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• Improving the performance of JDeveloper11g (part 2) and JVMs in general

  - by asantaga

  Just received an email from one of our JVM developers who read my blog entry on Performance tuning JDeveloper11g and he's confirmed that all of the above parameters are totally supported :-) He's also provided a description of the parameters so we can learn what magic is actually being applied. - -XX:+AggressiveOpts -- this enables the latest and greatest JVM optimizations. It will likely help most Java applications. It's fully supported. The downside of it is that because it has the latest and greatest optimizations, there is some small probability that it may not offer as good of an experience. As those features enabled with this command line option have "matured", they are made the default in a future JDK release. So, you can think of this command line option as the place where the newest optimizations get introduced. Some time later they are moved out from under AggressiveOpts to become default behavior. -XX:+OptimizeStringConcat -- only works with the -server JVM. It may be enabled by the default in a future JDK 7 update release. This option delays the construction of a StringBuilder/StringBuffer and attempts to avoid re-sizing the underlying char[] by attempting to detect the size of the char[] to allocate based on what's being appended to the StringBuilder/StringBuffer. -XX:+UseStringCache -- I would not suggest using this unless you knew that JDeveloper allocated the same string over and over again. And, the string that's allocated over and over again is one of the first 100,000 allocated strings. In short, I'd recommend against using it. And, in fact, in Java 7 (currently) does not include this feature. -XX:+UseCompressedOops -- applicable to 64-bit JVMs. And, if you're using a 64-bit JVM, I'd suggest you use it. It's auto enabled in JDK 7 64-bit JVMs and later JDK 6 64-bit JVMs enable it by default too. -XX:+UseGCOverheadLimit -- by default this option is already enabled. One other command line option to consider is -XX:+TieredCompilation for a JDK 6 Update 25 or later, or JDK 7. This gives you the startup of a -client JVM and the peak performance of a -server JVM. Awesome-ness!  Finally, Charlies also pointed out to me a "new" book he's just published where he goes into the details of JVM tuning, a must for all Fusion Middleware tuning exercises..  (click the book)  Thanks Charlie!

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• Help with Collision of spawned object(postion fixed) with objects that there are translating on screen

  - by Amrutha

  Hey guys I am creating a game using Corona SDK and so coding it in Lua. So there are 2 separate functions, To translate the hit objects and change their color when they are tapped The link below is the code I am using to for the first function http://developer.anscamobile.com/sample-code/fishies Spawn objects that will hit the translating objects on collision. Alos on collision the spawned object disappears and the translating object bears a color(indicating the collision). In addition the size of this spawned object is dependent on i/p volume level. The function I have written is as follows: --VOICE INPUT CODE local r = media.newRecording() r:startRecording() r:startTuner() --local function newBar() -- local bar = display.newLine( 0, 0, 1, 0 ) -- bar:setColor( 0, 55, 100, 20 ) -- bar.width = 5 -- bar.y=400 -- bar.x=20 -- return bar --end local c1 = display.newImage("str-minion-small.png") c1.isVisible=false local c2 = display.newImage("str-minion-mid.png") c2.isVisible=false local c3 = display.newImage("str-minion-big.png") c3.isVisible=false --SPAWNING local function spawnDisk( event ) local phase = event.phase local volumeBar = display.newLine( 0, 0, 1, 0 ) volumeBar.y = 400 volumeBar.x = 20 --volumeBar.isVisible=false local v = 20*math.log(r:getTunerVolume()) local MINTHRESH = 30 local LEFTMARGIN = 20 local v2 = MINTHRESH + math.max (v, -MINTHRESH) v2 = (display.contentWidth - 1 * LEFTMARGIN ) * v2 / MINTHRESH volumeBar.xScale = math.max ( 20, v2 ) local l = volumeBar.xScale local cnt1 = 0 local cnt2 = 0 local cnt3 = 0 local ONE =1 local val = event.numTaps --local px=event.x --local py=event.y if "ended" == phase then --audio.play( popSound ) --myLabel.isVisible = false if l > 50 and l <=150 then --c1:setFillColor(10,105,0) --c1.isVisible=false c1.x=math.random( 10, 450 ) c1.y=math.random( 10, 300 ) physics.addBody( c1, { density=1, radius=10.0 } ) c1.isVisible=true cnt1= cnt1+ ONE return c1 elseif l > 100 and l <=250 then --c2:setFillColor(200,10,0) c2.x=math.random( 10, 450 ) c2.y=math.random( 10, 300 ) physics.addBody( c2, { density=2, radius=9000.0 } ) c2.isVisible=true cnt2= cnt2+ ONE return c2 elseif l >=250 then c3.x=math.random( 40, 450 ) c3.y=math.random( 40, 300 ) physics.addBody( c3, { density=2, radius=7000.0 , bounce=0.0 } ) c3.isVisible=true cnt3= cnt3+ ONE return c3 end end end buzzR:addEventListener( "touch", spawnDisk ) -- touch the screen to create disks Now both functions work fine independently but there is no collision happening. Its almost as if the translating object and the spawn object are on different layers. The translating object passes through the spawn object freely. Can anyone please tell me how to resolve this problem. And how can I get them to collide. Its my first attempt at game development, that too for a mobile platform so would appreciate all help. Also if I have not been specific do let me know. I'll try to frame the query better :). Thanks in advance.

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• Running C++ AMP kernels on the CPU

  - by Daniel Moth

  One of the FAQs we receive is whether C++ AMP can be used to target the CPU. For targeting multi-core we have a technology we released with VS2010 called PPL, which has had enhancements for VS 11 – that is what you should be using! FYI, it also has a Linux implementation via Intel's TBB which conforms to the same interface. When you choose to use C++ AMP, you choose to take advantage of massively parallel hardware, through accelerators like the GPU. Having said that, you can always use the accelerator class to check if you are running on a system where the is no hardware with a DirectX 11 driver, and decide what alternative code path you wish to follow.  In fact, if you do nothing in code, if the runtime does not find DX11 hardware to run your code on, it will choose the WARP accelerator which will run your code on the CPU, taking advantage of multi-core and SSE2 (depending on the CPU capabilities WARP also uses SSE3 and SSE 4.1 – it does not currently use AVX and on such systems you hopefully have a DX 11 GPU anyway). A few things to know about WARP It is our fallback CPU solution, not intended as a primary target of C++ AMP. WARP stands for Windows Advanced Rasterization Platform and you can read old info on this MSDN page on WARP. What is new in Windows 8 Developer Preview is that WARP now supports DirectCompute, which is what C++ AMP builds on. It is not currently clear if we will have a CPU fallback solution for non-Windows 8 platforms when we ship. When you create a WARP accelerator, its is_emulated property returns true. WARP does not currently support double precision.   BTW, when we refer to WARP, we refer to this accelerator described above. If we use lower case "warp", that refers to a bunch of threads that run concurrently in lock step and share the same instruction. In the VS 11 Developer Preview, the size of warp in our Ref emulator is 4 – Ref is another emulator that runs on the CPU, but it is extremely slow not intended for production, just for debugging. Comments about this post by Daniel Moth welcome at the original blog.

