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• Verify client certificate CN in Tomcat(APR)

  - by Petter

  I'm running a tomcat installation with the APR libraries installed (with the OpenSSL HTTPS stack that comes with it). What I'm trying to do is to lock a specific HTTPS connector down to users of a specific certificate. Adding client certificate verification is no issue, but I can't get it to validate against a specific Common name only. I was perhaps a bit naïve and thought the mod_ssl attribute SSLRequire typically used in Apache Httpd would work, but that property is not recognized by the Tomcat implementation. (http://tomcat.apache.org/tomcat-7.0-doc/config/http.html#SSL%20Support points to some mod_ssl docs, but the Tomcat implementation does not seem to cover all aspects of mod_ssl). I can get this to work by using the Java version of the connector instead of APR (losing some performance) and just add a trust store with that one certificate in it. However, using openssl without the SSLRequire expressions, I'm not sure how to do this with Tomcat7 (on Windows if that matters). <Connector protocol="HTTP/1.1" port="443" maxThreads="150" scheme="https" secure="true" SSLEnabled="true" SSLCertificateFile="mycert.pem" SSLCertificateKeyFile="privkey.pem" SSLCACertificateFile="CABundle.pem" SSLVerifyClient="require" SSLProtocol="TLSv1" SSLRequire="(%{SSL_CLIENT_S_DN_CN} eq &quot;host.example.com&quot;)"/> Can you suggest a way to make this work using Tomcat/APR/OpenSSL?

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• Mac Backup Plan

  - by Chuy77

  I'm reviewing my backup plan and would appreciate any thoughts about what more I should do (if anything) to make sure I'm properly covered in case of all hell breaking loose. :-) I have one machine. 1) I run a nightly clone with SuperDuper. I alternate the clone drive weekly so I have two clones, one never more than a week old. 2) I use BackBlaze as a sort of Time Machine in the cloud. It runs all the time and keeps everything on my machine backed up online. 3) I sync all my 1Password logins, etc. to my iPhone once a week. ...And that's it. I feel pretty covered. But I'm always reading stuff like this: http://www.43folders.com/2010/03/15/yes-another-backup-lecture And that doesn't even mention online backup, and seems like a huge pain in the behind. But maybe I'm being naive? Should I have more backups? Thanks for any feedback. I really appreciate it.

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• Thundrbird 3: can't change column width?

  - by rumtscho

  I recently installed Thunderbird 3.0.3. Just noticed a suboptimal UI setting: in the upper pane, which lists the e-mails in the current folder, the Date column is about 200px wide. So when I keep the window at 480x600, all I see in a row is: | tree icon | favourites icon | attachment icon | read icon | junk icon | Date and time, followed by 5cm whitespace | ... | P Where "P" is the first letter of the name of the sender. And the "..." is actually shown this way, I have no idea which column it is meant to be. But I don't see neither the sender, nor the message subject, which makes scrolling a folder for a certain mail rather pointless. I see these when I maximize the window, actually the columns are then not only bigger, they are arranged in another sequence. But I feel that holding a mail client permanently maximised at 1600x1200 is a waste of screen real estate. My naive solution attempt was to try to go with the mouse cursor to the right edge of the date column and try to shrink it by moving the cursor left while holding down the left mouse button. Not only is this default behaviour for all resizable columns I've ever encountered in GUIs, the cursor actually turns into a horizontal double-headed arrow. But pulling has no effect at all. I cannot make a wide column narrow, and I cannot make the narrow columns wide. I didn't find anything in the preferences either. So can please somebody explain how to get the columns arranged sensibly?

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• Underbraces in Word math zones and dealing with stretchy parentheses

  - by Johannes Rössel

  Parentheses in Word usually stretch with whatever they're containing. This might be un-noticeable for things like but for stuff like it's definitely nice, especially compared to the fact that naïve LaTeX users often produce uglinesses such as There is a problem, however, when using under-/overbraces in math and putting parentheses around the complete term it becomes ugly. For simple things like shown here this can be solved by not letting the parentheses stretch which looks almost right. However, for more complex things it's certainly not an option: Both variants look horrible. So is there a way of letting the parentheses only stretch around the actual term parts, not including the under-/overbraces? Those are frequently used for annotations of individual pieces, so simply not using them is a bad idea too. In LaTeX you can get away with guesswork and using explicit sizes for the parentheses instead of relying on \left and \right but I haven't found a comparable option in Word yet. Since the underbrace is (tree-wise) a sibling of the term in parentheses it probably simply has to stretch and there probably can't be an algorithm that determines when to stretch or when not, considering that \above and \below are used for annotations as well but also for other things where perentheses have to stretch. Also, since the parenthesized expression is opaque from the outside one has to put the underbrace inside. From a markup point of view, at least. One can probably draw the rest around but that falls apart when styles change and wouldn't be a good idea either.

