial.
To divide a polynomial by monomial, divide each term of the polynomial by the monomial.
Divide the trinomial by the monomial $6{x}^{2}$
Simplify the terms which are under division.
Calculation:
Consider the polynomial $\frac{12{x}^{3}-24{x}^{2}}{6{x}^{2}}$.
Divide each term of the polynomial by the monomial $6{x}^{2}$.
$\frac{12{x}^{3}-24{x}^{2}}{6{x}^{2}}=\left(\frac{12{x}^{3}}{6{x}^{2}}-\left(\frac{24{x}^{2}}{6{x}^{2}}\right)=2x-4$
The simplified value of polynomial is $2x—4$.
Final statement:
The simplified value of polynomial after division is equals to $2x-4$.

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# lanlan

1. ### LanLan Skewb Review

Hi Everyone!!! Here is my official and complete review on the LanLan Skewb. I think this cube is really awesome, and I highly reccomend it Thanks! -RECuber http://youtu.be/XoGiXwhw6QM
2. ### Skewb Review/Comparison: Lanlan, Moyu, and Shengshou Skewbs

Hey guys, I noticed on youtube there wasn't a very good in-depth review/comparison on the Skewb so here it is:
3. ### Super Floppy Cube "Example Solve" Game

Not sure if this will work, as there is few super floppy cube solvers out there. but here it goes. For notation hold the cube horizontally, and then just use B, L, R, and F. First Scramble- L F B2 L' R' F L2 B Solve Back to square shape- B F L' R F' R Cross- B F' R' L' F' B Corners...
4. ### I like this Rex cube,but..

Hello,guys,i haven't been here for awhile because i have a long journey .Now i am back cubing, after some coffee,i watched video from CBC and got to know this video very occasional.I am really interested in this Rex Cube,but since it didn't show how to solve it,so,still a problem. Can anyone...
5. ### Looking For a 7x7 or 6x6 for trade or payment

Hey all, i need a new 7x7 and 6x6, and i don't want to have to go buy a new one if I can get a cheaper used one. im looking for preferrably SS for the 7x7, but YJ, Lanlan, and vcube will be fine, and for the 6x6, pretty much just SS, unless its a fully Modded Vcube. i have a price range from...
6. ### LanLan "Sepak Takraw"? 4x4 mod. No solutions exist.

This is the puzzle I have. (mine's black but exactly the same as this) Things I know: It is created by LanLan. It (i think) is called the "Sepak Takraw". It can be solved similarly to a 4x4. (which I do know how to solve) Lastly, I have searched the internet for hours upon hours hoping to find...
7. ### Best 2x2 speedcube?

There have been some relatively new cubes on the market like the wit two (type c), edison (havent heard anything about this one), and the v cube 2a. I already have a lanlan 2x2 but i am starting to speedcube 2x2 also. Is the lanlan still the best speedcube or have any of the newer cubes taken...

10. ### Looking for a new ball core 4x4.

I want to buy a new ball core 4x4. I already have a shengshou version 1 and I like it, but it's too hard to put back together when it pops and I just wanna try something different. I've been thinking about a Dayan+mf8, but it's too big for my small hands, I've heard a mini QJ breaks too easily...
11. ### Speedcubeshop Unboxing - LanLan Skweb und Alpha CC

Nothing much to say beforehand. All the infos - as well as some regarding speedcubeshops service - in the video. Enjoy:
12. ### [Unofficial] 2x2 In 1.69

This is my PB I got with my Lanlan 2x2. It was a PBL skip but I'm still proud of it. Scramble: R F U2 F2 R' F2
13. ### [Unofficial] 2x2 Solve 8.73

2x2 Solve 8.73 (feedback please) Here is another 2x2 solve that is great for me and is one of my best. dPpnCRiP0rQ
14. ### [Unofficial] 2x2 solve 2.00

I beat my old personal best on accident. I was doing my normal method to solve a side first ad then all I had to do was do a down turn. dWxFaZNVf2I
15. ### Unboxing of void cube and lanlan 2x2

This has an unboxing and review of the void cube and the lanlan 2x2. After these videos were made I replaced the stickers on the void cube with a japanese color scheme.

