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• Testing When Correctness is Poorly Defined?

  - by dsimcha

  I generally try to use unit tests for any code that has easily defined correct behavior given some reasonably small, well-defined set of inputs. This works quite well for catching bugs, and I do it all the time in my personal library of generic functions. However, a lot of the code I write is data mining code that basically looks for significant patterns in large datasets. Correct behavior in this case is often not well defined and depends on a lot of different inputs in ways that are not easy for a human to predict (i.e. the math can't reasonably be done by hand, which is why I'm using a computer to solve the problem in the first place). These inputs can be very complex, to the point where coming up with a reasonable test case is near impossible. Identifying the edge cases that are worth testing is extremely difficult. Sometimes the algorithm isn't even deterministic. Usually, I do the best I can by using asserts for sanity checks and creating a small toy test case with a known pattern and informally seeing if the answer at least "looks reasonable", without it necessarily being objectively correct. Is there any better way to test these kinds of cases?

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• LicenseChecker checkAccess leaks ServiceConnection

  - by Bill The Ape

  I am receiving this exception in LogCat every time I press the Back button in my app: Activity has leaked ServiceConnection com.android.vending.licensing.LicenseChecker@471cc039 that was originally bound here The code responsible for this leak in onCreate() is: mLicenseCheckerCallback = new MyLicenseCheckerCallback(); mChecker.checkAccess(mLicenseCheckerCallback); How do I get rid of this leak? I tried not assigning MyLicenseCheckerCallback to a member, thinking perhaps when the activity goes onPause() the reference to the callback is responsible for the leak: mChecker.checkAccess(new MyLicenseCheckerCallback()); But that didn't get rid of the leak. Update: Thanks to @zapl's comment below, I looked at Google's LicenseChecker.java: /** Unbinds service if necessary and removes reference to it. */ private void cleanupService() { if (mService != null) { try { mContext.unbindService(this); } catch (IllegalArgumentException e) { // Somehow we've already been unbound. This is a non-fatal error. Log.e(TAG, "Unable to unbind from licensing service (already unbound)"); } mService = null; } } At first I thought that I may be neglecting to call it, but I double-checked and I am calling mChecker.onDestroy(); in my activity's onDestroy(). I also checked onDestroy() in LicenseChecker.java and it is calling unbindService: /** * Inform the library that the context is about to be destroyed, so that * any open connections can be cleaned up. * <p> * Failure to call this method can result in a crash under certain * circumstances, such as during screen rotation if an Activity requests * the license check or when the user exits the application. */ public synchronized void onDestroy() { cleanupService(); mHandler.getLooper().quit(); } So, what is really going on? Is this a bug in LVL?

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• To use the 'I' prefix for interfaces or not to

  - by ng

  That is the question? So how big a sin is it not to use this convention when developing a c# project? This convention is widely used in the .NET class library. However, I am not a fan to say the least, not just for asthetic reasons but I don't think it makes any contribution. For example is IPSec an interface of PSec? Is IIOPConnection An interface of IOPConnection, I usually go to the definition to find out anyway. So would not using this convention cause confusion? Are there any c# projects or libraries of note that drop this convention? Do any c# projects that mix conventions, as unfortunately Apache Wicket does? The Java class libraries have existed without this for many years, I don't feel I have ever struggled to read code without it. Also, should the interface not be the most primitive description? I mean IList<T> as an interface for List<T> in c#, is it not better to have List<T> and LinkedList<T> or ArrayList<T> or even CopyOnWriteArrayList<T>? The classes describe the implementation? I think I get more information here, than I do from List<T> in c#.

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• I don't like Python functions that take two or more iterables. Is it a good idea?

  - by Xavier Ho

  This question came from looking at this question on Stackoverflow. def fringe8((px, py), (x1, y1, x2, y2)): Personally, it's been one of my pet peeves to see a function that takes two arguments with fixed-number iterables (like a tuple) or two or more dictionaries (Like in the Shotgun API). It's just hard to use, because of all the verbosity and double-bracketed enclosures. Wouldn't this be better: >>> class Point(object): ... def __init__(self, x, y): ... self.x = x ... self.y = y ... >>> class Rect(object): ... def __init__(self, x1, y1, x2, y2): ... self.x1 = x1 ... self.y1 = y1 ... self.x2 = x2 ... self.y2 = y2 ... >>> def fringe8(point, rect): ... # ... ... >>> >>> point = Point(2, 2) >>> rect = Rect(1, 1, 3, 3) >>> >>> fringe8(point, rect) Is there a situation where taking two or more iterable arguments is justified? Obviously the standard itertools Python library needs that, but I can't see it being pretty in maintainable, flexible code design.

