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  • Multi-threaded Pooled Allocators

    - by Darren Engwirda
    I'm having some issues using pooled memory allocators for std::list objects in a multi-threaded application. The part of the code I'm concerned with runs each thread function in isolation (i.e. there is no communication or synchronization between threads) and therefore I'd like to setup separate memory pools for each thread, where each pool is not thread-safe (and hence fast). I've tried using a shared thread-safe singleton memory pool and found the performance to be poor, as expected. This is a heavily simplified version of the type of thing I'm trying to do. A lot has been included in a pseudo-code kind of way, sorry if it's confusing. /* The thread functor - one instance of MAKE_QUADTREE created for each thread */ class make_quadtree { private: /* A non-thread-safe memory pool for int linked list items, let's say that it's * something along the lines of BOOST::OBJECT_POOL */ pooled_allocator<int> item_pool; /* The problem! - a local class that would be constructed within each std::list as the * allocator but really just delegates to ITEM_POOL */ class local_alloc { public : //!! I understand that I can't access ITEM_POOL from within a nested class like //!! this, that's really my question - can I get something along these lines to //!! work?? pointer allocate (size_t n) { return ( item_pool.allocate(n) ); } }; public : make_quadtree (): item_pool() // only construct 1 instance of ITEM_POOL per // MAKE_QUADTREE object { /* The kind of data structures - vectors of linked lists * The idea is that all of the linked lists should share a local pooled allocator */ std::vector<std::list<int, local_alloc>> lists; /* The actual operations - too complicated to show, but in general: * * - The vector LISTS is grown as a quadtree is built, it's size is the number of * quadtree "boxes" * * - Each element of LISTS (each linked list) represents the ID's of items * contained within each quadtree box (say they're xy points), as the quadtree * is grown a lot of ID pop/push-ing between lists occurs, hence the memory pool * is important for performance */ } }; So really my problem is that I'd like to have one memory pool instance per thread functor instance, but within each thread functor share the pool between multiple std::list objects.

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  • Choosing between WPF and Silverlight

    - by user43498
    Hi, We have an existing web application developed using ASP.NET/Ajax We are planning to move it to either WPF or Silverlight. Can someone please compare these 2 technologies with respect to productivity,performance, maintainability,trade-offs, their pros and cons etc ? Thanks for reading.

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  • Java equivalent of C++ std::map?

    - by Rudiger
    I'm looking for a Java class with the characteristics of C++ std::map's usual implementation (as I understand it, a self-balancing binary search tree): O(log n) performance for insertion/removal/search Each element is composed of a unique key and a mapped value Keys follow a strict weak ordering I'm looking for implementations with open source or design documents; I'll probably end up rolling my own support for primitive keys/values. This question's style is similar to: Java equivalent of std::deque, whose answer was "ArrayDeque from Primitive Collections for Java".

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  • Can I run a 64-bit VMWare image on a 32-bit machine?

    - by John Sibly
    Can I run a 64-bit VMWare image on a 32-bit machine? I've Googled this but there doesn't seem to be a conclusive answer. I know that it would have to be completely emulated and would run like a dog - but slow performance isn't necessarily an issue as I'm just interested in testing some of my background services code on 64-bit platforms.

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  • swing gui improving

    - by radi
    hi all , i am looking for some methods to improve swing gui for example i want to know about new components libraries , new methods to enhance swing performance , new methods to add special effect to swing gui and new plaf for swing . please i want to know how to use this topics and where to find some tutorials about it . thanks.

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  • What is the best way to scale images in Java?

    - by Peter Kelley
    I have a web application written in Java (Spring, Hibernate/JPA, Struts2) where users can upload images and store them in the file system. I would like to scale those images so that they are of a consistent size for display on the site. What libraries or built in functions will offer the best results? I will consider the following criteria in making my decision (in this order): Free/Open Source (essential) Easy to implement Quality of results Performance Size of executable

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  • .Net 4.0 Memory-Mapped Files verses RDMS Storage

    - by Harry
    I'm interested in people's thoughts comparing storing data in a traditional SQL based Database or utilising a Memory-Mapped File such as the one in the new .Net 4.0 runtime. The data in question would be arrays of simple structures. Obvious pros and cons: SQL Database Pros Adhoc query support SQL Management Tools Schema changes (adding more columns and setting default values) Memory-Mapped Pros Lighter overhead? (this is an assumption on my part) Shareable between process threads Any others? Is it worth it for performance gains?

