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• Implementation ideas to store multiple files within a single file for faster access?

  - by eminemence

  My requirement is to store a large number of files within a single file.The files stored could be anything like images, videos or simple text files as well. I want some ideas to implement the same. I am thinking of implementing a file system within a file, but am not sure if its a good idea. The main area of concern here is the access time. Also I want to provide encryption for this single file. Any suggestions are welcome.

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• How to create a manager class without global variables nor singletons?

  - by Omega

  I would like to implement some kind of manager class in my application. It will be in charge of loading textures, processing them, distributing them etc... At first, I wanted to make a global variable that simply contains an instance of my manager class. I found this question: http://stackoverflow.com/questions/4646577/global-variables-in-java. However, the users there seem to recommend to never use global variables. Fine then, I once heard about Singletons, so I though I could use that instead. I mean, creating just one instance of my manager class sounds good. However, I found this other question: When is Singleton appropriate?, which basically tells me that Singletons are, in most scenarios, some kind of anti-pattern. Now I am a bit lost - what other approach can I take to create my manager class, whose only requirement is to be accessible from anywhere?

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• How to get started on working with WebTrends locally using a DEV account access? [on hold]

  - by Knowledge Craving

  I'm a newbie developer on WebTrends Analytics, although I have worked extensively on Adobe SiteCatalyst. Currently I want to integrate WebTrends with the web pages of a local project on my local JBoss EAP application server, so that I can run it locally and see how WebTrends work, along with how the Analytics reports show up. Later on, I may customize the reports data as per the project requirements. However, I can't find anywhere how I can start working on a local development process using a DEV account access. I'm mainly trying to get data on number of user visits per day, as of now, which will cater to multichannel experience. And later on, I will start pulling more data based on targeting and segmentation. Can anyone of you please help and guide me in the right direction? Any help is highly appreciated. Thank you!

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• Xcode 4 and cocos2D 1.0.0 beta Uncategorized errors and Info.plist doesn't exist

  - by badben

  I just installed the xcode 4 sdk and the cocos2d 1.0.0 beta template. I just created a new project with the cocos2d template. But when I build I got these errors : (for information my previous projects developed with xcode 3 have the same problem) warning: couldn't add 'com.apple.XcodeGenerated' tag to '/Users/Benoit/Library/Developer/Xcode/DerivedData/xcode4-bswxazfuwbsguiasyatbtlmvbpps/Build/Intermediates/xcode4.build': Error Domain=NSPOSIXErrorDomain Code=2 UserInfo=0x201dde680 "The operation couldn’t be completed. No such file or directory" error: unable to create '/Users/Benoit/Library/Developer/Xcode/DerivedData/xcode4-bswxazfuwbsguiasyatbtlmvbpps/Build/Intermediates' (Permission denied) error: unable to create '/Users/Benoit/Library/Developer/Xcode/DerivedData/xcode4-bswxazfuwbsguiasyatbtlmvbpps/Build/Products' (Permission denied) Unable to create directory /Users/Benoit/Library/Developer/Xcode/DerivedData/xcode4-bswxazfuwbsguiasyatbtlmvbpps/Build/Intermediates/xcode4.build/Debug-iphonesimulator/xcode4.build/Objects-normal/i386 Unable to create directory /Users/Benoit/Library/Developer/Xcode/DerivedData/xcode4-bswxazfuwbsguiasyatbtlmvbpps/Build/PrecompiledHeaders/Prefix-dflnzjtztxdgjwhistrvvjxetfrg Unable to create directory /Users/Benoit/Library/Developer/Xcode/DerivedData/xcode4-bswxazfuwbsguiasyatbtlmvbpps/Build/Intermediates/xcode4.build/Debug-iphonesimulator/xcode4.build Unable to create directory /Users/Benoit/Library/Developer/Xcode/DerivedData/xcode4-bswxazfuwbsguiasyatbtlmvbpps/Build/Intermediates/xcode4.build/Debug-iphonesimulator/xcode4.build Unable to create directory /Users/Benoit/Library/Developer/Xcode/DerivedData/xcode4-bswxazfuwbsguiasyatbtlmvbpps/Build/Intermediates/xcode4.build/Debug-iphonesimulator/xcode4.build Unable to create directory /Users/Benoit/Library/Developer/Xcode/DerivedData/xcode4-bswxazfuwbsguiasyatbtlmvbpps/Build/Intermediates/xcode4.build/Debug-iphonesimulator/xcode4.build Unable to create directory /Users/Benoit/Library/Developer/Xcode/DerivedData/xcode4-bswxazfuwbsguiasyatbtlmvbpps/Build/PrecompiledHeaders/Prefix-fqemzerugrwojibbegzkffljkxqs Unable to create directory /Users/Benoit/Library/Developer/Xcode/DerivedData/xcode4-bswxazfuwbsguiasyatbtlmvbpps/Build/Intermediates/xcode4.build/Debug-iphonesimulator/xcode4.build Unable to create directory /Users/Benoit/Library/Developer/Xcode/DerivedData/xcode4-bswxazfuwbsguiasyatbtlmvbpps/Index/PrecompiledHeaders/Prefix-dbtcglhksokwygezixirqkgfipsr_ast Unable to create directory /Users/Benoit/Library/Developer/Xcode/DerivedData/xcode4-bswxazfuwbsguiasyatbtlmvbpps/Index/PrecompiledHeaders/Prefix-gdirtpasdqzasnclnkzguimarjpd_ast error: couldn't create directory /Users/Benoit/Library/Developer/Xcode/DerivedData/xcode4-bswxazfuwbsguiasyatbtlmvbpps/Build/Products/Debug-iphonesimulator/xcode4.app: Permission denied error: couldn't create directory /Users/Benoit/Library/Developer/Xcode/DerivedData/xcode4-bswxazfuwbsguiasyatbtlmvbpps/Build/Products/Debug-iphonesimulator/xcode4.app: Permission denied The file “Info.plist” doesn’t exist. Please help !!