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• What is the rationale to not allow overloading of C++ conversions operator with non-member function

  - by Vicente Botet Escriba

  C++0x has added explicit conversion operators, but they must always be defined as members of the Source class. The same applies to the assignment operator, it must be defined on the Target class. When the Source and Target classes of the needed conversion are independent of each other, neither the Source can define a conversion operator, neither the Target can define a constructor from a Source. Usually we get it by defining a specific function such as Target ConvertToTarget(Source& v); If C++0x allowed to overload conversion operator by non member functions we could for example define the conversion implicitly or explicitly between unrelated types. template < typename To, typename From > operator To(const From& val); For example we could specialize the conversion from chrono::time_point to posix_time::ptime as follows template < class Clock, class Duration> operator boost::posix_time::ptime( const boost::chrono::time_point<Clock, Duration>& from) { using namespace boost; typedef chrono::time_point<Clock, Duration> time_point_t; typedef chrono::nanoseconds duration_t; typedef duration_t::rep rep_t; rep_t d = chrono::duration_cast<duration_t>( from.time_since_epoch()).count(); rep_t sec = d/1000000000; rep_t nsec = d%1000000000; return posix_time::from_time_t(0)+ posix_time::seconds(static_cast<long>(sec))+ posix_time::nanoseconds(nsec); } And use the conversion as any other conversion. For a more complete description of the problem, see here or on my Boost.Conversion library.. So the question is: What is the rationale to non allow overloading of C++ conversions operator with non-member functions?

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• JavaScript code inside UpdatePanel

  - by Ed Woodcock

  Ok: I've got an UpdatePanel on an aspx page that contains a single Placeholder. Inside this placeholder I'm appending one of a selection of usercontrols depending on certain external conditions (this is a configuration page). In each of these usercontrols there is a bindUcEvents() javascript function that binds the various jQuery and javascript events to buttons and validators inside the usercontrol. The issue I'm having is that the usercontrol's javascript is not being recognised. Normally, javascript inside an updatepanel is executed when the updatepanel posts back, however none of this code can be found by the page (I've tried running the function manually via firebug's console, but it tells me it cannot find the function). Does anyone have any suggestions? Cheers, Ed. EDIT: cut down (but functional) example: Markup: <script src="/js/jquery-1.3.2.min.js"></script> <form id="form1" runat="server"> <div> <asp:ScriptManager ID="Script" runat="server" /> <asp:Button ID="Postback" runat="server" Text="Populate" OnClick="PopulatePlaceholder" /> <asp:UpdatePanel ID="UpdateMe" runat="server"> <Triggers> <asp:AsyncPostBackTrigger ControlID="Postback" EventName="Click" /> </Triggers> <ContentTemplate> <asp:Literal ID="Code" runat="server" /> <asp:PlaceHolder ID="PlaceMe" runat="server" /> </ContentTemplate> </asp:UpdatePanel> </div> </form> C#: protected void PopulatePlaceholder(object sender, EventArgs e) { Button button = new Button(); button.ID = "Push"; button.Text = "push"; button.OnClientClick = "javascript:return false;"; Code.Text = "<script type=\"text/javascript\"> function bindEvents() { $('#" + button.ClientID + "').click(function() { alert('hello'); }); } bindEvents(); </script>"; PlaceMe.Controls.Add(button); } You'll see that the button does not poput the alert message, even though the code is present on the page.

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• C: Fifo between threads, writing and reading strings

  - by Yonatan

  Hello once more dear internet, I writing a small program that among other things, writes a log file of commands received. to do that, I want to use a thread that all it should do is just attempt to read from a pipe, while the main thread will write into that pipe whenever it should. Since i don't know the length of each string command, i thought about writing and reading the pointer to the char buf[MAX_MESSAGE_LEN]. Since what i've tried so far doesn't work, i'll post my best effort :P char str[] = "hello log thread 123456789 10 11 12 13 14 15 16 17 18 19\n"; if (pipe(pipe_fd) != 0) return -1; pthread_t log_thread; pthread_create(&log_thread,NULL, log_thread_start, argv[2]); success_write = 0; do { write(pipe_fd[1],(void*)&str,sizeof(char*)); } while (success_write < sizeof(char*)); and the thread does this: char buffer[MAX_MSGLEN]; int success_read; success_read = 0; //while(1) { do { success_read += read(pipe_fd[0],(void*)&buffer, sizeof(char*)); } while (success_read < sizeof(char*)); //} printf("%s",buffer); (Sorry if this doesn't indent, i can't seem to figure out this editor...) oh, and pipe_fd[2] is a global parameter. So, any help with this, either by the way i thought of, or another way i could read strings without knowing the length, would be much appreciated. On a side note, i'm working on Eclipse IDE C/C++, version 1.2.1 and i can't seem to set up the compiler so it will link the pthread library to my project. I've resorted to writing my own Makefile to make it (pun intended :P) work. Anyone knows what to do ? i've looked online, but all i find are solutions that are probably good on an older version because the tabs and option keys are different. Anyways, Thanks a bunch internet ! Yonatan

