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• Why is C++ often the first language taught in college?

  - by Casey Patton

  My school starts the computer science curriculum with C++ programming courses, meaning this is the first language that many of the students learn. I've seen that many people dislike C++, and I've read a variety of reasons why. It almost seems to be popular opinion that C++ isn't a very good language. I get the impression it's not very liked based on some questions on StackExchange as well as posts such as: http://damienkatz.net/2004/08/why-c-sucks.html http://blogs.kde.org/node/2298 http://blogs.cio.com/esther_schindler/linus_torvalds_why_c_sucks http://www.dacris.com/blog/2010/02/16/why-c-sucks-part-2/ etc. (Note: It is not my opinion that C++ is a bad language. In fact, it's the main language I use. However, the internet as well as some professors have given me the impression that it's not a very widely liked language. In fact, one of my professor constantly rags on C++, yet it's still the starting language at my college!) With that in mind, why is this the first language taught at many schools? What are the reasons for starting a programming curriculum with C++? Note: This question is similar to "Is C++ suitable as a first language", but is a little different since I'm not interested in whether it's suitable, but why it's been chosen.

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• Music While Coding [closed]

  - by inspectorG4dget

  Hi SO, Generally, while I'm coding, I prefer to listen to some background music. Nothing that'll get me distracted, but something that'll help keep the rhythm and isn't counterproductive when I need to stop coding to debug or to think of a way to solve a small problem that stands in the way of progress. Now, I have read some similar questions on reddit and on SO - specifically: which songs do you find most productive to listen to while coding, Music while programming and more. Sadly a lot of these questions were closed as off-topic, etc. But (1) I don't think this question is off-topic and I think that a lot of programmers can benefit from it. (2) It's a real question. I really want to know what music you guys would recommend because music helps when I'm coding. It's sad that SO: Music to listen to while coding cannot be found and this isn't of much help. I hope this doesn't get closed. PS: I want to turn this into a community wiki, but I don't seem to know how. I'd appreciate any help. Thank you, all. In response to kirk.burleson's comment: In case the question isn't already clear, I'm asking for recommendations/opinions of music to listen to while coding. I would like to know what you listen to when you code so that I can try it too. I am running out of good "coding music" and this is a problem for me because good "coding music" helps me code better.

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• Rails: Law of Demeter Confusion

  - by user2158382

  I am reading a book called Rails AntiPatterns and they talk about using delegation to to avoid breaking the Law of Demeter. Here is their prime example: They believe that calling something like this in the controller is bad (and I agree) @street = @invoice.customer.address.street Their proposed solution is to do the following: class Customer has_one :address belongs_to :invoice def street address.street end end class Invoice has_one :customer def customer_street customer.street end end @street = @invoice.customer_street They are stating that since you only use one dot, you are not breaking the Law of Demeter here. I think this is incorrect, because you are still going through customer to go through address to get the invoice's street. I primarily got this idea from a blog post I read: http://www.dan-manges.com/blog/37 In the blog post the prime example is class Wallet attr_accessor :cash end class Customer has_one :wallet # attribute delegation def cash @wallet.cash end end class Paperboy def collect_money(customer, due_amount) if customer.cash < due_ammount raise InsufficientFundsError else customer.cash -= due_amount @collected_amount += due_amount end end end The blog post states that although there is only one dot customer.cash instead of customer.wallet.cash, this code still violates the Law of Demeter. Now in the Paperboy collect_money method, we don't have two dots, we just have one in "customer.cash". Has this delegation solved our problem? Not at all. If we look at the behavior, a paperboy is still reaching directly into a customer's wallet to get cash out. EDIT I completely understand and agree that this is still a violation and I need to create a method in Wallet called withdraw that handles the payment for me and that I should call that method inside the Customer class. What I don't get is that according to this process, my first example still violates the Law of Demeter because Invoice is still reaching directly into Customer to get the street. Can somebody help me clear the confusion. I have been searching for the past 2 days trying to let this topic sink in, but it is still confusing.

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• Is `break` and `continue` bad programming practice?

  - by Mikhail

  My boss keeps mentioning nonchalantly that bad programmers use break and continue in loops. I use them all the time because they make sense; let me show you the inspiration: function verify(object) { if (object->value < 0) return false; if (object->value > object->max_value) return false; if (object->name == "") return false; ... } The point here is that first the function checks that the conditions are correct, then executes the actual functionality. IMO same applies with loops: while (primary_condition) { if (loop_count > 1000) break; if (time_exect > 3600) break; if (this->data == "undefined") continue; if (this->skip == true) continue; ... } I think this makes it easier to read & debug; but I also don't see a downside. Please comment.