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• Is "If a method is re-used without changes, put the method in a base class, else create an interface" a good rule-of-thumb?

  - by exizt

  A colleague of mine came up with a rule-of-thumb for choosing between creating a base class or an interface. He says: Imagine every new method that you are about to implement. For each of them, consider this: will this method be implemented by more than one class in exactly this form, without any change? If the answer is "yes", create a base class. In every other situation, create an interface. For example: Consider the classes cat and dog, which extend the class mammal and have a single method pet(). We then add the class alligator, which doesn't extend anything and has a single method slither(). Now, we want to add an eat() method to all of them. If the implementation of eat() method will be exactly the same for cat, dog and alligator, we should create a base class (let's say, animal), which implements this method. However, if it's implementation in alligator differs in the slightest way, we should create an IEat interface and make mammal and alligator implement it. He insists that this method covers all cases, but it seems like over-simplification to me. Is it worth following this rule-of-thumb?

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• How do I create a popup banner before login with Lightdm?

  - by Rich Loring

  When Ubuntu was using gnome I was able to create a popup banner like the banner below before the login screen using zenity in the /etc/gdm/Init/Default. The line of code would be like this: if [ -f "/usr/bin/zenity" ]; then /usr/bin/zenity --info --text="`cat /etc/issue`" --no-wrap; else xmessage -file /etc/issue -button ok -geometry 540X480; fi How can I accomplish this with Unity? NOTICE TO USERS This is a Federal computer system (and/or it is directly connected to a BNL local network system) and is the property of the United States Government. It is for authorized use only. Users (authorized or unauthorized) have no explicit or implicit expectation of privacy. Any or all uses of this system and all files on this system may be intercepted, monitored, recorded, copied, audited, inspected, and disclosed to authorized site, Department of Energy, and law enforcement personnel, as well as authorized officials of other agencies, both domestic and foreign. By using this system, the user consents to such interception, monitoring, recording, copying, auditing, inspection, and disclosure at the discretion of authorized site or Department of Energy personnel. Unauthorized or improper use of this system may result in administrative disciplinary action and civil and criminal penalties. By continuing to use this system you indicate your awareness of and consent to these terms and conditions of use. LOG OFF IMMEDIATELY if you do not agree to the conditions stated in this warning.

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• How can I create a 4TB partition on my software RAID5 device?