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• java: libraries for immutable functional-style data structures

  - by Jason S

  This is very similar to another question (Functional Data Structures in Java) but the answers there are not particularly useful. I need to use immutable versions of the standard Java collections (e.g. HashMap / TreeMap / ArrayList / LinkedList / HashSet / TreeSet). By "immutable" I mean immutable in the functional sense (e.g. purely functional data structures), where updating operations on the data structure do not change the original data, but instead return a new instance of the same kind of data structure. Also typically new and old instances of the data structure will share immutable data to be efficient in time and space. From what I can tell my options include: Functional Java Scala Clojure but I'm not sure whether any of these are particularly appealing to me. I have a few requirements/desirements: the collections in question should be usable directly in Java (with the appropriate libraries in the classpath). FJ would work for me; I'm not sure if I can use Scala's or Clojure's data structures in Java w/o having to use the compilers/interpreters from those languages and w/o having to write Scala or Clojure code. Core operations on lists/maps/sets should be possible w/o having to create function objects with confusing syntaxes (FJ looks slightly iffy) They should be efficient in time and space. I'm looking for a library which ideally has done some performance testing. FJ's TreeMap is based on a red-black tree, not sure how that rates. Documentation / tutorials should be good enough so someone can get started quickly using the data structures. FJ fails on that front. Any suggestions?

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• Rotating png images using css in IE

  - by Ernest Shulikovski

  Here is a mockup for something called "Diversity Disc": http://diversity.iest.pl/ It is just three disks that you can rotate and read "results". I am using there just four png images, and rotate using jQuery f.i: $.fn.rleft = function() { return this.animate({ rotate: '-=45deg' }); }; It works not so bad in most new browser. But in all versions of IE things go terribly wrong. There is problem with rotation, and with png: after rotation, there is happening something very ugly with alpha transparency of those images. So my question is, is this possible to make it work in IE 8 and 7 (and, more or less IE 6?). If no I will be forced to order it in Flash. But I would like first to try to do it using just css and javascript (svg?). So what I am doing wrong? Do you have any tips, for using different technology, or js library? Thank you in advance for any answers.

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• Updating Textures on Runtime in OpenSceneGraph