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• Dependency injection: what belongs in the constructor?

  - by Adam Backstrom

  I'm evaluating my current PHP practices in an effort to write more testable code. Generally speaking, I'm fishing for opinions on what types of actions belong in the constructor. Should I limit things to dependency injection? If I do have some data to populate, should that happen via a factory rather than as constructor arguments? (Here, I'm thinking about my User class that takes a user ID and populates user data from the database during construction, which obviously needs to change in some way.) I've heard it said that "initialization" methods are bad, but I'm sure that depends on what exactly is being done during initialization. At the risk of getting too specific, I'll also piggyback a more detailed example onto my question. For a previous project, I built a FormField class (which handled field value setting, validation, and output as HTML) and a Model class to contain these fields and do a bit of magic to ease working with fields. FormField had some prebuilt subclasses, e.g. FormText (<input type="text">) and FormSelect (<select>). Model would be subclassed so that a specific implementation (say, a Widget) had its own fields, such as a name and date of manufacture: class Widget extends Model { public function __construct( $data = null ) { $this->name = new FormField('length=20&label=Name:'); $this->manufactured = new FormDate; parent::__construct( $data ); // set above fields using incoming array } } Now, this does violate some rules that I have read, such as "avoid new in the constructor," but to my eyes this does not seem untestable. These are properties of the object, not some black box data generator reading from an external source. Unit tests would progressively build up to any test of Widget-specific functionality, so I could be confident that the underlying FormFields were working correctly during the Widget test. In theory I could provide the Model with a FieldFactory() which could supply custom field objects, but I don't believe I would gain anything from this approach. Is this a poor assumption?

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• Documenting mathematical logic in code

  - by Kiril Raychev

  Sometimes, although not often, I have to include math logic in my code. The concepts used are mostly very simple, but the resulting code is not - a lot of variables with unclear purpose, and some operations with not so obvious intent. I don't mean that the code is unreadable or unmaintainable, just that it's waaaay harder to understand than the actual math problem. I try to comment the parts which are hardest to understand, but there is the same problem as in just coding them - text does not have the expressive power of math. I am looking for a more efficient and easy to understand way of explaining the logic behind some of the complex code, preferably in the code itself. I have considered TeX - writing the documentation and generating it separately from the code. But then I'd have to learn TeX, and the documentation will not be in the code itself. Another thing I thought of is taking a picture of the mathematical notations, equations and diagrams written on paper/whiteboard, and including it in javadoc. Is there a simpler and clearer way? P.S. Giving descriptive names(timeOfFirstEvent instead of t1) to the variables actually makes the code more verbose and even harder too read.

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• Samba new file ownership, permissions configuration

  - by Martin Melka

  I have recently installed Samba on my server. Now I have a question about permissions and how to set it up. Currently I mount the Samba shared drive to my laptop with this line in /etc/fstab: //<host>/share /mnt/melka-server-data/ cifs username=<usrname> password=<passwd> _netdev 0 0 This works, as I can read from the files and create them (as root). The problem is when I want to create files as a regular user. I always get a Permission Denied error. These are ll outputs of the mounted folder: magicmaster@magicmaster-kubuntu:/mnt$ ll total 8 drwxr-xr-x 3 root root 4096 lis 11 14:15 ./ drwxr-xr-x 26 root root 4096 ríj 26 11:01 ../ drwxrwxrwx 8 magicmaster magicmaster 0 lis 12 22:12 melka-server-data/ and the inside: magicmaster@magicmaster-kubuntu:/mnt/melka-server-data$ ll total 4 drwxrwxrwx 8 magicmaster magicmaster 0 lis 12 22:12 ./ drwxr-xr-x 3 root root 4096 lis 11 14:15 ../ drwxrwxrwx 5 magicmaster magicmaster 0 lis 12 09:35 downloads/ drwxrwxrwx 2 magicmaster magicmaster 0 ríj 28 12:57 lost+found/ drwxrwxrwx 15 magicmaster magicmaster 0 lis 12 09:45 movies/ drwxrwxrwx 2 magicmaster magicmaster 0 lis 1 21:15 newest/ drwxrwxrwx 3 magicmaster magicmaster 0 lis 2 23:14 photos/ drwxrwxrwx 2 magicmaster magicmaster 0 ríj 30 12:44 software/ -rw-r--r-- 1 nobody nogroup 0 lis 12 22:12 zdar I called sudo chown -R magicmaster:magicmaster melka-server-data/ to try and change all the files to belong to me. Then the file zdar was created by magicmaster just by calling touch. I got the Permission Denied, but it was still created, though it belongs to nobody and I can't write into it. When I create a file as root, it still belongs to nobody, but at least I can write into it. What am I missing? I didn't notice anything in Samba config that would be related to this and I don't like the idea of having to log on as root in order to copy files.. Thanks