  - by Kris Harper

  I have set up a RAID5 device with three 2TB hard drives using mdadm. The device was successfully created, but I cannot seem to create a partition on the device. When I try to make an ext3 or ext4 partition via Disk Utility, I get the following error Error creating partition: helper exited with exit code 1: In part_add_partition: device_file=/dev/md0, start=0, size=4000526106624, type= Entering MS-DOS parser (offset=0, size=4000526106624) MSDOS_MAGIC found found partition type 0xee => protective MBR for GPT Exiting MS-DOS parser Entering EFI GPT parser GPT magic found partition_entry_lba=2 num_entries=128 size_of_entry=128 Leaving EFI GPT parser EFI GPT partition table detected containing partition table scheme = 3 got it got disk new partition guid '' is not valid type '' for GPT appear to be malformed I have seen this question, but that seems to suggest using gparted to do the partitioning. I'm fine with doing that, but my RAID device doesn't show up in the list of gparted devices. I suspect because this is a RAID and not a regular disk. I have already created a GPT partition table on the device. How can I add a partition to my device?

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• Why does "quickly share --ppa share" abort with a "can't create" error?

  - by desgua

  I can not figure out what I am doing wrong. The package builds ok with quickly package, I could submit it, but I can not update my ppa. Here is what I got: desgua@desguai7:~/quickly/sbk$ quickly share --ppa sbk Get Launchpad Settings Launchpad connection is ok ..........An error has occurred when creating debian packaging ERROR: can't create or update ubuntu package ERROR: share command failed Aborting Edit The name of my ppa was wrong, but even using ppa:desgua/sbk still doesn't work: desgua@desguai7:~/quickly/sbk$ quickly share --ppa ppa:desgua/sbk Get Launchpad Settings Traceback (most recent call last): File "/usr/share/quickly/templates/ubuntu-application/share.py", line 101, in launchpad = launchpadaccess.initialize_lpi() File "/usr/lib/python2.7/dist-packages/quickly/launchpadaccess.py", line 91, in initialize_lpi allow_access_levels=["WRITE_PRIVATE"]) File "/usr/lib/python2.7/dist-packages/launchpadlib/launchpad.py", line 539, in login_with credential_save_failed, version) File "/usr/lib/python2.7/dist-packages/launchpadlib/launchpad.py", line 359, in _authorize_token_and_login service_root, cache, timeout, proxy_info, version) File "/usr/lib/python2.7/dist-packages/launchpadlib/launchpad.py", line 198, in __init__ credentials, service_root, cache, timeout, proxy_info, version) File "/usr/lib/python2.7/dist-packages/lazr/restfulclient/resource.py", line 460, in __init__ self._wadl = self._browser.get_wadl_application(self._root_uri) File "/usr/lib/python2.7/dist-packages/lazr/restfulclient/_browser.py", line 299, in get_wadl_application response, content = self._request(url, media_type=wadl_type) File "/usr/lib/python2.7/dist-packages/lazr/restfulclient/_browser.py", line 242, in _request str(url), method=method, body=data, headers=headers) File "/usr/lib/python2.7/dist-packages/lazr/restfulclient/_browser.py", line 211, in _request_and_retry url, method=method, body=body, headers=headers) File "/usr/lib/python2.7/dist-packages/httplib2/__init__.py", line 1414, in request (response, new_content) = self._request(conn, authority, uri, request_uri, method, body, headers, redirections, cachekey) File "/usr/lib/python2.7/dist-packages/launchpadlib/launchpad.py", line 126, in _request LaunchpadOAuthAwareHttp, self)._request(*args) File "/usr/lib/python2.7/dist-packages/lazr/restfulclient/_browser.py", line 130, in _request redirections, cachekey) File "/usr/lib/python2.7/dist-packages/httplib2/__init__.py", line 1196, in _request (response, content) = self._conn_request(conn, request_uri, method, body, headers) File "/usr/lib/python2.7/dist-packages/httplib2/__init__.py", line 1138, in _conn_request raise ServerNotFoundError("Unable to find the server at %s" % conn.host) httplib2.ServerNotFoundError: Unable to find the server at api.launchpad.net ERROR: share command failed Aborting Any ideas? How could I troubleshot this error?

