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• "Unable to create OpenGL 3.3 context (flags 0, profile 1)"

  - by Tsvetan

  Trying to run any of the well-known McKesson's tutorials on a friend's laptop results in the aforementioned exception. I read that in order to run applications which use OpenGL 3.3 you must at least have an ATI HD or Nvidia 8xxx GPU series. He has an ATI HD class graphics processor which eliminates (maybe) this issue. Also, I read that this error may result in having old drivers. He updated his drivers but that didn't solve the problem. The tutorials are built as said in the book introduction and glsdk is installed. If more information is needed, say so and I will provide it. What are the other reasons for this kind of exception? And how can I fix them?

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• Is throwing an error in unpredictable subclass-specific circumstances a violation of LSP?

  - by Motti Strom

  Say, I wanted to create a Java List<String> (see spec) implementation that uses a complex subsystem, such as a database or file system, for its store so that it becomes a simple persistent collection rather than an basic in-memory one. (We're limiting it specifically to a List of Strings for the purposes of discussion, but it could extended to automatically de-/serialise any object, with some help. We can also provide persistent Sets, Maps and so on in this way too.) So here's a skeleton implementation: class DbBackedList implements List<String> { private DbBackedList() {} /** Returns a list, possibly non-empty */ public static getList() { return new DbBackedList(); } public String get(int index) { return Db.getTable().getRow(i).asString(); // may throw DbExceptions! } // add(String), add(int, String), etc. ... } My problem lies with the fact that the underlying DB API may encounter connection errors that are not specified in the List interface that it should throw. My problem is whether this violates Liskov's Substitution Principle (LSP). Bob Martin actually gives an example of a PersistentSet in his paper on LSP that violates LSP. The difference is that his newly-specified Exception there is determined by the inserted value and so is strengthening the precondition. In my case the connection/read error is unpredictable and due to external factors and so is not technically a new precondition, merely an error of circumstance, perhaps like OutOfMemoryError which can occur even when unspecified. In normal circumstances, the new Error/Exception might never be thrown. (The caller could catch if it is aware of the possibility, just as a memory-restricted Java program might specifically catch OOME.) Is this therefore a valid argument for throwing an extra error and can I still claim to be a valid java.util.List (or pick your SDK/language/collection in general) and not in violation of LSP? If this does indeed violate LSP and thus not practically usable, I have provided two less-palatable alternative solutions as answers that you can comment on, see below. Footnote: Use Cases In the simplest case, the goal is to provide a familiar interface for cases when (say) a database is just being used as a persistent list, and allow regular List operations such as search, subList and iteration. Another, more adventurous, use-case is as a slot-in replacement for libraries that work with basic Lists, e.g if we have a third-party task queue that usually works with a plain List: new TaskWorkQueue(new ArrayList<String>()).start() which is susceptible to losing all it's queue in event of a crash, if we just replace this with: new TaskWorkQueue(new DbBackedList()).start() we get a instant persistence and the ability to share the tasks amongst more than one machine. In either case, we could either handle connection/read exceptions that are thrown, perhaps retrying the connection/read first, or allow them to throw and crash the program (e.g. if we can't change the TaskWorkQueue code).

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• CentOS / Redhat: Give file permission for apache and vsftp

  - by paskster

  I use CentOS 5.5 and Apache Webserver on my dedicated Server. My Folder "/var/www/myWebApp" is owned by apache, so that apache can read, write logs, etc.. But now I would like to use very secure FTP (vsftp) to upload my new files. I used to give every user rwx -Acess to "/var/www/myWebApp", but I guess this is way to insecure. On CentOS I created another user "ftpuser" for uploading files and that has "/var/www/myWebApp" as its home directory. How can I give him the permission to write into the "/var/www/myWebApp" without giving every user the same rights?