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• The Twelve Days of Geekmas

  - by YatriTrivedi

  Looking for some last minute shopping for your favorite geek? We put a few holiday shopping items into the form of a song to show off just how geeky your Christmas can be. Make sure that you read through the list to the tune of the Twelve Days of Christmas. Yes, we’re really being silly today. Have fun! Image by dawolf On the twelfth day of Geekmas, a dear friend gave to me… Latest Features How-To Geek ETC The Complete List of iPad Tips, Tricks, and Tutorials The 50 Best Registry Hacks that Make Windows Better The How-To Geek Holiday Gift Guide (Geeky Stuff We Like) LCD? LED? Plasma? The How-To Geek Guide to HDTV Technology The How-To Geek Guide to Learning Photoshop, Part 8: Filters Improve Digital Photography by Calibrating Your Monitor The Brothers Mario – Epic Gangland Style Mario Brothers Movie Trailer [Video] Score Awesome Games on the Cheap with the Humble Indie Bundle Add a Colorful Christmas Theme to Your Windows 7 Desktop This Windows Hack Changes the Blue Screen of Death to Red Edit Images Quickly in Firefox with Pixlr Grabber Zoho Writer, Sheet, and Show Now Available in Chrome Web Store

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• YouTube: Chrome Dev Tools Integration with NetBeans IDE!

  - by Geertjan

  Some time ago my colleague David Konecny discussed the question "What works better for you? NetBeans IDE or Chrome Developer Tools?". It's a good read. David highlights the point that it's not a question of either/or but both, since the two tools are like the apple/pear dichotmoy. However, good news! The two worlds are not divided in NetBeans IDE 7.4. Changes you make in Chrome Developer Tools (CDT) are automatically persisted to the related files in NetBeans IDE, as you can see in a new YouTube clip I made today. The new integration of CDT with NetBeans IDE has been mentioned in the NetBeans IDE 7.4 New & Noteworthy, while on Twitter this was sighted yesterday: Watch the movie above and within 5 minutes you too will see the simplicity and power of CDT integration with NetBeans IDE. In other news. I consider the above to be my favorite (though it's a tough choice, since there are so many new features in NetBeans IDE 7.4) new feature, for the article "What is your favorite new NetBeans IDE 7.4 feature?"

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• Another guvcview issue? Core dump!

  - by user290498

  guvcview is core dumping with my Sony Handycam plugged in. It works fine with my standard Logitech Webcam. I deleted the config file so it could re-create it. here is the output: $ guvcview guvcview 1.5.3 Could not open /home/rayj/.guvcviewrc for read, will try to create it write /home/rayj/.guvcviewrc OK ALSA lib pcm.c:2217:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.rear ALSA lib pcm.c:2217:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.center_lfe ALSA lib pcm.c:2217:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.side ALSA lib audio/pcm_bluetooth.c:1614:(audioservice_expect) BT_GET_CAPABILITIES failed : Input/output error(5) ALSA lib audio/pcm_bluetooth.c:1614:(audioservice_expect) BT_GET_CAPABILITIES failed : Input/output error(5) ALSA lib audio/pcm_bluetooth.c:1614:(audioservice_expect) BT_GET_CAPABILITIES failed : Input/output error(5) ALSA lib audio/pcm_bluetooth.c:1614:(audioservice_expect) BT_GET_CAPABILITIES failed : Input/output error(5) ALSA lib pcm_dmix.c:957:(snd_pcm_dmix_open) The dmix plugin supports only playback stream Cannot connect to server socket err = No such file or directory Cannot connect to server socket jack server is not running or cannot be started video device: /dev/video0 ERROR opening V4L2 interface for /dev/video1 Init. stk1160 (location: usb-0000:00:1d.0-1.5) { pixelformat = 'UYVY', description = '16 bpp YUY2, 4:2:2, packed' } VIDIOC_ENUM_FRAMESIZES - Error enumerating frame sizes: Inappropriate ioctl for device Unable to enumerate frame sizes. : Inappropriate ioctl for device { pixelformat = 'RGB3', description = 'RGB3' } { ?GSPCA? : width = 720, height = 480 } fmtind:2 fsizeind: 1 { pixelformat = 'BGR3', description = 'BGR3' } { ?GSPCA? : width = 720, height = 480 } fmtind:3 fsizeind: 1 { pixelformat = 'YU12', description = 'YU12' } { ?GSPCA? : width = 720, height = 480 } fmtind:4 fsizeind: 1 { pixelformat = 'YV12', description = 'YV12' } { ?GSPCA? : width = 720, height = 480 } fmtind:5 fsizeind: 1 vid:05e1 pid:0408 driver:stk1160 checking format: 1196444237 Format unavailable: 1196444237. Init v4L2 failed !! Init video returned -2 trying minimum setup ... Segmentation fault (core dumped)

