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• How can I build something like Amazon S3 in Perl?

  - by Joel G

  I am looking to code a file storage application in perl similar to amazon s3. I already have a amazon s3 clone that I found online called parkplace but its in ruby and is old also isn't built for high loads. I am not really sure what modules and programs I should use so id like some help picking them out. My requirements are listed below (yes I know there are lots but I could start simple then add more once I get it going): Easy API implementation for client side apps. (maybe REST (?) Centralized database server for the USERDB (maybe PostgreSQL (?). Logging of all connections, bandwidth used, well pretty much everything to a centralized server (maybe PostgreSQL again (?). Easy server side configuration (config file(s) stored on the servers). Web based control panel for admin(s) and user(s) to show logs. (could work just running queries from the databases) Fast High Uptime Low memory usage Some sort of load distribution/load balancer (maybe a dns based or pound or perlbal or something else (?). Maybe a cache of some sort (memcached or parlbal or something else (?). Thanks in advance

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• Array: mathematical sequence

  - by VaioIsBorn

  An array of integers A[i] (i 1) is defined in the following way: an element A[k] ( k 1) is the smallest number greater than A[k-1] such that the sum of its digits is equal to the sum of the digits of the number 4* A[k-1] . You need to write a program that calculates the N th number in this array based on the given first element A[1] . INPUT: In one line of standard input there are two numbers seperated with a single space: A[1] (1 <= A[1] <= 100) and N (1 <= N <= 10000). OUTPUT: The standard output should only contain a single integer A[N] , the Nth number of the defined sequence. Input: 7 4 Output: 79 Explanation: Elements of the array are as follows: 7, 19, 49, 79... and the 4th element is solution. I tried solving this by coding a separate function that for a given number A[k] calculates the sum of it's digits and finds the smallest number greater than A[k-1] as it says in the problem, but with no success. The first testing failed because of a memory limit, the second testing failed because of a time limit, and now i don't have any possible idea how to solve this. One friend suggested recursion, but i don't know how to set that. Anyone who can help me in any way please write, also suggest some ideas about using recursion/DP for solving this problem. Thanks.

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• Can the Diamond Problem be really solved?

  - by Mecki

  A typical problem in OO programming is the diamond problem. I have parent class A with two sub-classes B and C. A has an abstract method, B and C implement it. Now I have a sub-class D, that inherits of B and C. The diamond problem is now, what implementation shall D use, the one of B or the one of C? People claim Java knows no diamond problem. I can only have multiple inheritance with interfaces and since they have no implementation, I have no diamond problem. Is this really true? I don't think so. See below: [removed vehicle example] Is a diamond problem always the cause of bad class design and something neither programmer nor compiler needs to solve, because it shouldn't exist in the first place? Update: Maybe my example was poorly chosen. See this image Of course you can make Person virtual in C++ and thus you will only have one instance of person in memory, but the real problem persists IMHO. How would you implement getDepartment() for GradTeachingFellow? Consider, he might be student in one department and teach in another one. So you can either return one department or the other one; there is no perfect solution to the problem and the fact that no implementation might be inherited (e.g. Student and Teacher could both be interfaces) doesn't seem to solve the problem to me.

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• Does anyone know of a good Commercial WPF Web Browser Control?

  - by VoidDweller

  I have an MDI WPF app that I need to add web content too. At first, great it looks like I have 2 options built into the framework the Frame control and the WebBrowser control. Given that this is an MDI app it doesn't take long to discover that neither of these will work. The WebBrowser control wraps up the IE WebBrowser ActiveX Control which uses the Win32 graphics pipeline. The "Airspace" issue pretty much sums this up as "Sorry, the layouts will not play nice together". Yes, I have thought about taking snapshots of the web content rendering these and mapping the mouse and keyboard events back to the browser control, but I can't afford the performance penalty and I really don't have time to write and thoroughly test it. I have looked for third party controls, but so far I have only found Chris Cavanagh's WPF Chromium Web Browser control. Which wraps up Awesomium 1.5. Together these are very cool, they play nice with the WPF layouts. But they do not meet my performance requirements. They are VERY HEAVY on memory consumption and not to friendly with CPU usage either. Not to mention still quite buggy. I'll elaborate if you are interested. So, do any of you know of a stable performant WPF web browser control? Thanks.

