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• Screen brightness dull after upgrade to Ubuntu 14.04

  - by user288426

  After upgrading to Ubuntu 14.04 I found that I could not increase screen brightness. I'm using a Samsung NC110 netbook. Initially the function key to modify brightness did not respond at all. After implementation of the first part of the fix, the key came alive and the brightness bar could be modified. Yet at maximum brightness indicated the screen still remained very dull. The 2nd part of the fix cures that problem, at least for this type of machine. First part of the fix was copied and modified in line with my experience from following post: How to control Brightness Open a terminal (Ctrl + Alt + T). Then type sudo nano /etc/default/grub. It will ask for your password. Type it in. Around the 11th line, there will be something like: GRUB_CMDLINE_LINUX_DEFAULT="quiet splash". Change it to: GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_osi=Linux acpi_backlight=vendor" Save the file by Ctrl+O followed by Ctrl+X. Then run sudo update-grub in the terminal. Reboot and see if backlight adjustment works. Then I needed to modify the rc.local file. Therefore read below fix to understand the procedure: problem with adjusting brightness Ubuntu 14.04 In my case I had 2 folders listed under /sys/class/backlight which were: intel_backlight samsung I realized that the samsung folder is governing. I had to modify the check for max brightness to: cat /sys/class/backlight/samsung/max_brightness In my case the max value obtained is 8. Besides putting this into rc.local, I also had to uncomment the first line to get this working. My rc.local under /etc/ now looks as follows: !/bin/sh -e # # rc.local # # This script is executed at the end of each multiuser runlevel. # Make sure that the script will "exit 0" on success or any other # value on error. # # In order to enable or disable this script just change the execution # bits. # # By default this script does nothing. echo 8 > /sys/class/backlight/samsung/brightness exit 0 Now I can modify brightness on my netbook and also can get the screen up to its maximum brightness. Hope this is helpful.

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• Working with vectors and transformations

  - by user29163

  I am going to write an graphical 2D application that allows user to create polygons and transform them through transformation such as rotation an so on. I was hoping someone can give pro and cons arguments for the different choices I got in my mind. (Its all in Java btw!) a). Represent vectors by filling matrices with 'real' numbers. This means making a matrix datas tructure that supports multiplication, transposing etc b). Make a own vector class, such that I can make a matrix class that support those vectors.

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• What is upcasting/downcasting?

  - by acidzombie24

  When learning about polymorphism you commonly see something like this class Base { int prv_member; virtual void fn(){} } class Derived : Base { int more_data; virtual void fn(){} } What is upcasting or downcasting? Is (Derived*)base_ptr; an upcast or downcast? I call it upcast because you are going away from the base into something more specific. Other people told me it is a downcast because you are going down a hierarchy into something specific with the top being the root. But other people seem to call it what i call it. When converting a base ptr to a derived ptr is it called upcasting or downcasting? and if someone can link to an official source or explain why its called that than great.

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• Public versus private inheritance when some of the parent's methods need to be exposed?

  - by Vorac

  Public inheritance means that all fields from the base class retain their declared visibility, while private means that they are forced to 'private' within the derived class's scope. What should be done if some of the parent's members (say, methods) need to be publicly exposed? I can think of two solution. Public inheritance somewhat breaks encapsulation. Furthermore, when you need to find out where is the method foo() defined, one needs to look at a chain of base classes. Private inheritance solves these problems, but introduces burden to write wrappers (more text). Which might be a good thing in the line of verbosity, but makes changes of interfaces incredibly cumbersome. What considerations am I missing? What constraints on the type of project are important? How to choose between the two (I am not even mentioning 'protected')? Note that I am targeting non-virtual methods. There isn't such a discussion for virtual methods (or is there).

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• How to specialize a c++ variadic template?