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• Underbraces in Word math zones and dealing with parentheses

  - by Johannes Rössel

  Parentheses in Word usually stretch with whatever they're containing. This might be un-noticeable for things like but for stuff like it's definitely nice, especially compared to the fact that naïve LaTeX users often produce uglinesses such as There is a problem, however, when using under-/overbraces in math and putting parentheses around the complete term it becomes ugly. For simple things like shown here this can be solved by not letting the parentheses stretch which looks almost right. However, for more complex things it's certainly not an option: Both variants look horrible. So is there a way of letting the parentheses only stretch around the actual term parts, not including the under-/overbraces? Those are frequently used for annotations of individual pieces, so simply not using them is a bad idea too. In LaTeX you can get away with guesswork and using explicit sizes for the parentheses instead of relying on \left and \right but I haven't found a comparable option in Word yet. Since the underbrace is (tree-wise) a sibling of the term in parentheses it probably simply has to stretch and there probably can't be an algorithm that determines when to stretch or when not, considering that \above and \below are used for annotations as well but also for other things where perentheses have to stretch. Also, since the parenthesized expression is opaque from the outside one has to put the underbrace inside. From a markup point of view, at least. One can probably draw the rest around but that falls apart when styles change and wouldn't be a good idea either.

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• Local references to old server name remain after Windows 2003 server rename

  - by imagodei

  I have a standalone Win 2003 server with Windows Sharepoint Services (WSS3) running on it. I had to rename the server and I had bunch of problems resulting from this. Note that the server is not in AD environment. Most obvious problems were with Sharepoint, which didn't work. I was somewhat naive to think it will work in the first place, but OK - I've solved this using step 1 & 3 from this site (TNX) Other curious behavior/problems remain. Most disturbing is that Sharepoint isn't able to send email notifications to participants. I noticed there are several references to old server name everywhere I look: in Registry, in Windows Internal Database (MICROSOFT##SSEE). I see instances of old server name in the Sharepoint Central Administration - Operations - Servers in farm. There is reference to a servers: oldname.domain.local oldname.local On one of those servers there is also Windows SharePoint Services Outgoing E-Mail Service (Stopped). Also, when I try to telnet locally to the mail server (Simple Mail Transfer Protocol (SMTP) service), I get a response: 220 oldname.domain.local Microsoft ESMTP MAIL Service, Version: 6.0.3790.4675 ready at Tue, 15 Jun 2010 13:56:19 +0200 IMO these strange naming problems are also the reason why email notifications from within Sharepoint don't work. Can anyone tell me how to correct/replace those references to oldservername? Why is the email service insisting on old name? Of course I would like to try it without reinstalling the server. TNX!

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• Mutual piping on linux

  - by user21919

  I would like the output of A to be input for B and at the same time the output of B to be the input for A, is that possible? I tried the naïve thing: creating named pipes for A (pipeA) and B (pipeB) and then: pipeB | A | pipeA & pipeA | B | pipeB & But that does not work (pipeB is empty and switching the order would not help either). Any help would be appreciated. Example: Command A could be compiled form of this C program: #include <stdio.h> int main() { printf("0\n"); int x = 0; while (scanf("%d", &x) != EOF) { printf("%d\n", x + 1); } return 0; } Command B could be compiled form of this C program: #include <stdio.h> int main() { int x = 0; while (scanf("%d", &x) != EOF) { printf("%d\n", x + x); } return 0; }

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• Why would I need a firewall if my server is well configured?