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• Black screen on latest Nvidia Cards when starting LightDM/Ubuntu

  - by Luis Alvarado

  Today I installed an Nvidia GT440 on my computer, changing the one that existed there, an Nvidia 9500GT. After changing it I started getting a problem where the screen just went black when loading the lightdm login screen (Where I punt my user and password). The thing is, if I disconnect the VGA cable and connect it again I get to see the lightdm greeter and everything works perfect. The problem is that I have to connect/disconnect every time I reboot the PC. I tried installing the 285.xx drivers. Same problem. I removed the Nvidia drivers installed with Jockey, rebooted, same problem. I install the current 280.xx again, same problem. After all that I installed a fresh install of Ubuntu, selected to install the Nvidia drivers while installing it from the livecd. After booting the same problem appeared. Dmesg does not say anything wrong about it. Same goes for the log from Jockey. What else should I check or what to do to solve it. Just to clarify, this does not happen BEFORE the lightdm greeter appears. Am guessing before the actual use of the video card with X starts with all the 2D/3D stuff that is used in ligthdm and unity. I can use any tty and even see the Ubuntu logo when starting. UPDATE: When I open a game in fullscreen the problem appears again. I have to unplug the monitor cable and plug it back in to see the game. Then when I quit the game I have to do it again to see the desktop. UPDATE 2: Today I bought a HDMI cable, connected the video card to the TV am testing it with and it actually did log in correctly without any black screen but it shows the resolution a little over the actual size of the screen. So I see only half of the launcher since the left side of it is hidden outside of the real resolution and the top bar is beyond the resolution. So the black screen is related to the VGA connection.

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• Pay in the future should make you think in the present

  - by BuckWoody

  Distributed Computing - and more importantly “-as-a-Service” models of computing have a different cost model. This is something that sounds obvious on the surface but it’s often forgotten during the design and coding phase of a project. In on-premises computing, we’re used to purchasing a server and all of the hardware infrastructure and software licenses needed not only for one project, but several. This is an up-front or “sunk” cost that we consume by running code the organization needs to perform its function. Using a direct connection over wires you’ve already paid for, we don’t often have to think about bandwidth, hits on the data store or the amount of compute we use - we just know more is better. In a pay-as-you-go model, however, each of these architecture decisions has a potential cost impact. The amount of data you store, the number of times you access it, and the amount you send back all come with a charge. The offset is that you don’t buy anything at all up-front, so that sunk cost is freed up. And financial professionals know that money now is worth more than money later. Saving that up-front cost allows you to invest it in other things. It’s not just that you’re using things that now cost money - it’s that the design itself in distributed computing has a cost impact. That can be a really good thing, such as when you dynamically add capacity for paying customers. If you can tie back the cost of a series of clicks to what a user will pay to do so, you can set a profit margin that is easy to track. Here’s a case in point: Assume you are using a large instance in Windows Azure to compute some data that you retrieve from a SQL Azure database. If you don’t monitor the path of the application, you may not know what you are really using. Since you’re paying by the size of the instance, it’s best to maximize it all the time. Recently I evaluated just this situation, and found that downsizing the instance and adding another one where needed, adding a caching function to the application, moving part of the data into Windows Azure tables not only increased the speed of the application, but reduced the cost and more closely tied the cost to the profit. The key is this: from the very outset - the design - make sure you include metrics to measure for the cost/performance (sometimes these are the same) for your application. Windows Azure opens up awesome new ways of doing things, so make sure you study distributed systems architecture before you try and force in the application design you have on premises into your new application structure.

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• NetBeans IDE 7.3 Knows Null

  - by Geertjan

  What's the difference between these two methods, "test1" and "test2"? public int test1(String str) {     return str.length(); } public int test2(String str) {     if (str == null) {         System.err.println("Passed null!.");         //forgotten return;     }     return str.length(); } The difference, or at least, the difference that is relevant for this blog entry, is that whoever wrote "test2" apparently thinks that the variable "str" may be null, though did not provide a null check. In NetBeans IDE 7.3, you see this hint for "test2", but no hint for "test1", since in that case we don't know anything about the developer's intention for the variable and providing a hint in that case would flood the source code with too many false positives:  Annotations are supported in understanding how a piece of code is intended to be used. If method return types use @Nullable, @NullAllowed, @CheckForNull, the value is considered to be "strongly possible to be null", as well as if the variable is tested to be null, as shown above. When using @NotNull, @NonNull, @Nonnull, the value is considered to be non-null. (The exact FQNs of the annotations are ignored, only simple names are checked.) Here are examples showing where the hints are displayed for the non-null hints (the "strongly possible to be null" hints are not shown below, though you can see one of them in the screenshot above), together with a comment showing what is shown when you hover over the hint: There isn't a "one size fits all" refactoring for these various instances relating to null checks, hence you can't do an automated refactoring across your code base via tools in NetBeans IDE, as shown yesterday for class member reordering across code bases. However, you can, instead, go to Source | Inspect and then do a scan throughout a scope (e.g., current file/package/project or combinations of these or all open projects) for class elements that the IDE identifies as potentially having a problem in this area: Thanks to Jan Lahoda, who reports that this currently also works in NetBeans IDE 7.3 dev builds for fields but that may need to be disabled since right now too many false positives are returned, for help with the info above and any misunderstandings are my own fault!

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• Would someone please explain Octree Collisions to me?

  - by A-Type

  I've been reading everything I can find on the subject and I feel like the pieces are just about to fall into place, but I just can't quite get it. I'm making a space game, where collisions will occur between planets, ships, asteroids, and the sun. Each of these objects can be subdivided into 'chunks', which I have implemented to speed up rendering (the vertices can and will change often at runtime, so I've separated the buffers). These subdivisions also have bounding primitives to test for collision. All of these objects are made of blocks (yeah, it's that kind of game). Blocks can also be tested for rough collisions, though they do not have individual bounding primitives for memory reasons. I think the rough testing seems to be sufficient, though. So, collision needs to be fairly precise; at block resolution. Some functions rely on two blocks colliding. And, of course, attacking specific blocks is important. Now what I am struggling with is filtering my collision pairs. As I said, I've read a lot about Octrees, but I'm having trouble applying it to my situation as many tutorials are vague with very little code. My main issues are: Are Octrees recalculated each frame, or are they stored in memory and objects are shuffled into different divisions as they move? Despite all my reading I still am not clear on this... the vagueness of it all has been frustrating. How far do Octrees subdivide? Planets in my game are quite large, while asteroids are smaller. Do I subdivide to the size of the planet, or asteroid (where planet is in multiple divisions)? Or is the limit something else entirely, like number of elements in the division? Should I load objects into the octrees as 'chunks' or in the whole, then break into chunks later? This could be specific to my implementation, I suppose. I was going to ask about how big my root needed to be, but I did manage to find this question, and the second answer seems sufficient for me. I'm afraid I don't really get what he means by adding new nodes and doing subdivisions upon adding new objects, probably because I'm confused about whether the tree is maintained in memory or recalculated per-frame.