  - by Serge

  I'm trying to understand c++ variadic templates. I'm not much aware of the correct language to use to explain what I'd like to achieve, so it might be simpler if I provide a bit of code which illustrate what I'd like to achieve. #include <iostream> #include <string> using namespace std; template<int ...A> class TestTemplate1 { public: string getString() { return "Normal"; } }; template<int T, int ...A> string TestTemplate1<2, A...>::getString() { return "Specialized"; } template<typename ...A> class TestTemplate2 { }; int main() { TestTemplate1<1, 2, 3, 4> t1_1; TestTemplate1<1, 2> t1_2; TestTemplate1<> t1_3; TestTemplate1<2> t1_4; TestTemplate2<> t2_1; TestTemplate2<int, double> t2_2; cout << t1_1.getString() << endl; cout << t1_2.getString() << endl; cout << t1_3.getString() << endl; cout << t1_4.getString() << endl; } This throws several errors. error C2333: 'TestTemplate1<::getString' : error in function declaration; skipping function body error C2333: 'TestTemplate1<1,2,3,4::getString' : error in function declaration; skipping function body error C2333: 'TestTemplate1<1,2::getString' : error in function declaration; skipping function body error C2333: 'TestTemplate1<2::getString' : error in function declaration; skipping function body error C2977: 'TestTemplate1' : too many template arguments error C2995: 'std::string TestTemplate1::getString(void)' : function template has already been defined error C3860: template argument list following class template name must list parameters in the order used in template parameter list How can I have a specialized behavior for every TestTemplate1<2, ...> instances like t1_4?

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• Brightness fn key adjustment problems

  - by npCoder

  My brightness function key controls work after setting grub boot parameter to "acpi_osi=" but using them I cannot adjust the brightness higher than around 70% (there is empty bar left over and I can't adjust higher) unless I go to Brightness & Lock settings manually than I can use the slider to adjust it higher... I primarily use intel_backlight to adjust my backlight and I am running Linux kernel 3.14.1 on Ubuntu 14.04 LTS on an ASUS X550LA Laptop when I try: cd /sys/class/backlight/intel_backlight cat max_brightness 937 cat brightness 811 It seems that I can only adjust to a maximum of 811 using the fn brightness controls If I instead do cd /sys/class/backlight/acpi_video0 cat max_brightness 10 cat brightness 4 cat actual_brightness 10 With the FN keys actual_brightness is not equal to the value returned from brightness on acip_video0 (which is always 4) but on intel_backlight actual_brightness = brightness The adjustment problem seemingly arises because both intel_backlight and acpi_video0 are trying to adjust brightness

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• Weird appearance for a 3D XNA ground

  - by Belos

  I wanted to add a ground so I can know the position of a helicopter in the world. But the ground appeared in a weird way: http://i.stack.imgur.com/yTSuW.jpg The ground had the following texture: http://i.stack.imgur.com/pdpxB.png EDIT: Sorry, I forgot to post the code: public class ImportModel { public Vector3 Position { get; set; } public Vector3 Rotation { get; set; } public Vector3 Scale { get; set; } Model Model; Matrix[] modeltransforms; GraphicsDevice GraphicDevice; ContentManager Content; BoundingSphere sphere; bool boundingimplemented = false; public ImportModel(string model, GraphicsDevice gd, ContentManager cm, Vector3 position, Vector3 rot, Vector3 sca) { GraphicDevice = gd; Content = cm; Position = position; Rotation = rot; Scale = sca; Model = Content.Load<Model>(model); modeltransforms = new Matrix[Model.Bones.Count]; Model.CopyAbsoluteBoneTransformsTo(modeltransforms); } public void Draw(Camera camera) { Matrix baseworld = Matrix.CreateScale(Scale) * Matrix.CreateFromYawPitchRoll(Rotation.Y, Rotation.X, Rotation.Z) * Matrix.CreateTranslation(Position); foreach (ModelMesh mesh in Model.Meshes) { Matrix localworld = modeltransforms[mesh.ParentBone.Index] * baseworld; foreach (ModelMeshPart meshpart in mesh.MeshParts) { BasicEffect effect = (BasicEffect)meshpart.Effect; effect.World = localworld; effect.View = camera.View; effect.Projection = camera.Projection; effect.EnableDefaultLighting(); } mesh.Draw(); } } public BoundingSphere BoundingSphere { get { if (!boundingimplemented) { foreach (ModelMesh mesh in Model.Meshes) { BoundingSphere transformed = mesh.BoundingSphere.Transform( modeltransforms[mesh.ParentBone.Index]); sphere = BoundingSphere.CreateMerged(sphere, transformed); } Matrix worldTransform = Matrix.CreateScale(Scale) * Matrix.CreateTranslation(Position); BoundingSphere transforme = sphere; transforme = transforme.Transform(worldTransform); return transforme; } else { Matrix worldTransform = Matrix.CreateScale(Scale) * Matrix.CreateTranslation(Position); BoundingSphere transformed = sphere; transformed = transformed.Transform(worldTransform); return transformed; } } } } Then I call the class from the Game1 class: ImportModel ground = new ImportModel("ground", GraphicsDevice, Content, Vector3.Zero, Vector3.Zero, new Vector3(20f)); EDIT2:This is how the scene looks from top: i.stack.imgur.com/Hs983.jpg