23VtSG2rcSk
17. ### My order of Cubes

1. Type F-II 3x3x3 Cube (NIB) - Black 2. Alpha-V(Type A) 3x3x3 Cube (DIYKIT) - Black 3. Lanlan 2x2x2 Cube (NIB) - White 4. Cube4you Vinyl 3x3x3 Sticker - W 5. Eastsheen Super 5X5 Cube - A5S I paid 40\$ for all that stuff a few days back, bought from Cube4you. Still waiting for the...
18. ### LanLan 2x2 screw help?

I just got a LanLan but because i took it apart too much and unscrewed it a lot, the screw wont stay in the little hole no matter how many times i twist the screwdriver. will the cube still work if i glue it in?
19. ### LanLan 2x2 keeps popping!

whenever i turn it really fast one of the center pieces pops out of place. how can i stop this from happening?
20. ### Lanlan 3x3 Review?

Does anybody have a review on the lanlan 3x3? My Best friend is starting to cube =] and his mom told me that she was getting him a lanlan 2x2 and 3x3 for Christmas. This is because he borrowed my lanlan 2x2, and I told him where to buy it. So his mom got 2x2 AND 3x3. I can't find any reviews...


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# Put positive polynomial in finite intersection of half-spaces

This is a cross-posting of a MSE question (which did not attract any attention there so far).

Denote by $V={\mathcal P}_{n,d}$ the space of polynomials in $n$ variables with degree at most $d$, with rational coefficients. Thus ${\mathcal P}_{n,d}$ has dimension $\binom{n+d}{n}$ over $\mathbb Q$ .

We can consider arbitrary intersection of closed half-spaces in $V$ : $N_{\Phi}=\lbrace p \in V | \forall \phi \in \Phi, \ \phi(p) \geq 0 \rbrace$, where $\Phi$ is a subset of $V^{*}$. By analogy with nef polygones, I call $N_{\Phi}$ a nef, and I say that it is of finite or infinite type, according to whether $\Phi$ is finite or infinite (perhaps there is a better terminology for this, that I’m unaware of).

Let $W$ denote the polynomials in $V$ that are nonnegative on ${\mathbb N}^n$. Then $W$ is clearly a nef of infinite type. I ask if for any $p\in W$, one can find a nef $W'$ of finite type, with nonempty interior, such that $p \in W' \subseteq W$.

This is possible when $n=1$ : if $p_0$ is a polynomial of degree $d$, nonnegative on $\mathbb N$, then there is an integer $k_0$ such that all the derivatives of $p_0$ are nonnegative at $k_0$. Then, we can take

$$W'=\bigg\lbrace p \in V \ \bigg| \ p(k) \geq 0 \ {\rm for} \ k \leq k_0, p^{(j)}(k_0) \geq 0 \ {\rm for} \ 1\leq j \leq d \bigg\rbrace$$

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How does Blowfish avoid successful cryptanalysis? [closed]

I have researched the Blowfish algorithm and am curious as to why there exists no effective cryptanalysis for this algorithm as of yet. What basic principles or features allow Blowfish to achieve this?

closed as too broad by e-sushi, DrLecter, Gilles, Seth, ponchoOct 2 '14 at 21:11

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

• What do you mean with "effective cryptoanalysis"? You mean why it hasn't been broken? There has certainly been cryptoanalysis on Blowfish, and there seem to be results that make it less suitable for specific solutions. Nowadays you should try and use 128 bit or higher block ciphers. – Maarten Bodewes Oct 1 '14 at 23:47
• The blowfish key schedule is quite computation intensive (compared to other block ciphers). That might make it stronger than other ciphers with similar key and block size. But the block size of blowfish is too small for most usages today. – kasperd Oct 1 '14 at 23:49
• thank you for answering i appreciate it, this paper was what brought me to the question. All the proposed attacks in Section 3, "Cryptanalysis of Blowfish" never use the full 16 rounds. what part of the architecture prevents this? – ale g Oct 2 '14 at 0:57
• @owlstead: Can you give reference? I am not aware of attacks on the Blowfish algorithm (rather than: implementations thereof) which would represent a sizable threat in any semi-realistic use case. For example, I can't imagine an attacker exploiting Orhun Kara and Cevat Manap's A New Class of Weak Keys for Blowfish (in proceedings of FSE 2007). I'm rather on the impression that Blowfish is a rather fine cipher except for having a 64-bit block, lack of key agility, relatively high RAM usage, and significant hardware footprint. – fgrieu Oct 2 '14 at 5:33
• @fgrieu No I did assume a bit too much there in relation to the the weak keys... – Maarten Bodewes Oct 2 '14 at 13:12

