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  • Need advice on C++ coding pattern

    - by Kotti
    Hi! I have a working prototype of a game engine and right now I'm doing some refactoring. What I'm asking for is your opinion on usage of the following C++ coding patterns. I have implemented some trivial algorithms for collision detection and they are implemented the following way: Not shown here - class constructor is made private and using algorithms looks like Algorithm::HandleInnerCollision(...) struct Algorithm { // Private routines static bool is_inside(Point& p, Object& object) { // (...) } public: /** * Handle collision where the moving object should be always * located inside the static object * * @param MovingObject & mobject * @param const StaticObject & sobject * @return void * @see */ static void HandleInnerCollision(MovingObject& mobject, const StaticObject& sobject) { // (...) } So, my question is - somebody advised me to do it "the C++" way - so that all functions are wrapped in a namespace, but not in a class. Is there some good way to preserve privating if I will wrap them into a namespace as adviced? What I want to have is a simple interface and ability to call functions as Algorithm::HandleInnerCollision(...) while not polluting the namespace with other functions such as is_inside(...) Of, if you can advise any alternative design pattern for such kind of logics, I would really appreciate that...

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  • Small openmp programm freezes sometimes (gcc, c, linux)

    - by osgx
    Hello Just write a small omp test, and it does not work correctly all the times: #include <omp.h> int main() { int i,j=0; #pragma omp parallel for(i=0;i<1000;i++) { #pragma omp barrier j+= j^i; } return j; } The usage of j for writing from all threads is incorrect in this example, BUT there must be only nondeterministic value of j I have a freeze. Compiled with gcc-4.3.1 -fopenmp a.c -o gcc -static Run on 4-core x86_Core2 Linux server: $ ./gcc and got freeze (sometimes; like 1 freeze for 4-5 fast runs). Strace: [pid 13118] <... futex resumed> ) = 0 [pid 13118] futex(0x80d3014, FUTEX_WAIT, 2, NULL <unfinished ...> [pid 13120] <... futex resumed> ) = 0 [pid 13119] futex(0x80d3014, FUTEX_WAIT, 2, NULL <unfinished ...> [pid 13120] futex(0x80d3014, FUTEX_WAKE, 1) = 1 [pid 13120] futex(0x80cd798, FUTEX_WAIT, 1, NULL <unfinished ...> [pid 13109] <... futex resumed> ) = 0 [pid 13109] futex(0x80d3014, FUTEX_WAKE, 1) = 1 [pid 13109] futex(0x80d3020, FUTEX_WAIT, 251, NULL <unfinished ...> [pid 13118] <... futex resumed> ) = 0 [pid 13118] futex(0x80d3014, FUTEX_WAKE, 1) = 1 [pid 13119] <... futex resumed> ) = 0 [pid 13118] futex(0x80d3020, FUTEX_WAIT, 251, NULL <unfinished ...> [pid 13119] futex(0x80d3014, FUTEX_WAKE, 1) = 0 [pid 13119] futex(0x80d3020, FUTEX_WAIT, 251, NULL <freeze> Why do I have a freeze (deadlock)?

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  • Was Visual Studio 2008 or 2010 written to use multi cores?

    - by Erx_VB.NExT.Coder
    basically i want to know if the visual studio IDE and/or compiler in 2010 was written to make use of a multi core environment (i understand we can target multi core environments in 08 and 10, but that is not my question). i am trying to decide on if i should get a higher clock dual core or a lower clock quad core, as i want to try and figure out which processor will give me the absolute best possible experience with Visual Studio 2010 (ide and background compiler). if they are running the most important section (background compiler and other ide tasks) in one core, then the core will get cut off quicker if running a quad core, esp if background compiler is the heaviest task, i would imagine this would b e difficult to seperate in more then one process, so even if it uses multi cores you might still be better off with going for a higher clock cpu if the majority of the processing is still bound to occur in one core (ie the most significant part of the VS environment). i am a vb programmer, they've made great performance improvements in beta 2, congrats, but i would love to be able to use VS seamlessly... anyone have any ideas? thanks, erx