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• Black screen appears when booting new install of 11.10 on my desktop, cannot access Grub menu to fix

  - by Cee

  I installed 11.10 on my desktop PC but get a black screen after the BIOS screen when I try to boot it. I was able to run 10.04.04 on my hard drive before installing 11.10 and I am also able to use 11.10 on my usb pendrive and CD ROM. I've tried unplugging all USB devices before booting and also upgrading from 11.10 to 11.10. Holding the shift key from the BIOS screen doesn't allow me to access the GRUB menu to try: Highlight the first entry, press “e” to edit it. Navigate to words “quiet splash”, delete them and type “nomodeset” in their place (without quotes). Press Ctrl + X to continue boot. Once on the desktop, go to System Administration Additional Drivers and activate the recommended drivers. So running 11.10 on my pendrive, I tried editing /etc/default/grub, commenting out the GRUB_HIDDEN_TIMEOUT setting by putting a '#' in front of it to display the grub menu and setting GRUB_TIMEOUT setting to a value greater than or equal to 1 e.g. GRUB_TIMEOUT=10. However, when I run sudo update-grub, I get: /usr/sbin/grub-probe: error: cannot find a device for / (is /dev mounted?) I get the same error with update-grub after: sudo mount /dev/sda1 /mnt and after: sudo grub-install --root-directory=/mnt /dev/sda reboot sudo update-grub Other suggestions to fix the update-grub problem: Open synaptic, then purge all the related grub installed packages and reinstall grub-pc then and finally: sudo update-grub Or use Grub Customizer http://ubuntuforums.org/showthread.php?t=1195275 What would be the best way to approach this? I'm concerned about purging "all the related grub installed packages" but if it's true some files are corrupted this would seem necessary. Also, was I executing the correct commands i.e. with mount and grub-install, before running grub-update?

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• Should I create my own Assert class based on these reasons?

  - by Mike

  The main reason I don't like Debug.Assert is the fact that these assertions are disabled in Release. I know that there's a performance reason for that, but at least in my situation I believe the gains would outweigh the cost. (By the way, I'm guessing this is the situation in most cases). And yes, I know that you can use Trace.Assert instead. But even though that would work, I find the name Trace distracting, since I don't see this as tracing. The other reason to create my own class is laziness I guess, since I could write methods for the most usual cases like Assert.IsNotNull, Assert.Equals and so forth. The second part of my question has to do with using Environment.FailFast in this class. Would that be a good idea? I do like the ideas put forth in this document. That's pretty much where I got the idea from. One last point. Does creating a design like this imply having an untestable code path, as described in this answer by Eric Lippert on a different (but related) question?

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• What is the best way to restrict access to adult content on Ubuntu?

  - by Stephen Myall

  I bought my kids a PC and installed 12.04 (Unity) on it. The bottom line is, I want my children to use the computer unsupervised while I have confidence they cannot access anything inappropriate. What I have looked at: I was looking at Scrubit a tool which allows me configure my wifi router to block content and this solution would also protect my other PC and mobile devices. This may be overkill as I just want the solution to work on one PC. I also did some Google searches and came across the application called Nanny (it seems to look the part). My experience of OSS is that the best solutions frequently never appear first on a Google search list and in this case I need to trust the methods therefore my question is very specific. I want to leverage your knowledge and experience to understand “What is the best way to restrict adult content on 12.04 LTS” as this is important to me. It maybe a combination of things so please don't answer this question "try this or that", then give me some PPA unless you can share your experience of how good it is and of course if there are any contraints. Thanks in advance

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• Implmenting RLE into a tilemap or how to create a large 3D array?

  - by Smallbro

  Currently I've been using a 3D array for my tiles in a 2D world but the 3D side comes in when moving down into caves and whatnot. Now this is not memory efficient and I switched over to a 2D array and can now have much larger maps. The only issue I'm having now is that it seems that my tiles cannot occupy the same space as a tile on the same z level. My current structure means that each block has its own z variable. This is what it used to look like: map.blockData[x][y][z] = new Block(); however now it works like this map.blockData[x][y] = new Block(z); I'm not sure why but if I decide to use the same space on say the floor below it wont allow me to. Does anyone have any ideas on how I can add a z-axis to my 2D array? I'm using java but I reckon the concept carries across different languages. Edit: As Will posted, RLE sounds like the best method for achieving a fast 3D array. However I'm struggling to understand how I would even start to implement it? Would I create a 4D array the 4th being something which controls how many to skip? Or would the x-axis simply change altogether and have large gaps in between - for example [5][y][z] would skip 5 tiles? Is there something really obvious here which I am missing? The number of z levels I'm trying to have is around 66, it would be preferably that I can have up to or more than 1000 in x and y.