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• Out of Core Implementation of a Quadtree

  - by Nima

  Hi, I am trying to build a Quadtree data structure(or let's just say a tree) on the secondary memory(Hard Disk). I have a C++ program to do so and I use fopen to create the files. Also, I am using tesseral coding to store each cell in a file named with its corresponding code to store it on the disk in one directory. The problem is that after creating about 1,100 files, fopen just returns NULL and stops creating new files. I can create further files manually in that directory, but using C++ it can not create any further files. I know about max limit of inode on ext3 filesystem which is (from Wikipedia) 32,000 but mine is way less than that, also note that I can create files manually on the disk; just not through fopen. Also, I really appreciate any idea regarding the best way to store a very dynamic quadtree on disk(I need the nodes to be in separate files and the quadtree might have a depth of 50). Using nested directories is one idea, but I think it will slow down the performance because of following the links on the filesystem to access the file. Thanks, Nima

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• How do you dynamically allocate a contiguous 3D array in C?

  - by Derek

  In C, I want to loop through an array in this order for(int z = 0; z < NZ; z++) for(int x = 0; x < NX; x++) for(int y = 0; y < NY; y++) 3Darray[x][y][z] = 100; How do I create this array in such a way that 3Darray[0][1][0] comes right before 3Darray[0][2][0] in memory? I can get an initialization to work that gives me "z-major" ordering, but I really want a y-major ordering for this 3d array This is the code I have been trying to use: char *space; char ***Arr3D; int y, z; ptrdiff_t diff; space = malloc(X_DIM * Y_DIM * Z_DIM * sizeof(char)) Arr3D = malloc(Z_DIM * sizeof(char **)); for (z = 0; z < Z_DIM; z++) { Arr3D[z] = malloc(Y_DIM * sizeof(char *)); for (y = 0; y < Y_DIM; y++) { Arr3D[z][y] = space + (z*(X_DIM * Y_DIM) + y*X_DIM); } }

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• EJB3Unit testing no-tx-datasource

  - by justastefan

  Hello, I am doing tests on an ejb3-project using ejb3unit http://ejb3unit.sourceforge.net/Session-Bean.html for testing. All my Services long for @PersistenceContext (UnitName=bla). I set up the ejb3unit.properties like this: ejb3unit_jndi.1.isSessionBean=true ejb3unit_jndi.1.jndiName=ejb/MyServiceBean ejb3unit_jndi.1.className=com.company.project.MyServiceBean everything works with the in-memory-database. So now i want additionally test another servicebean with @PersistenceContext (UnitName=noTxDatasource) that goes for a defined in my datasources.xml: <datasources> <local-tx-datasource> ... </local-tx-datasource> <no-tx-datasource> <jndi-name>noTxDatasource</jndi-name> <connection-url>...</connection-url> <driver-class>oracle.jdbc.OracleDriver</driver-class> <user-name>bla</user-name> <password>bla</password> </no-tx-datasource> </datasources> How do I tell ejb3unit to make this work: Object object = InitialContext.doLookup("java:/noTxDatasource"); if (object instanceof DataSource) { return ((DataSource) object).getConnection(); } else { return null; } Currently it fails saying: javax.NamingException: Cannot find the name (noTxDataSource) in the JNDI tree Current bindings: (ejb/MyServiceBean=com.company.project.MyServiceBean) How can I add this no-tx-datasource to the jndi bindings?

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• read access violation error

  - by user293569

  class Node{ private: string name; Node** adjacent; int adjNum; public: Node(); Node(string, int adj_num); Node(const Node &); bool addAdjacent(const Node &); Node** getAdjacents(); string getName(); ~Node(); }; bool Node::addAdjacent(const Node &anode){ Node** temp; temp= new Node*[adjNum+1]; for(int i=0;i<adjNum+1;i++) temp[i]=adjacent[i]; temp[adjNum]=const_cast<Node *>(&anode); delete[] adjacent; adjacent=new Node*[adjNum+1]; adjacent=temp; delete[] temp; adjNum++; return true; } int main() { Node node1("A",0); Node node2("B",0); node1.getName(); node1.addAdjacent(node2); system("PAUSE"); return 0; } when the program comes to this part: for(int i=0;i<adjNum+1;i++) temp[i]=adjacent[i]; it says Access violation reading location 0xcccccccc. The class must allocate the memory fore adjacent, but I think it didn't how can I solve this problem?