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• Which Open Source Licenses can address concerns for an Open Source Game Engine?

  - by Chris

  I am on a team that is looking to open source an engine we are building. It's intended as an engine for Online RPG style games. We're writing it to work on both desktops and android platforms. I've been over to the OSI http://opensource.org/licenses/category to check out the most common licenses. However, this will be my first time going into an open source project and I wanted to know if the community had some insight into which licenses might be best suited. Key licensing concerns: Removing or limiting our liability (most already seem to cover this, but stating for completeness). We want other developers to be able to take part or all of our project and use it in their own projects with proper accreditation to our project. Licensing should not hinder someone's ability to quickly use the engine. They should be able to download a release and start using it without needing to wait on licensing issues. Game content (gfx, sound, etc.) that is not part of the engine should be allowed to be licensed separately. If someone is using our engine, they can retain full copy right of their content, including engine generated data. Our primary goal is exposure, which is why we're going open source to start with. Both for the project and for the individuals developing it. Are there any licenses that can require accreditation visible to players? While I'd put our primary goal as exposure, for licensing the accreditation is less of a concern. From what I've read through (and have been able to understand) it doesn't seem like any of the licenses cover anything that is produced by the licensed software. Are there any that state this specifically, or does simply not mentioning it leave it open for other licensing? Are there any other concerns that we should consider? Has anyone had any issues using any of these licenses?

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• Which language is more suitable heavy file tasks?

  - by All

  I need to write a script (based on basic functions) to process /image/audio/video files. The process is mainly filesystem tasks and converts. The database of files has been stored by mysql. The script is simple but cause heavy tasks on the system; for example renaming/converting/copying thousands of file in a run. The script does not read the content of files into memory, it just manage the commands for sub-processes. The main weight is on the communication with filesystem. The script will be used regularly for new files. My concern is about performance. I am thinking of Shell script a complied language like C Please advise which programming language is more suitable for this purpose and why? UPDATE: An example is to scan a folder for images, convert them with ImageMagick, move files to destination folder, get file info, then update the database. As you can see, the process has no room for optimization, and most of languages have similar APIs for popular programs like ImageMagick, MySQL, etc. Thus, it can be written in any language. I just wish to reduce resource usage by speeding up the long loop. NOTE: I know that questions about comparing languages are not favorable, but I really had problem to choose, because the problems can appear in action.

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• Negamax implementation doesn't appear to work with tic-tac-toe

