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  • C++ iterators & loop optimization

    - by Quantum7
    I see a lot of c++ code that looks like this: for( const_iterator it = list.begin(), const_iterator ite = list.end(); it != ite; ++it) As opposed to the more concise version: for( const_iterator it = list.begin(); it != list.end(); ++it) Will there be any difference in speed between these two conventions? Naively the first will be slightly faster since list.end() is only called once. But since the iterator is const, it seems like the compiler will pull this test out of the loop, generating equivalent assembly for both.

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  • Overhead of serving pages - JSPs vs. PHP vs. ASPXs vs. C

    - by John Shedletsky
    I am interested in writing my own internet ad server. I want to serve billions of impressions with as little hardware possible. Which server-side technologies are best suited for this task? I am asking about the relative overhead of serving my ad pages as either pages rendered by PHP, or Java, or .net, or coding Http responses directly in C and writing some multi-socket IO monster to serve requests (I assume this one wins, but if my assumption is wrong, that would actually be most interesting). Obviously all the most efficient optimizations are done at the algorithm level, but I figure there has got to be some speed differences at the end of the day that makes one method of serving ads better than another. How much overhead does something like apache or IIS introduce? There's got to be a ton of extra junk in there I don't need. At some point I guess this is more a question of which platform/language combo is best suited - please excuse the in-adroitly posed question, hopefully you understand what I am trying to get at.

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  • Breaking out of .emacs script

    - by prosseek
    I use two emacs (Aquamcs and text based emacs) on my Mac. I normally use text based emacs for just editing something, so I don't want to load anything with it. What I came up with is to have the checking code in .emacs to exit/break if it's text based emacs (darwin system but not aquamacs). (when (and (equal system-type 'darwin) (not (boundp 'aquamacs-version))) (exit) ??? (break) ???? ) It seems to work, but I don't know how to break out of .emacs. How to do that? ADDED I just wanted to speed up in loading text based emacs on my mac, and I thought about breaking out as a solution. Based on the helpful answers, I came up with the following code that runs .emacs only when it's not a text based emacs. (setq inhibit-splash-screen t) (unless (null window-system)

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  • Access static constant variable from multiple threads in C

    - by user325519
    I have some experience with multithread programming under Linux (C/C++ & POSIX threads), however most obvious cases are sometimes very complicated. I have several static constant variables (global and function local) in my code, can I access them simultaneously from multiple threads without using mutexes? Because I don't modify them it should be ok, but it's always better to ask. I have to do heavy speed optimization, so even as fast operations as mutex lock/unlock are quite expensive for me, especially because my application is going to access these variables form long loops.

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  • Reading a file over a network path

    - by Sin5k4
    I have this weird issue,when I use > File FileToRead = new File("\\\\MYSERVER\\MYFOLDER\\MYFOLDER\\MYPICTURE.JPG"); to read a file over a network,all I get is a null pointer exception.Normally a local path works with this,but when on a network path,I just couldn't manage to get it to work.Any ideas? PS:oh and my network connection seems to work,no issues when accessing data in windows explorer... More of the code: File FileToRead = new File("file://DOKSERVICE/Somefolder/ProductImage/01001.JPG"); // File FileToRead = new File("c:\\dog.jpg"); local test BufferedImage image = ImageIO.read(FileToRead); BufferedImage resizedimage = new BufferedImage(260, 260,BufferedImage.TYPE_INT_RGB ); Graphics2D g = resizedimage.createGraphics(); g.drawImage(image, 0, 0, 260, 260, null); g.dispose(); picture.setIcon(new ImageIcon(image));

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  • How do I change the class of an object to a subclass of its current class in C++?