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• C++ and function pointers assessment: lack of inspiration

  - by OlivierDofus

  I've got an assessment to give to my students. It's about C++ and function pointers. Their skill is middle: it the first year of a programming school after bachelor. To give you something precise, here's a sample of a solution of one of 3 exercices they had to do in 30 minutes (the question was: "here's a version of a code that could be written with function pointers, write down the same thing but with function pointers"): typedef void (*fcPtr) (istream &); fcPtr ArrayFct [] = { Delete , Insert, Swap, Move }; void HandleCmd (const string && Cmd) { string AvalaibleCommands ("DISM"); string::size_type Pos; istringstream Flux (Cmd); char CodeOp; Flux >> CodeOp; Pos = AvalaibleCommands.find (toupper (CodeOp)); if (Pos != string::npos) { ArrayFct [Pos](Flux); } } Any idea where I could find some inspiration? Some of the students have understood the principles, even though it's very hard for them to write C++ code. I know them, I know they're clever, and I'm pretty sure they should be very good project managers. So, writing C++ code is not that important after all. Understanding is the most important part (IMHO). I'm wondering about maybe break the habits, and give half of the questions about the principle, or even better, give some sample in other language and ask them why it's better to use function pointers instead of classical programming (usually a big switch case). Any idea where I could look? Find some inspiration?

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• White Paper on Parallel Processing

  - by Andrew Kelly

    I just ran across what I think is a newly published white paper on parallel  processing in SQL Server 2008 R2. The date is October 2010 but this is the first time I have seen it so I am not 100% sure how new it really is. Maybe you have seen it already but if not I recommend taking a look. So far I haven’t had time to read it extensively but from a cursory look it appears to be quite informative and this is one of the areas least understood by a lot of dba’s. It was authored by Don Pinto...(read more)

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• Pair Programming: Pros and Cons

  - by O.D

  Hi I need some experience reporting from the ones who have done pair programming,i notice that lots of people recommend that but my experience was that at one point its more efficient to set alone, think and then write code than to talk with the other programmer (which can be very annoying to other programmers in the same office), do you agree to this? and if yes can you mention situations where pair programing is less efficient than traditional programing? Actually im more interested in Cons than in Pros, but if its your own experience i would like to read both, the Cons and the Pros. I would like to read what you think about the Programmer who does'nt have the keyboard, what can he do in the meanwhile other than talking about the concept? or checking the code on the screen? Thank you

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• Guaranteeing ACID properties for InnoDB databases.

  - by plinehan

  What steps must one take to ensure that an otherwise defaultly-configured InnoDB server is truly ACID compliant? The InnoDB configuration page mentions that the hardware itself must be configured to honor fsync calls, i.e. disable any write-back caches. This page mentions some other concerns, but may be conflating the binary log and the InnoDB log, and may be a bit out of date regarding default settings for MySQL 5.x. Upon reading the binary log document page it would seem that the "sync_binlog=1" setting is not required for ACID properties in general, only for ACID properties vis a vis point-in-time recovery and replication. So, is disabling write-back disk caching sufficient, or are there other settings that must be tweaked?

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• What are the cons of using DrawableGameComponent for every instance of a game object?

  - by Kensai

  I've read in many places that DrawableGameComponents should be saved for things like "levels" or some kind of managers instead of using them, for example, for characters or tiles (Like this guy says here). But I don't understand why this is so. I read this post and it made a lot of sense to me, but these are the minority. I usually wouldn't pay too much attention to things like these, but in this case I would like to know why the apparent majority believes this is not the way to go. Maybe I'm missing something.

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• Recommendations for USB flash drive fast at writing small files

  - by Andrew Bainbridge

  I want a drive that I can be used as my work drive, storing a Subversion repo and sandbox for a small project. I'd also like it to be able to store a DVD rip. At the moment I've got a Super Talent pico-C 8gb. It's fast at reading and writing DVD rips, but the performance on small files (ie less than 4k) is utterly terrible (we're talking floppy disk speeds here). This Ars review measured a similar Super Talent drive and pretty much confirmed my measurements (take a look at the random write speeds on page 5). So, I'm looking for a 8gb or bigger drive that doesn't suck at read and write of small files and still has acceptable performance for very large files.

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• Mimic NTFS "Modify" Permissions on an ext3 acl enabled filesystem in linux?

  - by bobinabottle

  I am migrating our file share from Windows Server to Samba on Linux, and the only hurdle I have at the moment is the acl's. Currently we have a number of directories that use the "Modify" permission on NTFS, so users can write to a directory, but once the file is written it cannot be modified. On Linux, I had the idea that I would set an ACL for the directory to have read/write access, but have a default ACL associated with read only access. Is this possible? I'm not quite sure how to set a default ACL that differs from the parent directory. Thanks!