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• How to create a thread in XNA for pathfinding?

  - by Dan

  I am trying to create a separate thread for my enemy's A* pathfinder which will give me a list of points to get to the player. I have placed the thread in the update method of my enemy. However this seems to cause jittering in the game every-time the thread is called. I have tried calling just the method and this works fine. Is there any way I can sort this out so that I can have the pathfinder on its own thread? Do I need to remove the thread start from the update and start it in the constructor? Is there any way this can work? Here is the code at the moment: bool running = false; bool threadstarted; System.Threading.Thread thread; public void update() { if (running == false && threadstarted == false) { thread = new System.Threading.Thread(PathThread); //thread.Priority = System.Threading.ThreadPriority.Lowest; thread.IsBackground = true; thread.Start(startandendobj); //PathThread(startandendobj); threadstarted = true; } } public void PathThread(object Startandend) { object[] Startandendarray = (object[])Startandend; Point startpoint = (Point)Startandendarray[0]; Point endpoint = (Point)Startandendarray[1]; bool runnable = true; // Path find from 255, 255 to 0,0 on the map foreach(Tile tile in Map) { if(tile.Color == Color.Red) { if (tile.Position.Contains(endpoint)) { runnable = false; } } } if(runnable == true) { running = true; Pathfinder p = new Pathfinder(Map); pathway = p.FindPath(startpoint, endpoint); running = false; threadstarted = false; } }

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• How to procedurally (create) grow an artistic (2D) tree in real-time (L-System?).

  - by lalan

  Recently I programmed an L-system module, It got me interested further. I am a Plants vs Zombies junkie as well, really liked the concept of Tree of Wisdom. Would love to create similar procedural art just for fun and learn more. Question: How should I approach the process of creating an artistic tree (2d perhaps with fixed camera/perspective) dynamically? Ideally I would like to start with a plant (only a stem with a leaf) and grow it dynamically using some influence (input/user action) over its structure. These influences may result in different type of branching, curves in branches, its spread, location of fruits, color of flowers, etc. Want it to be really full of life/spirit. :) Plants vs Zombies: Tree of wisdom It would be great to dynamically grow a similar tree, but with lot more variation and animations happening. My Background: Student / Programmer, have used few game engines (Ogre3d, cocos2d, unity). Haven't really programmed directly using openGL, trying to fix that :). I am ready to spend considerable time, Please let me know about the APIs? and how would an expert like you would take on this problem? Why 2D? I think it's easier to solve the problem only considering 2 dimensions. Artistic inspirations: Only the tree, with fruits and leaves, without the shrubs at the bottom The large tree (visible branches, green leaves, flowers, fruits, etc) on the left, behind monkey. PixelJunk's Eden (Art style inspiration). Procedurally Generated Apple Tree using Fractals Please let me know if it was easy for you to understand the question, I may elaborate further. I hope a discussion of various approach would be helpful for everyone. You guys are awesome.

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• How to create an Orthographic display in OpenGL (ES) that handles different screen sizes and orientations?

  - by Piku

  I'm trying to create an iPad/iPhone game using GLES2.0 that contains a 3D scene with a heads-up-display/GUI overlaid on the top. However, this problem would also apply if I were to port my game to a computer and run the game in a resizable window, or allow the user to change screen resolutions... When trying to make the 2D GUI/HUD work I've made the assumption that all I'm really doing is drawing a load of 2D textured 'quads' on the screen and am trying to treat the orthographic projection as an old-style 2D display with 0,0 in the upper left and screenWidth,ScreenHeight in the lower right. This causes me all sorts of confusion when I rotate my ipad into Landscape mode since I can't work out what to put into my projection and modelview matrices to turn everything around the right way. It also gets messy if I want to support the iPad's large screen, an iPhone or a Retina display since I have to then draw three sets of textures for everything and work out which ones to use. Should I be trying to map the 2D OpenGL co-ords 1:1 with the screen? While typing out this question it occurs to me that I could keep my origin in the centre, still running -1/+1 along the axes. This would let me scale my 2D content appropriately on the different screen sizes, but wouldn't I end up with the textures being scaled and possibly losing quality? I'm using OpenGLES 2.0 and have a matrix library that has equivalents to the GLES1.1 glOrthof() and glFrustrum() calls.