  - by Abhishek Bansal

  I am working on a project in which i am required to capture frames from external device video and render them on openSceneGraph Node. I am also using GLSL shaders. But i dont know how to update textures on runtime. For other uniforms we need to make callbacks but do we also need to make callbacks for samplers in glsl and openSceneGraph ? My code looks like this. All i am getting right now is a black window. osg::ref_ptr<osg::Geometry> pictureQuad = osg::createTexturedQuadGeometry(osg::Vec3(0.0f,0.0f,0.0f), osg::Vec3(_deviceNameToImageFrameMap[deviceName].frame->s(),0.0f,0.0f), osg::Vec3(0.0f,0.0f,_deviceNameToImageFrameMap[deviceName].frame->t()), 0.0f, 1.0f,_deviceNameToImageFrameMap[deviceName].frame->s(), _deviceNameToImageFrameMap[deviceName].frame->t()); //creating texture and setting up parameters for video frame osg::ref_ptr<osg::TextureRectangle> myTex= new osg::TextureRectangle(_deviceNameToImageFrameMap[deviceName].frame.get()); myTex->setFilter(osg::Texture::MIN_FILTER,osg::Texture::LINEAR); myTex->setFilter(osg::Texture::MAG_FILTER,osg::Texture::LINEAR); myTex->setWrap(osg::Texture::WRAP_S, osg::Texture::CLAMP_TO_EDGE); myTex->setWrap(osg::Texture::WRAP_T, osg::Texture::CLAMP_TO_EDGE); _videoSourceNameToNodeMap[sourceName].geode = new osg::Geode(); _videoSourceNameToNodeMap[sourceName].geode->setDataVariance(osg::Object::DYNAMIC); _videoSourceNameToNodeMap[sourceName].geode->addDrawable(pictureQuad.get()); //apply texture to node _videoSourceNameToNodeMap[sourceName].geode->getOrCreateStateSet()->setTextureAttributeAndModes(0, myTex.get(), osg::StateAttribute::ON); _videoSourceNameToNodeMap[sourceName].geode->getOrCreateStateSet()->setMode(GL_DEPTH_TEST, osg::StateAttribute::OFF); _videoSourceNameToNodeMap[sourceName].geode->setDataVariance(osg::Object::DYNAMIC); //Set uniform sampler osg::Uniform* srcFrame = new osg::Uniform( osg::Uniform::SAMPLER_2D, "srcFrame" ); srcFrame->set(0); //Set Uniform Alpha osg::Uniform* alpha = new osg::Uniform( osg::Uniform::FLOAT, "alpha" ); alpha->set(.5f); alpha->setUpdateCallback(new ExampleCallback()); //Enable blending _videoSourceNameToNodeMap[sourceName].geode->getOrCreateStateSet()->setMode( GL_BLEND, osg::StateAttribute::ON); //Adding blend function to node osg::BlendFunc *bf = new osg::BlendFunc(); bf->setFunction(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA); _videoSourceNameToNodeMap[sourceName].geode->getOrCreateStateSet()->setAttributeAndModes(bf); //apply shader to quad _videoSourceNameToNodeMap[sourceName].geode->getOrCreateStateSet()->setAttributeAndModes(program, osg::StateAttribute::ON); //add Uniform to shader _videoSourceNameToNodeMap[sourceName].geode->getOrCreateStateSet()->addUniform( srcFrame ); _videoSourceNameToNodeMap[sourceName].geode->getOrCreateStateSet()->addUniform( alpha );

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• Calling a non-activeX DLL in a VB6 application in Vista/Win7

  - by user1490330

  I have a VB6 app that utilizes a non-activeX DLL (non-registering). It's declared via the classic Public Declare Function "Function Name" Lib "Library.DLL" syntax. On my dev machine (XP) it works fine but when I deploy to Vista or Win7 I'm constantly greeted with a Run Time Error 48 - File Not Found for the DLL in question. I have tried copying that DLL to every directory I can think of including every environment path on the test machine and the app path too. These are all 32-bit test environments so it's not a SysWow64 issue. Possibly throwing a wrench into the mix is the fact that the application in question is an Outlook COM Addin. I managed to install VB6 on Win7 and was able to run a tiny sample app that utilizes this DLL (outside of the Outlook process) so I know it works PROVIDED the DLL is located in App path. If I call App.Path from my DLL when I run it on the test environment it shows, to no surprise, my installation directory however the DLL is there. I tried turning off UAC. I tried making the App.Path directory permissions open to everyone, still no dice.

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• Which is the correct design pattern for my PHP application?

  - by user1487141

  I've been struggling to find good way to implement my system which essentially matches the season and episode number of a show from a string, you can see the current working code here: https://github.com/huddy/tvfilename I'm currently rewriting this library and want a nicer way to implement how the the match happens, currently essentially the way it works is: There's a folder with classes in it (called handlers), every handler is a class that implements an interface to ensure a method called match(); exists, this match method uses the regex stored in a property of that handler class (of which there are many) to try and match a season and episode. The class loads all of these handlers by instantiating each one into a array stored in a property, when I want to try and match some strings the method iterates over these objects calling match(); and the first one that returns true is then returned in a result set with the season and episode it matched. I don't really like this way of doing it, it's kind of hacky to me, and I'm hoping a design pattern can help, my ultimate goal is to do this using best practices and I wondered which one I should use? The other problems that exist are: More than one handler could match a string, so they have to be in an order to prevent the more greedy ones matching first, not sure if this is solvable as some of the regex patterns have to be greedy, but possibly a score system, something that shows a percentage of how likely the match is correct, i'd have no idea how to actually implement this though. I'm not if instantiating all those handlers is a good way of doing it, speed is important, but using best practices and sticking to design patterns to create good, extensible and maintainable code is my ultimate priority. It's worth noting the handler classes sometimes do other things than just regex matching, they sometimes prep the string to be matched by removing common words etc. Cheers for any help Billy

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• How to Create the Upload File for Application Loader?

