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  • Detect template presence at compilation time

    - by doublep
    GCC up to 4.5 doesn't have standard C++0x type trait template has_nothrow_move_constructor. I could use it in my package for optimization, but I don't want to rule out one of the common compilers and don't want to overload configuration with symbols like HAVE_STD_HAS_NOTHROW_MOVE_CONSTRUCTOR. Is it somehow possible to use that template if present and just fall back to copying if not present without using any predefined configuration symbols? I also don't want to depend on Boost, since my library is small and doesn't need Boost for any other reasons. In pseudocode, I need something like: template <typename type> struct has_nothrow_move_constructor_robust : public integral_constant <bool, /* if possible */ has_nothrow_move_constructor <type>::value /* otherwise */ false> { }; Since move constructors are only for C++0x anyway, I don't mind using other C++0x features for the above definition, if at all possible.

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  • MySQL: Get unique values across multiple columns in alphabetical order

    - by RuCh
    Hey everyone, If my table looks like this: id | colA | colB | colC =========================== 1 | red | blue | yellow 2 | orange | red | red 3 | orange | blue | cyan What SELECT query do I run such that the results returned are: blue, cyan, orange, red, yellow Basically, I want to extract a collective list of distinct values across multiple columns and return them in alphabetical order. I am not concerned with performance optimization, because the results are being parsed to an XML file that will serve as a cache (database is hardly updated). So even a dirty solution would be fine. Thanks for any help!

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  • Has Object in VB 2010 received the same optimalization as dynamic in C# 4.0?

    - by Abel
    Some people have argued that the C# 4.0 feature introduced with the dynamic keyword is the same as the "everything is an Object" feature of VB. However, any call on a dynamic variable will be translated into a delegate once and from then on, the delegate will be called. In VB, when using Object, no caching is applied and each call on a non-typed method involves a whole lot of under-the-hood reflection, sometimes totaling a whopping 400-fold performance penalty. Have the dynamic type delegate-optimization and caching also been added to the VB untyped method calls, or is VB's untyped Object still so slow?

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  • How to Software Service Industry get their Client from or where do they look for their Clients ?

    - by Rachel
    This question is inclined more towards Business Side of Software Industry, I am sure that we have two types in Software Industry as with any other Industry, i.e, Service side and Product Side. Basically for Product based company, we are looking more into product features and to see if market if mature or not for particular product but as far as Service Based company goes (may be it can be big giants like Infosys, TCS or Sapient or some midsize or small companies which provide services like:Web Design,Website Design,Corporate Identity,Logo Design,Flash Design,Web Applications,Enterprise Portal,Rich Internet Applications,Business Applications,Technology Consulting,Ecommerce,Online Store Creations,Custom Shopping Carts,Ecommerce Hosting,Website Marketing,Organic SEO,Pay-Per-Click,Social Media Optimization,Mobile,Mobile Website and Mobile Applications) where do they look for Client and how do they manage to get one ? So my basic question is Where do Service Based Companies Look for Client or get their Clients Form ?

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  • new image makes http request even though cached?

    - by joshs
    I have a javascript slide show that creates the next slide dynamically and then moves it into view. Since the images are actually sprites, the src is transparent.png and the actual image is mapped via background:url(.. in css. Everytime (well, most of the time) the script creates a new Element, Firefox makes an http request for transparent.png. I have a far-future expires header, and Firefox is respecting all other files' expiries. Is there a way to avoid these unnecessary requests. Even though the server is returning 304 unmodified responses, it would be nice if Firefox would respect the expiries on dynamically created images. I suspect that if I injected a simple string instead of using new Element, this might solve the problem, but I use some methods on Prototypes extended Element object, so I would like to avoid a bunch of html strings in my js file. This is a nit-picky question, but I'm working on front-end optimization now, so I thought I would address it. Thanks.