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• Setting a leader from a sprite array

  - by Craig

  I'm looking to set a leader from an array of sprites, I keep on getting a NullReferenceException was unhandled error from within my main game class when calling the UpdateMouse Method. What have I dont wrong here? class MouseSprite { Random random = new Random(); private MouseSprite leader; public void UpdateBoundaryBox() { mouseBounds.X = (int)mousePosition.X - mouseTexture.Width / 2; mouseBounds.Y = (int)mousePosition.Y - mouseTexture.Height / 2; } public void UpdateMouse(Vector2 position, MouseSprite [] mice, int numberMice, int index) { Vector2 catPosition = position; int enemies = numberMice; this.alive = true; mice[random.Next(0, mice.Length)] = leader;

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• Geometry Shader : points + Triangles

  - by CmasterG

  I have different Shaders and for each Shader a instance of the ShaderClass class, which initializes the Shaders, Renders the Shaders, etc. I use most of the Shaderclasses without Geometry Shader, but in one Shader Class i also use a Geometry Shader. The problem is, that when I render one object with the Shaderclass that uses the Geometry shader, all other object are rendered with the same geometry that I create in the Geometry Shader. Can you help me? Is it possible that I have to use a Geometry Shader for each object, when I use one for one object? I use DirectX 11 with C++.

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• Java best practice Interface - subclasses and constants

  - by Taiko

  In the case where a couple of classes implements an interface, and those classes have a couple of constants in common (but no functions), were should I put this constant ? I've had this problem a couple of times. I have this interface : DataFromSensors that I use to hide the implementations of several sub classes like DataFromHeartRateMonitor DataFromGps etc... For some reason, those classes uses the same constants. And there's nowere else in the code were it is used. My question is, were should I put those constants ? Not in the interface, because it has nothing to do with my API Not in a static Constants class, because I'm trying to avoid those Not in a common abstract class, that would stand between the interface and the subclasses, because I have no functions in common, only a couple of constants (TIMEOUT_DURATION, UUID, those kind of things) I've read best practice for constants and interface to define constants but they don't really answer my question. Thanks !

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• After update, audio won't play throw hdmi cable

  - by ckhenderson

  Yesterday (June 7th) I faithfully updated a bunch of stuff through update manager (though I'm not sure what since I never read what I updated any more because I'm a bad person). Afterward, I discovered that I could no longer play audio through my tv via HDMI. The sound settings menu seems to have completely changed and the shell script that I wrote a week ago (with much pain and effort as I had never before written a shell script) to toggle between my laptop speakers and the HDMI cable output no longer works. When I type in pactl set-card-profile 0 output:hdmi-surround in the command line I get Failure: No such entity Presumably this means something with Pulse Audio changed but, while I'm learning a lot about the inner workings of Ubuntu/Linux, I'm not an expert and would love some help. EDIT: So I noticed that pacmd set-card-profile 0 output:hdmi-stereo seems to get everything working. Still, shouldn't there be a way to do this through the GUI as well?

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• Creating a DrawableGameComponent

  - by Christian Frantz

  If I'm going to draw cubes effectively, I need to get rid of the numerous amounts of draw calls I have and what has been suggested is that I create a "mesh" of my cubes. I already have them being stored in a single vertex buffer, but the issue lies in my draw method where I am still looping through every cube in order to draw them. I thought this was necessary as each cube will have a set position, but it lowers the frame rate incredibly. What's the easiest way to go about this? I have a class CubeChunk that inherits Microsoft.Stuff.DrawableGameComponent, but I don't know what comes next. I suppose I could just use the chunk of cubes created in my cube class, but that would just keep me going in circles and drawing each cube individually. The goal here is to create a draw method that draws my chunk as a whole, and to not draw individual cubes as I've been doing.