• "Combining operations from different algebraic groups." (Blowfish uses XOR and addition modulo $2^{32}$.)


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# Question #70bb8

Dec 25, 2016

It is obvious from the given figure that three charge points are situated at thrre vertices of an isosceles triangle in which two equal sides of length $l$ is inclined at an angle ${120}^{\circ}$ and $- 2 q$ charge resides at the point of intersection of these two sides. So each of the other two angles of the isosceles triangle will be ${30}^{\circ}$ .The c.g of two $+ q$ charge will be at the mid point of the line segment joining other two vertices of the triangle and the distance of resultatant $+ 2 q$ charge at this middle point from $- 2 q$ charge will be $d = l \times \sin {30}^{\circ} = \frac{l}{2}$
$\mu = 2 q \times d = 2 q \times \frac{l}{2} = q l$


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Article Contents
Article Contents

# Keep right or left? Towards a cognitive-mathematical model for pedestrians

• In this paper we discuss the necessity of insight in the cognitive processes involved in environment navigation into mathematical models for pedestrian motion. We first provide a review of psychological literature on the cognitive processes involved in walking and on the quantitative one coming from applied mathematics, physics, and engineering. Then, we present a critical analysis of the experimental setting for model testing and we show experimental results given by observation. Finally we propose a cognitive model making use of psychological insight as well as optimization models from robotics.
Mathematics Subject Classification: 91E30, 49J15.

 Citation:

•  [1] G. Arechavaleta, J.-P. Laumond, H. Hicheur and A. Berthoz, An optimality principle governing human walking, Robotics, IEEE Transactions on, 24 (2008), 5-14.doi: 10.1109/TRO.2008.915449. [2] N. Bellomo and C. Dogbe, On the modeling of traffic and crowds: A survey of models, speculations, and perspectives, SIAM Review, 53 (2011), 409-463.doi: 10.1137/090746677. [3] E. M. Cepolina and N. Tyler, Understanding Capacity Drop for designing pedestrian environments, in Proceedings of the 6th International Walk21 Conference, Zurich, 2005, 1-11. [4] Y. Chitour, F. Jean and P. Mason, Optimal control models of goal-oriented human locomotion, SIAM Journal on Control and Optimization, 50 (2012), 147-170.doi: 10.1137/100799344. [5] F. Chittaro, F. Jean and P. Mason, On inverse optimal control problems of human locomotion: Stability and robustness of the minimizers, Journal of Mathematical Sciences, 195 (2013), 269-287.doi: 10.1007/s10958-013-1579-z. [6] R. Conroy-Dalton, The secret is to follow your nose: Route path selection and angularity, in 3rd International Space Syntax Symposium, Atlanta, 2003, 1-47. [7] E. Cristiani, B. Piccoli and A. Tosin, Multiscale Modeling of Pedestrian Dynamics, MS&A: Modeling, Simulation and Applications, 12, Springer-Verlag, 2014.doi: 10.1007/978-3-319-06620-2. [8] W. Daamen and S. Hoogendoorn, Experimental research of pedestrian walking behavior, Transportation Research Record: Journal of the Transportation Research Board, 1828 (2003), 20-30.doi: 10.3141/1828-03. [9] J. M. Dabbs Jr and N. A. Stokes III, Beauty is power: The use of space on the sidewalk, Sociometry, 551-557. [10] E. Goffman, Relations in Public: Microstudies of the Social Order, 1971. [11] R. G. Golledge, Human wayfinding and cognitive maps, in Wayfinding Behavior: Cognitive Mapping and Other Spatial Processes, JHU Press, 1999, 5-45. [12] H. L. Golson and J. M. Dabbs, et al., Line-following tendencies among pedestrians: A sex difference, Personality And Social Psychology Bulletin, 1 (1974), 16-18.doi: 10.1177/014616727400100106. [13] D. Helbing, Boltzmann-like and boltzmann-fokker-planck equations as a foundation of behavioral models, Physica A: Statistical Mechanics and its Applications, 196 (1993), 546-573.doi: 10.1016/0378-4371(93)90034-2. [14] D. Helbing, L. Buzna, A. Johansson and T. Werner, Self-organized pedestrian crowd dynamics: Experiments, simulations, and design solutions, Transportation Science, 39 (2005), 1-24.doi: 10.1287/trsc.1040.0108. [15] D. Helbing and P. Molnar, Social force model for pedestrian dynamics, Physical Review E, 51 (1995), 4282.doi: 10.1103/PhysRevE.51.4282. [16] D. Helbing, P. Molnar, I. J. Farkas and K. Bolay, Self-organizing pedestrian movement, Environment and Planning B, 28 (2001), 361-383.doi: 10.1068/b2697. [17] S. P. Hoogendoorn and P. H. Bovy, State-of-the-art of vehicular traffic flow modelling, Proceedings of the Institution of Mechanical Engineers, Part I: Journal of Systems and Control Engineering, 215 (2001), 283-303. [18] T. Ishikawa, H. Fujiwara, O. Imai and A. Okabe, Wayfinding with a gps-based mobile navigation system: A comparison with maps and direct experience, Journal of Environmental Psychology, 28 (2008), 74-82.doi: 10.1016/j.jenvp.2007.09.002. [19] T. Ishikawa and D. R. Montello, Spatial knowledge acquisition from direct experience in the environment: Individual differences in the development of metric knowledge and the integration of separately learned places, Cognitive Psychology, 52 (2006), 93-129.doi: 10.1016/j.cogpsych.2005.08.003. [20] A. Johansson, D. Helbing and P. K. Shukla, Specification of the social force pedestrian model by evolutionary adjustment to video tracking data, Advances in Complex Systems, 10 (2007), 271-288.doi: 10.1142/S0219525907001355. [21] H. S. Jung and H.-S. Jung, Survey of korean pedestrians' natural preference for walking directions, Applied Ergonomics, 44 (2013), 1015-1023.doi: 10.1016/j.apergo.2013.04.003. [22] A. Lachapelle and M.-T. Wolfram, On a mean field game approach modeling congestion and aversion in pedestrian crowds, Transportation Research Part B: Methodological, 45 (2011), 1572-1589.doi: 10.1016/j.trb.2011.07.011. [23] R. Lloyd and C. Heivly, Systematic distortions in urban cognitive maps, Annals of the Association of American Geographers, 77 (1987), 191-207.doi: 10.1111/j.1467-8306.1987.tb00153.x. [24] K. Mombaur, J.-P. Laumond and E. Yoshida, An optimal control-based formulation to determine natural locomotor paths for humanoid robots, Advanced Robotics, 24 (2010), 515-535.doi: 10.1163/016918610X487090. [25] K. Mombaur, A. Truong and J.-P. Laumond, From human to humanoid locomotion-an inverse optimal control approach, Autonomous Robots, 28 (2010), 369-383.doi: 10.1007/s10514-009-9170-7. [26] D. R. Montello, The perception and cognition of environmental distance: Direct sources of information, in Spatial Information Theory A Theoretical Basis for GIS, Springer, 1329 (1997), 297-311.doi: 10.1007/3-540-63623-4_57. [27] M. Moussaīd, D. Helbing and G. Theraulaz, How simple rules determine pedestrian behavior and crowd disasters, Proceedings of the National Academy of Sciences, 108 (2011), 6884-6888. [28] J. Ondřej, J. Pettré, A.-H. Olivier and S. Donikian, A synthetic-vision based steering approach for crowd simulation, in ACM Transactions on Graphics (TOG), ACM, 29 (2010), p123. [29] E. Papadimitriou, G. Yannis and J. Golias, A critical assessment of pedestrian behaviour models, Transportation Research Part F: Traffic Psychology and Behaviour, 12 (2009), 242-255.doi: 10.1016/j.trf.2008.12.004. [30] T. Rosenbloom, Crossing at a red light: Behaviour of individuals and groups, Transportation Research Part F: Traffic Psychology and Behaviour, 12 (2009), 389-394.doi: 10.1016/j.trf.2009.05.002. [31] J. van den Berg, S. Patil, J. Sewall, D. Manocha and M. Lin, Interactive navigation of multiple agents in crowded environments, in Proceedings of the 2008 symposium on Interactive 3D graphics and games, ACM, 2008, 139-147. [32] D. Vickers, P. Bovet, M. D. Lee and P. Hughes, The perception of minimal structures: Performance on open and closed versions of visually presented euclidean travelling salesperson problems, Perception-London, 32 (2003), 871-886.doi: 10.1068/p3416. [33] M. Wolff, Notes on the behaviour of pedestrians, People in Places: The Sociology of the Familiar, Praeger, New York, 1973, 35-48. [34] L. Yang, J. Li and S. Liu, Simulation of pedestrian counter-flow with right-moving preference, Physica A: Statistical Mechanics and its Applications, 387 (2008), 3281-3289.doi: 10.1016/j.physa.2008.01.107. [35] F. Zanlungo, T. Ikeda and T. Kanda, A microscopic "social norm" model to obtain realistic macroscopic velocity and density pedestrian distributions, PloS one, 7 (2012), e50720.doi: 10.1371/journal.pone.0050720.