  - by Aitch

  I admin a handful of cloud-based (VPS) servers for the company I work for. The servers are minimal ubuntu installs that run bits of LAMP stacks / inbound data collection (rsync). The data is large but not personal, financial or anything like that (ie not that interesting) Clearly on here people are forever asking about configuring firewalls and such like. I use a bunch of approaches to secure the servers, for example (but not restricted to) ssh on non standard ports; no password typing, only known ssh keys from known ips for login etc https, and restricted shells (rssh) generally only from known keys/ips servers are minimal, up to date and patched regularly use things like rkhunter, cfengine, lynis denyhosts etc for monitoring I have extensive experience of unix sys admin. I'm confident I know what I'm doing in my setups. I configure /etc files. I have never felt a compelling need to install stuff like firewalls: iptables etc. Put aside for a moment the issues of physical security of the VPS. Q? I can't decide whether I am being naive or the incremental protection a fw might offer is worth the effort of learning / installing and the additional complexity (packages, config files, possible support etc) on the servers. To date (touch wood) I've never had any problems with security but I am not complacent about it either.

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• MySQL slave server from dumps

  - by HTF

  I've created a slave server from live machine which is acting as a master now. I use the following procedure to create it: mysqldump --opt -Q -B --master-data=2 --all-databases > dump.sql then I imported this dump on the new machine, applied the "CHANGE MASTER TO..." directive with a log file/position from the dump. Please note that I have around 8000 databases and I didn't stop the master while the dumps were running. The replication works fine but is this a properly method for creating a slave server? I'm planning to promote this slave to a master (different location) so I would like to make sure that there is a 100% data consistency between the servers. I've found this article where it says: The naive approach is just to use mysqldump to export a copy of the master and load it on the slave server. This works if you only have one database. With multiple database, you'll end up with inconsistent data. Mysqldump will dump data from each database on the server in a different transaction. That means that your export will have data from a different point in time for each database. Thank you

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• What is the best hosting option for Flash web-widget?

  - by par

  Our Flash web-widget has got highly popular. It is downloaded around 100,000 times per day. And that is the problem. Our server bandwidth is too narrow to deliver the widget to the clients fast. The widget is loaded very slow. Probably 20 times slower than before (at peak times). Probably I have choosen not the right hoster for my task - delivering 1 MB Flash widget to 100,000 users per day. What is the best hosting solution in my case? I'm not good at server administration so forgive me if I sound naive. The details are the following. Our hoster options: -Dedicated server, Ubuntu -10 Mbit Connection -monthly bandwidth limit: 2000 GB Widget size is 1 MB. The widget consists of the main SWF and a number of loaded SWF and data files. This is a part of Apache Status report taken right now ---- Server uptime: 1 hour 2 minutes 38 seconds Total accesses: 74865 - Total Traffic: 5.8 GB CPU Usage: u28 s7.78 cu0 cs0 - .952% CPU load 19.9 requests/sec - 1.6 MB/second - 81.1 kB/request 200 requests currently being processed, 0 idle workers WWWWWWWWWWWWWWWWWWWWWWWWCWWWWWWWWWWWWWWWWWWWWWWWWWWCWWWWWWWCWWWW WWWWWCWWWWWWWWWWWWWWCWWWWWWWWWWWWCWWWWWWWWCWWCWWWWWWWWWWWWWWWWWW WWWWWWWWWWWWWWWWCWWWWWWWWWWWWWWWWWWWWWWWWWWWCWCWWWWWWWWWWWWWWWCW WWWWWWWW........................................................ ----

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• Accessing a webpage folder with .htaccess in it via apache webdav?

  - by pingo

  I have setup webdav access in order to enable an external user to upload the content of his web page to his folder on my server that is served by apache to the web. This way he could update his web page via webdav. Now the problem is that the user requires a .htaccess file and of course .htaccess breaks webdav probably because it overrides settings. (new files cannot be uploaded anymore via webdav if below specified .htaccess exists) I am running Apache2.2.17 and this is my webdav config: Alias /folderDAV "d:/wamp/www/somewebsite/" <Location /folderDAV> Order Allow,Deny Allow from all Dav On AuthType Digest AuthName DAV-upload AuthUserFile "D:/wamp/passtore/user.passwd" AuthDigestProvider file require valid-user </Location> This config is part of my naive solution to fixing this problem. The idea was to specify an alias to the web page folder where webdav would be enabled and then set AllowOverride to none so that the .htaccess would have no effect. Of course I then found out that in <Location /> AllowOverride directive is not valid. The .htaccess file looks like this: #opencart settings Options +FollowSymlinks Options -Indexes <FilesMatch "\.(tpl|ini)"> Order deny,allow Deny from all </FilesMatch> RewriteEngine On RewriteBase / RewriteCond %{REQUEST_FILENAME} !-f RewriteCond %{REQUEST_FILENAME} !-d RewriteRule ^(.*)\?*$ index.php?_route_=$1 [L,QSA] ErrorDocument 403 /403.html deny from 1.1.1.1/19 allow from 2.2.2.2 What would be the solution here? I would like to have the web page accessible from the web but at the same time be able to access and modify it via apache's webdav (with digest auth). How would I do that? Also if possible I would like a solution that permits the existence of the .htaccess so that the user still has the power to setup access rules for his web page.