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• Octrees as data structure

  - by Christian Frantz

  In my cube world, I want to use octrees to represent my chunks of 20x20x20 cubes for frustum and occlusion culling. I understand how octrees work, I just dont know if I'm going about this the right way. My base octree class is taken from here: http://www.xnawiki.com/index.php/Octree What I'm wondering is how to apply occlusion culling using this class. Does it make sense to have one octree for each cube chunk? Or should I make the octree bigger? Since I'm using cubes, each cube should fit into a node without overlap so that won't be an issue

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• Useful design patterns for working with FragmentManger on Android

  - by antman8969

  When working with fragments, I have been using a class composed of static methods that define actions on fragments. For any given project, I might have a class called FragmentActions, which contains methods similar to the following: public static void showDeviceFragment(FragmentManager man){ String tag = AllDevicesFragment.getFragmentTag(); AllDevicesFragment fragment = (AllDevicesFragment)man.findFragmentByTag(tag); if(fragment == null){ fragment = new AllDevicesFragment(); } FragmentTransaction t = man.beginTransaction(); t.add(R.id.main_frame, fragment, tag); t.commit(); } I'll usually have one method per application screen. I do something like this when I work with small local databases (usually SQLite) so I applied it to fragments, which seem to have a similar workflow; I'm not married to it though. How have you organized your applications to interface with the Fragments API, and what (if any) design patterns do you think apply do this?

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• Best way of accessing data on different pages

  - by Gaz83

  I'm looking for a way to load data into properties/variables etc and have this information accessible to all the pages of my app. I want the information to be loaded via a background thread to keep UI thread free. Some of the pages will have various properties of their controls binding to these global properties. Here is what I tried. Created a static class. All pages could access the data but can't bind. Changed the static class to a Singleton and used DependencyProperty's. All pages could access data and binding worked fine but cross-threading issues when accessing via background threads. I have read in various places on this subject but haven't really come up with the best method yet for my situation.

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• Wordpress Theme

  - by HotPizzaBox

  I'm trying to create a basic wordpress theme. As far as I know the basic files I need are the style.css, header.php, index.php, footer.php, functions.php. Then it should show a blank site with some meta tags in the header. These are my files: functions.php <?php // load the language files load_theme_textdomain('brianroyfoundation', get_template_directory() . '/languages'); // add menu support add_theme_support('menus'); register_nav_menus(array('primary_navigation' => __('Primary Navigation', 'BrianRoyFoundation'))); // create widget areas: sidebar $sidebars = array('Sidebar'); foreach ($sidebars as $sidebar) { register_sidebar(array('name'=> $sidebar, 'before_widget' => '<div class="widget %2$s">', 'after_widget' => '</div>', 'before_title' => '<h6><strong>', 'after_title' => '</strong></h6>' )); } // Add Foundation 'active' class for the current menu item function active_nav_class($classes, $item) { if($item->current == 1) { $classes[] = 'active'; } return $classes; } add_filter( 'nav_menu_css_class', 'active_nav_class', 10, 2); ?> header.php <!DOCTYPE html> <html <?php language_attributes(); ?>> <head> <meta charset="<?php bloginfo('charset'); ?>" /> <meta name="description" content="<?php bloginfo('description'); ?>"> <meta name="google-site-verification" content=""> <meta name="author" content="Your Name Here"> <!-- No indexing if Search page is displayed --> <?php if(is_search()){ echo '<meta name="robots" content="noindex, nofollow" />' } ?> <title><?php wp_title('|', true, 'right'); bloginfo('name'); ?></title> <link rel="stylesheet" type="text/css" href="<?php bloginfo('stylesheet_url'); ?>" /> <?php wp_head(); ?> </head> <body> <div id="page"> <div id="page-header"> <div id="page-title"> <a href="<?php bloginfo('url'); ?>" title="<?php bloginfo('name'); ?>"><?php bloginfo('name'); ?></a> </div> <div id="page-navigation"> <?php wp_nav_menu( array( 'theme_location' => 'primary_navigation', 'container' =>false, 'menu_class' => '' ); ?> </div> </div> <div id="page-content"> index.php <?php get_header(); ?> <div class="page-blog"> <?php get_template_part('loop', 'index'); ?> </div> <div class="page-sidebar"> <?php get_sidebar(); ?> </div> <?php get_footer(); ?> footer.php </div> <div id="page-footer"> &copy; 2008 - <?php echo date('Y'); ?> All rights reserved. </div> </div> <?php wp_footer(); ?> </body> </html> I activated the theme in wordpress. But it just shows nothing. Not even if I view the page source. Can anyone help?