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# Abstract

Recent DESY-HERA data on J/Y elasticity distribution show that it emerges mostly as a fast particle. Interpreting photoproduction as a collision between a pre-formed charmed hadron and the proton, the outcoming J/Y is a leading particle of the collision. We analyse these data using a model formulated to describe energy flow in hadron-hadron reactions. The measured J/Y spectrum can be successfully described in terms of this model. We conclude that the observed transparency of the charmed hadron-proton collisions arises because of the particularly small gluonic content of the initial c -  state.

Leading particle effect in the J/y elasticity distribution

F.O. Durães1,2* * e-mail: fduraes@if.usp.br  e-mail: navarra@if.usp.br  e-mail: Grzegorz.Wilk@fuw.edu.pl 1 By gluonic clouds we understand a sort of "effective gluons'' which include also their fluctuations seen as sea pairs. , F.S. Navarra2,3 * e-mail: fduraes@if.usp.br  e-mail: navarra@if.usp.br  e-mail: Grzegorz.Wilk@fuw.edu.pl 1 By gluonic clouds we understand a sort of "effective gluons'' which include also their fluctuations seen as sea pairs. and G. Wilk3 * e-mail: fduraes@if.usp.br  e-mail: navarra@if.usp.br  e-mail: Grzegorz.Wilk@fuw.edu.pl 1 By gluonic clouds we understand a sort of "effective gluons'' which include also their fluctuations seen as sea pairs.

1Instituto Superior Técnico, Universidade Técnica de Lisboa

Av. Rovisco Pais 1, 1-1096 Lisboa Codex, Portugal

2Instituto de Física, Universidade de São Paulo

C.P. 66318, 05389-970 São Paulo, SP, Brazil

3Soltan Institute for Nuclear Studies, Nuclear Theory Department

ul. 69, 00-681 Warsaw, Poland

Recent DESY-HERA data on J/Y elasticity distribution show that it emerges mostly as a fast particle. Interpreting photoproduction as a collision between a pre-formed charmed hadron and the proton, the outcoming J/Y is a leading particle of the collision. We analyse these data using a model formulated to describe energy flow in hadron-hadron reactions. The measured J/Y spectrum can be successfully described in terms of this model. We conclude that the observed transparency of the charmed hadron-proton collisions arises because of the particularly small gluonic content of the initial c - state.