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• Network Sniffing and Hubs

  - by Chris_K

  This will likely seem naive to the experts... but it has been on my mind lately. For years I've been using ntop and a cheap 4 port hub to sniff client networks to determine who's doing what -- and how much. Great way to see what's going on when they call and say "Geeze, the network seems really slow today." No need to bring in a managed switch (or access the existing one) and no need to configure spanning or mirroring. I just drop in the hub inline where I want to measure. Lately I noticed it is just about impossible to buy a real honest-to-goodness hub anymore. While looking for a new one, I had someone tell me that I should be sure to get a full-duplex hub or I'd only be seeing half the traffic when I monitor. Really? I've been using a crusty old Netgear DS104 all this time. No clue if it is half or FD. Have I really been understating my measurements? I'm just not bright enough about the physical layer to really know... Side note: Just ordered a Dualcomm Ethernet Switch TAP as a hub replacement. Seems like a nifty gadget. Any notes or tips about it would be welcome in the comments :-)

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• Read non-blocking from multiple fifos in parallel

  - by Ole Tange

  I sometimes sit with a bunch of output fifos from programs that run in parallel. I would like to merge these fifos. The naïve solution is: cat fifo* > output But this requires the first fifo to complete before reading the first byte from the second fifo, and this will block the parallel running programs. Another way is: (cat fifo1 & cat fifo2 & ... ) > output But this may mix the output thus getting half-lines in output. When reading from multiple fifos, there must be some rules for merging the files. Typically doing it on a line by line basis is enough for me, so I am looking for something that does: parallel_non_blocking_cat fifo* > output which will read from all fifos in parallel and merge the output on with a full line at a time. I can see it is not hard to write that program. All you need to do is: open all fifos do a blocking select on all of them read nonblocking from the fifo which has data into the buffer for that fifo if the buffer contains a full line (or record) then print out the line if all fifos are closed/eof: exit goto 2 So my question is not: can it be done? My question is: Is it done already and can I just install a tool that does this?

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• PCI-E riser card prevents server from starting at all

  - by user68623

  I need to replace the RAID controller in a server, and the new one is PCI Express while the old one was 64bit PCI. The server has both slots, but the riser card that was installed does not contain the PCI Express part. So I bought a new 4x PCI Express riser card (Delock 89103), but the moment I put it into the slot the server does not start up at all. It does not even get to POST, at most the power LED flashed once but nothing else happens at all. It does not power up the server at all. If I remove the riser card it starts up fine. If I put the riser card into a regular desktop computer it seems to work in general. Is there anything else I have to pay attention to when buying a riser card? My naive assumption would be that any PCI Express riser card should work. Or is my riser card likely to be damaged or out-of-spec and the server is just more picky? How do I get it to work, or how can I at least find a riser card that will work with my server? The server mainboard is a Super Micro PDSMi+.

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• Loading not-so-well-formed XML into XDocument (multiple DTD)

  - by Gart

  I have got a problem handling data which is almost well-formed XHTML document except for it has multiple DTD declarations in the beginning: <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> ... </head> <body> ... </body> </html> I need load this data into XDocument object using only the first DTD and ignoring the rest declarations. It is not possible to completely ignore DTD processing because the document may have unusual characters like &acirc; or &euro; etc. The text is retrieved from external source and I have no idea why it comes like this. Obviously my naive attempt to load this document fails with System.Xml.XmlException : Cannot have multiple DTDs: var xmlReaderSettings = new XmlReaderSettings { DtdProcessing = DtdProcessing.Parse XmlResolver = new XmlPreloadedResolver(), ConformanceLevel = ConformanceLevel.Document, }; using (var xmlReader = XmlReader.Create(stream, xmlReaderSettings)) { return XDocument.Load(xmlReader); } What would be the best way to handle this kind of data?

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• Writing an efficient cron job script utilizing Zend_Mail_Storage_Imap.