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• Pair Programming: Pros and Cons

  - by O.D

  I need some experience reporting from the ones who have done pair programming, I noticed that lots of people recommend it but my experience was that at one point it's more efficient to sit alone, think and then write code than to talk with the other programmer (which can be very annoying to other programmers in the same office), do you agree to this? and if yes can you mention situations where pair programming is less efficient than traditional programming? Actually, I'm more interested in Cons than in Pros, but if it's your own experience I would like to read both, the Cons and the Pros. I would like to read what you think about the Programmer who doesn't have the keyboard, what can he do in the meanwhile other than talking about the concept? or checking the code on the screen?

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• links for 2011-01-04

  - by Bob Rhubart

  Webcasts (tags: ping.fm) Five Key Trends in Enterprise 2.0 for 2011 (Oracle Enterprise 2.0 Blog) Kellsey Ruppel shares insight from Oracle's Andy MacMillan. (tags: oracle otn enterprise2.0) Victor Bax: Lost in Service Oriented Architecture? "SOA is a concept, no more, no less. SOA is not a technology, or a piece of software. It is an architecture, a model." - Victor Bax (tags: oracle soa) Jan-Leendert: Oracle 11g SOA Suite read multi record data from csv file with the file adapter (master-detail) "The file adapter is a very powerlful tool to read files with structured data. Most of the time you will read simple csv files with one record per row. But what if your csv file contains multiple records with different types?" - Jan-Leendert (tags: oracle soa soasuite) @myfear: Five ways to know how your data looked in the past. Entity Auditing. "Whatever requirements you have. I can promise you, that it will never be a simple solution. In general it's best to evaluate your purpose for auditing in detail." - Oracle ACE Director Markus Eisele (tags: oracle otn oracleace java) @fteter: Buffing Up The Crystal Ball "While I'm already tired of seeing these types of posts (I'm writing on New Year's Day), I'm also feeling guilty about not making my own set of predictions." - Oracle ACE Director Floyd Teter (tags: oracle otn oracleace ec2 cloud fusionmiddleware) @bex: ECM New Year's Resolutions "Happy new year! Most people use the first post of the year to go over their own blog statistics of popular posts... but since my blog's fiscal year ends in April, I decided to do new years resolutions instead." - Oracle ACE Director Bex Huff (tags: oracle otn oracleace ecm enterprise2.0) Izaak de Hullu: Embedded Java in a 11g BPEL process "In an earlier blog my colleague Peter Ebell explained how you can create an extension of com.collaxa.cube.engine.ext.BPELXExecLet to do your coding in a regular Java environment so you have code completion and validation..." - Izaak de Hullu (tags: oracle otn bpel java soa) @gschmutz: Cannot access EM console after installing SOA Suite 11g PS2 Oracle ACE Director Guido Schmutz encounters a problem and shares the solution. (tags: oracle otn oracleace soa soasuite)

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• Nearly technical books that you enjoyed reading

  - by pablo

  I've seen questions about "What books you recommend" in several of the Stack Exchange verticals. Perhaps these two questions (a and b) are the most popular. But, I'd like to ask for recommendations of a different kind of books. I have read in the past "The Passionate Programmer" and I am now reading "Coders at Work". Both of them I would argue that are almost a biography (or biographies in the "Coders at work") or even a bit of "self-help" book (that is more the case of the "Passionate programmer"). And please don't get me wrong. I loved reading the first one, and I am loving reading the second one. There's a lot of value in it, mostly in "lessons of the trade" kind of way. So, here is what I'd like to know. What other books that you read that are similar to these ones in intent that you enjoyed? Why?

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• LibGdx efficient data saving/loading?