PACS number(s): 13.85.Qk, 11.55.Jy

The leading particle effect is one of the most interesting features of multiparticle production in hadron-hadron collisions [1]. In these reactions the valence quarks of the projectile emerge from the collision carrying the initial state quantum numbers. All produced particles come essentially from the gluons and quark-anti-quark pairs already pre-existing in the projectile and target, or radiated during the collision. This qualitative picture takes different implementations in the many existing multiparticle production models. In one of them, the Interacting Gluon Model (IGM) [2, 3, 4, 5], the produced particles (and consequently the energy released in the secondaries and lost by the projectiles) come almost entirely from the pre-existing gluons in the incoming hadrons. This conjecture may be directly tested using a high energy, nearly gluonless hadronic projectile. In this case, according to the IGM, inspite of the high energy involved, the production of secondaries would be suppressed (in comparison to the production observed in ordinary hadron induced reactions) and the energy would be mostly carried away by the projectile leading particle (LP) which would then be observed with a hard xF spectrum. This type of gluonless projectile is available in J/Y photoproduction, where the photon can be understood as a virtual c - pair which reacts with the proton and turns into the finally observed J/Y. There are low energy data taken by the FTPS Collaboration [6] and very recently high energy data became available at HERA [7].

It has been shown by a number of authors that the simple vector meson dominance mechanism (VDM), in which the photon is converted directly to a J/Y before the interaction with the proton, does not describe many aspects of data. However, as it was shown in ref. [8], the charm anti-charm pair can be understood as a supperposition of many hadronic states: J/Y, Y¢, ... . Whereas relevant for the calculation of the cross sections, the inclusion of all the other charmonium states does not change the fact that the projectile, whatever it may be, is a hadron with low gluonic content. For the study of the outgoing J/Y momentum spectrum, this is the most important information, which allows us to test the picture proposed by the IGM.

At lower energies we can compare the momentum spectrum of the J/Y measured in gp ® J/Y X collisions [6] with the leading meson (p and K) momentum spectra measured [1] in p p ® p X and K p ® K X reactions at the same c.m.s. energy. One observes that the charmed leading particles are much harder. This comparison is however not completely meaningful because the J/Y data contain a diffractive component which was subtracted in the hadronic data.

At HERA a J/Y z (z = EJ/Y/Eg) spectrum presumably free from the diffractive component was presented. Although the energy is different a comparison with the leading particle spectra measured in hadronic reactions is still meaningful because the LP spectra have a relatively weak energy dependence. The J/Y momentum spectrum is clearly harder, according to what we expect in the IGM. The ¡ z spectra, which will be eventually measured at HERA in a near future, will be even harder.

In J/Y photoproduction, because of the large charm mass, perturbative QCD (PQCD) is expected to be valid. Indeed, all the main features of both J/Y hadro and photoproduction are well described by PQCD. However, in hadroproduction perturbative calculations fail at large xF [9], where non-perturbative effects become stronger. In the eighties charmonium production was studied with the color singlet model [10]. In the nineties this model was seen to fail badly when applied to Tevatron data. At the same time was developed the non-relativistic effective field theory of QCD, called just non-relativistic QCD (NRQCD) [11]. The main new feature of NRQCD is the introduction of the color octet components of the quarkonium wave function. In the HERA experiments, the z distributions have been studied using pT ³ 1 GeV. The surprising features of the comparisons [12] of the NRQCD results with data is that the color-singlet model prediction is in agreement with data while including the color-octet component leads to violent disagreement with the data at large z. In ref. [13] the failure of NRQCD was discussed and attributed to the pT kinematic cuts. At such small values of pT (and also for z very close to unity) there could be significant non-perturbative soft physics effects. The way, chosen in ref. [13], to parametrize these effects is to include the transverse momentum smearing of the partons inside the proton. In this way one introduces the effect of the "hadron walls''. The resulting z distributions become then flatter, in better agreement with data. The highest z data points, however, are still not accounted for. This situation justifies, in our opinion, the more phenomenological examination of these spectra given by the IGM.