  - by George Jiglau

  I've implemented Negamax as it can be found on wikipedia, which includes alpha/beta pruning. However, it seems to favor a losing move, which should be an invalid result. The game is Tic-Tac-Toe, I've abstracted most of the game play so it should be rather easy to spot an error within the algorithm. Here is the code, nextMove, negamax or evaluate are probably the functions that contain the fault: #include <list> #include <climits> #include <iostream> //#define DEBUG 1 using namespace std; struct Move { int row, col; Move(int row, int col) : row(row), col(col) { } Move(const Move& m) { row = m.row; col = m.col; } }; struct Board { char player; char opponent; char board[3][3]; Board() { } void read(istream& stream) { stream >> player; opponent = player == 'X' ? 'O' : 'X'; for(int row = 0; row < 3; row++) { for(int col = 0; col < 3; col++) { char playa; stream >> playa; board[row][col] = playa == '_' ? 0 : playa == player ? 1 : -1; } } } void print(ostream& stream) { for(int row = 0; row < 3; row++) { for(int col = 0; col < 3; col++) { switch(board[row][col]) { case -1: stream << opponent; break; case 0: stream << '_'; break; case 1: stream << player; break; } } stream << endl; } } void do_move(const Move& move, int player) { board[move.row][move.col] = player; } void undo_move(const Move& move) { board[move.row][move.col] = 0; } bool isWon() { if (board[0][0] != 0) { if (board[0][0] == board[0][1] && board[0][1] == board[0][2]) return true; if (board[0][0] == board[1][0] && board[1][0] == board[2][0]) return true; } if (board[2][2] != 0) { if (board[2][0] == board[2][1] && board[2][1] == board[2][2]) return true; if (board[0][2] == board[1][2] && board[1][2] == board[2][2]) return true; } if (board[1][1] != 0) { if (board[0][1] == board[1][1] && board[1][1] == board[2][1]) return true; if (board[1][0] == board[1][1] && board[1][1] == board[1][2]) return true; if (board[0][0] == board[1][1] && board[1][1] == board[2][2]) return true; if (board[0][2] == board [1][1] && board[1][1] == board[2][0]) return true; } return false; } list<Move> getMoves() { list<Move> moveList; for(int row = 0; row < 3; row++) for(int col = 0; col < 3; col++) if (board[row][col] == 0) moveList.push_back(Move(row, col)); return moveList; } }; ostream& operator<< (ostream& stream, Board& board) { board.print(stream); return stream; } istream& operator>> (istream& stream, Board& board) { board.read(stream); return stream; } int evaluate(Board& board) { int score = board.isWon() ? 100 : 0; for(int row = 0; row < 3; row++) for(int col = 0; col < 3; col++) if (board.board[row][col] == 0) score += 1; return score; } int negamax(Board& board, int depth, int player, int alpha, int beta) { if (board.isWon() || depth <= 0) { #if DEBUG > 1 cout << "Found winner board at depth " << depth << endl; cout << board << endl; #endif return player * evaluate(board); } list<Move> allMoves = board.getMoves(); if (allMoves.size() == 0) return player * evaluate(board); for(list<Move>::iterator it = allMoves.begin(); it != allMoves.end(); it++) { board.do_move(*it, -player); int val = -negamax(board, depth - 1, -player, -beta, -alpha); board.undo_move(*it); if (val >= beta) return val; if (val > alpha) alpha = val; } return alpha; } void nextMove(Board& board) { list<Move> allMoves = board.getMoves(); Move* bestMove = NULL; int bestScore = INT_MIN; for(list<Move>::iterator it = allMoves.begin(); it != allMoves.end(); it++) { board.do_move(*it, 1); int score = -negamax(board, 100, 1, INT_MIN + 1, INT_MAX); board.undo_move(*it); #if DEBUG cout << it->row << ' ' << it->col << " = " << score << endl; #endif if (score > bestScore) { bestMove = &*it; bestScore = score; } } if (!bestMove) return; cout << bestMove->row << ' ' << bestMove->col << endl; #if DEBUG board.do_move(*bestMove, 1); cout << board; #endif } int main() { Board board; cin >> board; #if DEBUG cout << "Starting board:" << endl; cout << board; #endif nextMove(board); return 0; } Giving this input: O X__ ___ ___ The algorithm chooses to place a piece at 0, 1, causing a guaranteed loss, do to this trap(nothing can be done to win or end in a draw): XO_ X__ ___ Perhaps it has something to do with the evaluation function? If so, how could I fix it?

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• scary islamic messages on mouse in libreoffice - a virus?

  - by yuvi

  This is weird. Today I opened an excel file with libre office. Suddenly I saw the mouse changed color, and stuck to it was a message in Arabic, which changed every second in a loop. I can actually read Arabic so I immediatly recognized it as Islamic messages praising Allah (including the Takbir). Here's a screenshot: At first I thought this was something with the file, but then I saw that this happens with any libre office program (but only libre-office programs), and even when they're open, it only changes the mouse when it's hovering over the libre program, and goes back to normal anywhere else. Also, re-installing did not help. I tried running software updater - but I got an error where it couldn't load some steam repositories, but that seems like a coincidence: Failed to fetch http://repo.steampowered.com/steam/dists/precise/steam/i18n/Translation-en_US Failed to fetch http://repo.steampowered.com/steam/dists/precise/steam/i18n/Translation-en Here's another hint - I tried taking several screenshots of several messages, but they all ended up showing the same message (the one above). Hopefully that means anything. I should note I haven't installed anything fishy lately, and I hardly ever use libre office at all (I prefer Google Drive whenever I need to work with documents), so I'm really unsure as to how this happened. Anyway, this is scary. Any help would be greatly appreciated!

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• Detecting Browser Types?