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• Generate exe in .Net

  - by rwallace

  In .Net, you can generate byte code in memory, and presumably save the resulting program to a .exe file. To do the first step, I have the following test code adapted from http://www.code-magazine.com/Article.aspx?quickid=0301051 var name = new AssemblyName(); name.Name = "MyAssembly"; var ad = Thread.GetDomain(); var ab = ad.DefineDynamicAssembly(name, AssemblyBuilderAccess.Run); var mb = ab.DefineDynamicModule("MyModule"); var theClass = mb.DefineType("MathOps", TypeAttributes.Public); var retType = typeof(System.Int32); var parms = new Type[2]; parms[0] = typeof(System.Int32); parms[1] = typeof(System.Int32); var meb = theClass.DefineMethod("ReturnSum", MethodAttributes.Public, retType, parms); var gen = meb.GetILGenerator(); gen.Emit(OpCodes.Ldarg_1); gen.Emit(OpCodes.Ldarg_2); gen.Emit(OpCodes.Add_Ovf); gen.Emit(OpCodes.Stloc_0); gen.Emit(OpCodes.Br_S); gen.Emit(OpCodes.Ldloc_0); gen.Emit(OpCodes.Ret); theClass.CreateType(); How do you do the second step, and save the result to a .exe?

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• Why do i get exc bad access in cases when object is not nil?

  - by DixieFlatline

  I have an app that receives remote notifications. My view controller that is shown after push has a tableview. App crashes very randomly (1 in 20 tries) at line setting frame: if (!myTableView) { NSLog(@"self.myTableView is nil"); } myTableView.frame=CGRectMake(0, 70, 320, 376); This only happens when i open the app, then open some other apps and then receive the push notification. I guess it has something to do with memory. I use ARC (ios 5). The strange thing is that nslog is not displayed, so tableview is not nil. Crash log: Exception Type: EXC_BAD_ACCESS (SIGSEGV) Exception Codes: KERN_INVALID_ADDRESS at 0x522d580c Crashed Thread: 0 Thread 0 name: Dispatch queue: com.apple.main-thread Thread 0 Crashed: 0 libobjc.A.dylib 0x352b1f7e objc_msgSend + 22 1 Foundation 0x37dc174c NSKVOPendingNotificationCreate + 216 2 Foundation 0x37dc1652 NSKeyValuePushPendingNotificationPerThread + 62 3 Foundation 0x37db3744 NSKeyValueWillChange + 408 4 Foundation 0x37d8a848 -[NSObject(NSKeyValueObserverNotification) willChangeValueForKey:] + 176 5 Foundation 0x37e0ca14 _NSSetPointValueAndNotify + 76 6 UIKit 0x312af25a -[UIScrollView(Static) _adjustContentOffsetIfNecessary] + 1890 7 UIKit 0x312cca54 -[UIScrollView setFrame:] + 548 8 UIKit 0x312cc802 -[UITableView setFrame:] + 182 9 POViO 0x000913cc -[FeedVC viewWillAppear:] (FeedVC.m:303) Dealloc is not called because it is not logged: - (void)dealloc { NSLog(@"dealloc"); }

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• Generic allocator class without variadic templates?

  - by rainer

  I am trying to write a generic allocator class that does not really release an object's memory when it is free()'d but holds it in a queue and returns a previously allocated object if a new one is requested. Now, what I can't wrap my head around is how to pass arguments to the object's constructor when using my allocator (at least without resorting to variadic templates, that is). The alloc() function i came up with looks like this: template <typename... T> inline T *alloc(const &T... args) { T *p; if (_free.empty()) { p = new T(args...); } else { p = _free.front(); _free.pop(); // to call the ctor of T, we need to first call its DTor p->~T(); p = new( p ) T(args...); } return p; } Still, I need the code to be compatible with today's C++ (and older versions of GCC that do not support variadic templates). Is there any other way to go about passing an arbitrary amount of arguments to the objects constructor?