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  • Incremental Compilation in Eclipse. ASTNode-s and SVN versioning

    - by Alex
    Hi there, I am building up some statistics after analyzing the source code in eclipse. But the overall process is too slow because i rebuild my model every time from scratch after each compilation. I am looking for a way to get only the changed parts of the code (as ASTNodes) and to rebuild just that part of my model. I suppose that even the changed compilation units and not the exact code elements would be enough after the user compiles and still would be a nice optimization. I am sure eclipse is capable of knowing what code elements are changed (and even to know their semantics), because when I use the subclipse plugin my changes are ordered by a code element (an import, a method, a variable declaration, etc). Well.. at least that plugin is capable of knowing that info. Thanks in advance

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  • In .NET which loop runs faster for or foreach

    - by Binoj Antony
    In c#/VB.NET/.NET which loop runs faster for or foreach? Ever since I read that for loop works faster than foreach a long time ago I assumed it stood true for all collections, generic collection all arrays etc. I scoured google and found few articles but most of them are inconclusive (read comments on the articles) and open ended. What would be ideal is to have each scenarios listed and the best solution for the same e.g: (just example of how it should be) for iterating an array of 1000+ strings - for is better than foreach for iterating over IList (non generic) strings - foreach is better than for Few references found on the web for the same: Original grand old article by Emmanuel Schanzer CodeProject FOREACH Vs. FOR Blog - To foreach or not to foreach that is the question asp.net forum - NET 1.1 C# for vs foreach [Edit] Apart from the readability aspect of it I am really interested in facts and figures, there are applications where the last mile of performance optimization squeezed do matter.

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  • How to implement square root and exponentiation on arbitrary length numbers?

    - by tomp
    I'm working on new data type for arbitrary length numbers (only non-negative integers) and I got stuck at implementing square root and exponentiation functions (only for natural exponents). Please help. I store the arbitrary length number as a string, so all operations are made char by char. Please don't include advices to use different (existing) library or other way to store the number than string. It's meant to be a programming exercise, not a real-world application, so optimization and performance are not so necessary. If you include code in your answer, I would prefer it to be in either pseudo-code or in C++. The important thing is the algorithm, not the implementation itself. Thanks for the help.

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  • Where is the chink in Google Chrome's armor?

    - by kudlur
    While browsing with Chrome, I noticed that it responds extremely fast (in comparison with IE and Firefox on my laptop) in terms of rendering pages, including JavaScript heavy sites like gmail. This is what googlebook on Chrome has to say tabs are hosted in process rather than thread. compile javascript using V8 engine as opposed to interpreting. Introduce new virtual machine to support javascript heavy apps introduce "hidden class transitions" and apply dynamic optimization to speed up things. Replace inefficient "Conservative garbage colllection" scheme with more precise garbage collection scheme. Introduce their own task scheduler and memory manager to manage the browser environment. All this sounds so familiar, and Microsoft has been doing such things for long time.. Windows os, C++, C# etc compilers, CLR, and so on. So why isn't Microsoft or any other browser vendor taking Chrome's approach? Is there a flaw in Chrome's approach? If not, is the rest of browser vendor community caught unaware with Google's approach?

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  • How to partition a plane

    - by puls200
    Let's say I have a fixed number (X) of points, e.g. coordinates within a given plane (I think you can call it a 2-D point cloud). These points should be partitioned into Y polygons where Y < X. The polygons should not overlap. It would be wonderful if the polygons were konvex (like a Voronoi diagram). Imagine it like locations forming countries. For example, I have 12 points and want to create 3 polygons with 4 points each. I thought about creating a grid which covers the points. Then iterate across the points, assigning them to the closest grid cells. Maybe I miss the obvious? I am sure there are better solutions. Thanks, Daniel I just found an optimization (kmeans++) .Maybe this will yield better results..

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  • Dynamic binding in C++

    - by chmike
    I'm implementing a CORBA like server. Each class has remotely callable methods and a dispatch method with two possible input, a string identifying the method or an integer which would be the index of the method in a table. A mapping of the string to the corresponding integer would be implemented by a map. The caller would send the string on the first call and get back the integer with the response so that it simply has to send the integer on subsequent calls. It is just a small optimization. The integer may be assigned dynamically on demand by the server object. The server class may be derived from another class with overridden virtual methods. What could be a simple and general way to define the method binding and the dispatch method ?

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  • Is it inefficient to access a python class member container in a loop statement?

    - by Dave
    Hi there. I'm trying to adopt some best practices to keep my python code efficient. I've heard that accessing a member variable inside of a loop can incur a dictionary lookup for every iteration of the loop, so I cache these in local variables to use inside the loop. My question is about the loop statement itself... if I have the following class: class A(object): def init(self) self.myList = [ 'a','b','c', 'd', 'e' ] Does the following code in a member function incur one, or one-per-loop-iteration (5) dictionary lookups? for letter in self.myList: print letter IE, should I adopt the following pattern, if I am concerned about efficiency... localList = self.myList for letter in localList: print letter or is that actually LESS efficient due to the local variable assign? Note, I am aware that early optimization is a dangerous pitfall if I'm concerned about the overall efficiency of code development. Here I am specifically asking about the efficiency of the code, not the coding. Thanks in advance! D