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• Finding a new programming language for web development?

  - by Xeoncross

  I'm wondering if there are any un-biased resources that give good, specific overviews of programming languages and their intended goals. I would like to learn a new language, but visiting the sites of each language isn't working. Each one talks about how great it is without much mention of it's weaknesses or specific goals. Ruby is a dynamic, open source programming language with a focus on simplicity and productivity. Python is a programming language that lets you work more quickly and integrate your systems more effectively. Having been a PHP developer for years, Vic Cherubini sums up my plight well: I knew PHP well, had my own framework, and could work quickly to get something up and running. I programmed like this throughout the MVC revolution. I got better and better jobs (read: better paying, better title) as a PHP developer, but all along the way realizing that the code I wrote on my own time was great, and the code I worked with at work was horrible. Like, worse than horrible. Atrocious. OS Commerce level bad. Having side projects kept me sane, because the code I worked with at work made me miserable. This is why I'm retiring from PHP for my side projects and new programming ventures. I'm spent with PHP. Exhausted, if you will. I've reached a level where I think I'm at the top with it as a language and if I don't move on to a new language soon, I'll be done completely with programming and I do not want that. Languages I've looked at include JavaScript (for node.js), Ruby, Python, & Erlang. I've even thought about Scala or C++. The problem is figuring out which ones are built to handle my needs the best. So where can I go to skip the hype and get real information about the maturity of a platform, the size of the community, and the strengths & weaknesses of that language. If I know these then picking a language to continue my web development should be easy.

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• SEO to ensure visibility for a narrow, non-competitive, non-commercial site

  - by hen3ry

  I'm webmaster of a non-commercial site in English. A non-native-English speaker asked me why our site doesn't produce hits in Google searches she conducts for relevant keywords in her native language. I asked her for a list of keywords in her native language, and I naively tried inserting those into the META info in the page headers and waited a couple of weeks. No help. A little searching informed me that Google doesn't use the META info, and has not done so for a very long time. D'oh! To be entirely concrete, suppose the StackExchange folks want Russian speakers to find this site, Pro Webmasters. The direct translation in Russian of "webmaster" --thanks, Google Translator-- is: "?????????". (Not sure this will render properly, but that's not essential to my question.) Assuming Pro Webmasters has a common template for all pages it generates, inserting "?????????" into the Keywords META for that template won't help, it seems. What could StackExchange do to make this site visible to users searching with the Russian keyword "?????????" ? Pretty much all the advice I've seen boils down to this, if I understand correctly: use the desired search term often (but not too often) among site content, and the problem will be solved. That's great, but I don't think sprinkling "?????????" visibly all over Pro Webmasters is going to fly. Just for completeness, crawlers must be long immune to the invisible-to-visitors scheme, e.g, format "?????????" in a tiny text size in a color the same as an existing background, e.g. white-over-white. Or, put that text inside a div styled: ' style="visibility: hidden" '. Probably some other equivalents. I can only think of one slightly effective method, along these lines: place an unobtrusive link on the common template to a page titled "for international users" , and on that page list desired synonyms for "webmaster" in various languages on that page. A test case --admittedly, just one-- using my site implies that a Google search for "international users" ????????? will produce a hit for this page, and thus make the site minimally visible, despite the fact that the page will almost never be visited. At the moment, anyway. Note: All the SEO discussions I have found so far are about competitive and --almost certainly-- commercial sites. To repeat: my site is non-commercial, and it is about an obscure, narrow topic that is of interest to only a small number of people worldwide. This isn't about clawing our way to the top of competitive rankings, just making this content minimally visible to interested non-native-English speakers. Ideas? TIA

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• how do I set quad buffering with jogl 2.0

  - by tony danza

  I'm trying to create a 3d renderer for stereo vision with quad buffering with Processing/Java. The hardware I'm using is ready for this so that's not the problem. I had a stereo.jar library in jogl 1.0 working for Processing 1.5, but now I have to use Processing 2.0 and jogl 2.0 therefore I have to adapt the library. Some things are changed in the source code of Jogl and Processing and I'm having a hard time trying to figure out how to tell Processing I want to use quad buffering. Here's the previous code: public class Theatre extends PGraphicsOpenGL{ protected void allocate() { if (context == null) { // If OpenGL 2X or 4X smoothing is enabled, setup caps object for them GLCapabilities capabilities = new GLCapabilities(); // Starting in release 0158, OpenGL smoothing is always enabled if (!hints[DISABLE_OPENGL_2X_SMOOTH]) { capabilities.setSampleBuffers(true); capabilities.setNumSamples(2); } else if (hints[ENABLE_OPENGL_4X_SMOOTH]) { capabilities.setSampleBuffers(true); capabilities.setNumSamples(4); } capabilities.setStereo(true); // get a rendering surface and a context for this canvas GLDrawableFactory factory = GLDrawableFactory.getFactory(); drawable = factory.getGLDrawable(parent, capabilities, null); context = drawable.createContext(null); // need to get proper opengl context since will be needed below gl = context.getGL(); // Flag defaults to be reset on the next trip into beginDraw(). settingsInited = false; } else { // The following three lines are a fix for Bug #1176 // http://dev.processing.org/bugs/show_bug.cgi?id=1176 context.destroy(); context = drawable.createContext(null); gl = context.getGL(); reapplySettings(); } } } This was the renderer of the old library. In order to use it, I needed to do size(100, 100, "stereo.Theatre"). Now I'm trying to do the stereo directly in my Processing sketch. Here's what I'm trying: PGraphicsOpenGL pg = ((PGraphicsOpenGL)g); pgl = pg.beginPGL(); gl = pgl.gl; glu = pg.pgl.glu; gl2 = pgl.gl.getGL2(); GLProfile profile = GLProfile.get(GLProfile.GL2); GLCapabilities capabilities = new GLCapabilities(profile); capabilities.setSampleBuffers(true); capabilities.setNumSamples(4); capabilities.setStereo(true); GLDrawableFactory factory = GLDrawableFactory.getFactory(profile); If I go on, I should do something like this: drawable = factory.getGLDrawable(parent, capabilities, null); but drawable isn't a field anymore and I can't find a way to do it. How do I set quad buffering? If I try this: gl2.glDrawBuffer(GL.GL_BACK_RIGHT); it obviously doesn't work :/ Thanks.