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• Service php-fpm does not support chkconfig

  - by ychian

  Everything is working fine. Just that when i chkconfig –add php-fpm It throws me an error Service php-fpm does not support chkconfig php-5.2.13 php-5.2.13-fpm-0.5.13.diff.gz Below is the configuration i use ./configure --enable-fastcgi --enable-fpm --build=x86_64-redhat-linux-gnu --host=x86_64-redhat-linux-gnu --target=x86_64-redhat-linux-gnu --program-prefix= --prefix=/usr --exec-prefix=/usr --bindir=/usr/bin --sbindir=/usr/sbin --sysconfdir=/etc --datadir=/usr/share --includedir=/usr/include --libdir=/usr/lib64 --libexecdir=/usr/libexec --localstatedir=/var --sharedstatedir=/usr/com --mandir=/usr/share/man --infodir=/usr/share/info --cache-file=../config.cache --with-libdir=lib64 --with-config-file-path=/etc --with-config-file-scan-dir=/etc/php.d --disable-debug --with-pic --disable-rpath --with-pear --with-bz2 --with-curl --with-exec-dir=/usr/bin --with-freetype-dir=/usr --with-png-dir=/usr --enable-gd-native-ttf --without-gdbm --with-gettext --with-gmp --with-iconv --with-jpeg-dir=/usr --with-openssl --with-png --with-expat-dir=/usr --with-pcre-regex=/usr --with-zlib --with-layout=GNU --enable-exif --enable-ftp --enable-magic-quotes --enable-sockets --enable-sysvsem --enable-sysvshm --enable-sysvmsg --enable-track-vars --enable-trans-sid --enable-yp --enable-wddx --with-kerberos --enable-ucd-snmp-hack --with-unixODBC=shared,/usr --enable-memory-limit --enable-shmop --enable-calendar --enable-dbx --enable-dio --with-mime-magic=/usr/share/file/magic.mime --without-sqlite --with-libxml-dir=/usr --with-xml --with-system-tzdata --without-mysql --without-gd --without-odbc --disable-dom --disable-dba --without-unixODBC --disable-pdo --disable-xmlreader --disable-xmlwriter

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• Understanding OOP Principles in passing around objects/values

  - by Hans

  I'm not quite grokking a couple of things in OOP and I'm going to use a fictional understanding of SO to see if I can get help understand. So, on this page we have a question. You can comment on the question. There are also answers. You can comment on the answers. Question - comment - comment - comment Answer -comment Answer -comment -comment -comment Answer -comment -comment So, I'm imagining a very high level understanding of this type of system (in PHP, not .Net as I am not yet familiar with .Net) would be like: $question = new Question; $question->load($this_question_id); // from the URL probably echo $question->getTitle(); To load the answers, I imagine it's something like this ("A"): $answers = new Answers; $answers->loadFromQuestion($question->getID()); // or $answers->loadFromQuestion($this_question_id); while($answer = $answers->getAnswer()) { echo $answer->showFormatted(); } Or, would you do ("B"): $answers->setQuestion($question); // inject the whole obj, so we have access to all the data and public methods in $question $answers->loadFromQuestion(); // the ID would be found via $this->question->getID() instead of from the argument passed in while($answer = $answers->getAnswer()) { echo $answer->showFormatted(); } I guess my problem is, I don't know when or if I should be passing in an entire object, and when I should just be passing in a value. Passing in the entire object gives me a lot of flexibility, but it's more memory and subject to change, I'd guess (like a property or method rename). If "A" style is better, why not just use a function? OOP seems pointless here. Thanks, Hans

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• Problem building STLport NDK r5/ Android

