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• Alternative to c++ static virtual methods

  - by Jaime Pardos

  In C++ is not possible to declare a static virtual function, neither cast a non-static function to a C style function pointer. Now, I have a plain ol' C SDK that uses function pointers heavily. I have to fill a structure with several function pointers. I was planning to use an abstract class with a bunch of static pure virtual methods, and redefine them in derived classes and fill the structure with them. It wasn't until then that I realized that static virtual are not allowed in C++. Is there any good alternative? The best I can think of is defining some pure virtual methods GetFuncA(), GetFuncB(),... and some static members FuncA()/FuncB() in each derived class, which would be returned by the GetFuncX(). Then a function in the abstract class would call those functions to get the pointers and fill the structure.

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• Why is .NET faster than C++ in this case?

  - by acidzombie24

  -edit- I LOVE SLaks comment. "The amount of misinformation in these answers is staggering." :D Calm down guys. Pretty much all of you were wrong. I DID make optimizations. It turns out whatever optimizations I made wasn't good enough. I ran the code in GCC using gettimeofday (I'll paste code below) and used g++ -O2 file.cpp and got slightly faster results then C#. Maybe MS didn't create the optimizations needed in this specific case but after downloading and installing mingw I was tested and found the speed to be near identical. Justicle Seems to be right. I could have sworn I use clock on my PC and used that to count and found it was slower but problem solved. C++ speed isn't almost twice as slower in the MS compiler. When my friend informed me of this I couldn't believe it. So I took his code and put some timers onto it. Instead of Boo I used C#. I constantly got faster results in C#. Why? The .NET version was nearly half the time no matter what number I used. C++ version: #include <iostream> #include <stdio.h> #include <intrin.h> #include <windows.h> using namespace std; int fib(int n) { if (n < 2) return n; return fib(n - 1) + fib(n - 2); } int main() { __int64 time = 0xFFFFFFFF; while (1) { int n; //cin >> n; n = 41; if (n < 0) break; __int64 start = __rdtsc(); int res = fib(n); __int64 end = __rdtsc(); cout << res << endl; cout << (float)(end-start)/1000000<<endl; break; } return 0; } C# version: using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Runtime.InteropServices; using System.ComponentModel; using System.Threading; using System.IO; using System.Diagnostics; namespace fibCSTest { class Program { static int fib(int n) { if (n < 2)return n; return fib(n - 1) + fib(n - 2); } static void Main(string[] args) { //var sw = new Stopwatch(); //var timer = new PAB.HiPerfTimer(); var timer = new Stopwatch(); while (true) { int n; //cin >> n; n = 41; if (n < 0) break; timer.Start(); int res = fib(n); timer.Stop(); Console.WriteLine(res); Console.WriteLine(timer.ElapsedMilliseconds); break; } } } } GCC version: #include <iostream> #include <stdio.h> #include <sys/time.h> using namespace std; int fib(int n) { if (n < 2) return n; return fib(n - 1) + fib(n - 2); } int main() { timeval start, end; while (1) { int n; //cin >> n; n = 41; if (n < 0) break; gettimeofday(&start, 0); int res = fib(n); gettimeofday(&end, 0); int sec = end.tv_sec - start.tv_sec; int usec = end.tv_usec - start.tv_usec; cout << res << endl; cout << sec << " " << usec <<endl; break; } return 0; }

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• Objects in interface

  - by Peter Kowalchuk

  I created my own object, PKSurvey. In the interface of the View Controller I can define a pointer to it, then in a method I can alloc it and have an instance. How do I keep the instance beyond the method where it was allocated? I assign values in one method and want to be able to use those values in other methods. Should I allocate it in the viewDidLoad method or should I do it somewhere else? @interface DIrectionalDrillerViewController : UIViewController { PKSurvey *Survey=[PKSurvey new]; ---------------- - (void)viewDidLoad { [Survey new];

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• How to determine what in my script is blocking my HTML rendering?

  - by Vicki

  I have a web application that uses quite a bit of JavaScript. When the page loads, it's very clear visually that something is blocking the rendering of a particular portion of the web site. This portion is generated by a Tabber Tabify JavaScript library. How can I determine what's blocking the HTML rendering specifically so that I can modify my code to prevent this blocking? Can I use Firebug, or some other tool, to walk through my HTML/JavaScript to determine where the HTML rendering is being blocked and if so, how? UPDATE: YSlow gives my web-application a score of "A" and Page Speed give a score of 94/100. UPDATE 2: The live site is linked below. http://www.uptownelite.com/index.uncompressed.html?city=Dallas,TX What I'm specifically referring too is the actual Tabs themselves being rendering (and NOT the panel content inside the tab panes). It seems strange to me that the Tab headings themselves are taking so long to generate on the first (empty cache) page load.