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• How to tell what part of a 3D cube was touched

  - by user2539517

  I am writing a rather simple android game and I am implementing Open GL to draw a 3D cube that spins upon the X, Y and Z axis and I need to know where the user has clicked on the texture of the cube. The texture is a simple square bitmap (100x100) that has a smaller square in the center. I need to know if the user touches the inner square. As well was tell which face of the cube the user touches. Does anyone know how this can be accomplished if not can anyone give some pseudo code on how to tell where the ray correlates to the texture? Or at least point me in the right direction. The textures of each face are like this: The code I am using is from: http://www3.ntu.edu.sg/home/ehchua/programming/android/Android_3D.html2.9 It is a port to android from Lesson 6 NeHe. Example 6a: Photo-Cube

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• Custom Font in Property Sheets

  CCBPropertySheet: an MFC-extension class for creating property sheets with custom fonts.

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• Collaborative Whiteboard using WebSocket in GlassFish 4 - Text/JSON and Binary/ArrayBuffer Data Transfer (TOTD #189)

  - by arungupta

  This blog has published a few blogs on using JSR 356 Reference Implementation (Tyrus) as its integrated in GlassFish 4 promoted builds. TOTD #183: Getting Started with WebSocket in GlassFish TOTD #184: Logging WebSocket Frames using Chrome Developer Tools, Net-internals and Wireshark TOTD #185: Processing Text and Binary (Blob, ArrayBuffer, ArrayBufferView) Payload in WebSocket TOTD #186: Custom Text and Binary Payloads using WebSocket One of the typical usecase for WebSocket is online collaborative games. This Tip Of The Day (TOTD) explains a sample that can be used to build such games easily. The application is a collaborative whiteboard where different shapes can be drawn in multiple colors. The shapes drawn on one browser are automatically drawn on all other peer browsers that are connected to the same endpoint. The shape, color, and coordinates of the image are transfered using a JSON structure. A browser may opt-out of sharing the figures. Alternatively any browser can send a snapshot of their existing whiteboard to all other browsers. Take a look at this video to understand how the application work and the underlying code. The complete sample code can be downloaded here. The code behind the application is also explained below. The web page (index.jsp) has a HTML5 Canvas as shown: <canvas id="myCanvas" width="150" height="150" style="border:1px solid #000000;"></canvas> And some radio buttons to choose the color and shape. By default, the shape, color, and coordinates of any figure drawn on the canvas are put in a JSON structure and sent as a message to the WebSocket endpoint. The JSON structure looks like: { "shape": "square", "color": "#FF0000", "coords": { "x": 31.59999942779541, "y": 49.91999053955078 }} The endpoint definition looks like: @WebSocketEndpoint(value = "websocket",encoders = {FigureDecoderEncoder.class},decoders = {FigureDecoderEncoder.class})public class Whiteboard { As you can see, the endpoint has decoder and encoder registered that decodes JSON to a Figure (a POJO class) and vice versa respectively. The decode method looks like: public Figure decode(String string) throws DecodeException { try { JSONObject jsonObject = new JSONObject(string); return new Figure(jsonObject); } catch (JSONException ex) { throw new DecodeException("Error parsing JSON", ex.getMessage(), ex.fillInStackTrace()); }} And the encode method looks like: public String encode(Figure figure) throws EncodeException { return figure.getJson().toString();} FigureDecoderEncoder implements both decoder and encoder functionality but thats purely for convenience. But the recommended design pattern is to keep them in separate classes. In certain cases, you may even need only one of them. On the client-side, the Canvas is initialized as: var canvas = document.getElementById("myCanvas");var context = canvas.getContext("2d");canvas.addEventListener("click", defineImage, false); The defineImage method constructs the JSON structure as shown above and sends it to the endpoint using websocket.send(). An instant snapshot of the canvas is sent using binary transfer with WebSocket. The WebSocket is initialized as: var wsUri = "ws://localhost:8080/whiteboard/websocket";var websocket = new WebSocket(wsUri);websocket.binaryType = "arraybuffer"; The important part is to set the binaryType property of WebSocket to arraybuffer. This ensures that any binary transfers using WebSocket are done using ArrayBuffer as the default type seem to be blob. The actual binary data transfer is done using the following: var image = context.getImageData(0, 0, canvas.width, canvas.height);var buffer = new ArrayBuffer(image.data.length);var bytes = new Uint8Array(buffer);for (var i=0; i<bytes.length; i++) { bytes[i] = image.data[i];}websocket.send(bytes); This comprehensive sample shows the following features of JSR 356 API: Annotation-driven endpoints Send/receive text and binary payload in WebSocket Encoders/decoders for custom text payload In addition, it also shows how images can be captured and drawn using HTML5 Canvas in a JSP. How could this be turned in to an online game ? Imagine drawing a Tic-tac-toe board on the canvas with two players playing and others watching. Then you can build access rights and controls within the application itself. Instead of sending a snapshot of the canvas on demand, a new peer joining the game could be automatically transferred the current state as well. Do you want to build this game ? I built a similar game a few years ago. Do somebody want to rewrite the game using WebSocket APIs ? :-) Many thanks to Jitu and Akshay for helping through the WebSocket internals! Here are some references for you: JSR 356: Java API for WebSocket - Specification (Early Draft) and Implementation (already integrated in GlassFish 4 promoted builds) Subsequent blogs will discuss the following topics (not necessary in that order) ... Error handling Interface-driven WebSocket endpoint Java client API Client and Server configuration Security Subprotocols Extensions Other topics from the API