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  • Do the 'up to date' guarantees provided by final field in Java's memory model extend to indirect ref

    - by mattbh
    The Java language spec defines semantics of final fields in section 17.5: The usage model for final fields is a simple one. Set the final fields for an object in that object's constructor. Do not write a reference to the object being constructed in a place where another thread can see it before the object's constructor is finished. If this is followed, then when the object is seen by another thread, that thread will always see the correctly constructed version of that object's final fields. It will also see versions of any object or array referenced by those final fields that are at least as up-to-date as the final fields are. My question is - does the 'up-to-date' guarantee extend to the contents of nested arrays, and nested objects? An example scenario: Thread A constructs a HashMap of ArrayLists, then assigns the HashMap to final field 'myFinal' in an instance of class 'MyClass' Thread B sees a (non-synchronized) reference to the MyClass instance and reads 'myFinal', and accesses and reads the contents of one of the ArrayLists In this scenario, are the members of the ArrayList as seen by Thread B guaranteed to be at least as up to date as they were when MyClass's constructor completed?

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  • jquery ui dialog open multiple dialog boxes using the same class on the button and the content div

    - by MichaelAntoni
    Hello there, i want to open multiple dialog boxes by using the same class on both the button and the content div. The below works but only for the first time. jQuery('.helpDialog').hide(); jQuery('.helpButton').click(function() { jQuery(this).next('.helpDialog').dialog({ autoOpen: true, title: 'Help', width: 500, height: 300, position: [180,10], draggable: true, resizable: false, modal: false }); return false; }); we know the reason for this http://blog.nemikor.com/2009/04/08/basic-usage-of-the-jquery-ui-dialog/ "the second call is ignored because the dialog has already been instantiated on that element." But when i fix that problem by trying the code below, the dialog box no longer opens. Can anyone help? Thanks in advance jQuery('.helpDialog').hide(); jQuery(function() { jQuery('.helpDialog').dialog({ autoOpen: false, modal: true, title: 'Info', width: 600, height: 400, position: [200,0], draggable: false }); }); jQuery('.helpButton').click(function() { jQuery(this).next('.helpDialog').dialog('open'); return false; });

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  • Expose webservice directly to webclients or keep a thin server-side script layer in between?

    - by max
    Hi, I'm developing a REST webservice (Java, Jersey). The people I'm doing this for want to directly access the webservice via Javascript. Some instinct tells me this is not a good idea, but I cannot really explain that instinct. My natural approach would have been to have the webservice do the real logic and database access, but also have some (relatively thin) server-side script layer (e.g. in PHP). Clients would talk to the PHP layer which in turn would talk to the webservice. (The webservice would be pretty local to the apache/PHP server and implicitly trust calls from the script layer. The script layer would take care of session management.) (Btw, I am not talking about just hiding the webservice behind an Apache which simply redirects calls.) But as I find myself at a lack of words/arguments to explain my instinct, I wonder whether my instinct is right - note that while I have been developing all kinds of software in all kinds of languages and frameworks for like 17 years, this is the first time I develop a webservice. So my question is basically: what are your opinions? Are there any standard setups? Is my instinct totally wrong? Or partially? ;P Many thanks, Max PS: I might add a few bits of information about the planned usage of the whole application: will be accessed by different kinds of users, partly general public, partly privileged thus, all major OS/browser combinations can be expected as clients however, writing the client is not my responsibility will potentially have very high load/traffic logic of webservice will later be massively expanded for another product which is basically a superset of the functionality of the current project there is a significant likelihood that at some point an API should be exposed which can be used by 3rd party developers - obviously, with some restrictions at some point, the public view of the product should become accessible via smartphones, too (in other words, maybe a customized version of the site to adapt to the smaller display and different input methods)

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  • How do you hide a Swing Popup when you click somewhere else.