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• How to dynamically replace a method implement in ObjC2?

  - by Abhi

  I am trying to learn how to write plugins using SIMBL. I got my plugin to load with the target application, and also know the method that I wish to override. However, I am not able to use class_getInstanceMethod correctly based on snippets on the Internet. Have things changed in OSX 10.6 and/or ObjC2? The following code from culater.net gives "Dereferencing pointer to incomplete type": BOOL DTRenameSelector(Class _class, SEL _oldSelector, SEL _newSelector) { Method method = nil; // First, look for the methods method = class_getInstanceMethod(_class, _oldSelector); if (method == nil) return NO; method->method_name = _newSelector; return YES; } Is there a complete example of how to override a method using SIMBL plugins? Thanks!

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• drupal bootstrap script: how to get list of all nodes of type x?

  - by groovehunter

  hi. I create a custom import and export, at the moment as an external script (via bootstrap), i plan to create a module in a more generic fashion lateron. I am building a frontend for nagios and for our host management and nagios configuration btw. Maybe it might become useful for other environments (networkmanagement) Now i need to know how to get list of all nodes of type x? I want to avoid direct SQL. A suggestion i got was to make an rss and parse it but i acess the drupal db a dozen times to extract various nodes, so it feels strange to do a web request for one thing So what i am looking for as newbie drupal dev is just a pointer to basic search module api for this task TIA florian

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• How do I read an arbitrary chunk from a PNG file?

  - by Mason Wheeler

  I've got some custom metadata to put into a PNG file. It's being saved through libpng, and it's not difficult to write out a custom chunk. I just call png_write_chunk with the name, length and data. But I can't see how to get the data back out again. I'd expect there to be a png_read_chunk function that takes a chunk name and returns a pointer to the data or something like that, but there's nothing like that in png.h. Does anyone know how to accomplish this?

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• Division to the nearest 1 decimal place without floating point math?

  - by John Sheares

  I am having some speed issues with my C# program and identified that this percentage calculation is causing a slow down. The calculation is simply n/d * 100. Both the numerator and denominator can be any integer number. The numerator can never be greater than the denominator and is never negative. Therefore, the result is always from 0-100. Right now, this is done by simply using floating point math and is somewhat slow, since it's being calculated tens of millions of times. I really don't need anything more accurate than to the nearest 0.1 percent. And, I just use this calculated value to see if it's bigger than a fixed constant value. I am thinking that everything should be kept as an integer, so the range with 0.1 accuracy would be 0-1000. Is there some way to calculate this percentage without floating point math?

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• How can one use the "Add view" dialog in Visual Studio efficiently when working with ASP.NET MVC?

  - by Marek

  Does anyone else think that the add view dialog in VS is useless or is it just me? Why is there no search/filtering in there? I can not even paste the type name (without namespace) there to speed up the view creation. Plus, there are a lot of irrelevant classes there, including classes from all referenced libraries. Am I missing something or Microsoft never did any usability testing with that?? Is it possible to filter out types/assemblies in the dialog and/or better navigation compared to manually scrolling the combobox with all the types listed? Is it possible to include only types from a particular directory/assembly/namespace? (the ViewModels namespace for example) EDIT: As it seems from the answers that there is no usable workaround for this, I have filed a suggestion at Connect: https://connect.microsoft.com/VisualStudio/feedback/ViewFeedback.aspx?FeedbackID=507784 Please vote for the suggestion if you find this is an important issue.

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• Shared Variable Among Ruby Processes

  - by Jesse J

  I have a Ruby program that loads up two very large yaml files, so I can get some speed-up by taking advantage of the multiple cores by forking off some processes. I've tried looking, but I'm having trouble figuring how, or even if, I can share variables in different processes. The following code is what I currently have: @proteins = "" @decoyProteins = "" fork do @proteins = YAML.load_file(database) exit end fork do @decoyProteins = YAML.load_file(database) exit end p @proteins["LVDK"] P displays nil though because of the fork. So is it possible to have the forked processes share the variables? And if so, how?

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• CKeditor 3.0 - How to know which toolbar button is clicked

  - by understack

  Hi, I want to update few variables when any of the toolbar button (like bold, italic etc) is clicked. I'm unable to trap 'click' event on any of these buttons. Could somebody give me an example when clicking on 'bold' button would also pop up an alert box? How can I trap 'paste' event? I've googled a lot and searched ckeditor forum but couldn't find any solution. Any pointer would be really helpful. Thanks.

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• How can I get read-ahead bytes?