  - by Ohad Regev

  When I use Application Loader, I get to the point where it asks me to "Choose..." the file to be uploaded. If I understand correctly, it supposes to be the appName.app file I see under "Products" on my app bundle (I right click it and select "Show in Finder" to get to the specific file in library; then I'm supposed to ZIP it and the ZIP file is what I will choose in Application Loader). First, am I correct with this assumption? if yes... What should I define different in XCode than the way I used to build the application for testing (on simulator and on my personal iPhone)? Should I change the Info---Command-line build use from Debug to Release? How should I define the Build Settings---Code Signing section (in which field should I select the "iPhone Developer" option and in which should it be "iPhone Distribution")? Are there any other important Info/Build Settings/p.list/etc... fields I should relate to? any help will be appreciated...

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• Combining Java hashcodes into a "master" hashcode

  - by Nick Wiggill

  I have a vector class with hashCode() implemented. It wasn't written by me, but uses 2 prime numbers by which to multiply the 2 vector components before XORing them. Here it is: /*class Vector2f*/ ... public int hashCode() { return 997 * ((int)x) ^ 991 * ((int)y); //large primes! } ...As this is from an established Java library, I know that it works just fine. Then I have a Boundary class, which holds 2 vectors, "start" and "end" (representing the endpoints of a line). The values of these 2 vectors are what characterize the boundary. /*class Boundary*/ ... public int hashCode() { return 1013 * (start.hashCode()) ^ 1009 * (end.hashCode()); } Here I have attempted to create a good hashCode() for the unique 2-tuple of vectors (start & end) constituting this boundary. My question: Is this hashCode() implementation going to work? (Note that I have used 2 different prime numbers in the latter hashCode() implementation; I don't know if this is necessary but better to be safe than sorry when trying to avoid common factors, I guess -- since I presume this is why primes are popular for hashing functions.)

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• App is fast on 3GS but slow on 3G

  - by Anthony Chan

  Hi all, I'm new to computer coding and have just finished coding an app and tested it on both 3G and 3GS. On 3GS, it worked as normal as on the simulator. However, when I tried to run it on 3G, the app becomes extremely slow. I'm not sure what's the reason and I hope someone could shed some light on me. Generally, my app has a couple of view controller classes, with one of them being the title page, one being the main page, one is setting, etc. I used a dissolve to transition from the title page to the main page. But even this simple transition shows un-smooth performance on a 3G! My other part of the app involves zooming in to some images by scaling up the images, switching images by push or dissolve upon receiving touch events, saving photos into photo library and storing and retrieving some photos in a folder and some data in a SQlite database, each showing un-smooth actions. Compared with some heavy graphic or heavy maths app, I think mine is pretty simple. I totally have no clue why the app would behave so slow and un-smooth that it is barely useful on a 3G. Any help/ direction would be much appreciated. Thanks for helping out.

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• PDFParsing & extracting the images only in iPhone application.

  - by sagar

  Hello - Every one. ** : My Query : ** I want to extract only images from entire pdf document. ( Using Objective C - for iPhone Application ) : My Efforts : I have gone through this link which has details regarding different operators of PDF Document. ( http://mail-archives.apache.org/mod_mbox/pdfbox-commits/200912.mbox/%[email protected]%3E ) I also studied this document - ( http://developer.apple.com/mac/library/documentation/GraphicsImaging/Conceptual/drawingwithquartz2d/dq_pdf_scan/dq_pdf_scan.html#//apple_ref/doc/uid/TP30001066-CH220-TPXREF101 ) I also have gone through entire document of PDFReference.pdf ( From original Adobe Site ) PDFReference.pdf (Adobe Document - says that - for image there are following operators ) q Q BI EI I have placed following table get the image myTable = CGPDFOperatorTableCreate(); CGPDFOperatorTableSetCallback(myTable, "q", arrayCallback2); CGPDFOperatorTableSetCallback(myTable, "TJ", arrayCallback); CGPDFOperatorTableSetCallback(myTable, "Tj", stringCallback); I have following arrayCallback2 method for getting image void arrayCallback2(CGPDFScannerRef inScanner, void *userInfo) { // how to extract image from this code // means I have tried too many different ways. following is incorrect way & not giving image // CGPDFStreamRef stream; // represents a sequence of bytes // if (CGPDFDictionaryGetStream (d, "BI", &stream)){ // CGPDFDataFormat t=CGPDFDataFormatJPEG2000; // CFDataRef data = CGPDFStreamCopyData (stream, &t); // } } above arrayCallback2 method is called for operator "q", But I don't know How to extract the image from it. In short. What should be the solution for extracting the images from the pdf documents? Thanks in advance for your kind help. Sagar kothari.