    - by Casey Watson
    I have a Popup that is shown when a user clicks on a button. I would like to hide the popup when any of the following events occur: The user clicks somewhere else in the application. (The background panel for example) The user minimizes the application. The JPopupMenu has this behavior, but I need more than just JMenuItems. The following code block is a simplified illustration to demonstrate the current usage. import java.awt.*; import java.awt.event.ActionEvent; import javax.swing.*; public class PopupTester extends JFrame { public static void main(String[] args) { final PopupTester popupTester = new PopupTester(); popupTester.setLayout(new FlowLayout()); popupTester.setSize(300, 100); popupTester.add(new JButton("Click Me") { @Override protected void fireActionPerformed(ActionEvent event) { Point location = getLocationOnScreen(); int y = (int) (location.getY() + getHeight()); int x = (int) location.getX(); JLabel myComponent = new JLabel("Howdy"); Popup popup = PopupFactory.getSharedInstance().getPopup(popupTester, myComponent, x, y); popup.show(); } }); popupTester.add(new JButton("No Click Me")); popupTester.setVisible(true); popupTester.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); } }

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  • Handling large (object) datasets with PHP

    - by Aron Rotteveel
    I am currently working on a project that extensively relies on the EAV model. Both entities as their attributes are individually represented by a model, sometimes extending other models (or at least, base models). This has worked quite well so far since most areas of the application only rely on filtered sets of entities, and not the entire dataset. Now, however, I need to parse the entire dataset (IE: all entities and all their attributes) in order to provide a sorting/filtering algorithm based on the attributes. The application currently consists of aproximately 2200 entities, each with aproximately 100 attributes. Every entity is represented by a single model (for example Client_Model_Entity) and has a protected property called $_attributes, which is an array of Attribute objects. Each entity object is about 500KB, which results in an incredible load on the server. With 2000 entities, this means a single task would take 1GB of RAM (and a lot of CPU time) in order to work, which is unacceptable. Are there any patterns or common approaches to iterating over such large datasets? Paging is not really an option, since everything has to be taken into account in order to provide the sorting algorithm.

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  • Determing if an unordered vector<T> has all unique elements

    - by Hooked
    Profiling my cpu-bound code has suggested I that spend a long time checking to see if a container contains completely unique elements. Assuming that I have some large container of unsorted elements (with < and = defined), I have two ideas on how this might be done: The first using a set: template <class T> bool is_unique(vector<T> X) { set<T> Y(X.begin(), X.end()); return X.size() == Y.size(); } The second looping over the elements: template <class T> bool is_unique2(vector<T> X) { typename vector<T>::iterator i,j; for(i=X.begin();i!=X.end();++i) { for(j=i+1;j!=X.end();++j) { if(*i == *j) return 0; } } return 1; } I've tested them the best I can, and from what I can gather from reading the documentation about STL, the answer is (as usual), it depends. I think that in the first case, if all the elements are unique it is very quick, but if there is a large degeneracy the operation seems to take O(N^2) time. For the nested iterator approach the opposite seems to be true, it is lighting fast if X[0]==X[1] but takes (understandably) O(N^2) time if all the elements are unique. Is there a better way to do this, perhaps a STL algorithm built for this very purpose? If not, are there any suggestions eek out a bit more efficiency?

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  • Drawing line graphics leads Flash to spiral out of control!