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• InputLayout handling

  - by Kikaimaru

  Where are you supposed to store InputLayout? Suppose i have some basic structure like. class Mesh { List<MeshPart> MeshParts } class MeshPart { Effect Effect; VertexBufferBinding VertexBuffer; ... } Where should I store input layout? It's a connection between vertex buffer and specific pass, i can live with just 1 pass but I still have diffferent techniques so i need at least an array with some connection to effecttechniques, but I would appriciate something not crazy like dictionary. I could also create wrapper for Effect and EffectTechnique, but there must be some normal solution.

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• CuteFTP Professional

  The business class, ultra-secure commercial release of <a href = "/ftp-cuteftp.html">CuteFTP</a>

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• High Tech Product Companies: Benchmark Your Sales & Marketing Data Management

  - by user709269

  Aberdeen’s Q4 2010 Quarterly Business Review found that 74% of the Sales and Marketing organizations in High Tech product manufacturing have strategic CRM initiatives in 2011. Aberdeen Group is conducting a survey that will help high tech product companies such as yours determine the Best-in-Class procedures for capturing, managing, and disseminating business data. If your product company is planning on implementing a CRM solution or is simply evaluating the potential benefits, we would appreciate your feedback in this brief, 10-minute survey. You will be able to compare your experiences in leveraging customer information for sales and marketing compare with your peers, benchmark your performance, and see how you can achieve Best-in-Class results. Individual responses will be kept strictly confidential, and data will only be used in aggregate. In appreciation for sharing your time and thoughts with us, we will provide complimentary access for you to the full benchmark report as soon as it is published (a $399 value). Take the survey.

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• Deduping your redundancies

  - by nospam(at)example.com (Joerg Moellenkamp)