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• Is MongoDB a good choice or not for my application?

  - by shubham

  I have a Reporting application which stores the reports in xml format as recieved from source (XML schema is not defined, it can be any format) and those reports contain some keys and values. Like jobid, setid be keys for 1 type of report and userid, groupId for another type of report etc. The type of keys that can be referred from the document is determined by the namespaces used in the xml doc. These keys are stored on the basis of namespace used in the xml document. For e.g. If a tag in xml fragment uses namespace= "myspace1", then I have keys A and B for myspace1 stored in another table. It will fetch those keys from that table for this namespace, look for their values in xml doc and store it in another table along with the pointer to this xml document (Id of a record storing complete xml document in a cell). Use cases: When the user comes and queries for that key and value, I return the document or a set of documents that are having those key/value pairs. When the user comes and queries for a certain key and provide a name for xslt (pre stored), I fetch the set of documents fulfilling that criteria and convert that xml to html with the specified xslt. When the user comes and asks for a particular fragment of a doc then it can fetch a subset from a particular document also. When the user comes and queries for top x values of a certain key, I return the set of documents that are having top 10 values of that key. I am using DB2 database for its support of xml along with relational capabilities. That makes easier for me to run xpath expressions and fetch values of keys and also aggregate a set of documents fullfilling a criteria, all on the database side. Problems: DB2 stores XML doc of upto 2GB in size. Retrieval is very slow. If some thing involves many documents, then it takes significant time for things to show up in browser, and the user has to wait. Can MongoDb help in this case, as it is document oriented? can I do xml related xpath queries and document transformations on db side? Or is it ok to use both in such a case?

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• Now Shipping! NetAdvantage for .NET 2010 Volume 3!

  The new NetAdvantage Ultimate includes all four Line of Business user interface control sets for ASP .NET, Windows Forms, WPF and Silverlight plus two advanced Data Visualization UI control sets for WPF and Silverlight. With six NetAdvantage products in one robust package, Infragistics® gives you hundreds of controls and infinite development possibilities. Unified XAML Product Strategy-Share Code, Get More Controls In the 10.3 release, Infragistics continues to deliver code parity between the XAML platforms, WPF and Silverlight. In the line of business toolsets, Infragistics introduces the new xamSchedule™, full-featured, Outlook® 2010-style schedule controls, and the new xamDataTree™, a data bound tree view that comfortably handles tens of thousands of tree nodes. Mimicking our Silverlight Drag and Drop Framework, the WPF Drag and Drop Framework CTP empowers you to add your own rich touches to your applications. Track Users' Behaviors New to all NetAdvantage Silverlight controls is the Infragistics Analytics Framework (IGAF), which empowers you to track user behavior in RIAs running on Silverlight 4. Building on the Microsoft® Silverlight Analytics Framework, with IGAF you can analyze the user's behaviors to ensure the experience you want to deliver. NetAdvantage for Windows Forms--New Office® 2010 Ribbon and Application Menu 2010 Create new experiences with Windows Forms. Now with Office 2010 styling, NetAdvantage for Windows Forms has new features such as Microsoft® Office 2010 ribbon and enhanced Infragistics.Excel to export the contents of the high performance WinGrid™ into Microsoft Excel® 2010. The new Windows Message Support enables Infragistics standalone editor controls to process numerous Windows® OS messages, allowing them to respond just like native controls to changes in the Windows environment. Create Faster Web 2.0 Experiences with NetAdvantage for ASP .NET Infragistics continues to push the envelope to deliver the fastest ASP .NET WebForms controls available on the market. Our lightning fast ASP .NET grids are now enhanced with XPS/PDF Exporting and Summary Rows. This release also includes support for jQuery Templating (as a CTP) within our WebDataGrid™ and WebDataTree™ controls allowing you to quickly cut down overall page size. Deliver Business Intelligence with Power, Flexibility and the Office 2010 Experience NetAdvantage for WPF Data Visualization and NetAdvantage for Silverlight Data Visualization help you deliver flexible, powerful and usable end user experiences in Business Intelligence applications. Both suites include the Pivot Grid that delivers the full power of online analytical processing (OLAP) to present multi-dimensional data, sliced and diced in cross-tabulated form for end users to drill down into, interact with and easily extract meaning from the data. Mapping Made Easy 10.3 marks the official release of the WPF Data Visualization xamMap™ control to map anything and everything from geographic to geo-spacial mapping data. Map layers allow you to add successive levels of detail, navigational panes for panning in all directions, color swatch panes that facilitate value scales like Choropleth shading, and scale panes allowing users to zoom-in and out. Both toolsets introduce the first of many relationship maps! With the xamOrgChart™ CTP you can map out organizational charts of up to 50K employees, competitive brackets (think World Cup) and any other relational, organizational map your application needs. http://www.infragistics.com span.fullpost {display:none;}

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• Randomly generate directed graph on a grid

  - by Talon876

  I am trying to randomly generate a directed graph for the purpose of making a puzzle game similar to the ice sliding puzzles from Pokemon. This is essentially what I want to be able to randomly generate: http://bulbanews.bulbagarden.net/wiki/Crunching_the_numbers:_Graph_theory. I need to be able to limit the size of the graph in an x and y dimension. In the example given in the link, it would be restricted to an 8x4 grid. The problem I am running into is not randomly generating the graph, but randomly generating a graph, which I can properly map out in a 2d space, since I need something (like a rock) on the opposite side of a node, to make it visually make sense when you stop sliding. The problem with this is that sometimes the rock ends up in the path between two other nodes or possibly on another node itself, which causes the entire graph to become broken. After discussing the problem with a few people I know, we came to a couple of conclusions that may lead to a solution. Including the obstacles in the grid as part of the graph when constructing it. Start out with a fully filled grid and just draw a random path and delete out blocks that will make that path work. The problem then becomes figuring out which ones to delete to avoid introducing an additional, shorter path. We were also thinking a dynamic programming algorithm may be beneficial, though none of us are too skilled with creating dynamic programming algorithms from nothing. Any ideas or references about what this problem is officially called (if it's an official graph problem) would be most helpful. Here are some examples of what I have accomplished so far by just randomly placing blocks and generating the navigation graph from the chosen start/finish. The idea (as described in the previous link) is you start at the green S and want to get to the green F. You do this by moving up/down/left/right and you continue moving in the direction chosen until you hit a wall. In these pictures, grey is a wall, white is the floor, and the purple line is the minimum length from start to finish, and the black lines and grey dots represented possible paths. Here are some bad examples of randomly generated graphs: http://i.stack.imgur.com/9uaM6.png Here are some good examples of randomly generated (or hand tweaked) graphs: i.stack.imgur.com/uUGeL.png (can't post another link, sorry) I've also seemed to notice the more challenging ones when actually playing this as a puzzle are ones which have lots of high degree nodes along the minimum path.