    - by drpepper
    Hi, I'm having problems with some AS3 code that simply draws on a Sprite's Graphics object. The drawing happens as part of a larger procedure called on every ENTER_FRAME event of the stage. Flash neither crashes nor returns an error. Instead, it starts running at 100% CPU and grabs all the memory that it can, until I kill the process manually or my computer buckles under the pressure when it gets up to around 2-3 GB. This will happen at a random time, and without any noticiple slowdown beforehand. WTF? Has anyone seen anything like this? PS: I used to do the drawing within a MOUSE_MOVE event handler, which brought this problem on even faster. PPS: I'm developing on Linux, but reproduced the same problem on Windows. UPDATE: You asked for some code, so here we are. The drawing function looks like this: public static function drawDashedLine(i_graphics : Graphics, i_from : Point, i_to : Point, i_on : Number, i_off : Number) : void { const vecLength : Number = Point.distance(i_from, i_to); i_graphics.moveTo(i_from.x, i_from.y); var dist : Number = 0; var lineIsOn : Boolean = true; while(dist < vecLength) { dist = Math.min(vecLength, dist + (lineIsOn ? i_on : i_off)); const p : Point = Point.interpolate(i_from, i_to, 1 - dist / vecLength); if(lineIsOn) i_graphics.lineTo(p.x, p.y); else i_graphics.moveTo(p.x, p.y); lineIsOn = !lineIsOn; } } and is called like this (m_graphicsLayer is a Sprite): m_graphicsLayer.graphics.clear(); if (m_destinationPoint) { m_graphicsLayer.graphics.lineStyle(2, m_fixedAim ? 0xff0000 : 0x333333, 1); drawDashedLine(m_graphicsLayer.graphics, m_initialPos, m_destinationPoint, 10, 10); }

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  • How can I specify dependencies in the manifest file and then to include it into my .jar file?

    - by Roman
    I generated .class files by the following command: javac -cp \directoryName\external.jar myPackageDirectory\First.java myPackageDirectory\Second.java I needed to use -cp during compilation and name of .jar file of an "external" library (external.jar) to be able to use this library from my code. Using my .class files I have generated my .jar file in the following way: jar cfm app.jar manifest.txt myPackageDirectory\*.class manifest.txt contains just one line: Main-Class: myPackageName.First My problem is that I am not sure that I will be able to run my .jar file on other computers. I think so because during the compilation I specified the location of the .jar file of the external library. So, my .class files (included into the .jar file will try to find the .jar file of the external library in a specific directory and there is no guaranty that that the .jar file of the external library will be in the same directory as on the my computer. I heard that the above problem can be solved by a usage of a MANIFEST file that I include in my own jar, and which will list dependency locations but I do not understand how it works. I do need to specify location of the "external.jar" at the compilation stage (otherwise the compiler complains).

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  • Using an embedded DB (SQLite / SQL Compact) for Message Passing within an app?

    - by wk1989
    Hello, Just out of curiosity, for applications that have a fairly complicated module tree, would something like sqlite/sql compact edition work well for message passing? So if I have modules containing data such as: \SubsystemA\SubSubSysB\ModuleB\ModuleDataC, \SubSystemB\SubSubSystemC\ModuleA\ModuleDataX Using traditional message passing/routing, you have to go through intermediate modules in order to pass a message to ModuleB to request say ModuleDataC. Instead of doing that, if we we simply store "\SubsystemA\SubSubSysB\ModuleB\ModuleDataC" in a sqlite database, getting that data is as simple as a sql query and needs no routing and passing stuff around. Has anyone done this before? Even if you haven't, do you foresee any issues & performance impact? The only concern I have right now would be the passing of custom types, e.g. if ModuleDataC is a custom data structure or a pointer, I'll need some way of storing the data structure into the DB or storing the pointer into the DB. Thanks, JW EDIT One usage case I haven't thought about is when you want to send a message from ModuleA to ModuleB to get ModuleB to do something rather than just getting/setting data. Is it possible to do this using an embedded DB? I believe callback from the DB would be needed, how feasible is this?

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  • power and modulo on the fly for big numbers