  - by fireeyedboy

  I'm new to the IMAP protocol and Zend_Mail_Storage and I'm writing a small php script for a cron job that should regularly poll an IMAP account and check for new messages, and send an e-mail if new messages have arrived. As you can imagine, I want to only poll the IMAP account for relevant messages, and I only want to send a new e-mail if new messages have arrived since the last polled new message. So I thought of keeping track of the last message I polled with some unique identifier for a message. But I'm a bit uncertain about whether the methods I want to utilize for this do what I expect them to do though. So my questions are: Does the iterator position of Zend_Mail_Storage_Imap actually resemble some IMAP unique identifier for messages, or is it simply only and internal position of Zend_Mail_Storage_Abstract? For instance, if I tell it to seek() to message 5 (which I stored from an earlier session) will it indeed seek to the appropriate message on the IMAP server, even if for instance messages have been deleted since last session? Would keeping track of this latest polled message id in a file suffice for a cron job that, say, polls the account every 5 or 10 minutes? Or is this too naive, and should I be using a database for instance. Or is there maybe a much easier way to keep track of such state with Zend_Mail_Storage_Abstract? Also, do I need to poll every IMAP folder? Or is everything accumulated when I poll INBOX? If you could shed some light on any of these matters, I'ld appreciate it. Thanks in advance.

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• Delphi: RTTI and TObjectList<TObject>

  - by conciliator

  Based on one answer to an earlier post, I'm investigating the possibility of the following design TChildClass = class(TObject) private FField1: string; FField2: string; end; TMyClass = class(TObject) private FField1: TChildClass; FField2: TObjectList<TChildClass>; end; Now, in the real world, TMyClass will have 10 different lists like this, so I would like to be able to address these lists using RTTI. However, I'm not interested in the other fields of this class, so I need to check if a certain field is some sort of TObjectList. This is what I've got so far: procedure InitializeClass(RContext: TRttiContext; AObject: TObject); var ROwnerType: TRttiType; RObjListType: TRttiType; RField: TRttiField; SchInf: TSchemaInfoDetail; begin ROwnerType := RContext.GetType(AObject.ClassInfo); RObjListType := RContext.GetType(TObjectList<TObject>); for RField in ROwnerType.GetFields do begin // How do I check if the type of TMyClass.FField2 (which is TObjectList<TChildClass>) is some sort of TObjectList? end; Clearly, RField.FieldType <> RObjListType.FieldType. However, they do have some relation, don't they? It seems horrible (and wrong!) to make a very elaborate check for common functionality in order to make it highly probable that RField.FieldType is in fact a TObjectList. To be honest, I am quite uncomfortable with generics, so the question might be very naïve. However, I'm more than happy to learn. Is the above solution possible to implement? TIA!

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• Design patter to keep track UITableView rows correspondance to underlying data in constant time.

  - by DenNukem

  When my model changes I want to animate changes in UITableView by inserting/deleting rows. For that I need to know the ordinal of the given row (so I can construct NSIndexPath), which I find hard to do in better-than-linear time. For example, consider that I have a list of addressbook entries which are manualy sorted by the user, i.e. there is no ordering "key" that represents the sort order. There is also a corresponding UITableView that shows one row per addressbook entry. When UITableView queries the datasource I query the NSMUtableArray populated with my entries and return required data in constant time for each row. However, if there is a change in underlying model I am getting a notification "Joe Smith, id#123 has been removed". Now I have a dilemma. A naive approach would be to scan the array, determine the index at which Joe Smith is and then ask UITableView to remove that precise row from the view, also removing it form the array. However, the scan will take linear time to finish. Now I could have an NSDictionary which allows me to find Joe Smith in constant time, but that doesn't do me a lot of good because I still need to find his ordinal index within the array in order to instruct UITableView to remove that row, which is again a linear search. I could further decide to store each object's ordinal inside the object itself to make it constant, but it will become outdated after first such update as all subsequent index values will have changed due to removal of an object. So what is the correct design pattern to accurately reflect model changes in the UITableView in costant (or at least logarithmic) time?