  Robin Harris of Storagemojo pointed to an interesting article about about deduplication and it's impact to the resiliency of your data against data corruption on ACM Queue. The problem in short: A considerable number of filesystems store important metadata at multiple locations. For example the ZFS rootblock is copied to three locations. Other filesystems have similar provisions to protect their metadata. However you can easily proof, that the rootblock pointer in the uberblock of ZFS for example is pointing to blocks with absolutely equal content in all three locatition (with zdb -uu and zdb -r). It has to be that way, because they are protected by the same checksum. A number of devices offer block level dedup, either as an option or as part of their inner workings. However when you store three identical blocks on them and the devices does block level dedup internally, the device may just deduplicated your redundant metadata to a block stored just once that is stored on the non-voilatile storage. When this block is corrupted, you have essentially three corrupted copies. Three hit with one bullet. This is indeed an interesting problem: A device doing deduplication doesn't know if a block is important or just a datablock. This is the reason why I like deduplication like it's done in ZFS. It's an integrated part and so important parts don't get deduplicated away. A disk accessed by a block level interface doesn't know anything about the importance of a block. A metadata block is nothing different to it's inner mechanism than a normal data block because there is no way to tell that this is important and that those redundancies aren't allowed to fall prey to some clever deduplication mechanism. Robin talks about this in regard of the Sandforce disk controllers who use a kind of dedup to reduce some of the nasty effects of writing data to flash, but the problem is much broader. However this is relevant whenever you are using a device with block level deduplication. It's just the point that you have to activate it for most implementation by command, whereas certain devices do this by default or by design and you don't know about it. However I'm not perfectly sure about that ? given that storage administration and server administration are often different groups with different business objectives I would ask your storage guys if they have activated dedup without telling somebody elase on their boxes in order to speak less often with the storage sales rep. The problem is even more interesting with ZFS. You may use ditto blocks to protect important data to store multiple copies of data in the pool to increase redundancy, even when your pool just consists out of one disk or just a striped set of disk. However when your device is doing dedup internally it may remove your redundancy before it hits the nonvolatile storage. You've won nothing. Just spend your disk quota on the the LUNs in the SAN and you make your disk admin happy because of the good dedup ratio However you can just fall in this specific "deduped ditto block"trap when your pool just consists out of a single device, because ZFS writes ditto blocks on different disks, when there is more than just one disk. Yet another reason why you should spend some extra-thought when putting your zpool on a single LUN, especially when the LUN is sliced and dices out of a large heap of storage devices by a storage controller. However I have one problem with the articles and their specific mention of ZFS: You can just hit by this problem when you are using the deduplicating device for the pool. However in the specifically mentioned case of SSD this isn't the usecase. Most implementations of SSD in conjunction with ZFS are hybrid storage pools and so rotating rust disk is used as pool and SSD are used as L2ARC/sZIL. And there it simply doesn't matter: When you really have to resort to the sZIL (your system went down, it doesn't matter of one block or several blocks are corrupt, you have to fail back to the last known good transaction group the device. On the other side, when a block in L2ARC is corrupt, you simply read it from the pool and in HSP implementations this is the already mentioned rust. In conjunction with ZFS this is more interesting when using a storage array, that is capable to do dedup and where you use LUNs for your pool. However as mentioned before, on those devices it's a user made decision to do so, and so it's less probable that you deduplicating your redundancies. Other filesystems lacking acapability similar to hybrid storage pools are more "haunted" by this problem of SSD using dedup-like mechanisms internally, because those filesystem really store the data on the the SSD instead of using it just as accelerating devices. However at the end Robin is correct: It's jet another point why protecting your data by creating redundancies by dispersing it several disks (by mirror or parity RAIDs) is really important. No dedup mechanism inside a device can dedup away your redundancy when you write it to a totally different and indepenent device.

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• Is it appropriate to try to control the order of finalization?

  - by Strilanc

  I'm writing a class which is roughly analogous to a CancellationToken, except it has a third state for "never going to be cancelled". At the moment I'm trying to decide what to do if the 'source' of the token is garbage collected without ever being set. It seems that, intuitively, the source should transition the associated token to the 'never cancelled' state when it is about to be collected. However, this could trigger callbacks who were only kept alive by their linkage from the token. That means what those callbacks reference might now in the process of finalization. Calling them would be bad. In order to "fix" this, I wrote this class: public sealed class GCRoot { private static readonly GCRoot MainRoot = new GCRoot(); private GCRoot _next; private GCRoot _prev; private object _value; private GCRoot() { this._next = this._prev = this; } private GCRoot(GCRoot prev, object value) { this._value = value; this._prev = prev; this._next = prev._next; _prev._next = this; _next._prev = this; } public static GCRoot Root(object value) { return new GCRoot(MainRoot, value); } public void Unroot() { lock (MainRoot) { _next._prev = _prev; _prev._next = _next; this._next = this._prev = this; } } } intending to use it like this: Source() { ... _root = GCRoot.Root(callbacks); } void TransitionToNeverCancelled() { _root.Unlink(); ... } ~Source() { TransitionToNeverCancelled(); } but now I'm troubled. This seems to open the possibility for memory leaks, without actually fixing all cases of sources in limbo. Like, if a source is closed over in one of its own callbacks, then it is rooted by the callback root and so can never be collected. Presumably I should just let my sources be collected without a peep. Or maybe not? Is it ever appropriate to try to control the order of finalization, or is it a giant warning sign?

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• Why are only some of my objects being rendered?