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• How do I create a third Person View using DXUTCamera in DX10?

  - by David

  I am creating a 3d flying game and using DXUTCamera for my view. I can get the camera to take on the characters position, But I would like to view my character in the 3rd person. Here is my code for first person view: //Put the camera on the object. D3DXVECTOR3 viewerPos; D3DXVECTOR3 lookAtThis; D3DXVECTOR3 up ( 5.0f, 1.0f, 0.0f ); D3DXVECTOR3 newUp; D3DXMATRIX matView; //Set the viewer's position to the position of the thing. viewerPos.x = character->x; viewerPos.y = character->y; viewerPos.z = character->z; // Create a new vector for the direction for the viewer to look character->setUpWorldMatrix(); D3DXVECTOR3 newDir, lookAtPoint; D3DXVec3TransformCoord(&newDir, &character->initVecDir, &character->matAllRotations); // set lookatpoint D3DXVec3Normalize(&lookAtPoint, &newDir); lookAtPoint.x += viewerPos.x; lookAtPoint.y += viewerPos.y; lookAtPoint.z += viewerPos.z; g_Camera.SetViewParams(&viewerPos, &lookAtPoint); So does anyone have an ideas how I can move the camera to the third person view? preferably timed so there is a smooth action in the camera movement. (I'm hoping I can just edit this code instead of bringing in another camera class)

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• Would it be possible to create an open source software library, entirely developed and moderated by an open community?

  - by Steven Jeuris

  Call it democratic software development, or open source on steroids if you will. I'm not just talking about the possibility of providing a patch which can be approved by the library owner. Think more along the lines of how Stack Exchange works. Anyone can post code, and through community moderation it is cleaned up and eventually valid code ends up in the final library. For complex libraries an elaborate system should probably be created, but for a simple library it is my belief this is already possible even within the Stack Exchange platform. Take a library of extension methods for .NET for example. Everybody goes their own way and implements their own subset of what they feel is important, open-source library or not. People want to share their code, but there is no suitable platform for it. extensionmethod.net is the result of answering this call for extension methods, but the framework hopelessly falls short; there is no order, or structure at all. You don't know whether an idea is any good until you try it, so I decided to create an Extension Methods proposal on Area51. I belief with proper moderation, it could be possible for the site to be more than a Q&A site, and that an actual library (or subsets of it) could be extracted from it. Has anything like this been attempted before? Are there platforms better suited for this?

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• Create a thread in xna Update method to find path?

  - by Dan

  I am trying to create a separate thread for my enemy's A* pathfinder which will give me a list of points to get to the player. I have placed the thread in the update method of my enemy. However this seems to cause jittering in the game every-time the thread is called. I have tried calling just the method and this works fine. Is there any way I can sort this out so that I can have the pathfinder on its own thread? Do I need to remove the thread start from the update and start it in the constructor? Is there any way this can work. Here is the code at the moment: bool running = false; bool threadstarted; System.Threading.Thread thread; public void update() { if (running == false && threadstarted == false) { thread = new System.Threading.Thread(PathThread); //thread.Priority = System.Threading.ThreadPriority.Lowest; thread.IsBackground = true; thread.Start(startandendobj); //PathThread(startandendobj); threadstarted = true; } } public void PathThread(object Startandend) { object[] Startandendarray = (object[])Startandend; Point startpoint = (Point)Startandendarray[0]; Point endpoint = (Point)Startandendarray[1]; bool runnable = true; // Path find from 255, 255 to 0,0 on the map foreach(Tile tile in Map) { if(tile.Color == Color.Red) { if (tile.Position.Contains(endpoint)) { runnable = false; } } } if(runnable == true) { running = true; Pathfinder p = new Pathfinder(Map); pathway = p.FindPath(startpoint, endpoint); running = false; threadstarted = false; } }

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• Why create a Huffman tree per character instead of a Node?