We present now our quantitative calculations, which illustrate the qualitative discussion made above. The IGM is a model which has been developed primarily to analyse energy-momentum spectra of leading particles [2, 3, 4, 5]. This work continues therefore the application of the IGM to photon initiated reactions presented in [5] putting them on an equal footing with the hadronic processes studied before [2, 3] (including diffractive dissociation ones [4]).

In Fig. 1 we show schematically the IGM picture of a photon-proton collision. According to it, during the interaction the photon is converted into a hadronic state which interacts with the incoming proton. This hadronic state contains the c - and some gluons and we call it simply "hadron''. The hadron-proton interaction follows then the usual IGM picture, namely: the valence quarks fly through essentially undisturbed whereas the gluonic clouds of both projectiles interact strongly with each other1 * e-mail: fduraes@if.usp.br  e-mail: navarra@if.usp.br  e-mail: Grzegorz.Wilk@fuw.edu.pl 1 By gluonic clouds we understand a sort of "effective gluons'' which include also their fluctuations seen as sea pairs. . In the course of interaction the hadronic state looses fraction x of its original momentum and gets excited forming what we call a leading jet (LJ) which carries fraction z = 1 - x of the initial momentum. The proton looses fraction y of its momentum forming another leading jet. In the IGM we consider two possible types of g+ p interactions: non-diffractive and diffractive. In each of these reactions the J/Y can come either from the fragmentation of the mesonic leading jet or from the hadronization of the central gluonic fireball. In this work we shall concentrate only on the data taken at HERA [7] for GeV2 and 0.5 £ z £ 0.9. In this case, it is enough to consider the single non-diffractively J/Y produced from the fragmentation of the photonic leading jet, cf. Fig. 1. All other contributions can be safely neglected here.

Figure 1. IGM description of a photon-proton scattering with J/y production.

In order to calculate this spectrum we start (cf., [4, 5] for details) with the function c(x, y), which describes the probability to form a central gluonic fireball (CF) carrying momentum fractions x and y of the two colliding projectiles:

where

Here c0 denotes the normalization factor provided by the requirement that being the minimal inelasticity defined by the mass m0 of the lightest possible central fireball CF (represented by the blob in Fig. 1). The dynamical input of the IGM is contained in the, so called, spectral function w(x, y) given by

where G(x) and G(y) denote the effective number of gluons in the charmed hadron and in the proton, respectively. They are approximated by the respective gluonic structure functions. W is the photon-proton c.m. energy. sgg is the gluon-gluon cross section, which is computed over a wide range of scales given by xyW2. Whenever the scale is larger than 2.3 GeV lowest order perturbative QCD formulas are used. Otherwise a parametrization which represents non-perturbative physics is employed [2]. At the energies W considered here the bulk of the interaction happens in the non-perturbative domain. s is the relevant meson-proton cross section.

The final momentum spectrum of the produced J/Y is then given in terms of c(x, y) as follows:

where

and is the J/Y energy fraction (which in the IGM, where all masses have been consistently neglected coincides with the momentum fraction). Because we are dealing here with the leading particle spectra, we have to introduce the additional kinematical constraint, , which ensures that the mass MX ( MX

W, see Fig. 1) is large enough to produce both the measured J/Y particle of mass MJ/Y and the minimal CF of mass m0, as demanded by the IGM. (In fact, in our case we have to replace GeV2, to account for the minumum transverse momentum present at our data points).

Whenever possible we keep all parameters the same as in the previous applications of the IGM [2]-[5]. However, the inelastic (c-) - p scattering cross section and the number of gluons in the charmonium state are different from the corresponding quantities encountered so far.