    - by user unknown
    I raise some basis b to the power p and take the modulo m of that. Let's assume b=55170 or 55172 and m=3043839241 (which happens to be the square of 55171). The linux-calculator bc gives the results (we need this for control): echo "p=5606;b=55171;m=b*b;((b-1)^p)%m;((b+1)^p)%m" | bc 2734550616 309288627 Now calculating 55170^5606 gives a somewhat large number, but since I have to do a modulooperation, I can circumvent the usage of BigInt, I thought, because of: (a*b) % c == ((a%c) * (b%c))%c i.e. (9*7) % 5 == ((9%5) * (7%5))%5 => 63 % 5 == (4 * 2) %5 => 3 == 8 % 5 ... and a^d = a^(b+c) = a^b * a^c, therefore I can divide b+c by 2, which gives, for even or odd ds d/2 and d-(d/2), so for 8^5 I can calculate 8^2 * 8^3. So my (defective) method, which always cut's off the divisor on the fly looks like that: def powMod (b: Long, pot: Int, mod: Long) : Long = { if (pot == 1) b % mod else { val pot2 = pot/2 val pm1 = powMod (b, pot, mod) val pm2 = powMod (b, pot-pot2, mod) (pm1 * pm2) % mod } } and feeded with some values, powMod (55170, 5606, 3043839241L) res2: Long = 1885539617 powMod (55172, 5606, 3043839241L) res4: Long = 309288627 As we can see, the second result is exactly the same as the one above, but the first one looks quiet different. I'm doing a lot of such calculations, and they seem to be accurate as long as they stay in the range of Int, but I can't see any error. Using a BigInt works as well, but is way too slow: def calc2 (n: Int, pri: Long) = { val p: BigInt = pri val p3 = p * p val p1 = (p-1).pow (n) % (p3) val p2 = (p+1).pow (n) % (p3) print ("p1: " + p1 + " p2: " + p2) } calc2 (5606, 55171) p1: 2734550616 p2: 309288627 (same result as with bc) Can somebody see the error in powMod?

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  • Flash browser game - HTTP + PHP vs Socket + Something else

    - by Maurycy Zarzycki
    I am developing a non-real time browser RPG game (think Kingdom of Loathing) which would be played from within a Flash app. At first I just wanted to make the communication with server using simply URLLoader to tell PHP what I am doing, and using $_SESSION to store data needed in-between request. I wonder if it wouldn't be better to base it on a socket connection, an app residing on a server written in Java or Python. The problem is I have never ever written such an app so I have no idea how much I'd have to "shift" my thoughts from simple responding do request (like PHP) to continuously working application. I won't hide I am also concerned about the memory and CPU usage of such Server app, when for example there would be hundreds of users connected. I've done some research. I have tried to do some research, but thanks to my nil knowledge on the sockets subject I haven't found anything helpful. So, considering the fact I don't need real time data exchange, will it be wise to develop the server side part as socket server, not in plain ol' PHP?

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  • Transparently surround a component with a link in Wicket

    - by Toni Menzel
    I want to be able to add links on certain items in an ListView. If an items is surrounded by the link or not is up to the code, so its not in the normal page markup. Say i have a markup like this: <div class="column" wicket:id="columnRepeater"> <span wicket:id="column"></span> </div> So essentially, while filling the repeater with a ListView i am able to find a custom renderer for the column component. (not my playingfield). What i want is to add a Link/Ajax Link around the column component. I learned using wicket:border lets you surround additional stuff. Now, the border markup looks like this: <wicket:border> <a wicket:id="link"><wicket:body/></a> </wicket:border> Now, i am a bit puzzled what the Border implementation looks like. Anyone there who can suggest a working java part? I have a couple of "work in progress" solutions but none works. Most questions have to do with usage of component ids. Is the border id = column ? Whats the id of the inner (border body) id then?

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  • How to make a plot from summaryRprof?

    - by ThorDivDev
    This is a question for an university assignment. I was given three algorithms to calculate the GCD that I already did. My problem is getting the Rprof results to a plot so I can compare them side by side. From what little understanding I have about Rprof, summaryRprof and plot is that Rprof is used like this: Rprof() #To start #functions here Rprof(NULL) #TO end summaryRprof() # to print results I understand that plot has many different types of inputs, x and y values and something called a data frame which I assume is a fancy word for table. and to draw different lines and things I need to use this: http://www.harding.edu/fmccown/r/ what I cant figure out is how to get the summaryRprof results to the plot() function. > Rprof(filename="RProfOut2.out", interval=0.0001) > gcdBruteForce(10000, 33) [1] 1 > gcdEuclid(10000, 33) [1] 1 > gcdPrimeFact(10000, 33) [1] 1 > Rprof(NULL) > summaryRprof() ?????plot???? I have been reading on stack overflow that and other sites that I can also try to use profr and proftools although I am not very clear on the usage. The only graph I have been able to make is one using plot(system.time(gcdFunction(10,100))) As always any help is appreciated.