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• Sql Table Refactoring Challenge

  Ive been working a bit on cleaning up a large table to make it more efficient.  I pretty much know what I need to do at this point, but I figured Id offer up a challenge for my readers, to see if they can catch everything I have as well as to see if Ive missed anything.  So to that end, I give you my table: CREATE TABLE [dbo].[lq_ActivityLog]( [ID] [bigint] IDENTITY(1,1) NOT NULL, [PlacementID] [int] NOT NULL, [CreativeID] [int] NOT NULL, [PublisherID] [int] NOT NULL, [CountryCode] [nvarchar](10) NOT NULL, [RequestedZoneID] [int] NOT NULL, [AboveFold] [int] NOT NULL, [Period] [datetime] NOT NULL, [Clicks] [int] NOT NULL, [Impressions] [int] NOT NULL, CONSTRAINT [PK_lq_ActivityLog2] PRIMARY KEY CLUSTERED ( [Period] ASC, [PlacementID] ASC, [CreativeID] ASC, [PublisherID] ASC, [RequestedZoneID] ASC, [AboveFold] ASC, [CountryCode] ASC)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]) ON [PRIMARY] And now some assumptions and additional information: The table has 200,000,000 rows currently PlacementID ranges from 1 to 5000 and should support at least 50,000 CreativeID ranges from 1 to 5000 and should support at least 50,000 PublisherID ranges from 1 to 500 and should support at least 50,000 CountryCode is a 2-character ISO standard (e.g. US) and there is a country table with an integer ID already.  There are < 300 rows. RequestedZoneID ranges from 1 to 100 and should support at least 50,000 AboveFold has values of 1, 0, or 1 only. Period is a date (no time). Clicks range from 0 to 5000. Impressions range from 0 to 5000000. The table is currently write-mostly.  Its primary purpose is to log advertising activity as quickly as possible.  Nothing in the rest of the system reads from it except for batch jobs that pull the data into summary tables. Heres the current information on the database tables size: Design Goals This table has been in use for about 5 years and has performed very well during that time.  The only complaints we have are that it is quite large and also there are occasionally timeouts for queries that reference it, particularly when batch jobs are pulling data from it.  Any changes should be made with an eye toward keeping write performance optimal  while trying to reduce space and improve read performance / eliminate timeouts during read operations. Refactor There are, I suggest to you, some glaringly obvious optimizations that can be made to this table.  And Im sure there are some ninja tweaks known to SQL gurus that would be a big help as well.  Ill post my own suggested changes in a follow-up post for now feel free to comment with your suggestions. Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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• Facebook Game database design

  - by facebook-100000781341887

  Hi, I'm currently develop a facebook mafia like PHP game(of course, a light weight version), here is a simplify database(MySQL) of the game id-a <int3> <for index> uid <chr15> <facebook uid> HP <int3> <health point> exp <int3> <experience> money <int3> <money> list_inventory <chr5> <the inventory user hold...some special here, talk next> ... and 20 other fields just like reputation, num of combat... *the number next to the type is the size(byte) of the type For the list_inventory, there have 40 inventorys in my game, (actually, I have 5 these kind of list in my database), and each user can only contain 1 qty of each inventory, therefore, I assign 5 char for this field and each bit of char as 1 item(5 char * 8 bit = 40 slot), and I will do some manipulation by PHP to extract the data from this 5 byte. OK, I was thinking on this, if this game contains 100,000 user, and only 10% are active, therefore, if use my method, for the space use, 5 byte * 100,000 = 500 KB if I use another method, create a table user_hold_inventory, if the user have the inventory, then insert a record into this table, so, for 10,000 active user, I assume they got all item, but for other, I assume they got no item, here is the fields of the new table id-b <int3> <for index> id-a <int3> <id of the user table> inv_no <int1> <inventory that user hold> for the space use, ([id] (3+3) byte + [inv_no] 1 byte ) * [active user] 10,000 * [all inventory] * 40 = 2.8 MB seems method 2 have use more space, but it consume less CPU power. Please comment these 2 method or please correct me if there have another better method rather than what I think. Another question is, my database contain 26 fields, but I counted 5 of them are not change frquently, should I need to separate it on the other table or not? So many words, thanks for reading :)

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• What's Bringing SharePoint 2007 Server to a hault?

  - by juanlarios

  I've been having issues with my teste environment and I'm hoping someone has run into this problem and can point me in the right direction. I noticed: SharePoint Server Memory is through the roof at times and so is the CPU usage. Most of CPU usage is a sql proccess. Running out of disk space all the time. I looked in the Logs located in the 12 hive and sure enough I have 1G log files that are hard to open because of the size. The following are the 3 error messages that are flooding my SharePoint logs:   04/05/2010 16:02:36.99     OWSTIMER.EXE (0x0B94)                       0x0BA4    Windows SharePoint Services       Timer                             5uuf    Monitorable    The previous instance of the timer job 'Variations Propagate Page Job Definition', id '{F9A73EB4-90FE-4574-AD99-B4034056F915}' for service '{F89169F9-707B-4588-9ED0-E6D399FE5E3D}' is still running, so the current instance will be skipped.  Consider increasing the interval between jobs.    04/05/2010 15:59:51.51     OWSTIMER.EXE (0x0B94)                       0x0BA4    Windows SharePoint Services       Timer                             5uuf    Monitorable    The previous instance of the timer job 'Profile Synchronization', id '{A05E3439-8DCD-449A-9D9E-46D601CACAA2}' for service '{F89169F9-707B-4588-9ED0-E6D399FE5E3D}' is still running, so the current instance will be skipped.  Consider increasing the interval between jobs.     04/05/2010 15:56:25.53     OWSTIMER.EXE (0x0B94)                       0x0BA4    Windows SharePoint Services       Timer                             5uuf    Monitorable    The previous instance of the timer job 'Scheduled Unpublish', id '{6298F93F-388D-46B9-809E-CEDBB8659661}' for service '{F89169F9-707B-4588-9ED0-E6D399FE5E3D}' is still running, so the current instance will be skipped.  Consider increasing the interval between jobs.     04/05/2010 15:54:14.73     OWSTIMER.EXE (0x0B94)                       0x0BA4    Windows SharePoint Services       Timer                             5uuf    Monitorable    The previous instance of the timer job 'Config Refresh', id '{C42DA970-3DA3-4AA2-94E5-8499C5B80A3E}' for service '{7F6D2CBE-8071-4A30-B313-7C9989FC2D87}' is still running, so the current instance will be skipped.  Consider increasing the interval between jobs.       I'm googling around but haven't found much. I know one other person posted something about this back in 2008, but no answers were reached. I have already checked the databases to see if any of them have gone offline for whatever reason, but from SQL everything is fine. I recently re-created an SSP and deleted an old ssp. So I thought maybe that was causing it, and who knows? maybe that causes some of the problems or maybe all. I'm running configuration wizard and see if anything changes. Please if someone has had similar issues let me know.