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• jQuery Manual Resizable DIV

  - by JC

  Hi, I'm trying to create a resizable div without using jQuery's interface library. var myY = 0; var mouseDown = false; var originalHeight = 0; function resize(e){ if(mouseDown == true){ $("#cooldiv").height(originalHeight+e.pageY-myY); } } $(document).ready(function(){ $().mouseup(function(e){ myY = 0; mouseDown = false; originalHeight = 0; $().unbind("mousemove", resize); }); $("#resizeBar").mousedown(function(e){ myY = e.pageY; originalHeight = $("#cooldiv").height(); mouseDown = true; $().bind("mousemove", resize); }); }); ... <div id="cooldiv" style="width: 500px; height: 300px; background-color: #cccccc; position: relative;"> <div id="resizeBar" style="height: 10px; width: 500px; background-color: #aaaaaa; position: absolute; bottom: 0;"></div> </div> The first resize works fine(i.e. mousedown, mousemove then mouseup), but on subsequent (mousedown+mousemove)s, the browser attempts to drag the whole resizeBar div instead of properly resizing its parent container. On mouseup, the div then starts resizing "cooldiv" on mousemove without any mousedown required, until a further click of the mouse. These problems don't show up in Internet Explorer.

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• What OpenGL functions are not GPU accelerated?

  - by Xavier Ho

  I was shocked when I read this (from the OpenGL wiki): glTranslate, glRotate, glScale Are these hardware accelerated? No, there are no known GPUs that execute this. The driver computes the matrix on the CPU and uploads it to the GPU. All the other matrix operations are done on the CPU as well : glPushMatrix, glPopMatrix, glLoadIdentity, glFrustum, glOrtho. This is the reason why these functions are considered deprecated in GL 3.0. You should have your own math library, build your own matrix, upload your matrix to the shader. For a very, very long time I thought most of the OpenGL functions use the GPU to do computation. I'm not sure if this is a common misconception, but after a while of thinking, this makes sense. Old OpenGL functions (2.x and older) are really not suitable for real-world applications, due to too many state switches. This makes me realise that, possibly, many OpenGL functions do not use the GPU at all. So, the question is: Which OpenGL function calls don't use the GPU? I believe knowing the answer to the above question would help me become a better programmer with OpenGL. Please do share some of your insights.

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• Parameter meaning of CBasePin::GetMediaType(int iPosition, ...) method

  - by user325320

  Thanks to everyone who views my question. http://msdn.microsoft.com/en-us/library/windows/desktop/dd368709(v=vs.85).aspx It is not very clear from the documentation regarding the iPosition parameter for virtual HRESULT GetMediaType( int iPosition, CMediaType *pMediaType ); It is said "Zero-based index value.", but what kind of index it is? the index of the samples? I have a source filter sending the H.264 NALU flows (MEDIASUBTYPE_AVC1) and it works very well except that the SPS/PPS may be changed after the video is played for a while. The SPS and PPS are appended to the MPEG2VIDEOINFO structure, which is passed in CMediaType::SetFormat method when GetMediaType method is called. and there is another version of GetMediaType which accepts the iPosition parameter. It seems I can use this method to update the SPS / PPS. My question is: What does the iPosition param mean, and how does Decoder Filter know which SPS/PPS are assigned for each NALU sample. HRESULT GetMediaType(int iPosition, CMediaType *pMediaType) { ATLTRACE( "\nGetMediaType( iPosition = %d ) ", iPosition); CheckPointer(pMediaType,E_POINTER); CAutoLock lock(m_pFilter->pStateLock()); if (iPosition < 0) { return E_INVALIDARG; } if (iPosition == 0) { pMediaType->InitMediaType(); pMediaType->SetType(&MEDIATYPE_Video); pMediaType->SetFormatType(&FORMAT_MPEG2Video); pMediaType->SetSubtype(&MEDIASUBTYPE_AVC1); pMediaType->SetVariableSize(); } int nCurrentSampleID; DWORD dwSize = m_pFlvFile->GetVideoFormatBufferSize(nCurrentSampleID); LPBYTE pBuffer = pMediaType->ReallocFormatBuffer(dwSize); memcpy( pBuffer, m_pFlvFile->GetVideoFormatBuffer(nCurrentSampleID), dwSize); pMediaType->SetFormat(pBuffer, dwSize); return S_OK; }

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• Call .NET Webservice with Android