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  • C#: Thread.CurrentThread.CurrentUICulture not working consistently

    - by xTRUMANx
    I've been working on a pet project on the weekends to learn more about C# and have encountered an odd problem when working with localization. To be more specific, the problem I have is with System.Threading.Thread.CurrentThread.CurrentUICulture. I've set up my app so that the user can quickly change the language of the app by clicking a menu item. The menu item in turn, saves the two-letter code for the language (e.g. "en", "fr", etc.) in a user setting called 'Language' and then restarts the application. Properties.Settings.Default.Language = "en"; Properties.Settings.Default.Save(); Application.Restart(); When the application is started up, the first line of code in the Form's constructor (even before InitializeComponent()) fetches the Language string from the settings and sets the CurrentUICulture like so: public Form1() { Thread.CurrentThread.CurrentUICulture = new CultureInfo(Properties.Settings.Default.Language); InitializeComponent(); } The thing is, this doesn't work consistently. Sometimes, all works well and the application loads the correct language based on the string saved in the settings file. Other times, it doesn't, and the language remains the same after the application is restarted. At first I thought that I didn't save the language before restarting the application but that is definitely not the case. When the correct language fails to load, if I were to close the application and run it again, the correct language would come up correctly. So this implies that the Language string has been saved but the CurrentUICulture assignment in my form constructor is having no effect sometimes. Any help? Is there something I'm missing of how threading works in C#? This could be machine-specific, so if it makes any difference I'm using Pentium Dual-Core CPU.

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  • Fastest reliable way for Clojure (Java) and Ruby apps to communicate

    - by jkndrkn
    Hi There, We have cloud-hosted (RackSpace cloud) Ruby and Java apps that will interact as follows: Ruby app sends a request to Java app. Request consists of map structure containing strings, integers, other maps, and lists (analogous to JSON). Java app analyzes data and sends reply to Ruby App. We are interested in evaluating both messaging formats (JSON, Buffer Protocols, Thrift, etc.) as well as message transmission channels/techniques (sockets, message queues, RPC, REST, SOAP, etc.) Our criteria: Short round-trip time. Low round-trip-time standard deviation. (We understand that garbage collection pauses and network usage spikes can affect this value). High availability. Scalability (we may want to have multiple instances of Ruby and Java app exchanging point-to-point messages in the future). Ease of debugging and profiling. Good documentation and community support. Bonus points for Clojure support. What combination of message format and transmission method would you recommend? Why? I've gathered here some materials we have already collected for review: Comparison of various java serialization options Comparison of Thrift and Protocol Buffers (old) Comparison of various data interchange formats Comparison of Thrift and Protocol Buffers Fallacies of Protocol Buffers RPC features Discussion of RPC in the context of AMQP (Message-Queueing) Comparison of RPC and message-passing in distributed systems (pdf) Criticism of RPC from perspective of message-passing fan Overview of Avro from Ruby programmer perspective

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  • Strange compiler complaint when using similar code

    - by Jason
    For a project, I have to ask the user for a file name, and I'm reading it in character by character using getchar. From the main, I call the function char *coursename= introPrint(); //start off to print the usage directions and get the first bit of input. That function is defined as char *introPrint(){ int size= 20; int c; int length=0; char buffer[size]; //instructions printout, cut for brevity //get coursename from user and return it while ( (c=getchar()) != EOF && (c != '\n') ){ buffer[length++]= c; if (length==size-1) break; } buffer[length]=0; return buffer; } This is basically identical code I wrote to ask the user for input, replace the character echo with asterisks, then print out the results. Here, though, I'm getting a function returns address of local variable warning for the return statement. So why am I getting no warnings from the other program, but trigger one for this code?