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• How can I fix broken i915 drivers for Intel GPUs?

  - by Alen Mujezinovic

  I've got troubles getting the i915 drivers to work correctly on my laptop (HP Pavilion DM4 2101ea). Specifically, the laptop screen goes black and stays black after the splash graphic when booting both from USB key and from harddrive. To get anything on to the display after the splash screen I have to boot either with acpi=off nomodeset i915.modeset=0 I'd rather not turn ACPI off because I like my fans spinning and nomodeset is a bit overkill, so for now I'm booting with i915.modeset=0. Unfortunately, this turns off KMS and my current maximum resolution on the laptop screen is fixed to 1024x768 instead of its real capability. When not setting any of the above boot flags and I plug in an external monitor, the external monitor works fine. When booting with the flags, the external monitor works fine too, but can only do 1024x768 and can't do anything else than mirroring the laptop display. I did upgrade the i915 drivers from 2.17 that ship with Precise to 2.19 which are the most recent ones but without luck of getting anything to display. Here's my lspci output: 00:00.0 Host bridge: Intel Corporation 2nd Generation Core Processor Family DRAM Controller (rev 09) 00:02.0 VGA compatible controller: Intel Corporation 2nd Generation Core Processor Family Integrated Graphics Controller (rev 09) 00:16.0 Communication controller: Intel Corporation 6 Series/C200 Series Chipset Family MEI Controller #1 (rev 04) 00:1a.0 USB controller: Intel Corporation 6 Series/C200 Series Chipset Family USB Enhanced Host Controller #2 (rev 05) 00:1b.0 Audio device: Intel Corporation 6 Series/C200 Series Chipset Family High Definition Audio Controller (rev 05) 00:1c.0 PCI bridge: Intel Corporation 6 Series/C200 Series Chipset Family PCI Express Root Port 1 (rev b5) 00:1c.2 PCI bridge: Intel Corporation 6 Series/C200 Series Chipset Family PCI Express Root Port 3 (rev b5) 00:1c.4 PCI bridge: Intel Corporation 6 Series/C200 Series Chipset Family PCI Express Root Port 5 (rev b5) 00:1d.0 USB controller: Intel Corporation 6 Series/C200 Series Chipset Family USB Enhanced Host Controller #1 (rev 05) 00:1f.0 ISA bridge: Intel Corporation HM65 Express Chipset Family LPC Controller (rev 05) 00:1f.2 SATA controller: Intel Corporation 6 Series/C200 Series Chipset Family 6 port SATA AHCI Controller (rev 05) 00:1f.3 SMBus: Intel Corporation 6 Series/C200 Series Chipset Family SMBus Controller (rev 05) 01:00.0 Network controller: Broadcom Corporation BCM4313 802.11b/g/n Wireless LAN Controller (rev 01) 02:00.0 Unassigned class [ff00]: Realtek Semiconductor Co., Ltd. RTS5116 PCI Express Card Reader (rev 01) 08:00.0 Ethernet controller: Atheros Communications Inc. AR8151 v2.0 Gigabit Ethernet (rev c0) Here's lshw -C video *-display UNCLAIMED description: VGA compatible controller product: 2nd Generation Core Processor Family Integrated Graphics Controller vendor: Intel Corporation physical id: 2 bus info: pci@0000:00:02.0 version: 09 width: 64 bits clock: 33MHz capabilities: msi pm vga_controller bus_master cap_list configuration: latency=0 resources: memory:c0000000-c03fffff memory:b0000000-bfffffff ioport:4000(size=64) Both outputs are generated after booting with i915.modeset=0. Here's a complete Xorg.log file from a boot into a black screen: https://gist.github.com/479ce06454e47d6123e1 The graphics card is a Intel HD 3000 integrated GPU. I've never had problems with Intel hardware on Ubuntu before so this is very surprising. If you could provide a method to make i915 work, suggest alternative drivers a way to boot with i915.modeset=0 but higher resolutions and KMS on or explain what is happening and how to fix it I'll give you an answer badge. :) Thanks

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• SQL Azure Security: DoS Part II

  - by Herve Roggero

  Ah!  When you shoot yourself in the foot... a few times... it hurts! That's what I did on Sunday, to learn more about the behavior of the SQL Azure Denial Of Service prevention feature. This article is a short follow up to my last post on this feature. In this post, I will outline some of the lessons learned that were the result of testing the behavior of SQL Azure from two machines. From the standpoint of SQL Azure, they look like one machine since they are behind a NAT. All logins affected The first thing to note is that all the logins are affected. If you lock yourself out to a specific database, none of the logins will work on that database. In fact the database size becomes "--" in the SQL Azure Portal.   Less than 100 sessions I was able to see 50+ sessions being made in SQL Azure (by looking at sys.dm_exec_sessions) before being locked out. The the DoS feature appears to be triggered in part by the number of open sessions. I could not determine if the lockout is triggered by the speed at which connection requests are made however.   Other Databases Unaffected This was interesting... the DoS feature works at the database level. Other databases were available for me to use.   Just Wait Initially I thought that going through SQL Azure and connecting from there would reset the database and allow me to connect again. Unfortunately this doesn't seem to be the case. You will have to wait. And the more you lock yourself out, the more you will have to wait... The first time the database became available again within 30 seconds or so; the second time within 2-3 minutes and the third time... within 2-3 hours...   Successful Logins The DoS feature appears to engage only for valid logins. If you have a login failure, it doesn't seem to count. I ran a test with over 100 login failures without being locked.

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• Why does creating dynamic bodies in JBox2D freeze my app?