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• Extract known pattern substring from NSString (without regex)

  - by d11wtq

  I'm really tempted to drop RegexKit (or my own libpcre wrapper) into my project in order to do this, but before I do that I want to know how Cocoa developers manage to do half of this basic stuff without really convoluted code or without linking with RegexKit or another regular expression library. I find it gobsmacking that Cocoa does not include any regular expression matching features. I've so accustomed to using regular expressions for all kinds of things that I'm lost without them. I can do what I need without them, but the code would be rather convoluted. So, Cocoa devs, I ask you, what's the "Cocoa way" to do this... The problem is an everyday problem in programming as far as I'm concerned. Cocoa must have ways of doing this with the built-in features. Note that the position of the elements I want to match changes, and sometimes "quotes" are present. Whitespace is variable. Take the following strings: Content-Type: application/xml; charset=utf-8 Content-Type: text/html; charset="iso-8859-1" Content-Type: text/plain; charset=us-ascii Content-Type: text/plain; name="example.txt"; charset=utf-8 From all of these strings, how would you go about determining the mime type (e.g. text/plain) and the charset (e.g. utf-8) using just the built-in Cocoa classes? I'd end up performing a series of -rangeOfString: and substring calls, with conditional checks to deal with the optional quotes etc. Is there a way to do this with NSScanner? The NSScanner class seems to have a pretty naive API to me. Something like C's sscanf() that works for NSString objects would be an ideal fit. Most of my string parsing needs are simple such as this example so maybe regular expressions, while I'm accustomed to them, are overkill?

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• Natural language processing - Ideas for beginner's projects

  - by Microkernel

  Hi guys, I am a beginner in NLP and NLTK. I am very interested in NLP and hence joined a weekend course on AI in some local institution, which requires me to do a project for completion of the course, and I decided to do it in NLP. The problem is,the instructor is not good at all for this course (According to me she is just a charlatan) (or may not be very interested in teaching as this is her last batch here after which the institute is going to send her out). So I am stuck in a situation where where I got to finish this project in a month to one and half months period, but as a naive person in the field I am feeling it very difficult to comprehend the things required to decide on project. (Also, as I am working full time, I am not finding enough time to dedicate on this). I considered using NLTK toolkit in python for the project for following reasons. (1) Python is famous for ease of use, rapid prototyping and very active community (considering very short span of time I have, and as I am a C programmer by profession, I need a language that I can learn fast and is simple to use). (2) NLTk has good review, and extensive documentation and a very active community. So the problem is what project should I take up, so that I can learn something and will be able to finish project in time. (I know almost nothing in NLP, don't even know what exactly corpora is... :( ) So, please suggest me some topics that I should consider for the project. Regards, MicroKernel :)

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• Worse is better. Is there an example?

  - by J.F. Sebastian

  Is there a widely-used algorithm that has time complexity worse than that of another known algorithm but it is a better choice in all practical situations (worse complexity but better otherwise)? An acceptable answer might be in a form: There are algorithms A and B that have O(N**2) and O(N) time complexity correspondingly, but B has such a big constant that it has no advantages over A for inputs less then a number of atoms in the Universe. Examples highlights from the answers: Simplex algorithm -- worst-case is exponential time -- vs. known polynomial-time algorithms for convex optimization problems. A naive median of medians algorithm -- worst-case O(N**2) vs. known O(N) algorithm. Backtracking regex engines -- worst-case exponential vs. O(N) Thompson NFA -based engines. All these examples exploit worst-case vs. average scenarios. Are there examples that do not rely on the difference between the worst case vs. average case scenario? Related: The Rise of ``Worse is Better''. (For the purpose of this question the "Worse is Better" phrase is used in a narrower (namely -- algorithmic time-complexity) sense than in the article) Python's Design Philosophy: The ABC group strived for perfection. For example, they used tree-based data structure algorithms that were proven to be optimal for asymptotically large collections (but were not so great for small collections). This example would be the answer if there were no computers capable of storing these large collections (in other words large is not large enough in this case). Coppersmith–Winograd algorithm for square matrix multiplication is a good example (it is the fastest (2008) but it is inferior to worse algorithms). Any others? From the wikipedia article: "It is not used in practice because it only provides an advantage for matrices so large that they cannot be processed by modern hardware (Robinson 2005)."