  - by grimrader22

  Currently, my LibGDX game consists of a 512 x 512 map of Tiles and entities such as players and monsters. I am wondering how to efficiently save and load the data of my levels. At the moment I am using JSON serialization for each class I want to save. I implement the Json.Serializable interface for all of these classes and write only the variables that are necessary. So my map consists of 512 x 512 tiles, that's 260,000 tiles. Each tile on the map consists of a Tile object, which points to some final Tile object like a GRASS_TILE or a STONE_TILE. When I serialize each level tile, the final Tile that it points to is re-serialized over and over again, so if I have 100 Tiles all pointing to GRASS_TILE, the data of GRASS_TILE is written 100 times over. When I go to load/deserialize my objects, 100 GrassTile objects are created, but they are each their own object. They no longer point to the final tile object. I feel like this reading/writing files very slow. If I were to abandon JSON serialization, to my knowledge my next best option would be saving the level data to a sql database. Unless there is a way to speed up serializing/deserializing 260,000 tiles I may have to do this. Is this a good idea? Could I really write that many tiles to the database efficiently? To sum all this up, I am trying to save my levels using JSON serialization, but it is VERY slow. What other options do I have for saving the data of so many tiles. I also must note that the JSON serialization is not slow on a PC, it is only VERY slow on a mobile device. Since file writing/reading is so slow on mobile devices, what can I do?

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• Why does this script not open parallel gnome-terminals on a server?

  - by broiyan

  Why am I not able to have parallel gnome-terminals on my server while I can on my client. Here is a test that illustrates the problem. #!/bin/bash # this is the parent script gnome-terminal --command "./left.sh" sleep 10 gnome-terminal --command "./right.sh" #!/bin/bash echo "this is the left script" read -p "press any key to close this terminal" key #!/bin/bash echo "this is the right script" read -p "press any key to close this terminal" key When I run this on a regular ubuntu desktop (maverick) I see two terminals after 10 seconds. When I run this on a maverick server at a server farm, the second window does not appear until after I close the first one and wait 10 seconds. I am using tightvncserver to view the server desktop. (I could have simplified a bit more. The 10 second sleep is extraneous to the problem. In my real world application I need the first terminal to do some real work before starting the second. The problem probably still exists even if there is no sleep.)

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• How to shorten brain context switch delay when need to use new technology\framework?

  - by gasan

  The problem is when I have to deal with a new framework\library\language it completely slows my work process, at first it's kind of shock, you're sitting on your place about a day doing nothing surfing the net, because you simply can't do anything even read docs, then, on the second day I realize that I definitely should do something and starting read about it, then I realize that I don't understand it, then I'm reading until I got feeling that I should show some results immediately and then I'm writing the code quite fast and the job doesn't seem to be difficult. Then job is done and I won't probably return to that technology\framework for a month or a year or never at all. And I will almost certainly forget almost everything about it after a month. To illustrate by checkpoints I experience: shock, long studying times, work with the new tech briefly, never use it afterwards, then I completely forget it. So what would be the solution here?

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• Log rotation with automatic *.log file discovery

  - by Mikko Ohtamaa

  I am hosting several websites which each of run their own Python process and write *.log output files, but the directory structure is not standardized. Example: -rw-r--r-- 1 plone plone 125M 2012-08-29 11:35 ./x/var/log/instance-Z2.log -rw-r--r-- 1 plone plone 19M 2012-08-29 00:07 ./zope2.9/y/log/event.log -rw-r--r-- 1 plone plone 188M 2012-08-13 00:09 ./zope2.9/y/log/Z2.log -rw-r--r-- 1 plone plone 137M 2010-11-16 09:41 ./zope2.9/y/log/event.log I'd like to make log rotate autodiscovery these log files and run a log rotation on them, as opposite to manually type in every log file to logrotate conf. Does any existing tools offer this kind of log file discovery and rotation capabilities, without manually specifying each file? If not... then just write a shell script which generates the logrotate conf?

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• How did programmers resolve their problems before the internet?

  - by 9a3eedi

  When programming, anytime I get stuck, perhaps with a compiler error that doesn't make sense, or from a GUI function that didn't do what I expected, I automatically google my problem, find someone else that faced the same thing, and read what's going on and why I'm getting the problem. Before the internet, how did people handle these situations? People used to read books and manuals more, I know. But books don't explain everything, like the odd compiler problem that you get sometimes, or nothing showing up on your screen despite you clearly writing correct OpenGL code. How did people cope when facing challenges? Did they simply "bash their head" on the wall till they figured it out? Is there something people used to do regularly on the side that gave them the ability to get themselves unstuck more easily? Were libraries/compilers much simpler back then? I've been asking this question because I sometimes feel guilty depending on Google so much when I'm pretty sure programmers before my time were more independent when it comes to facing these matters.

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• Now you know it's true !