  - by Amplify91

  My game hangs/freezes when I create dynamic bullet objects with Box2D and I don't know why. I am making a game where the main character can shoot bullets by the user tapping on the screen. Each touch event spawns a new FireProjectileEvent that is handled properly by an event queue. So I know my problem is not trying to create a new body while the box2d world is locked. My bullets are then created and managed by an object pool class like this: public Projectile getProjectile(){ for(int i=0;i<mProjectiles.size();i++){ if(!mProjectiles.get(i).isActive){ return mProjectiles.get(i); } } return mSpriteFactory.createProjectile(); } mSpriteFactory.createProjectile() leads to the physics component of the Projectile class creating its box2d body. I have narrowed the issue down to this method and it looks like this: public void create(World world, float x, float y, Vec2 vertices[], boolean dynamic){ BodyDef bodyDef = new BodyDef(); if(dynamic){ bodyDef.type = BodyType.DYNAMIC; }else{ bodyDef.type = BodyType.STATIC; } bodyDef.position.set(x, y); mBody = world.createBody(bodyDef); PolygonShape dynamicBox = new PolygonShape(); dynamicBox.set(vertices, vertices.length); FixtureDef fixtureDef = new FixtureDef(); fixtureDef.shape = dynamicBox; fixtureDef.density = 1.0f; fixtureDef.friction = 0.0f; mBody.createFixture(fixtureDef); mBody.setFixedRotation(true); } If the dynamic parameter is set to true my game freezes before crashing, but if it is false, it will create a projectile exactly how I want it just doesn't function properly (because a projectile is not a static object). Why does my program fail when I try to create a dynamic object at runtime but not when I create a static one? I have other dynamic objects (like my main character) that work fine. Any help would be greatly appreciated. This is a screenshot of a method profile I did: Especially notable is number 8. I'm just still unsure what I'm doing wrong. Other notes: I am using JBox2D 2.1.2.2. (Upgraded from 2.1.2.1 to try to fix this problem) When the application freezes, if I hit the back button, it appears to move my game backwards by one update tick. Very strange.

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• Can see samba shares but not access them

  - by nitefrog

  For the life of me I cannot figure this one out. I have samba installed and set up on the ubuntu box and on the Win7 box I CAN SEE all the shares I created. I created two users on ubuntu that map to the users in windows. On ubuntu they are both admins, user A & B on Windows User A is admin and user B is poweruser. User A can see both shares and access them, but user B can see everythin, but only access the homes directory, the other directory throws an error. I have two drives in Ubuntu and this is the smb.config file (I am new to samba): [global] workgroup = WORKGROUP server string = %h server (Samba, Ubuntu) wins support = no dns proxy = yes name resolve order = lmhosts host wins bcast log file = /var/log/samba/log.%m max log size = 1000 syslog = 0 panic action = /usr/share/samba/panic-action %d security = user encrypt passwords = true passdb backend = tdbsam obey pam restrictions = yes unix password sync = yes passwd program = /usr/bin/passwd %u passwd chat = *Enter\snew\s*\spassword:* %n\n *Retype\snew\s*\spassword:* %n\n *password\supdated\ssuccessfully* . pam password change = yes map to guest = bad user ; usershare max shares = 100 usershare allow guests = yes And here is the share section: Both user A & B can access this from windows. No problems. [homes] comment = Home Directories browseable = no writable = yes Both User A & B can see this share, but only user A can access it. User B get an error thrown. [stuff] comment = Unixmen File Server path = /media/data/appinstall/ browseable = yes ;writable = no read only = yes hosts allow = The permission for the media/data/appinstall/ is as follows: appInstall properties: share name: stuff Allow others to create and delete files in this folder is cheeked Guest access (for people without a user account) is checked permissions: Owner: user A Folder Access: Create and delete files File Access: --- Group: user A Folder Access: Create and delete files File Access: --- Others Folder Access: Create and delete files File Access: --- I am at a loss and need to get this work. Any ideas? The goal is to have a setup like this. 3 users on window machines. Each user on the data drive will have their own personal folder where they are the ones that can only access, then another folder where 2 of the users will have read only and one user full access. I had this setup before on windows, but after what happened I am NEVER going back to windows, so Unix here I am to stay! I am really stuck. I am running Ubuntu 11. I could reformat again and put on version 10 if that would make life easier. I have been dealing with this since Wed. 3pm. Thanks.

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• PeopleSoft New Design Solves Navigation Problem

  - by Applications User Experience

  Anna Budovsky, User Experience Principal Designer, Applications User Experience In PeopleSoft we strive to improve User Experience on all levels. Simplifying navigation and streamlining access to the most important pages is always an important goal. No one likes to waste time waiting for pages to load and watching a spinning glass going on and on. Those performance-affecting server trips, page-load waits and just-too-many clicks were complained about for a long time. Something had to be done. A few new designs came in PeopleSoft 9.2 helping users to access their everyday work areas easier and faster. For example, Dashboard and Work Center aggregate most accessed information sections on a single page; Related Information allows users to complete transaction-related-research without interrupting a transaction and Secure Search gets users to a specific page directly. Today we’ll talk about the Actions menu. Most PeopleSoft pages are shared between individual products and product lines. It means changing the content on a single page involves Oracle development and quality assurance time for making and testing the changes. In order to streamline the navigation and cut down on accessing PeopleSoft pages one-page-at-a-time, we introduced a new menu design. The new menu allows accessing shared pages without the Oracle development team making any local changes, and it works as an additional one-click-path to specific high-traffic actionable pages. Let’s look at how many steps it took to Change Salary for an employee in HCM 9.1 before: Figure 1. BEFORE: The 6 steps a user would take to Change Salary in PeopleSoft HCM 9.1 In PeopleSoft 9.1 it took 5 steps + page loading time + additional verification time for making sure a correct employee is selected from the table. In PeopleSoft 9.2 it only takes 2 steps. To complete Ad Hoc Change Salary action, the user can start from the HCM Manager's Dashboard, click the Action menu within a table, choose a menu option, and access a correct employee’s details page to take an action. Figure 2. AFTER: The 2 steps a user would take to Change Salary in PeopleSoft HCM 9.2 The new menu is placed on a row level which ensures the user accesses the correct employee’s details page. The Actions menu separates menu options into hierarchical sections which help to scan and access the correct option quickly. The new menu’s small size and its structure enabled users to access high-traffic pages from any page and from any part of the page. No more spinning hourglass, no more multiple pages upload. The flexible design fits anywhere on a page and provides a fast and reliable path to the correct destination within the product. Now users can: Access any target page no matter how far it is buried from the starting point; Reduce navigation and page-load time; Improve productivity and reduce errors. The new menu design is available and widely used in all PeopleSoft 9.2 product lines.