  - by Bruno Martinez

  Operating systems read from disk more than what a program actually requests, because a program is likely to need nearby information in the future. In my application, when I fetch an item from disk, I would like to show an interval of information around the element. There's a trade off between how much information I request and show, and speed. However, since the OS already reads more than what I requested, accessing these bytes already in memory is free. What API can I use to find out what's in the OS caches? Alternatively, I could use memory mapped files. In that case, the problem reduces to finding out whether a page is swapped to disk or not. Can this be done in any common OS?

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• High performance querying - Suggestions please

  - by Alex Takitani

  Supposing that I have millions of user profiles, with hundreds of fields (name, gender, preferred pet and so on...). You want to make searches on profiles. Ex.:All profiles that has age between x and y, loves butterflies, hates chocolate.... With database would you choose? Suppose that You have a Facebook like load. Speed is a must. Open Source preferred. I've read a lot about Cassandra, HBase, Mongo, Mysql... I just can't decide.....

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• Data-separation in a Symfony Multi-tenant app using Doctrine

  - by Prasad

  I am trying to implement a multi-tenant application, that is - data of all clients in a single database - each shared table has a tenant_id field to separate data I wish to achieve data separation by adding where('tenant_id = ', $user->getTenantID()) {pseudoc-code} to all SELECT queries I could not find any solution up-front, but here are possible approaches I am considering. 1) crude approach: customizing all fetchAll and fetchOne functions in every class (I will go mad!) 2) using listeners: possibly coding for the preDqlSelect event and adding the 'where' to all queries 3) override buildQuery(): could not find an example of this for front-end 4) implement contentformfilter: again need a pointer Would appreciate if someone could validate these & comment on efficieny, suitability. Also, if anyone has achieved multitenancy using another strategy, pl share. Thanks

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• Is being a programmer a younger person's job?

  - by Saobi

  After you get old, say past 30 or 40. Can you still keep up with the young coders from your company, those fresh out of school, who can code for 15+ hours on 10 cans of redbulls (most people in Google, Facebook, etc) ? And given the lightning speed with which today's programming frameworks and architectures evolve, can you keep up with the most up to date stuff and be as proficient at them as the next college grad? I know for jobs like unix/c/embedded programming, it might be that the older the better. But for programming jobs in say web development, social media, search engine technology, etc. Do you become less and less competitive career-wise versus youngsters? For example, most coders in Google and Facebook, I believe are under 25 years old. In other words, once you reach a certain age, would it be unwise to continue to be a coder, and is it better to try becoming a project manager or architect?

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• How to unmangle exported symbols from C++ in dynamic libraries in XCode on OSX

  - by Gerald

  I've been trying to develop a dynamic library in C++ that can be run-time loaded in an application. I finally got it working, but it's a little ugly. I have a function that takes a pointer to a C++ class as an argument, which looks like this: bool registerGrindPlugin( Grind::PluginManager* mgr ); But of course it's being exported as: _Z19registerGrindPluginPN5Grind13PluginManagerE I tried a .c file with a simple function and it exported fine as "registerGrindPlugin", but of course I can't pass a C++ class as the argument that way. Soo... my question is, is there a way to unmangle or alias the exported symbol so that I don't have to use a monstrosity like Z19registerGrindPluginPN5Grind13PluginManagerE in my dlsym call? I did see something about -alias_list as a linker option, but I haven't quite figured out how to use it in XCode. If that is the solution, can somebody provide some more details on how to use this?

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• Sending BLOBs in a JSON service,... how?

  - by Marten Sytema

  Hello I have a webservice (ie. servlet) implemented in Java. It gets some data from a MySQL table, with one column being of type BLOB (an image), and some other columns are just plain text. Normally I would store the file outside the database with a pointer to it in the database, but due to circumstance I now have to use this BLOB column... What is the proper way to send this? How to encode the image in a JSONObject, and how to parse (and RENDER!) it on the otherside ? I want to use JSONP, to avoid having to proxy it through the consumer's webserver. So that the consumer can just put in a tag pointing to the webservice, calling a callback. Any thoughts how to handle images in this situation? Also thoughts on performance etc. are interesting!

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• PyPy -- How can it possibly beat CPython?

  - by Vulcan Eager

  From the Google Open Source Blog: PyPy is a reimplementation of Python in Python, using advanced techniques to try to attain better performance than CPython. Many years of hard work have finally paid off. Our speed results often beat CPython, ranging from being slightly slower, to speedups of up to 2x on real application code, to speedups of up to 10x on small benchmarks. How is this possible? Which Python implementation was used to implement PyPy? CPython? And what are the chances of a PyPyPy or PyPyPyPy beating their score? (On a related note... why would anyone try something like this?)