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  • Using *.html extension in dynamic URL's for SEO

    - by lostaman
    Hi all My situation is. I have a project planned to be built on ASP.NET MVC 2. And one of the major requirements is SEO optimization. A customer wants to use static-like URLs that end up with .html extension for this project that make URLs more SEO friendly. E.g. "mysite.com/about.html " or "mysite.com/items/getitem/5.html" etc. I wonder is there any benefit from SEO perspective to use .html extension in dynamic URLs? Are Google and other search engines rank work better with such URLs?

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  • Custom sort logic in OrderBy using LINQ

    - by Bala R
    What would be the right way to sort a list of strings where I want items starting with an underscore '_', to be at the bottom of the list, otherwise everything is alphabetical. Right now I'm doing something like this, autoList.OrderBy(a => a.StartsWith("_") ? "ZZZZZZ"+a : a ) EDIT: I ended up using something like this; optimization suggestions welcome! private class AutoCompleteComparer : IComparer<String> { public int Compare(string x, string y) { if (x.StartsWith("_") && y.StartsWith("_") || (!x.StartsWith("_") && !y.StartsWith("_"))) { return x.CompareTo(y); } else if (x.StartsWith("_")) { return 1; } else if (y.StartsWith("_")) { return -1; } return 0; } }

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  • Can Graphical Operations be combined in Qt or any other library ?

    - by Sunny
    Hi, Here is a Scenario, A series of operations that I will call for painting, QPainter p(this); 1). p.fillRect(0,0,320,240, RED_COLOR) 2) p.drawLine(0,0,100,100, BLUE_COLOR) 3) p.fillRect(0,0,320,240, YELLOW_COLOR) Now I want that painter should not draw first FillRect Function. It should not draw line. It should only perform last operation. Is there any way to achive this optimization in Qt. Is this type of drawing/painting optimizations are supported by any library?

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  • Why do debug symbols so adversely affect the performance of threaded applications on Linux?

    - by fluffels
    Hi. I'm writing a ray tracer. Recently, I added threading to the program to exploit the additional cores on my i5 Quad Core. In a weird turn of events the debug version of the application is now running slower, but the optimized build is running faster than before I added threading. I'm passing the "-g -pg" flags to gcc for the debug build and the "-O3" flag for the optimized build. Host system: Ubuntu Linux 10.4 AMD64. I know that debug symbols add significant overhead to the program, but the relative performance has always been maintained. I.e. a faster algorithm will always run faster in both debug and optimization builds. Any idea why I'm seeing this behavior?

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  • Create an seo and web accessibility analyzer

    - by rebellion
    I'm thinking of making a little web tool for analyzing the search engine optimization and web accessiblity of a whole website. First of all, this is just a private tool for now. Crawling a whole website takes up alot of resources and time. I've found out that wget is the best option for downloading the markup for a whole site. I plan on using PHP/MySQL (maybe even CodeIgniter), but I'm not quite sure if that's the right way to do it. There's always someone who recommends Python, Ruby or Perl. I only know PHP and a little bit Rails. I've also found a great HTML DOM parser class in PHP on SourceForge. But, the thing is, I need some feedback on what I should and should not do. Everything from how I should make the crawl process to what I should be checking for in regards to SEO and WCAG. So, what comes to your mind when you hear this?

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  • What is the time taken by java to call a method in another package?

    - by satish
    I have an assignment where i need to do feasibility study on two of my approaches and find optimized one. There are two packages A and B User input is gathered in A and then sent to B for execution. Now my approaches are 1. Call B methods from package A one by one. 2. Create a common method in B and send all the input as parameters. Which is feasible and best one, I know 2 is good in terms of code optimization and less number of calls. But, I want to understand what will be the execution time difference in above approaches How much time does java take to call method in another package? Is there any default value like x nano seconds or y milli seconds. Based on the time taken I can choose the appropiate one. Thanks

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  • Non-Latin characters in URLs - is it better to encode them or replace with their Latin "counterparts

    - by Pawel Krakowiak
    We're implementing a blog for a site which supports six different languages and five of them have non-Latin characters in their alphabets. We are not sure whether we should have them encoded (that is what we're doing at the moment) Létání s potravinami: Co je dovoleno? becomes l%c3%a9t%c3%a1n%c3%ad-s-potravinami-co-je-dovoleno and the browser displays it as létání-s-potravinami-co-je-dovoleno. or if we should replace them with their Latin "counterparts" (similar looking letters) Létání s potravinami: Co je dovoleno? becomes letani-s-potravinami-co-je-dovoleno. I can't find a definitive answer as to what's better from SEO perspective? Search engine optimization is very important for us. Which approach would you suggest?