  - by user558299

  Hi all, I'm trying to build STLport for Android. I got the following steps, but they are not working: 1 - Clone STLport repository using: git clone git://stlport.git.sourceforge.net/gitroot/stlport/stlport 2 - Configure environment using : ./configure --target=arm-eabi --with-extra-cxxflags="-fshort-enums" --with-extra-cflags="-fshort-enums" 3 - From src directory build it using make SYSROOT"{MY NDK path}/platforms/android-5/arch-arm/" release-static But I got the following errors: In file included from ../stlport/stl/_alloc.h:45, from ../stlport/memory:29, from dll_main.cpp:41: ../stlport/stl/_new.h:45:24: error: new: No such file or directory In file included from ../stlport/stl/_limits.h:36, from ../stlport/limits:29, from dll_main.cpp:48: ../stlport/stl/_cwchar.h:26:30: error: cstddef: No such file or directory In file included from ../stlport/stl/_utility.h:35, from ../stlport/utility:35, from dll_main.cpp:40: ../stlport/type_traits:889: error: 'declval' was not declared in this scope ../stlport/type_traits:889: error: expected primary-expression before '>' token ../stlport/type_traits:889: error: expected primary-expression before ')' token ../stlport/type_traits:889: error: 'declval' was not declared in this scope ../stlport/type_traits:889: error: expected primary-expression before '>' token ../stlport/type_traits:889: error: expected primary-expression before ')' token ../stlport/type_traits:889: error: ISO C++ forbids declaration of 'decltype' with no type ../stlport/type_traits:889: error: ISO C++ forbids in-class initialization of non-const static member 'decltype' ../stlport/type_traits:889: error: template declaration of 'int std::tr1::detail::decltype' ../stlport/type_traits:942: error: ISO C++ forbids declaration of 'decltype' with no type ../stlport/type_traits:942: error: ISO C++ forbids in-class initialization of non-const static member 'decltype' ../stlport/type_traits:942: error: template declaration of 'int std::tr1::detail::decltype' make: *** [obj/arm-eabi-gcc/so/dll_main.o] Error 1 Is there any include dir or configuration I´m missing? Thanks, Sergio

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• Load Ruby on Rails models without loading the entire framework

  - by epochwolf

  I'm looking to create a custom daemon that will run various database tasks such as delaying mailings and user notifications (each notice is a separate row in the notifications table). I don't want to use script/runner or rake to do these tasks because it is possible that some of the tasks only require the create of one or two database rows or thousands of rows depending on the task. I don't want the overhead of launching a ruby process or loading the entire rails framework for each operation. I plan to keep this daemon in memory full time. To create this daemon I would like to use my models from my ruby on rails application. I have a number of rails plugins such as acts_as_tree and AASM that I will need loaded if I where to use the models. Some of the plugins I need to load are custom hacks on ActiveRecord::Base that I've created. (I am willing to accept removing or recoding some of the plugins if they need components from other parts of rails.) My questions are Is this a good idea? And - Is this possible to do in a way that doesn't have me manually including each file in my models and plugins? If not a good idea What is a good alternative? (I am not apposed to doing writing my own SQL queries but I would have to add database constraints and a separate user for the daemon to prevent any stupid accidents. Given my lack of familiarity with configuring a database, I would like to use active record as a crutch.)

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• ASP.net download page

  - by Russel

  Hi I have a Reports.aspx ASP.NET page that allows users to download excel report files by clicking on several hyperlinks. When a report hyperlink is clicked, I open a new window using the javascript window.open method and navigate off to the download.aspx page. The code-behind for the download page creates a excel file on the fly using openxml(in memory) and send it back to the browser. Here is some code from the download.aspx page: byte[] outputFileBytes = CreateExcelReport().ToArray(); Response.Clear(); Response.BufferOutput = true; Response.ContentType = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"; Response.AddHeader("Content-Disposition", string.Format("attachment; filename={0}", "tempReport.xlsx")); Response.BinaryWrite(outputFileBytes); Response.Flush(); Response.Close(); Response.End(); My problem : Some of these reports take some time to generate. I would like to display a loading.gif file on my Reports.aspx page, while the download.aspx page is requested. Once the page request is completed, the loading.gif file should be made invisible. Is there a way to achieve this. Perhaps some kind of event. I have mootools to my disposal. Thanks PS. I know that generating reports like this is not ideal, but thats a different story all together...