  - by Lasse P

  Hi, I know this question has been asked here before, but I don't think those answers were adequate for my needs. We have a SOAP webservice that is used for an iPhone application, but it is possible that we need an Android specific version or a proxy of the service, so we have the option to go with either SOAP or JSON. I have a few concerns about both methods: SOAP solution: Is it possible to generate java source code from a WSDL file, if so, will it include some kind of proxy class to invoke the webservice and will it work in the Android environment at all? Google has not provided any SOAP library in Android, so i need to use 3rd party, any suggestion? What about the performance/overhead with parsing and transmitting SOAP xml over the wire versus the JSON solution? JSON solution: There is a few classes in the Android sdk that will let me parse JSON, but does it support generic parsing, like if I want the result to be parsed as a complex type? Or would I need to implement that myself? I have read about 2 libraries before here on Stackoverflow, GSON an Jackson. What is the difference performance and usability (from a developers perspective) wise? Do you guys have any experince with either of those libraries? So i guess the big question is, what method to go with? I hope you can help me out. Thanks in advance :-)

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• Does F# documentation have a way to search for functions by their types?

  - by Nathan Sanders

  Say I want to know if F# has a library function of type ('T -> bool) -> 'T list -> int ie, something that counts how many items of a list that a function returns true for. (or returns the index of the first item that returns true) I used to use the big list at the MSR site for F# before the documentation on MSDN was ready. I could just search the page for the above text because the types were listed. But now the MSDN documentation only lists types on the individual pages--the module page is a mush of descriptive text. Google kinda-sorta works, but it can't help with // compatible interfaces ('T -> bool) -> Seq<'T> -> int // argument-swaps Seq<'T> -> ('T -> bool) -> int // type-variable names ('a -> bool) -> Seq<'a> -> int // wrappers ('a -> bool) -> 'a list -> option<int> // uncurried versions ('T -> bool) * 'T list -> int // .NET generic syntax ('T -> bool) -> List<'T> -> int // methods List<'T> member : ('T -> bool) -> int Haskell has a standalone program for this called Hoogle. Does F# have an equivalent, like Fing or something?

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• Compiling scalafx for Java 7u7 (that contains JavaFX 2.2) on OS X

  - by akauppi

  The compilation instructions of scalafx says to do: export JAVAFX_HOME=/Path/To/javafx-sdk2.1.0-beta sbt clean compile package make-pom package-src However, with the new packaging of JavaFX as part of the Java JDK itself (i.e. 7u7 for OS X) there no longer seems to be such a 'javafx-sdkx.x.x' folder. The Oracle docs say that JavaFX JDK is placed alongside the main Java JDK (in same folders). So I do: $ export JAVAFX_HOME=/Library/Java/JavaVirtualMachines/jdk1.7.0_07.jdk $ sbt clean [warn] Using project/plugins/ (/Users/asko/Sources/scalafx/project/plugins) for plugin configuration is deprecated. [warn] Put .sbt plugin definitions directly in project/, [warn] .scala plugin definitions in project/project/, [warn] and remove the project/plugins/ directory. [info] Loading project definition from /Users/asko/Sources/scalafx/project/plugins/project [info] Loading project definition from /Users/asko/Sources/scalafx/project/plugins [error] java.lang.NullPointerException [error] Use 'last' for the full log. Project loading failed: (r)etry, (q)uit, (l)ast, or (i)gnore? Am I doing something wrong or is scalafx not yet compatible with the latest Java release (7u7, JavaFX 2.2). What can I do? http://code.google.com/p/scalafx/ Addendum ..and finally (following Igor's solution below) sbt run launches the colorful circles demo easily (well, if one has a supported GPU that is). Oracle claims that "JavaFX supports graphic hardware acceleration on any Mac OS X system that is Lion or later" but I am inclined to think the NVidia powered Mac Mini I'm using does software rendering. A recent MacBook Air (core i7) is a complete different beast! :)

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• Appropriate uses of Monad `fail` vs. MonadPlus `mzero`

  - by jberryman

  This is a question that has come up several times for me in the design code, especially libraries. There seems to be some interest in it so I thought it might make a good community wiki. The fail method in Monad is considered by some to be a wart; a somewhat arbitrary addition to the class that does not come from the original category theory. But of course in the current state of things, many Monad types have logical and useful fail instances. The MonadPlus class is a sub-class of Monad that provides an mzero method which logically encapsulates the idea of failure in a monad. So a library designer who wants to write some monadic code that does some sort of failure handling can choose to make his code use the fail method in Monad or restrict his code to the MonadPlus class, just so that he can feel good about using mzero, even though he doesn't care about the monoidal combining mplus operation at all. Some discussions on this subject are in this wiki page about proposals to reform the MonadPlus class. So I guess I have one specific question: What monad instances, if any, have a natural fail method, but cannot be instances of MonadPlus because they have no logical implementation for mplus? But I'm mostly interested in a discussion about this subject. Thanks! EDIT: One final thought occured to me. I recently learned (even though it's right there in the docs for fail) that monadic "do" notation is desugared in such a way that pattern match failures, as in (x:xs) <- return [] call the monad's fail. It seems like the language designers must have been strongly influenced by the prospect of some automatic failure handling built in to haskell's syntax in their inclusion of fail in Monad.