  - by Omega

  For a school assignment we're supposed to make a Java implementation of a compressor/decompresser using Huffman's algorithm. I've been reading a bit about it, specially this C++ tutorial: http://www.cprogramming.com/tutorial/computersciencetheory/huffman.html In my program, I've been thinking about having Nodes that have the following properties: Total Frequency Character (if a leaf) Right child (if any) Left child (if any) Parent (if any) So when building the Huffman tree, it is just a matter of linking a node to others, etc. However, I'm a bit confused with the following quote (emphasis mine): First, every letter starts off as part of its own tree and the trees are ordered by the frequency of the letters in the original string. Then the two least-frequently used letters are combined into a single tree, and the frequency of that tree is set to be the combined frequency of the two trees that it links together. My question: why should I create a tree per letter, instead of just a node per letter and then do the linking later? I have not begun coding, I'm just studying the algorithm first, so I guess I'm missing an important detail. What is it?

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• How do I require use of the 5 GHz band when connecting to a Wireless N access point?

  - by cqcallaw

  What is says in the topic: there's a Wireless N access point to which I'd like to connect using the 5 GHz band exclusively. How does one accomplish this? Using the directive band=a in the connection configuration file in /etc/NetworkManager/system-connections doesn't seem to affect anything (/var/log/syslog still shows attempts by wpa_supplicant to connect using the 2.4 GHz band), and running iwconfig wlan0 freq 5G per this question results in the following error: Error for wireless request "Set Frequency" (8B04) : SET failed on device wlan0 ; Invalid argument. [Edit] I'm hoping the answer won't depend on the hardware in use, but here's some information about the hardware, just in case: System is an Asus ZenBook Prime UX31A-DB51, running Ubuntu 12.04. lspci output: 00:00.0 Host bridge: Intel Corporation Ivy Bridge DRAM Controller (rev 09) 00:02.0 VGA compatible controller: Intel Corporation Ivy Bridge Graphics Controller (rev 09) 00:04.0 Signal processing controller: Intel Corporation Device 0153 (rev 09) 00:14.0 USB controller: Intel Corporation Panther Point USB xHCI Host Controller (rev 04) 00:16.0 Communication controller: Intel Corporation Panther Point MEI Controller #1 (rev 04) 00:1a.0 USB controller: Intel Corporation Panther Point USB Enhanced Host Controller #2 (rev 04) 00:1b.0 Audio device: Intel Corporation Panther Point High Definition Audio Controller (rev 04) 00:1c.0 PCI bridge: Intel Corporation Panther Point PCI Express Root Port 1 (rev c4) 00:1c.1 PCI bridge: Intel Corporation Panther Point PCI Express Root Port 2 (rev c4) 00:1d.0 USB controller: Intel Corporation Panther Point USB Enhanced Host Controller #1 (rev 04) 00:1f.0 ISA bridge: Intel Corporation Panther Point LPC Controller (rev 04) 00:1f.2 SATA controller: Intel Corporation Panther Point 6 port SATA Controller [AHCI mode] (rev 04) 00:1f.3 SMBus: Intel Corporation Panther Point SMBus Controller (rev 04) 00:1f.6 Signal processing controller: Intel Corporation Panther Point Thermal Management Controller (rev 04) 02:00.0 Network controller: Intel Corporation Centrino Advanced-N 6235 (rev 24) The driver for the wireless interface is iwlwifi.

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• How to prevent duplicate data access methods that retrieve similar data?

  - by Ronald Wildenberg

  In almost every project I work on with a team, the same problem seems to creep in. Someone writes UI code that needs data and writes a data access method: AssetDto GetAssetById(int assetId) A week later someone else is working on another part of the application and also needs an AssetDto but now including 'approvers' and writes the following: AssetDto GetAssetWithApproversById(int assetId) A month later someone needs an asset but now including the 'questions' (or the 'owners' or the 'running requests', etc): AssetDto GetAssetWithQuestionsById(int assetId) AssetDto GetAssetWithOwnersById(int assetId) AssetDto GetAssetWithRunningRequestsById(int assetId) And it gets even worse when methods like GetAssetWithOwnerAndQuestionsById start to appear. You see the pattern that emerges: an object is attached to a large object graph and you need different parts of this graph in different locations. Of course, I'd like to prevent having a large number of methods that do almost the same. Is it simply a matter of team discipline or is there some pattern I can use to prevent this? In some cases it might make sense to have separate methods, i.e. getting an asset with running requests may be expensive so I do not want to include these all the time. How to handle such cases?