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• Django upload failing on request data read error

  - by Jake

  Hi All, I've got a Django app that accepts uploads from jQuery uploadify, a jQ plugin that uses flash to upload files and give a progress bar. Files under about 150k work, but bigger files always fail and almost always at around 192k (that's 3 chunks) completed, sometimes at around 160k. The Exception I get is below. exceptions.IOError request data read error File "/usr/lib/python2.4/site-packages/django/core/handlers/wsgi.py", line 171, in _get_post self._load_post_and_files() File "/usr/lib/python2.4/site-packages/django/core/handlers/wsgi.py", line 137, in _load_post_and_files self._post, self._files = self.parse_file_upload(self.META, self.environ[\'wsgi.input\']) File "/usr/lib/python2.4/site-packages/django/http/__init__.py", line 124, in parse_file_upload return parser.parse() File "/usr/lib/python2.4/site-packages/django/http/multipartparser.py", line 192, in parse for chunk in field_stream: File "/usr/lib/python2.4/site-packages/django/http/multipartparser.py", line 314, in next output = self._producer.next() File "/usr/lib/python2.4/site-packages/django/http/multipartparser.py", line 468, in next for bytes in stream: File "/usr/lib/python2.4/site-packages/django/http/multipartparser.py", line 314, in next output = self._producer.next() File "/usr/lib/python2.4/site-packages/django/http/multipartparser.py", line 375, in next data = self.flo.read(self.chunk_size) File "/usr/lib/python2.4/site-packages/django/http/multipartparser.py", line 405, in read return self._file.read(num_bytes) When running locally on the Django development server, big files work. I've tried setting my FILE_UPLOAD_HANDLERS = ("django.core.files.uploadhandler.TemporaryFileUploadHandler",) in case it was the memory upload handler, but it made no difference. Does anyone know how to fix this?

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• haskell: a data structure for storing ascending integers with a very fast lookup

  - by valya

  Hello! (This question is related to my previous question, or rather to my answer to it.) I want to store all qubes of natural numbers in a structure and look up specific integers to see if they are perfect cubes. For example, cubes = map (\x -> x*x*x) [1..] is_cube n = n == (head $ dropWhile (<n) cubes) It is much faster than calculating the cube root, but It has complexity of O(n^(1/3)) (am I right?). I think, using a more complex data structure would be better. For example, in C I could store a length of an already generated array (not list - for faster indexing) and do a binary search. It would be O(log n) with lower ?oefficient than in another answer to that question. The problem is, I can't express it in Haskell (and I don't think I should). Or I can use a hash function (like mod). But I think it would be much more memory consuming to have several lists (or a list of lists), and it won't lower the complexity of lookup (still O(n^(1/3))), only a coefficient. I thought about a kind of a tree, but without any clever ideas (sadly I've never studied CS). I think, the fact that all integers are ascending will make my tree ill-balanced for lookups. And I'm pretty sure this fact about ascending integers can be a great advantage for lookups, but I don't know how to use it properly (see my first solution which I can't express in Haskell).

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• OpenGL - drawing 2D polygons shapes with texture

  - by plonkplonk

  I am trying to make a few effects in a C+GL game. So far I draw all my sprites as a quad, and it works. However, I am trying to make a large ring appear at times, with a texture following that ring, as it takes less memory than a quad with the ring texture inside. The type of ring I want to make is not a round-shaped GL mesh ring (the "tube" type) but a "paper" 2D ring. That way I can modify the "width" of the ring, getting more of the effect than a simple quad+ring texture. So far all my attempts have been...kind of ridiculous, as I don't understand GL's coordinates too well (and I can't really understand the available documentation...I am just a designer with no coder help or background. A n00b, basically). glBegin(GL_POLYGON); for(i = 0;i < 360; i += 10){ glTexCoord2f(0, 0); glVertex2f(Cos(i)*(H-10),Sin(i)H); glTexCoord2f(0, HP); glVertex2f(Sin(i)(H-10),Cos(i)*(H-10)); glTexCoord2f(WP, HP); glVertex2f(Cos(i)H,Sin(i)(H-10)); glTexCoord2f(WP, 0); glVertex2f(Sin(i)*H,Cos(i)*H); } glEnd(); This is my last attempt, and it seems to generate a "sunburst" from the right edge of the circle instead of a ring. It's an amusing effect but definitely not what I want. Other results included the circle looking exactly the same as the quad textured (aka drawing a sprite literally) or something that looked like a pop-art filter, by working on this train of thought. Seems like my logic here is entirely flawed, so, what would be the easiest way to obtain such a ring? No need to reply in code, just some guidance for a non-math-skilled user...