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  • Any way to avoid a filesort when order by is different to where clause?

    - by Julian
    I have an incredibly simple query (table type InnoDb) and EXPLAIN says that MySQL must do an extra pass to find out how to retrieve the rows in sorted order. SELECT * FROM `comments` WHERE (commentable_id = 1976) ORDER BY created_at desc LIMIT 0, 5 exact explain output: table select_type type extra possible_keys key key length ref rows comments simple ref using where; using filesort common_lookups common_lookups 5 const 89 commentable_id is indexed. Comments has nothing trick in it, just a content field. The manual suggests that if the order by is different to the where, there is no way filesort can be avoided. http://dev.mysql.com/doc/refman/5.0/en/order-by-optimization.html I also tried order by id as well as it's equivalent but makes no difference, even if I add id as an index (which I understand is not required as id is indexed implicitly in MySQL). thanks in advance for any ideas!

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  • how to optimize sql server table for faster response?

    - by Thomas
    i found a in a table there are 50 thousands records and it takes one minute when we fetch data from sql server table just by issuing a sql. there are one primary key that means a already a cluster index is there. i just do not understand why it takes one minute. beside index what are the ways out there to optimize a table to get the data faster. in this situation what i need to do for faster response. also tell me how we can write always a optimize sql. please tell me all the steps in detail for optimization. thanks.

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  • How to Optimize Combined Graphical Operations?

    - by Sunny
    Hi, Here is a Scenario, A series of operations that I will call for painting, QPainter p(this); 1). p.fillRect(0,0,320,240, RED_COLOR) 2) p.drawLine(0,0,100,100, BLUE_COLOR) 3) p.fillRect(0,0,320,240, YELLOW_COLOR) Now I want that painter should not draw first FillRect Function. It should not draw line. It should only perform last operation. Is there any way to achive this optimization in Qt. Is this type of drawing/painting optimizations are supported by any library?

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  • JSF Pages call ManagedBeans that are not defined on the page and call all getters sometimes more tha

    - by Bill Leeper
    I have several JSF pages that are initializing and accessing ManagedBeans that are not even used on that page. This is creating a really hairy problem for initialization. I either have to make them all session scope and continually make calls to re-inialize or take the performance hit of having them read large amounts of data from the DB whenever they decide to initialize. Some of the managed beans being accessed are not even defined on the page in question. I have done some optimization based on comments related to multiple calls to getters, but I still have the issue that I have a very specialized (and expensive to initialize) bean that is getting called when I don't want it initialized. Any insight into why/what JSF calls might do something like this. I have a very complex page making use of JSTL, Tomahawk and standard JSF tags. I could include code, but its very complex and sensitive in nature.

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  • Is "}while(0);" always equal to "break;}while(1);" ?

    - by Hernán Eche
    I have compared gcc assembler output of do{ //some code }while(0); with do{ //some code break; }while(1); The output is equal, with or without optimization but.. It's always that way? No experiment can prove theories, they can only show they are wrong And because (I hope) programming is not an experimental science, and results can be predicted (at least simple things) I want to be sure next time I reeplace a break;}while(1); for the clearer (and less risky) while(0); Thank you for reading

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  • ASP NET forms Authorization: how to reduce duration?

    - by eddo
    I've got a web page which is implementing cookie based ASPNET Forms Authentication. Once the user has logged in the page, he can edit some information using a form which is created using a partialview and returned to him as a dialog for editing. The action linked to the partial view is decorated as follows: [HttpGet] [OutputCache(Duration = 0, VaryByParam = "None")] [Authorize(Roles = "test")] public ActionResult changeTripInfo(int tripID, bool ovride=false) { ... } The problem i am experiencing is the latency between the request and the time when the dialog is shown to the user: time ranges between 800 and 1100 ms which is not justified by the complexity of the form. Investigating with Glimpse turns out that the time to process the AuthorizeAttribute (see snip) sums up to at least 650 ms which is troubling me. Looking at the Sql server log, the call which checks the user roles takes, as expected, virtually nothing (duration 0). How can I reduce this time? Am I missing some optimization?

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