    - by Jared P
    I have an array of pointers to a base class, so that I can make those pointers point to (different) subclasses of the base class, but still interact with them. (really only a couple of methods which I made virtual and overloaded) I'm wondering if I can avoid using the pointers, and instead just make an array of the base class, but have some way to set the class to the subclass of my choosing. I know there must be something there specifying the class, as it needs to use that to look up the function pointer for virtual methods. By the way, the subclasses all have the same ivars and layout. Note: the design is actually based on using a template argument instead of a variable, due to performance increases, so really the abstract base class is just the interface for the subclasses, which are all the same except for their compiled code. Thanks

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  • C# Spawn Multiple Threads for work then wait until all finished

    - by pharoc
    just want some advice on "best practice" regarding multi-threading tasks. as an example, we have a C# application that upon startup reads data from various "type" table in our database and stores the information in a collection which we pass around the application. this prevents us from hitting the database each time this information is required. at the moment the application is reading data from 10 tables synchronously. i would really like to have the application read from each table in a different thread all running in parallel. the application would wait for all the threads to complete before continuing with the startup of the application. i have looked into BackGroundWorker but just want some advice on accomplishing the above. Does the method sound logical in order to speed up the startup time of our application How can we best handle all the threads keeping in mind that each thread's work is independent of one another, we just need to wait for all the threads to complete before continuing. i look forward to some answers

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  • Centre of a circle that intersects two points

    - by Jason
    Given two points in a 2D plane, and a circle of radius r that intersects both of those points, what would be the formula to calculate the centre of that circle? I realise there would two places the circle can be positioned. I would want the circle whose centre is encountered first in a clockwise direction when sweeping the line that joins the two points around one of those points, starting from an arbitrary angle. I guess that is the next stage in my problem, after I find an answer for the first part. I'm hoping the whole calculation can be done without trigonometry for speed. I'm starting with integer coordinates and will end with integer coordinates, if that helps.

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  • Memory leak in chrome.extension.sendRequest()

    - by jprim
    Chrome Version : 9.0.597.19 (Build 68937) beta & current stable I have simplified my code as far as possible. I ended up with the attached extension: content.js (content script run on every site): setInterval(function() { chrome.extension.sendRequest({ }, function(response) { //Do nothing }); }, 1); background.js (background page script): chrome.extension.onRequest.addListener(function(request, sender, sendResponse) { sendResponse({ }); }); When you install this extension, you can observe it eating up memory extremely fast (I got 90MB in 1 min with 9 tabs opened). You can speed up the process by opening more tabs. Of course, the extension I am actually developing does not send requests every millisecond, but only every 3 seconds. This just slows it down, though. A user who has run it in the background for a long time with many tabs opened has reported 100MB of memory usage, and I can reproduce it to a less extreme extent, too.

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  • WPF Books in 2010

    - by notJim
    I'm looking to learn WPF, and I'd like to get a book to help in the process. Most of the popular questions on SO regarding actual books are from 2008, and I wanted to see if recommendations for books had changed at all. WPF Unleashed, which seems to be the most popular recommendation, was published in 2006, which is quite a while ago, with the lightening-quick pace that Microsoft has been following with .NET. Does this book still work? For some background, I'm a web developer (using MVC, so MVVM makes sense to me conceptually), looking to make the jump to desktop development. I did C# a while ago, but I'll be picking up a separate C# book to get up to speed on that. I am not interested in Silverlight. I am not necessarily interested in flashy UIs right now, as I'm working on business software but what I am interested in is good, clean, intuitive user interfaces.

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  • sql: DELETE + INSERT vs UPDATE + INSERT

    - by user93422
    A similar question has been asked, but since it always depends, I'm asking for my specific situation separately. I have a web-site page that shows some data that comes from a database, and to generate the data from that database I have to do some fairly complex multiple joins queries. The data is being updated once a day (nightly). I would like to pre-generate the data for the said view to speed up the page access. For that I am creating a table that contains exact data I need. Question: for my situation, is it reasonable to do complete table wipe followed by insert? or should I do update,insert? SQL wise seems like DELETE + INSERT will be easier (it is single SQL expression). EDIT: RDBMS: MS SQL Server 2008 Ent

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  • Looking at the C++ new[] cookie. How portable is this code?