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• How to create shared home directories across multiple computers?

  - by Joe D

  I know there are ways to share a folder across computers making it easy to move files. But I was wondering how one would setup a single login which lets you access the same files regardless of which machine you login on? What I would like is something similar to something you would see in a college campus where students login on machines in the lab and see their files regardless of which machine they use. I know there are server involved here. I have a need to create this on a smaller scale where we have a few computers available (and one of these could act as the server if needed and host the files) that every one shares. Note, the specific install of software might be different on each computer but the login and OS are the same. Since some computers have additional capability that our group members will need to use at rotating schedules (software licenses or hardware components, etc.). I have not done this before, so I would appreciate detailed instructions if possible or a reference to a guide that describes this. Thanks in advance.

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• How can I create an orthographic display that handles different screen dimensions?

  - by Piku

  I'm trying to create an iPad/iPhone game using GLES2.0 that contains a 3D scene with a heads-up-display/GUI overlaid on the top. However, this problem would also apply if I were to port my game to a computer and run the game in a resizable window, or allow the user to change screen resolutions... When trying to make the 2D GUI/HUD work I've made the assumption that all I'm really doing is drawing a load of 2D textured 'quads' on the screen and am trying to treat the orthographic projection as an old-style 2D display with 0,0 in the upper left and screenWidth,ScreenHeight in the lower right. This causes me all sorts of confusion when I rotate my ipad into Landscape mode since I can't work out what to put into my projection and modelview matrices to turn everything around the right way. It also gets messy if I want to support the iPad's large screen, an iPhone or a Retina display since I have to then draw three sets of textures for everything and work out which ones to use. Should I be trying to map the 2D OpenGL co-ords 1:1 with the screen? While typing out this question it occurs to me that I could keep my origin in the centre, still running -1/+1 along the axes. This would let me scale my 2D content appropriately on the different screen sizes, but wouldn't I end up with the textures being scaled and possibly losing quality? I'm using OpenGLES 2.0 and have a matrix library that has equivalents to the GLES1.1 glOrthof() and glFrustrum() calls.

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• How to Create a Grid for a 2D Game?

  - by SoulBeaver

  So I'm currently writing the engine for my videogame. I've almost integrated Tiled (I think) so I should have a map-creator here soon. My question is, how do I actually make the grid? I'm really confused here. If I create a large map with, say, 20x20 grids the size of 32x32 (screen size 640x640), then what do I do with it? Let's say I have the code for creating a window, and then place a player sprite that I can move with input, that's fine. If I use one map that's as big as the screen, then every pixel on the map is also a pixel on the game screen. The mapping is exact. Now what happens if I have a 2000x2000 map, for example? My character would have to keep moving and move the map around (or rather the camera focused on the player moves). Then I can no longer say that the screen maps exactly to the pixel position of the map. I tried making a Grid class that maps out the screen area to 32x32 tiles, but I'm not sure if that makes any sense. Once the map moves each tile would have to update its information, or something. I'm just really confused here. How do I actually make the tiles and a grid and map them to the data I get from tiled, or that I make myself? Are there any good examples of source code that I could look at?

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• Permissions issue: how can Apache access files in my Home directory?

  - by richzilla

  I know file permissions have been covered on here before, but im struggling to get my head around the concept for my scenario. I created the files on an old ubuntu installation. Ive copied the files into my new ubuntu installation and put them in my webroot. When i attempt to run the files (theyre PHP files) i get an error relating to permissions in an attempt to fix this, i assumed that they must still be owned by the previous owner, so i ran chown -R on the directory, with my username as an argument, in order to take ownership of all of the files in the directory. It should be noted that the usernames between new and old ubuntu installations were the same. When i attempt to run the files again, same problem: 500 error due to permissions problems. Can anyone tell me what other steps i should take? The webroot for my apache installation is inside my home folder. If i create new files in my webroot, they also work as expected, its only the old files that are causing the problem.

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