  - by Mike Schinkel

  My client has asked me to implement a browser detection system for the admin login with the following criteria, allow these: Internet Explorer 8 or newer Firefox 3.6 or newer Safari 5 or newer for Mac only And everything else should be blocked. They want me to implement a page telling the user what browser they need to upgrade/switch to in order to access the CMS. Basically I need to know the best way to detect these browsers with PHP, distinct from any other browsers, and I've read that browser sniffing per se is not a good idea. The CMS is WordPress but this is not a WordPress question (FYI I am a moderator on the WordPress Answers site.) Once I figure out the right technique to detect the browser I'm fully capable to make WordPress react as my client wants, I just need to know what the best ways are with PHP (or worse case jQuery, but I much prefer to do on the server) to figure how what works and what doesn't. Please understand that "Don't do it" is not an acceptable answer for this question. I know this client too well and when they ask me to implement something I need to do it (they are a really good client so I'm happy to do what they ask.) Thanks in advance for your expertise. -Mike

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• RDA and Fusion Middleware Diagnostic Framework Integration

  - by Daniel Mortimer

  Further to my last blog entry "FMw Diagnostic Framework : Automatic Capture of Diagnostic Data Upon First Failure!" I have spent some time exploring how Remote Diagnostic Agent (RDA) integrates with Diagnostic Framework. Remote Diagnostic Agent, by default, collects the information about the last 10 incidents which have been captured in the Automatic Diagnostic Repository (ADR). This information can be located via RDA's Start Page Menu system. See screenshot below. Screenshot - Viewing Diagnostic Framework Incident Information in a RDA Package Note: In the next release of RDA - version 4.30 - the Diagnostic Repository menu label will have it's own position in the weblogic managed server sub menu hierarchy rather than be a child menu item of the logs menuDiagnostic Framework is also capable of launching RDA engine and including the output in an incident package. This is achieved via the command "IPS GENERATE PACKAGE". The RDA output is written to DOMAIN_HOME/servers/<server name>/adr/diag/ofm/<domain name>/<server name>/incpkg/pkg_[number]/seq_[number]/rda The RDA collected files are best viewed (as shown in the screenshot above) by opening the RDA Start Page - "DFW__start.htm" - from this directory in a browser. If you do not have a browser available on the host machine, zip the contents of the rda directory and transfer and extract to a machine which has a browser.  The explanation of the integration goes a little deeper. If you want to know more, read My Oracle Support document: Understanding RDA and FMW 11g Diagnostic Framework Integration [Document 1503644.1]

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• Simple monitoring of a Raspberry Pi powered screen - Part 2

  - by Chris Houston

  If you have read my previous blog post Raspberry Pi entrance signed backed by Umbraco - Part 1 which describes how we used a Raspberry Pi to drive an Entrance sign for QV Offices you will have seen I mentioned a follow up post about monitoring the sign.As the sign is mounted in the entrance of the building on the ground floor and the reception is on the 1st floor, this meant that if there was a fault of any kind showing on the screen, the first person to see this was inevitably one of QV Offices' clients as they walked into the building.Although the QV Offices' team were able to check the Umbraco website address that the sign uses, this did not always mean that everything was working as expected. We noticed a couple of times that the sign had Wifi issues (it is now hard wired) and this caused the Chromium browser to render a 404 error when it tried to refresh the screen.The simple monitoring solutionWe added the following line to our refresh script, so that after the sign had been refreshed a screen shot of the Raspberry Pi would be taken:import -display :0 -window root ~/screenshot.jpgFinally we wrote a small Crontab task that ran on a QV Offices Mac that grabs this screen shot and saved it on the desktop, admittedly we have used a package that it not mega secure, but in reality this is an internal system that only runs an office sign, so we are not to concerned about it being hacked.*/5 * * * * /usr/local/bin/sshpass -p 'password' /usr/bin/scp [email protected]:screenshot.jpg Desktop/QVScreenShot.jpgAs the file icon updates, if the image changes, this gives a quick visual indication of the status of the sign, if for some reason the icon does not look correct the QV Offices administrator can just click on the file to see the exact image currently displayed on the sign.Sometimes a quick and easy solution is better than a more complex and expensive one.

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• Running multiple box2D world objects on a server