The charmonium-hadron cross section, which we shall approximate by , has been subject of intensive research in the context of nuclear physics and signatures of quark gluon plasma. Calculations seem to converge to @ 6-9 mb [14]. As for the distribution G(x), which we may call GJ/y(x), we shall assume that it has the same shape as in other mesons, i.e., GJ/y(x) = Gr0(x) = Gp(x) and use, for the latter, the SMRS parametrization [15]. The specific shape chosen for these distributions does not affect much the results. Their normalization ph = ò01dx x Gh(x), i.e., the amount of momentum allocated to the gluonic component, plays, however, a crucial role here and we should try to estimate it somehow. It is known that in a nucleon or in a light meson ph 0.5 , i.e., gluons carry half of the momentum of the hadron. The charmonium, however, is a non-relativistic system and almost all its mass comes from the quark masses. The gluonic field, responsible for a weak binding, carries only a small fraction of the energy (and momentum) of the bound state. We expect therefore the normalization factor pJ/y of GJ/y(x) to be of the order of the energy stored in the field divided by the mass of the state. In the case of a J/y we have:

where mc has been taken 1.5 GeV and MJ/y = 3.1 GeV. In the IGM those two parameters are in fact entering only as a combination pJ/Y/. Because out of those two quantities relevant here only the pJ/Y is so far completely unknown, we shall, in what follows, take for definiteness = 9 mb and leave pJ/Y to be a free parameter.

In Fig. 2 we compare our results (F(z)) with the experimental data. As it can be seen the agreement is very good and it was obtained with essentially only one new (but heavily constrained) parameter equal to the ratio of the amount of momentum carried by gluons in the c state and its inelastic cross section with the proton. The observed flatteness comes (once is fixed) entirely from the small value of the pJ/Y parameter, what can be seen if we compare our best result (pJ/Y = 0.033) shown in the full line, with results for other values of pJ/Y. The dashed line represents the choice pJ/Y = 0.066 and the dotted line corresponds to pJ/Y = 0.016. Notice the high sensitivity of the results to the changes of the parameter pJ/Y.

Figure 2.
Comparison of the IGM distribution F(z) with data of ref. [7] with restricted acceptance pT2³ 1 (GeV/c)2 and 0.5 £ z £ 0.9 for fixed value of

To summarize: assuming that the photon may be represented by a hadronic state containing a charm anti-charm pair, we have successfully described the leading spectra of photoproduced J/Y's in terms of the IGM. At the same time we have demonstrated that (again: within the IGM scheme) they depend crucially on the amount of momentum carried by gluons in the charmed hadron, pJ/Y (provided its cross section with the nucleon is known from somewhere else, otherwise they depend of the ratio of these two parameters). It means that the knowledge of the leading spectra and the inelastic cross section should allow us to estimate the amount of the gluonic momenta in the projectile. For high energies (as those encountered here) this result is universal and insensitive to the mass of the projectile under consideration.

Acknowledgements: This work has been supported by CNPq, CAPES and FAPESP under contract number 93/2463-2.

References

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• *
e-mail:

e-mail:

e-mail:
1
By gluonic clouds we understand a sort of "effective gluons'' which include also their fluctuations seen as
sea pairs.
• [7] S.Aid et al., (H1 Collab.), Nucl. Phys.,  B472, 3 (1996) ; M.Derrick et al. (ZEUS Collab.), Phys. Lett. B350, 120 (1995) ;
• [10] R. Baier and R. Ruckl, Z. Phys. C19, 251 (1983)1; E.L. Berger and D. Jones, Phys.Rev. D23, 2349 (1992) .
• [12] Cf., for example, P.Hoyer, Nucl. Phys. A622, 284c (1997)  and Charmonium production at ELFE energies, hep-ph/9702385, and references therein;
• M. Kramer, Nucl. Phys. B459, 3 (1996) ; M. Cacciari and M. Kramer, Phys. Rev. Lett. 76, 4128 (1996).
* e-mail: fduraes@if.usp.br  e-mail: navarra@if.usp.br  e-mail: Grzegorz.Wilk@fuw.edu.pl 1 By gluonic clouds we understand a sort of "effective gluons'' which include also their fluctuations seen as sea pairs.

# Publication Dates

• Publication in this collection
26 Aug 1999
• Date of issue
Dec 1998
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