  - by BleedObsidian

  Every time I create a new asteroid the previous one is no longer rendered? I did some debugging and printed out the size of Array-List 'Small' and when a new asteroid is created it doesn't go down, so the thread is still there it's just not being rendered, Why? StatePlay: package me.bleedobsidian.astroidjump; import org.newdawn.slick.GameContainer; import org.newdawn.slick.Graphics; import org.newdawn.slick.SlickException; import org.newdawn.slick.state.BasicGameState; import org.newdawn.slick.state.StateBasedGame; public class StatePlay extends BasicGameState { int stateID = 10; Player player; Asteroids asteroids; StatePlay(int stateID) { this.stateID = stateID; } @Override public int getID() { return stateID; } @Override public void init(GameContainer gc, StateBasedGame sbg) throws SlickException { ResManager.loadImages(); player = new Player(); asteroids = new Asteroids(); } @Override public void render(GameContainer gc, StateBasedGame sbg, Graphics g) throws SlickException { g.setAntiAlias(true); player.render(g); asteroids.render(g); g.drawString("Asteroids: " + Asteroids.small.size(), 10, 25); } @Override public void update(GameContainer gc, StateBasedGame sbg, int delta) throws SlickException { player.update(gc, delta); asteroids.update(delta); } } Asteroids: package me.bleedobsidian.astroidjump; import java.util.ArrayList; import java.util.Timer; import org.newdawn.slick.Graphics; import org.newdawn.slick.Image; import org.newdawn.slick.SpriteSheet; public class Asteroids { public static ArrayList<Asteroid_Small> small = new ArrayList<Asteroid_Small>(); static SpriteSheet small_sprites = new SpriteSheet(ResManager.asteroids_small_ss, 32, 32); static Image small_1 = small_sprites.getSubImage(0, 0); static Image small_2 = small_sprites.getSubImage(1, 0); static Image small_3 = small_sprites.getSubImage(2, 0); static Image small_4 = small_sprites.getSubImage(3, 0); static boolean asteroids = true; static int diff = 0; Asteroids() { Task_Asteroids TaskA = new Task_Asteroids(); Timer timer = new Timer("Asteroids"); if(diff == 0) { timer.schedule(TaskA, 0, 4000); } else if(diff == 1) { timer.schedule(TaskA, 0, 3000); } } public static Image chooseSmallImage(int i) { if(i == 0) { return small_1; } else if(i == 1) { return small_2; } else if(i == 2) { return small_3; } else if(i == 3) { return small_4; } else { return small_1; } } public static void level_manager(float x) { if(x < 1000) { diff = 0; } else if(x < 2000) { diff = 1; } else if(x < 3000) { diff = 2; } else if(x < 5000) { diff = 3; } else if(x < 10000) { diff = 4; } else { diff = 5; } } public void update(int delta) { for(int s = 0; s < small.size(); s++) { Asteroid_Small as = small.get(s); as.update(delta); } } public void render(Graphics g) { for(int s = 0; s < small.size(); s++) { Asteroid_Small as = small.get(s); as.render(g); } } public static void setAsteroids(boolean tf) { asteroids = tf; } } Asteroid_Small: package me.bleedobsidian.astroidjump; import org.newdawn.slick.Graphics; import org.newdawn.slick.Image; public class Asteroid_Small { private static Image me; private static float x = 0; private static float y = 0; private static float speed = 0; private static float rotation = 0; private static float rotation_speed = 0; Asteroid_Small(Image i, float x, float y, float rs, float sp) { me = i; Asteroid_Small.x = x; Asteroid_Small.y = y; Asteroid_Small.rotation_speed = rs; Asteroid_Small.speed = sp; } public void update(int delta) { x -= speed * delta; rotation += rotation_speed * delta; me.setRotation(rotation); } public void render(Graphics g) { g.drawImage(me, x, y); } } Task_Asteroid: package me.bleedobsidian.astroidjump; import java.util.TimerTask; public class Task_Asteroids extends TimerTask { public void run() { if(Asteroids.diff == 0) { int randImage = (int) (Math.random() * 4); int randHeight = (int) (Math.random() * 480); Asteroids.small.add(new Asteroid_Small(Asteroids.chooseSmallImage(randImage), Player.x + 960, randHeight, 0.05f, 0.04f)); } } }

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