  - by CharbelAbdo

  I'm creating a multiplayer game using LibGdx (with Box2d) and Kryonet. Since this is the first time I work on multiplayer games, I read a bit about server - client implementations, and it turns out that the server should handle important tasks like collision detection, hits, characters dying etc... Based on some articles (like the excellent Gabriel Gambetta Fast paced multiplayer series), I also know that the client should work in parallel to avoid the lag while the server responds to commands. Physics wise, each game will have 2 players, and any projectiles fired. What I'm thinking of doing is the following: Create a physics world on the client When the game is signaled to start, I create the same physics world on the server (without any rendering obviously). Whenever the player issues a command (move or fire), I send the command to the server and immediately start processing it on the client. When the server receives the command, it applies it on the server's world (set velocity etc...) Each 100ms, the server sends the new state to the client which corrects what was calculated locally. Any critical action (hit, death, level up) is calculated only on the server and sent to the client. Essentially, I would have a Box2d World object running on the server for each game in progress, in sync with the worlds running on the clients. The alternative would be to do my own calculations on the server instead of relying on Box2D to do them for me, but I'm trying to avoid that. My question is: Is it wise to have, for example, 1000 instances of the World object running and executing steps on the server? Tomcat used around 750 MBytes of memory when trying it without any object added to the world. Anybody tried that before? If not, is there any alternative? Google did not help me, are there any guidelines to use when you want to have physics on both the client and the server? Thanks for any help.

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• Web Development Environment: How to distribute edited hosts files over bunch of mac machines?

  - by Alex Reds

  I am doing some research to prepare some web development environment for our small(10ppl and growing) new office. User Case: For each new web project usually we create new alias on an Apache server someproject.companywebsite From my understanding in order to see this website locally for all the rest of our team(including mangers and directors) they will need to edit hosts file (e.g. "192.168.1.10 someproject.companywebsite"), and like that each time for a new project(can be 2-5 each week) Solution: And I looking for a solution how to edit this hosts file only once and distribute it over all mac machines in our network at once or much more flawlessly than poking around with each machine every time over and over again. Is that possible? Or that a very wrong way of doing that? Perhaps we better set up own local dns server and point to it our router? Though own dns server a bit concerns me because of might be some network interruption and others lags, if you know what I mean. Or perhaps there are another workflows for that? What's the best way for such things? So I'll be so grateful to hear some advices from experienced admins. I couldn't find that info on internet, so if you know where to read about it, point me in a right direction. Thank you in advance Alex

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• Strange robots.txt - how and why did it get there?

  - by Mick

  I recently created a very simple, pure HTML website which I have hosted with "hostmonster". Hostmonster had very good reviews on some comparison website and in general so far they appear to be perfectly good in every way... At least I thought so until just now... I have been making lots of edits to my site on an almost daily basis. My site now appears on the first page (7th on the list) for my most important keyphrase when doing a google search. But I did notice some problem with the snippet chosen by google. I asked a question on this site about snippets and got some great answers. I then made some modifications to my meta data and within 48hrs the google snippet for my search was perfect. The odd thing though was that looking at the "cached" version google had, it appeared that the cache was still very odl- like three weeks previous. This seemed very odd - how could it be that the google robots had read my new metadata without updating the cache? This puzzled me greatly. Just now it occurred to me that maybe I had some goofey setting in my robots.txt file. I didn't actually remember even making one - but I thought I'd have a look just in case. Much to my horror, I saw that there was a robots.txt and it contained the disturbing text below: sitemap: http://cdn.attracta.com/sitemap/728687.xml.gz Intuitively this looks like some kind of junk, spam trick, and I had indeed been getting some spam from "attracta". So my questions are: 1. Should I simply delete this robots.txt? 2. Was the file there all along - placed there because of some commercial tie-in between attracta and hostmonster. 3. Does the attracta robots file explain the lack of re-caching?

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• An Oracle Exastack Recap

  - by Kristin Rose

  For those ISVs and OEMs who tuned into Oracle’s FY13 Partner Kickoff, thank you! It was with your participation and presence that helped make this year’s show another great success. The OPN Communications team was lucky enough to get a chance to sit down with Chris Baker, Oracle SVP of Worldwide ISV, OEM & Java, all the way from London, as he recapped the achievements that were seen over the past year with the Oracle Exastack Program. Be sure to watch his short video below: Here are some highlights: 1000 “Readies”- Those partners that are ready to use the latest version of our products Over 100 partners that are ready to use Oracle Exastack,  Oracle Exadata Database Machine, and Oracle Exalogic Elastic Cloud New Oracle Exalytics machine for analysis In less than one year, more than 100 ISV applications have achieved an Oracle Exastack Ready status and more than 35 ISV applications have achieved Oracle Exastack Optimized status. These partners can be found by Oracle customers listed in the Oracle Solutions Catalog.Demonstrating to customers that their solutions are tuned to deliver optimum speed, scalability and reliability on Oracle Engineered Systems, Oracle partners are rapidly achieving Oracle Exastack Optimized certification. Read the press release here. By simplifying your company’s architecture with the Oracle Exastack program, both ISV’s and OEMs are able to better concentrate on their application and deliver enhanced benefits to their customers.Cheers!The OPN Communications Team