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  • HIbernate 3.5.1 - can I just drop in EHCache 2.0.1?

    - by caerphilly
    I'm using Hibernate 3.5.1, which comes with EHCache 1.5 bundled. If I want to use the latest EHCache release (2.0.1), is it just a matter of removing the ehcache-1.5.jar from my project, and replacing with ehcache-core-2.0.1.jar? Any issues to be aware of? Also - is a cache "region" in the Hibernate mapping file that same as a cache "name" in the ehcache configuration xml? What I want to do is define 2 named cache regions - one for read-only reference entities that won't change (lookup lists etc), and one for all other entities. So in ehcache I want to define two elements; <cache name="readonly"> ... </cache> <cache name="mutable"> ... </cache> And then in my Hibernate mapping files, I will specify the cache to be used for each entity: <hibernate-mapping> <class name="lookuplist"> <cache region="readonly" usage="read-only"/> <property> ... </property> </class> </hibernate-mapping> Will that work? Some of the documentation seems to imply that a separate region/cache gets created for each mapped class... Thanks.

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  • OpenGL Pixel Format Attributes (NSOpenGLPixelFormatAttibutes) explanation?

    - by nacho4d
    Hi, I am not new to OpenGL, but not an expert. Many tutorials teach how to draw, 3D, 2D, projections, orthogonal, etc, but How about setting a the view? (NSOpenGLView in Cocoa, Macs). For example I have this: - (id) initWithFrame: (NSRect) frame { GLuint attribs[] = { //PF: PixelAttibutes NSOpenGLPFANoRecovery, NSOpenGLPFAWindow, NSOpenGLPFAAccelerated, NSOpenGLPFADoubleBuffer, NSOpenGLPFAColorSize, 24, NSOpenGLPFAAlphaSize, 8, NSOpenGLPFADepthSize, 24, NSOpenGLPFAStencilSize, 8, NSOpenGLPFAAccumSize, 0, 0 }; NSOpenGLPixelFormat* fmt = [[NSOpenGLPixelFormat alloc] initWithAttributes: (NSOpenGLPixelFormatAttribute*) attribs]; return self = [super initWithFrame:frame pixelFormat: [fmt autorelease]]; } And I don't understand very well their usage, specially when combining them. For example: If I want my view to be capable of full screen should I write NSOpenGLPFAFullScreen only ? or both? (by capable I mean not always in full screen) Regarding Double Buffer, what is this exactly? (Below: Apple's definition) If present, this attribute indicates that only double-buffered pixel formats are considered. Otherwise, only single-buffered pixel formats are considered Regarding Color: if NSOpenGLPFAColorSize is 24 and NSOpenGLPFAColorSize is 8 then it means that alpha and RGB components are treated differently? what happen if I set the former to 32 and the later to 0? Etc, etc,In general how do I learn to set my view from scratch? Thanks in advance. Ignacio.

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  • Stable/repeatable random sort (MySQL, Rails)

    - by Matt Rogish
    I'd like to paginate through a randomly sorted list of ActiveRecord models (rows from MySQL database). However, this randomization needs to persist on a per-session basis, so that other people that visit the website also receive a random, paginate-able list of records. Let's say there are enough entities (tens of thousands) that storing the randomly sorted ID values in either the session or a cookie is too large, so I must temporarily persist it in some other way (MySQL, file, etc.). Initially I thought I could create a function based on the session ID and the page ID (returning the object IDs for that page) however since the object ID values in MySQL are not sequential (there are gaps), that seemed to fall apart as I was poking at it. The nice thing is that it would require no/minimal storage but the downsides are that it is likely pretty complex to implement and probably CPU intensive. My feeling is I should create an intersection table, something like: random_sorts( sort_id, created_at, user_id NULL if guest) random_sort_items( sort_id, item_id, position ) And then simply store the 'sort_id' in the session. Then, I can paginate the random_sorts WHERE sort_id = n ORDER BY position LIMIT... as usual. Of course, I'd have to put some sort of a reaper in there to remove them after some period of inactivity (based on random_sorts.created_at). Unfortunately, I'd have to invalidate the sort as new objects were created (and/or old objects being removed, although deletion is very rare). And, as load increases the size/performance of this table (even properly indexed) drops. It seems like this ought to be a solved problem but I can't find any rails plugins that do this... Any ideas? Thanks!!