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• Microsoft and Application Architectures

  Microsoft has dealt with several kinds of application architectures to include but not limited to desktop applications, web applications, operating systems, relational database systems, windows services, and web services. Because of the size and market share of Microsoft, virtually every modern language works with or around a Microsoft product. Some of the languages include: Visual Basic, VB.Net, C#, C++, C, ASP.net, ASP, HTML, CSS, JavaScript, Java and XML. From my experience, Microsoft strives to maintain an n-tier application standard where an application is comprised of multiple layers that perform specific functions, for example: presentation layer, business layer, data access layer are three general layers that just about every formally structured application contains. The presentation layer contains anything to do with displaying information to the screen and how it appears on the screen. The business layer is the middle man between the presentation layer and data access layer and transforms data from the data access layer in to useable information to be stored later or sent to an output device through the presentation layer. The data access layer does as its name implies, it allows the business layer to access data from a data source like MS SQL Server, XML, or another data source. One of my favorite technologies that Microsoft has come out with recently is the .Net Framework. This framework allows developers to code an application in multiple languages and compiles them in to one intermediate language called the Common Language Runtime (CLR). This allows VB and C# developers to work seamlessly together as if they were working in the same project. The only real disadvantage to using the .Net Framework is that it only natively runs on Microsoft operating systems. However, Microsoft does control a majority of the operating systems currently installed on modern computers and servers, especially with personal home computers. Given that the Microsoft .Net Framework is so flexible it is an ideal for business to develop applications around it as long as they wanted to commit to using Microsoft technologies and operating systems in the future. I have been a professional developer for about 9+ years now and have seen the .net framework work flawlessly in just about every instance I have used it. In addition, I have used it to develop web applications, mobile phone applications, desktop applications, web service applications, and windows service applications to name a few.

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• Opengl-es picking object

  - by lacas

  I saw a lot of picking code opengl-es, but nothing worked. Can someone give me what am I missing? My code is (from tutorials/forums) Vec3 far = Camera.getPosition(); Vec3 near = Shared.opengl().getPickingRay(ev.getX(), ev.getY(), 0); Vec3 direction = far.sub(near); direction.normalize(); Log.e("direction", direction.x+" "+direction.y+" "+direction.z); Ray mouseRay = new Ray(near, direction); for (int n=0; n<ObjectFactory.objects.size(); n++) { if (ObjectFactory.objects.get(n)!=null) { IObject obj = ObjectFactory.objects.get(n); float discriminant, b; float radius=0.1f; b = -mouseRay.getOrigin().dot(mouseRay.getDirection()); discriminant = b * b - mouseRay.getOrigin().dot(mouseRay.getOrigin()) + radius*radius; discriminant = FloatMath.sqrt(discriminant); double x1 = b - discriminant; double x2 = b + discriminant; Log.e("asd", obj.getName() + " "+discriminant+" "+x1+" "+x2); } } my camera vectors: //cam Vec3 position =new Vec3(-obj.getPosX()+x, obj.getPosZ()-0.3f, obj.getPosY()+z); Vec3 direction =new Vec3(-obj.getPosX(), obj.getPosZ(), obj.getPosY()); Vec3 up =new Vec3(0.0f, -1.0f, 0.0f); Camera.set(position, direction, up); and my picking code: public Vec3 getPickingRay(float mouseX, float mouseY, float mouseZ) { int[] viewport = getViewport(); float[] modelview = getModelView(); float[] projection = getProjection(); float winX, winY; float[] position = new float[4]; winX = (float)mouseX; winY = (float)Shared.screen.width - (float)mouseY; GLU.gluUnProject(winX, winY, mouseZ, modelview, 0, projection, 0, viewport, 0, position, 0); return new Vec3(position[0], position[1], position[2]); } My camera moving all the time in 3d space. and my actors/modells moving too. my camera is following one actor/modell and the user can move the camera on a circle on this model. How can I change the above code to working?

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• How to interview a natural scientist for a dev position?

  - by Silas

  I already did some interviews for my company, mostly computer scientists for dev positions but also some testers and project managers. Now I have to fill a vacancy in our research group within the R&D department (side note: “research” means that we try to solve problems in our professional domain/market niche using software in research projects together with universities, other companies, research centres and end user organisations. It’s not computer science research; we’re not going to solve the P=NP problem). Now we invited a guy holding an MSc in chemistry (with a lot of physics in his CV, too), who never had any computer science lesson. I already talked with him about half an hour at a local university’s career days and there’s no doubt the guy is smart. Also his marks are excellent and he graduated with distinction. For his BSc he needed to teach himself programming in Mathematica and told me believably that he liked programming a lot. Also he solved some physical chemistry problem that I probably don’t understand using his own software, implemented in Mathematica, for his MSc thesis. It includes a GUI and a notable size of 8,000 LoC. He seems to be very attracted by what we’re doing in our research group and to be honest it’s quite difficult for an SME like us to get good people. I also am very interested in hiring him since he could assist me in writing project proposals, reports, doing presentations and so on. He would probably fit to our team, too. The only question left is: How can I check if he will get the programming skills he needs to do software implementation in our projects since this will be a significant part of the job? Of course I will ask him what it is, that is fascinating him about programming. I’ll also ask how he proceeded to write his natural science software and how he structured it. I’ll ask about how he managed to obtain the skills and information about software development he needed. But is there something more I could ask? Something more concrete perhaps? Should I ask him to explain his Mathematica solution? To be clear: I’m not looking for knowledge in a particular language or technology stack. We’re a .NET shop in product development but I want to have a free choice for our research projects. So I’m interested in the meta-competence being able to learn whatever is actually needed. I hope this question is answerable and not open-ended since I really like to know if there is a default way to check for the ability to get further programming skills on the job. If something is not clear to you please give me some comments and let me improve my question.

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• How to refactor my design, if it seems to require multiple inheritance?

  - by Omega

  Recently I made a question about Java classes implementing methods from two sources (kinda like multiple inheritance). However, it was pointed out that this sort of need may be a sign of a design flaw. Hence, it is probably better to address my current design rather than trying to simulate multiple inheritance. Before tackling the actual problem, some background info about a particular mechanic in this framework: It is a simple game development framework. Several components allocate some memory (like pixel data), and it is necessary to get rid of it as soon as you don't need it. Sprites are an example of this. Anyway, I decided to implement something ala Manual-Reference-Counting from Objective-C. Certain classes, like Sprites, contain an internal counter, which is increased when you call retain(), and decreased on release(). Thus the Resource abstract class was created. Any subclass of this will obtain the retain() and release() implementations for free. When its count hits 0 (nobody is using this class), it will call the destroy() method. The subclass needs only to implement destroy(). This is because I don't want to rely on the Garbage Collector to get rid of unused pixel data. Game objects are all subclasses of the Node class - which is the main construction block, as it provides info such as position, size, rotation, etc. See, two classes are used often in my game. Sprites and Labels. Ah... but wait. Sprites contain pixel data, remember? And as such, they need to extend Resource. But this, of course, can't be done. Sprites ARE nodes, hence they must subclass Node. But heck, they are resources too. Why not making Resource an interface? Because I'd have to re-implement retain() and release(). I am avoiding this in virtue of not writing the same code over and over (remember that there are multiple classes that need this memory-management system). Why not composition? Because I'd still have to implement methods in Sprite (and similar classes) that essentially call the methods of Resource. I'd still be writing the same code over and over! What is your advice in this situation, then?

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