  - by GrumpyOldDBA

  Grumpy is good - official !! http://news.bbc.co.uk/1/hi/8339647.stm...(read more)

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• Mounting FTP as filesystem in debian using curlftpfs

  - by Karel Bílek

  I am trying to mount a FTP as filesystem in debian using curlftpfs. What I get after running curlftpfs -o allow_other username:[email protected] /mnt/myftp/ is just: fuse: failed to open /dev/fuse: Permission denied even when run as root. What am I doing wrong? (curlftpfs is in version curlftpfs 0.9.2 libcurl/7.21.0 fuse/2.8) edit: When I write ls -lah /dev/fuse, I see crw-rw---- 1 root fuse 10, 229 Apr 9 00:34 /dev/fuse ...but even when I add both myself and user root to group fuse, neither me (as a user) or user root can mount ftp, I still see fuse: failed to open /dev/fuse: Permission denied edit2: Even if I write this fairly insecure and crazy line: sudo chmod a+rwx /dev/fuse I still get the permission denied message. Which permissions could be denied? edit3: I forgot to mention I am on VPS with OpenVZ. I thought that there is no issue with this, but apparently, there is! I am adding the resolution as the answer.

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• Aptana Ext code completion in .php files

  - by Frederik Wordenskjold

  I'm having problems getting the code-completion for the Ext 3.2 plugin to work, when working with .php files. I've also installed the php plugin for Aptana, and the same thing applies for php - I cannot access php code-completion when working with a html-file, so it seems like a general issue... It's also not possible to write Ext in .js files, which is weird... The latter case does make sense of course. But I should be able to write both php and Ext in .php files! Is this possible in any way? I have of course tested the code-completion for php in a .php file, which works. The same applies for Ext code in .html documents!

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• Office 2011 Mac - Unable to save Word files, plus normal.dot alert errors

  - by Jeff D

  There are actually 3 errors here. When I open Word, I get: Word cannot open the existing global template. () If I create a file, type a character and try to save to the desktop (that I have no problems writing to otherwise), I get: Word cannot save or create this file. The disk may be full or write-protected. Try one or more of the following: * Free more memory * Make sure that the disk you want to save the file on is not full, write-protected, or damaged. () I am just saving to the desktop, and I can save excel files (or anything else) there. After the failure, if I save again, the default file name becomes: .doc...doc Weird. Finally, when I close word completely, I get: Do you want to replace the existing Normal.dotm.

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• What are some easy techniques to scan books for new information?

  - by aditya menon

  I find it irresistible to keep purchasing cheap programming and technical e-books in fields such as Drupal, PHP, etc., and also compulsively download free material made available such as those from Microsoft's developer blog... The main problem with the large library I've developed is that there are many chapters (especially the first few) in these books packed with information I already know, but with helpful tidbits hidden in between. The logical step would be to skip those chapters and read the ones I don't seem to know anything about, but I'm afraid I may lose out on really important information this way. But naturally it is tedious to have to read about variables, functions and objects all over again when you are trying to know more about the Registry pattern, for example. It's hard to research on the net for this, because my question itself seems vague and difficult to formulate into a single search query. I need people-advice - what do you do in this situation?

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• sending notification mail to users for password expiry on linux server

  - by pavan

  how to write a script in linux BASH shell for sending mails to users for warning about the password expiry before 2 weeks.

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• Should I pick up a functional programming language?

  - by Statement

  I have recently been more concerned about the way I write my code. After reading a few books on design patterns (and overzealous implementation of them, I'm sure) I have shifted my thinking greatly toward encapsulating that which change. I tend to notice that I write less interfaces and more method-oriented code, where I love to spruce life into old classes with predicates, actions and other delegate tasks. I tend to think that it's often the actions that change, so I encapsulate those. I even often, although not always, break down interfaces to a single method, and then I prefer to use a delegate for the task instead of forcing client code to create a new class. So I guess it then hit me. Should I be doing functional programming instead? Edit: I may have a misconception about functional programming. Currently my language of choice is C#, and I come from a C++ background. I work as a game developer but I am currently unemployed. I have a great passion for architecture. My virtues are clean, flexible, reusable and maintainable code. I don't know if I have been poisoned by these ways or if it is for the better. Am I having a refactoring fever or should I move on? I understand this might be a question about "use the right tool for the job", but I'd like to hear your thoughts. Should I pick up a functional language? One of my fear factors is to leave the comfort of Visual Studio.

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