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• Crash using WscRegisterForChanges.

  - by user335126

  I'm trying to use the WscRegisterForChanges with C++ function in Windows 7. Documentation located here: http://msdn.microsoft.com/en-us/library/bb432507(v=VS.85).aspx My problem is that even though the callback properly executes, the code crashes when it gets to the end of the callback's execution. Here's the code in question. It's very simple, so I'm not sure why it's crashing: #include #include #include void SecurityCenterChangeOccurred(void *param) { printf("Change occurred!\n"); } int main() { HRESULT result = S_OK; HANDLE callbackRegistration = NULL; result = WscRegisterForChanges( NULL, &callbackRegistration, (LPTHREAD_START_ROUTINE)SecurityCenterChangeOccurred, NULL); while(1) { Sleep(100); } return 0; } My call stack looks like this when the crash occurs: 00faf6e8() ntdll.dll!_TppWorkerThread@4() + 0x1293 bytes kernel32.dll!@BaseThreadInitThunk@12() + 0x12 bytes ntdll.dll!___RtlUserThreadStart@8() + 0x27 bytes ntdll.dll!__RtlUserThreadStart@8() + 0x1b bytes If I add ExitThread(0); to the end of SecurityCenterChangeOccurred, I get an error and the following trace (So I don't think I should be using ExitThread): Unhandled exception at 0x7799852b (ntdll.dll) in WscRegisterForChangesCrash.exe: 0xC000071C: An invalid thread, handle %p, is specified for this operation. Possibly, a threadpool worker thread was specified. ntdll.dll!_TpCheckTerminateWorker@4() + 0x3ca2f bytes ntdll.dll!_RtlExitUserThread@4() + 0x30 bytes WscRegisterForChangesCrash.exe!SecurityCenterChangeOccurred(void * param=0x00000000) Line 8 + 0xa bytes C++ wscapi.dll!WorkItemWrapper() + 0x19 bytes ntdll.dll!_RtlpTpWorkCallback@8() + 0xdf bytes ntdll.dll!_TppWorkerThread@4() + 0x1293 bytes kernel32.dll!@BaseThreadInitThunk@12() + 0x12 bytes ntdll.dll!___RtlUserThreadStart@8() + 0x27 bytes ntdll.dll!__RtlUserThreadStart@8() + 0x1b bytes Does anyone have any ideas why this might be happening? To trigger the crash run the program and turn the firewall on or off.

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• How to pass data to a C++0x lambda function that will run in a different thread?

  - by Dimitri C.

  In our company we've written a library function to call a function asynchronously in a separate thread. It works using a combination of inheritance and template magic. The client code looks as follows: DemoThread thread; std::string stringToPassByValue = "The string to pass by value"; AsyncCall(thread, &DemoThread::SomeFunction, stringToPassByValue); Since the introduction of lambda functions I'd like to use it in combination with lambda functions. I'd like to write the following client code: DemoThread thread; std::string stringToPassByValue = "The string to pass by value"; AsyncCall(thread, [=]() { const std::string someCopy = stringToPassByValue; }); Now, with the Visual C++ 2010 this code doesn't work. What happens is that the stringToPassByValue is not copied. Instead the "capture by value" feature passes the data by reference. The result is that if the function is executed after stringToPassByValue has gone out of scope, the application crashes as its destructor is called already. So I wonder: is it possible to pass data to a lambda function as a copy? Note: One possible solution would be to modify our framework to pass the data in the lambda parameter declaration list, as follows: DemoThread thread; std::string stringToPassByValue = "The string to pass by value"; AsyncCall(thread, [=](const std::string stringPassedByValue) { const std::string someCopy = stringPassedByValue; } , stringToPassByValue); However, this solution is so verbose that our original function pointer solution is both shorter and easier to read. Update: The full implementation of AsyncCall is too big to post here. In short, what happens is that the AsyncCall template function instantiates a template class holding the lambda function. This class is derived from a base class that contains a virtual Execute() function, and upon an AsyncCall() call, the function call class is put on a call queue. A different thread then executes the queued calls by calling the virtual Execute() function, which is polymorphically dispatched to the template class which then executes the lambda function.

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