    - by carleeto
    I came up with this as a quick solution to a debugging problem - I have the pointer variable and its type, I know it points to an array of objects allocated on the heap, but I don't know how many. So I wrote this function to look at the cookie that stores the number of bytes when memory is allocated on the heap. template< typename T > int num_allocated_items( T *p ) { return *((int*)p-4)/sizeof(T); } //test #include <iostream> int main( int argc, char *argv[] ) { using std::cout; using std::endl; typedef long double testtype; testtype *p = new testtype[ 45 ]; //prints 45 std::cout<<"num allocated = "<<num_allocated_items<testtype>(p)<<std::endl; delete[] p; return 0; } I'd like to know just how portable this code is.

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  • No optimization causes wrong search result

    - by KailZhang
    I just took over our solr/lucene stuff from my ex-colleague. But there is a weird bug. If there is no optimization after dataimport, actually if there are multiple segment files, the search result then will be wrong. We are using a customized solr searchComponent. As far as I know about lucene, optimization is only optimization which could improve the speed of indexing and should not affect search result. I doubt this may be related to multithreading or unclosed searcher/reader or something. Anybody can help? Thank you.

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  • std::out_of_range error?

    - by vette982
    I'm dealing with a file with a linked list of lines with each node looking like this: struct TextLine{ //The actual text string text; //The line number of the document int line_num; //A pointer to the next line TextLine * next; }; and I'm writing a function that adds spaces at the beginning of the lines found in the variable text, by calling functions like linelist_ptr->text.insert(0,1,'\t'); The program compiles, but when I run it I get this error: terminate called after throwing an instance of 'std::out_of_range' what(): basic_string::at Aborted Any ideas?

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  • What exactly does a self-describing type in .Net mean?

    - by tzup
    Given this MSDN article, we learn that the Common Type System in .Net has this classification of reference types: "Reference types can be self-describing types, pointer types, or interface types. The type of a reference type can be determined from values of self-describing types. Self-describing types are further split into arrays and class types." So an array, for instance, is a self-describing type because we can determine it's type from its values? How? Is that it, or is there more to this definition?

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  • iPhone Accelerometer Values

    - by Mike
    My question is about the iPhone accelerometer. Does the accelerometer measure acceleration or movement of the iPhone? What I mean is if I hold the iPhone and go from 0mph to 60mph, I would expect the measure of acceleration to increase in value from 0 to 60, but once I reach 60, I expect the value to return to 0 since I am "no longer accelerating" but am moving at a constant speed. Now if the accelerometer measure motion, I would expect it to register 0 to 60 and continue to provide a change in value as I move forward at 60mph. Sorry, I looked at a few books, programmed some code (values seemed to small to give a recognizable result over short distances or speeds), and a lot of web searches, and I am trying to get an answer to this question. Thanx!

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  • const ready only local copies

    - by robUK
    Hello gcc 4.4.4 c89 I am just wondering is it worth passing a const into a function. i.e. void do_something(const char *dest, const int size) The size is a ready-only so I don't want to change it. However, some developers never have this as const has it is a local copy that is being used. The pointer is const as you can change the value in the calling routine. I always have a const on ready-only local copies, as it confirms to anyone reading my code that it is a ready-only variable. And also, when coding I don't make the mistake of changing it without realizing. Many thanks for any suggestions,

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  • Change Interval Of CADisplayLink

    - by user3679109
    I have replaced an NSTimer with a CADisplayLink. I have it working properly but it is running too slowly. How could I go about speeding this up? This is the code that I'm using: ViewController.h (In {} with @interface: CADisplayLink *displayLink; ViewController.m (viewDidLoad): displayLink = [CADisplayLink displayLinkWithTarget:self selector:@selector(onTimer)]; [displayLink addToRunLoop:[NSRunLoop currentRunLoop] forMode:NSRunLoopCommonModes]; onTimer is the method that it is calling. So my question is how do I speed up how often this is being called? Thanks

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  • Passing arguments to Shared Function - C

    - by SpyrosR
    I have used dlopen to load an object and dlsym to get a function pointer to a shared object function. Everything works fine. I have tested it calling then the shared function which (for now) only prints and it works-prints fine in the main program calling it. Now I want to pass two arguments to this function. An int and a char * .Can anyone help me understand how can I pass arguments to a shared function? I have searched in the web but I cannot understand how it works.