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• How to get generate WSDL using GroovyWS

  - by James Black

  I am implementing SOAP web services for a commercial application, and I am using GroovyWS to speed up the development. But, when I deploy it on Tomcat, I am not using Grails, as the software has it's own J2EE framework, so how I do I get it to react to wsdl requests? Do I need to write a groovy-based servlet? Ideally I would like the WSDL generated upon request, so I can easily change the interface and see the change. It seems I will miss the annotations that JAX-WS provides for, though, to help fine-tune the WSDL.

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• Speeding up inner joins between a large table and a small table

  - by Zaid

  This may be a silly question, but it may shed some light on how joins work internally. Let's say I have a large table L and a small table S (100K rows vs. 100 rows). Would there be any difference in terms of speed between the following two options?: OPTION 1: OPTION 2: --------- --------- SELECT * SELECT * FROM L INNER JOIN S FROM S INNER JOIN L ON L.id = S.id; ON L.id = S.id; Notice that the only difference is the order in which the tables are joined. I realize performance may vary between different SQL languages. If so, how would MySQL compare to Access?

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• Timestamp as int field, query performance

  - by Kirzilla

  Hello, I'm storing timestamp as int field. And on large table it takes too long to get rows inserted at date because I'm using mysql function FROM_UNIXTIME. SELECT * FROM table WHERE FROM_UNIXTIME(timestamp_field, '%Y-%m-%d') = '2010-04-04' Is there any ways to speed this query? Maybe I should use query for rows using timestamp_field >= x AND timestamp_field < y? Thank you I've just tried this query... SELECT * FROM table WHERE timestamp_field >= UNIX_TIMESTAMP('2010-04-14 00:00:00') AND timestamp_field <= UNIX_TIMESTAMP('2010-04-14 23:59:59') but there is no any performance bonuses. :(

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• How to improve performance

  - by Ram

  Hi, In one of mine applications I am dealing with graphics objects. I am using open source GPC library to clip/merge two shapes. To improve accuracy I am sampling (adding multiple points between two edges) existing shapes. But before displaying back the merged shape I need to remove all the points between two edges. But I am not able to find an efficient algorithm that will remove all points between two edges which has same slope with minimum CPU utilization. Currently all points are of type PointF Any pointer on this will be a great help.

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• EXC_BAD_ACCESS when not using self.

  - by chris

  I got nabbed by the following bug again and would like some clarification to exactly why it is a bug. I have a simple UITableView that loads some data: // myclass.h @property (nonatomic, retain) NSArray *myData // myclass.m @synthesize myData; - (void) viewDidLoad { ... myData = someDataSource // note the lack of self } - (UITableViewCell *) cellForRowAtIndexPath ... { ... cell.textLabel.text = [self.myData objectAtIndex:indexPath.row]; // EXC_BAD_ACCESS } The table first loads fine, but when scrolling up enough that one of the cells is totally out of the view I then get the EXC_BAD_ACCESS error. Am I missing something in regards to @property retain. My understanding is that it releases anything that the pointer was previously pointing to before the reassignment. If I am correct then why would not using self. cause any problems? Thanks for the help.

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• Struct size containing vector<T> different sizes between DLL and EXE..

  - by Michael Peddicord

  I have this situation where an EXE program imports a DLL for a single function call. It works by passing in a custom structure and returning a different custom structure. Up till now it's worked fine until I wanted one of the structs data members to be a vector < MyStruct When I do a sizeof(vector< MyStruct ) in my program I get a size of 20 but when I do it from inside the DLL I get a size of 24. This size inconsistency is causing a ESP pointer error. Can anyone tell me why a Vector < MyStruct would be a different size in the DLL than in the program? I have reverified that my structs in both the DLL and the Program are identical. I would appreciate any help on the subject. Thank you.

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• Is Alpha Five Version 10 really all that its reported to be?

  - by Gary B2312321321

  I came across this RDMS via the advert on stackoverflow. Seems to be in the vein of MS Access / Filemaker / Apex database devlopment tools but focused on web based applications. It quotes rave reviews from EWeek and a favourable mention from Dr Dobbs regarding its ability to create AJAX web applications without coding. The Eweek review, apparently written by an ASP.NET programmer, goes on to proclaim the ease at which apps can be extended using the inbuilt XBasic language and how custom javascript can easily be added without wading through code. Has anyone here built a web app with Alpha 5? Does anyone have comments on the development process, the speed of it or limitations they encountered along the way? To me it seems Oracle APEX comes closest to the feature set, has anyone programmed in both and have any comments?

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