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  • Caching vector addition over changing collections

    - by DRMacIver
    I have the following setup: I have a largish number of uuids (currently about 10k but expected to grow unboundedly - they're user IDs) and a function f : id - sparse vector with 32-bit integer values (no need to worry about precision). The function is reasonably expensive (not outrageously so, but probably on the order of a few 100ms for a given id). The dimension of the sparse vectors should be assumed to be infinite, as new dimensions can appear over time, but in practice is unlikely to ever exceed about 20k (and individual results of f are unlikely to have more than a few hundred non-zero values). I want to support the following operations efficiently: add a new ID to the collection invalidate an existing ID retrieve sum f(id) in O(changes since last retrieval) i.e. I want to cache the sum of the vectors in a way that's reasonable to do incrementally. One option would be to support a remove ID operation and treat invalidation as a remove followed by an add. The problem with this is that it requires us to keep track of all the old values of f, which is expensive in space. I potentially need to use many instances of this sort of cached structure, so I would like to avoid that. The likely usage pattern is that new IDs are added at a fairly continuous rate and are frequently invalidated at first. Ids which have been invalidated recently are much more likely to be invalidated again than ones which have remained valid for a long time, but in principle an old Id can still be invalidated. Ideally I don't want to do this in memory (or at least I want a way that lets me save the result to disk efficiently), so an idea which lets me piggyback off an existing DB implementation of some sort would be especially appreciated.

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  • Design for fastest page download

    - by mexxican
    I have a file with millions of URLs/IPs and have to write a program to download the pages really fast. The connection rate should be at least 6000/s and file download speed at least 2000 with avg. 15kb file size. The network bandwidth is 1 Gbps. My approach so far has been: Creating 600 socket threads with each having 60 sockets and using WSAEventSelect to wait for data to read. As soon as a file download is complete, add that memory address(of the downloaded file) to a pipeline( a simple vector ) and fire another request. When the total download is more than 50Mb among all socket threads, write all the files downloaded to the disk and free the memory. So far, this approach has been not very successful with the rate at which I could hit not shooting beyond 2900 connections/s and downloaded data rate even less. Can somebody suggest an alternative approach which could give me better stats. Also I am working windows server 2008 machine with 8 Gig of memory. Also, do we need to hack the kernel so as we could use more threads and memory. Currently I can create a max. of 1500 threads and memory usage not going beyond 2 gigs [ which technically should be much more as this is a 64-bit machine ]. And IOCP is out of question as I have no experience in that so far and have to fix this application today. Thanks Guys!

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  • How do software events work internally?

    - by Duddle
    Hello! I am a student of Computer Science and have learned many of the basic concepts of what is going on "under the hood" while a computer program is running. But recently I realized that I do not understand how software events work efficiently. In hardware, this is easy: instead of the processor "busy waiting" to see if something happened, the component sends an interrupt request. But how does this work in, for example, a mouse-over event? My guess is as follows: if the mouse sends a signal ("moved"), the operating system calculates its new position p, then checks what program is being drawn on the screen, tells that program position p, then the program itself checks what object is at p, checks if any event handlers are associated with said object and finally fires them. That sounds terribly inefficient to me, since a tiny mouse movement equates to a lot of cpu context switches (which I learned are relatively expensive). And then there are dozens of background applications that may want to do stuff of their own as well. Where is my intuition failing me? I realize that even "slow" 500MHz processors do 500 million operations per second, but still it seems too much work for such a simple event. Thanks in advance!

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