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  • Using a single PHP script for an entire site

    - by briggins5
    I had an idea today (that millions of others have probably already had) of putting all the sites script into a single file, instead of having multiple, seperate ones. When submitting a form, there would also be a hidden field called something like 'action' which would represent which function in the file would handle it. I know that things like Code Igniter and CakePHP exist which help seperate/organise the code. Is this a good or bad idea in terms of security, speed and maintenance? Do things like this already exist that i am not aware of?

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  • How to return a copy of the data in C++

    - by Josh Curren
    I am trying to return a new copy of the data in a C++ Template class. The following code is getting this error: invalid conversion from ‘int*’ to ‘int’. If I remove the new T then I am not returning a copy of the data but a pointer to it. template<class T> T OrderedList<T>::get( int k ) { Node<T>* n = list; for( int i = 0; i < k; i++ ) { n=n->get_link(); } return new T( n->get_data() ); // This line is getting the error ********** }

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  • Store data in Ruby on Rails without Database

    - by snowmaninthesun
    I have a few data values that I need to store on my rails app and wanted to know if there are any alternatives to creating a database table just to do this simple task. Background: I'm writing some analytics and dashboard tools for my ruby on rails app and i'm hoping to speed up the dashboard by caching results that will never change. Right now I pull all users for the last 30 days, and re arange them so I can see the number of new users per day. It works great but takes quite a long time, in reality I should only need to calculate the most recent day and just store the rest of the array somewhere else. Where is the best way to store this array? Creating a database table seems a bit overkill, and i'm not sure that global variables are the correct answer. Is there a best practice for persisting data like this? If anyone has done anything like this before let me know what you did and how it turned out.

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  • MS DOS function like ipconfig to get system performance specs?

    - by JustADude
    I am aware of MSINFO32, but I'm wondering if there is a MS DOS command similar to ipconfig in order to get system specifications? I would like for the system specifications to be displayed in the MS DOS prompt. I would like to see at least: CPU RAM BUS speed Thanks for any insights. Edit: I am unable to install any other software, so just have to use existing DOS programming commands to extract this information. Thank you again. 2nd Edit: Whoops. Using Windows XP and Windows Vista.

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  • Develop iPhone application remotely?

    - by ANE
    4 java developers are new to iPod Touch/iPhone app development. They have an idea for an app. They have never used Xcode or Macs before. Instead of spending money for a new iMac or Mac Mini for each of them, my boss would like to sell them a $999 Apple server, hosted at a facility connected a single T1 line, and have all 4 people work remotely in Xcode. Is this feasible? Is anyone doing anything like this? Specifically, is 1 T1 enough for realistic remote app development? Would they have to work in black & white via Logmein or Gotomeeting to get decent speed? Can four people work remotely together on an Xcode project at the same time? Do they absolutely need their own Macs to connect their iPod Touches or iPhones physically to, or can they connect to their existing PCs with iTunes and install their in-development apps that way?

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  • Official definition of CSCI (Computer Software Configuration Item)

    - by Andreas_D
    I'm looking for the most official definition of CSCI / Configuration Item - not just what it is but what we have to deliver / can expect when a contract defines subsystems which shall be developed as configuration items. I spend some time with my famous search tool and found a lot of explanations for CSCI (wikipedia, acronym directories, ...) but I haven't found a standard or a pointer to a standard (like ISO-xxx) yet which tells (1) what it is and (2) what has to be done from a QM/CM point of view. I just ask, because a contractors QM representative stated during an acceptance test, that CI only requires to not forget the CI in the configuration plan and to assign a serial number ... I expected to see some SRS, SDD, ICD, SVD, SIP, ... documents and acceptance test documentation for those subsystems...

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