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• Managing Kindle Fire with on 12.04 via Micro-USB

  - by pirtle

  To begin, I have read both Is there a way to get a Kindle Fire to work with 12.04? and How can I transfer files to a Kindle Fire with a Micro-USB cable? My problem is that I am unable to mount my Kindle Fire in order to add books to it. I have installed calibre, but it is unable to manage any devices until the computer itself has recognized it. The latter post had an excellent answer (provided by @jeremiah) that was making some progress. Unfortunately, I think I don't know enough about the -t flag used with mount. This is what I've done... Ran dmesg to locate the device: [ 3.920886] sd 6:0:0:0: [sdb] Attached SCSI removable disk Confirmed it's location: $ sudo ls -l /dev/disk/by-id lrwxrwxrwx 1 root root 9 Aug 18 15:52 usb-Amazon_Kindle_3C6C002600000001-0:0 -> ../../sdb So we know that my Kindle is recognized on /dev/sdb. I then used the mount command suggested by @jeremiah: $ sudo mount -t ext3 /dev/sdb/ /mnt/kindle/ mount: no medium found on /dev/sdb The same error occurs for sudo mount /dev/sdb /mnt/kindle. Note: I have created the 'kindle' directory in 'mnt' Any suggestions?

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• Scene graphs and spatial partitioning structures: What do you really need?

  - by tapirath

  I've been fiddling with 2D games for awhile and I'm trying to go into 3D game development. I thought I should get my basics right first. From what I read scene graphs hold your game objects/entities and their relation to each other like 'a tire' would be the child of 'a vehicle'. It's mainly used for frustum/occlusion culling and minimizing the collision checks between the objects. Spatial partitioning structures on the other hand are used to divide a big game object (like the map) to smaller parts so that you can gain performance by only drawing the relevant polygons and again minimizing the collision checks to those polygons only. Also a spatial partitioning data structure can be used as a node in a scene graph. But... I've been reading about both subjects and I've seen a lot of "scene graphs are useless" and "BSP performance gain is irrelevant with modern hardware" kind of articles. Also some of the game engines I've checked like gameplay3d and jmonkeyengine are only using a scene graph (That also may be because they don't want to limit the developers). Whereas games like Quake and Half-Life only use spatial partitioning. I'm aware that the usage of these structures very much depend on the type of the game you're developing so for the sake of clarity let's assume the game is a FPS like Counter-Strike with some better outdoor environment capabilities (like a terrain). The obvious question is which one is needed and why (considering the modern hardware capabilities). Thank you.

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• What's the best project management software for internal dev. 5 man shop

  - by P.Brian.Mackey

  I work for a large corporation, but we do small intranet web application development. Our project management tracking sucks. Its custom software built by a jr. intern. For what its worth, our development style is akin to agile, but there's nothing set in stone...very customer oriented approach. I need project tracking that meets the criteria: Intranet, internal products. Mostly maintenance, some new development. 5 developers 12 products 1 hands-off manager. He really just wants to know estimated man hours, due date for dev, QA and release. Along with a short description of the project. Free or super cheap. Bonus Simple pretty UI. Think pretty charts. Hope I covered everything. Please ask for any clarification. If you read dreaming in code, the company uses some project tracking software that sounds pretty sweet. Note, we do have Team Foundation Server. I already tried pushing its use as PM tracking, but its too complicated. I can't get people to sit and train. So this software has to be easy.

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• Ray Tracing concers: Efficient Data Structure and Photon Mapping

  - by Grieverheart

  I'm trying to build a simple ray tracer for specific target scenes. An example of such scene can be seen below. I'm concerned as to what accelerating data structure would be most efficient in this case since all objects are touching but on the other hand, the scene is uniform. The objects in my ray tracer are stored as a collection of triangles, thus I also have access to individual triangles. Also, when trying to find the bounding box of the scene, how should infinite planes be handled? Should one instead use the viewing frustum to calculate the bounding box? A few other questions I have are about photon mapping. I've read the original paper by Jensen and many more material. In the compact data structure for the photon they introduce, they store photon power as 4 chars, which from my understanding is 3 chars for color and 1 for flux. But I don't understand how 1 char is enough to store a flux of the order of 1/n, where n is the number of photons (I'm also a bit confused about flux vs power). The other question about photon mapping is, if it would be more efficient in my case to store photons per object (or even per Object's triangle) instead of using a balanced kd-tree. Also, same question about bounding box of the scene but for photon mapping. How should one find a bounding box from the pov of the light when infinite planes are involved?

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