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• Hibernate ScrollableResults Do Not Return The Whole Set of Results

  - by mlaverd

  Some of the queries we run have 100'000+ results and it takes forever to load them and then send them to the client. So I'm using ScrollableResults to have a paged results feature. But we're topping at roughly 50k results (never exactly the same amount of results). I'm on an Oracle9i database, using the Oracle 10 drivers and Hibernate is configured to use the Oracle9 dialect. I tried with the latest JDBC driver (ojdbc6.jar) and the problem was reproduced. We also followed some advice and added an ordering clause, but the problem was reproduced. Here is a code snippet that illustrates what we do: Criteria crit = sess.createCriteria(ABC.class); crit.add(Restrictions.eq("property", value)); crit.setFetchSize(pageSize); crit.addOrder(Order.asc("property")); ScrollableResults sr = crit.scroll(); ... ... do{ for (Object entry : page) sess.evict(entry); //to avoid having our memory just explode out of proportion page.clear(); for (int i =0 ; i < pageSize && ! metLastRow; i++){ if (resultSet.next()) page.add(sr.get(0)); else metLastRow = true; } metLastRow = metLastRow?metLastRow:sr.isLast(); sendToClient(page); }while(!metLastRow); So, why is it that I get the result set to tell me its at the end when it should be having so much more results?

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• jQuery performance

  - by jAndy

  Hi Folks, imagine you have to do DOM manipulation like a lot (in my case, it's kind of a dynamic list). Look at this example: var $buffer = $('<ul/>', { 'class': '.custom-example', 'css': { 'position': 'absolute', 'top': '500px' } }); $.each(pages[pindex], function(i, v){ $buffer.append(v); }); $buffer.insertAfter($root); "pages" is an array which holds LI elements as jQuery object. "$root" is an UL element What happens after this code is, both UL's are animated (scrolling) and finally, within the callback of animate this code is executed: $root.detach(); $root = $buffer; $root.css('top', '0px'); $buffer = null; This works very well, the only thing I'm pi**ed off is the performance. I do cache all DOM elements I'm laying a hand on. Without looking too deep into jQuery's source code, is there a chance that my performance issues are located there? Does jQuery use DocumentFragments to append things? If you create a new DOM element with var new = $('<div/>') it is only stored in memory at this point isnt it?

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• Error while compiling Hello world program for CUDA

  - by footy

  I am using Ubuntu 12.10 and have sucessfully installed CUDA 5.0 and its sample kits too. I have also run sudo apt-get install nvidia-cuda-toolkit Below is my hello world program for CUDA: #include <stdio.h> /* Core input/output operations */ #include <stdlib.h> /* Conversions, random numbers, memory allocation, etc. */ #include <math.h> /* Common mathematical functions */ #include <time.h> /* Converting between various date/time formats */ #include <cuda.h> /* CUDA related stuff */ __global__ void kernel(void) { } /* MAIN PROGRAM BEGINS */ int main(void) { /* Dg = 1; Db = 1; Ns = 0; S = 0 */ kernel<<<1,1>>>(); /* PRINT 'HELLO, WORLD!' TO THE SCREEN */ printf("\n Hello, World!\n\n"); /* INDICATE THE TERMINATION OF THE PROGRAM */ return 0; } /* MAIN PROGRAM ENDS */ The following error occurs when I compile it with nvcc -g hello_world_cuda.cu -o hello_world_cuda.x /tmp/tmpxft_000033f1_00000000-13_hello_world_cuda.o: In function `main': /home/adarshakb/Documents/hello_world_cuda.cu:16: undefined reference to `cudaConfigureCall' /tmp/tmpxft_000033f1_00000000-13_hello_world_cuda.o: In function `__cudaUnregisterBinaryUtil': /usr/include/crt/host_runtime.h:172: undefined reference to `__cudaUnregisterFatBinary' /tmp/tmpxft_000033f1_00000000-13_hello_world_cuda.o: In function `__sti____cudaRegisterAll_51_tmpxft_000033f1_00000000_4_hello_world_cuda_cpp1_ii_b81a68a1': /tmp/tmpxft_000033f1_00000000-1_hello_world_cuda.cudafe1.stub.c:1: undefined reference to `__cudaRegisterFatBinary' /tmp/tmpxft_000033f1_00000000-1_hello_world_cuda.cudafe1.stub.c:1: undefined reference to `__cudaRegisterFunction' /tmp/tmpxft_000033f1_00000000-13_hello_world_cuda.o: In function `cudaError cudaLaunch<char>(char*)': /usr/lib/nvidia-cuda-toolkit/include/cuda_runtime.h:958: undefined reference to `cudaLaunch' collect2: ld returned 1 exit status I am also making sure that I use gcc and g++ version 4.4 ( As 4.7 there is some problem with CUDA)