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• Gridview empty when SelectedIndexChanged called

  - by xan

  I have a DataGrid which is being bound dynamically to a database query. The user enters some search text into a text field, clicks search, and the code behind creates the appropriate database query using LINQ (searches a table based on the string and returns a limited set of the columns). It then sets the GridView datasource to be the query and calls DataBind(). protected void btnSearch_Click(object sender, EventArgs e) { var query = from record in DB.Table where record.Name.Contains(txtSearch.Text) //Extra string checking etc. removed. select new { record.ID, record.Name, record.Date }; gvResults.DataSource = query; gvResults.DataBind(); } This works fine. When a user selects a row in the grid, the SelectedIndexChanged event handler gets the id from the row in the grid (one of the fields), queries the full record from the DB and then populates a set of editor / details fields with the records full details. protected void gvResults_SelectedIndexChanged(object sender, EventArgs e) { int id = int.Parse(gvResults.SelectedRow.Cells[1].Text); DisplayDetails(id); } This works fine on my local machine where I'm developing the code. On the production server however, the function is called successfully, but the row and column count on gvResults, the GridVeiw is 0 - the table is empty. The GridView's viewstate is enabled and I can't see obvious differences. Have I made some naive assumptions, or am I relying on something that is likely to be configured differently in debug? Locally I am running an empty asp.net web project in VS2008 to make development quicker. The production server is running the sitecore CMS so is configured rather differently. Any thoughts or suggestions would be most welcome. Thanks in advance!

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• How to determine the (natural) language of a document?

  - by Robert Petermeier

  I have a set of documents in two languages: English and German. There is no usable meta information about these documents, a program can look at the content only. Based on that, the program has to decide which of the two languages the document is written in. Is there any "standard" algorithm for this problem that can be implemented in a few hours' time? Or alternatively, a free .NET library or toolkit that can do this? I know about LingPipe, but it is Java Not free for "semi-commercial" usage This problem seems to be surprisingly hard. I checked out the Google AJAX Language API (which I found by searching this site first), but it was ridiculously bad. For six web pages in German to which I pointed it only one guess was correct. The other guesses were Swedish, English, Danish and French... A simple approach I came up with is to use a list of stop words. My app already uses such a list for German documents in order to analyze them with Lucene.Net. If my app scans the documents for occurrences of stop words from either language the one with more occurrences would win. A very naive approach, to be sure, but it might be good enough. Unfortunately I don't have the time to become an expert at natural-language processing, although it is an intriguing topic.

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• Android HttpPost: how to get the result

  - by Sumit M Asok

  I have been trying long to send an HttpPost request and retrieve response but even though I was able to make a connection I don't yet get how to get the string message which is returned by the request-response HttpClient httpclient = new DefaultHttpClient(); HttpPost httppost = new HttpPost("http://www.myurl.com/app/page.php"); // Add your data List<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>(5); nameValuePairs.add(new BasicNameValuePair("type", "20")); nameValuePairs.add(new BasicNameValuePair("mob", "919895865899")); nameValuePairs.add(new BasicNameValuePair("pack", "0")); nameValuePairs.add(new BasicNameValuePair("exchk", "1")); try { httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs)); Log.d("myapp", "works till here. 2"); try { HttpResponse response = httpclient.execute(httppost); Log.d("myapp", "response " + response.getEntity()); } catch (ClientProtocolException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } } catch (UnsupportedEncodingException e) { e.printStackTrace(); } I'm sorry, I sound very naive because I'm new to java. Please help me.

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• Multiplication algorithm for abritrary precision (bignum) integers.

  - by nn

  Hi, I'm writing a small bignum library for a homework project. I am to implement Karatsuba multiplication, but before that I would like to write a naive multiplication routine. I'm following a guide written by Paul Zimmerman titled "Modern Computer Arithmetic" which is freely available online. On page 4, there is a description of an algorithm titled BasecaseMultiply which performs gradeschool multiplication. I understand step 2, 3, where B^j is a digit shift of 1, j times. But I don't understand step 1 and 3, where we have A*b_j. How is this multiplication meant to be carried out if the bignum multiplication hasn't been defined yet? Would the operation "*" in this algorithm just be the repeated addition method? Here is the parts I have written thus far. I have unit tested them so they appear to be correct for the most part: The structure I use for my bignum is as follows: #define BIGNUM_DIGITS 2048 typedef uint32_t u_hw; // halfword typedef uint64_t u_w; // word typedef struct { unsigned int sign; // 0 or 1 unsigned int n_digits; u_hw digits[BIGNUM_DIGITS]; } bn; Currently available routines: bn *bn_add(bn *a, bn *b); // returns a+b as a newly allocated bn void bn_lshift(bn *b, int d); // shifts d digits to the left, retains sign int bn_cmp(bn *a, bn *b); // returns 1 if a>b, 0 if a=b, -1 if a<b

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