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• How do we greatly optimize our MySQL database (or replace it) when using joins?

  - by jkaz

  Hi there, This is the first time I'm approaching an extremely high-volume situation. This is an ad server based on MySQL. However, the query that is used incorporates a lot of JOINs and is generally just slow. (This is Rails ActiveRecord, btw) sel = Ads.find(:all, :select = '*', :joins = "JOIN campaigns ON ads.campaign_id = campaigns.id JOIN users ON campaigns.user_id = users.id LEFT JOIN countries ON countries.campaign_id = campaigns.id LEFT JOIN keywords ON keywords.campaign_id = campaigns.id", :conditions = [flashstr + "keywords.word = ? AND ads.format = ? AND campaigns.cenabled = 1 AND (countries.country IS NULL OR countries.country = ?) AND ads.enabled = 1 AND campaigns.dailyenabled = 1 AND users.uenabled = 1", kw, format, viewer['country'][0]], :order = order, :limit = limit) My questions: Is there an alternative database like MySQL that has JOIN support, but is much faster? (I know there's Postgre, still evaluating it.) Otherwise, would firing up a MySQL instance, loading a local database into memory and re-loading that every 5 minutes help? Otherwise, is there any way I could switch this entire operation to Redis or Cassandra, and somehow change the JOIN behavior to match the (non-JOIN-able) nature of NoSQL? Thank you!

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• How to append new elements to Xml from a stream

  - by Wololo

  I have a method which returns some xml in a memory stream private MemoryStream GetXml() { XmlWriterSettings settings = new XmlWriterSettings(); settings.Indent = true; using (MemoryStream memoryStream = new MemoryStream()) { using (XmlWriter writer = XmlWriter.Create(memoryStream, settings)) { writer.WriteStartDocument(); writer.WriteStartElement("root"); writer.WriteStartElement("element"); writer.WriteString("content"); writer.WriteEndElement(); writer.WriteEndElement(); writer.WriteEndDocument(); writer.Flush(); } return memoryStream; } } In this example the format of the xml will be: <?xml version="1.0" encoding="utf-8"?> <root> <element>content</element> </root> How can i insert a new element under the root e.g <?xml version="1.0" encoding="utf-8"?> <root> <element>content</element> ----->New element here <------ </root> EDIT: Also please suggest the most efficient method as returning a memorystream may not be the best solution. The final xml will be passed to a custom HttpHandler so what are the best options for writing the output? context.Response.Write vs context.Response.OutputStream

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• Determining whether geographic point is within X meters of a state border (using shapefile for borde

  - by DanM

  So I'm writing a Java app, and I've got an ESRI Shapefile which contains the borders of all the U.S. states. What I need is to be able to determine whether any given lat/lon point is within a specified distance from ANY state border line - i.e., I will not be specifying a particular border line, just need to see whether the point is close to any of them. The solution does NOT have to be very precise at all; e.g. I don't need to be dealing with measuring perpendicular to the border, or whatever. Just checking to see if going X meters north, south, east or west would result in crossing a border would be more than sufficient. The solution DOES have to be computationally efficient, as I'll be performing a huge number of these calculations. I'm planning to use the GeoTools library (though if there's a simpler option, I'm all for it) with the Shapefile plugin. What I don't really understand is: Once I've got the shapefile loaded into memory, how do I check to see whether I'm near a border? Thanks! -Dan

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