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  • What is the best method to convert to an Integer in JavaScript?

    - by Mathew Byrne
    There are several different methods for converting floating point numbers to Integers in JavaScript. My question is what method gives the best performance, is most compatible, or is considered the best practice? Here are a few methods that I know of: var a = 2.5; window.parseInt(a); // 2 Math.floor(a); // 2 a | 0; // 2 I'm sure there are others out there. Suggestions?

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  • Linq Expression Trees in Compact Framework.

    - by Michal Drozdowicz
    The lack of expression trees in Compact Framework has bugged me for some time now, but I haven't really looked for a solution. Today, I've found a blog post about an alternative System.Linq.Expressions built on top of Mono System.Core and used e.g. by db4o (you can find it here). My question is - have you used this library and if so, what were your experiences with it (especially regarding performance)?

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  • Alternative to Firebug for Firefox?

    - by Geuis
    The latest versions of Firebug in Firefox feel like they've been regressing. Performance is abysmal. This is a common complaint amongs everyone on my team, and increasingly among many other web developers online. Are there any alternative extensions for Firefox that gives similar functionality(DOM inspector, Net tab, console)?

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  • Is it wrong to use Deprecated methods or classes in Java?

    - by Umesh Aawte
    I am using eclipse to develop one web application. Just today I have updated my struts version by changing the JAR file. I am getting warnings at some places that methods are deprecated, but the code is working fine. I want to know some things Is it wrong to use Deprecated methods or classes in Java? what if don't change any method and run my application with warnings that I have, will it create any performance issue.

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  • Why multitasking is not supported in iPhone ?

    - by srikanth rongali
    Many are saying that Apple has restricted it for better performance. It should increase the size of RAM to support multitasking. So, they Apple is not allowing it. But some say that Cocoa Touch applications can't be multitasking as iPhone has only one window and views on it. But I could not understand what is the correct reason for this ? Please clarify me.

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  • Approach for authentication and storing user details.

    - by cappuccino
    Hey folks, I am using the Zend Framework but my question is broadly about sessions / databases / auth (PHP MySQL). Currently this is my approach to authentication: 1) User signs in, the details are checked in database. - Standard stuff really. 2) If the details are correct only the user's unique ID is stored in the session and a security token (user unique ID + IP + Browser info + salt). The session in written to the filesystem. I've been reading around and many are saying that storing stuff in sessions is not a good idea, and that you should really only write a unique ID which refers back to the user's details and a security token to prevent session hijacking. So this is the approach i've taken, i use to write the user's details in session, but i've moved that out. Wanted to know your opinions on this. I'm keeping sessions in the filesystem since i don't run on multiple servers, and since i'm only writting a tiny tiny bit of data to sessions, i thought that performance would be greater keeping sessions in the filesystem to reduce load on the database. Once the session is written on authentication, it really is only read-only from then on. 3) The rest of the user's details (like subscription details, permissions, account info etc) are cached in the filesystem (this can always be easily moved to memory if i wanted even more performance). So rather than keeping the user's details in session, the user's details are cached in the file system. I'm using Zend_Cache and the unique cache id is something like md5(/cache/auth/2892), the number is the unique id of the user. I guess the benefit of this method is that once the user is logged in, there is essentially not database queries being run to get the user's details. Just wonder if this approach is better than keeping the whole lot in session... 4) As the user moves throughout the site the only thing that is checked is the ID in the session and the security token. So, overall the first question is 1) is the filesystem more efficient than a database for this purpose 2) have i taken enough security precautions 3) is separating user detail's from the session into a cached file a pointless task? Thanks.

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  • Linux Scheduling Mechanism in 2.6.22?

    - by Mazen
    Hello, I'm doing some kind of performance evaluation using two different vanilla Linux kernels, 2.6.22 and 2.6.31, since I assume each of them uses a different scheduling mechanism: 2.6.22 uses the old O(1) scheduler, whilst 2.6.31 adopts the CFS. Could anybody confirm the correction of this assumption?

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  • Jave JIT compiler compiles at compile time or runtime ?

    - by Tony
    From wiki: In computing, just-in-time compilation (JIT), also known as dynamic translation, is a technique for improving the runtime performance of a computer program. So I guess JVM has another compiler, not javac, that only compiles bytecode to machine code at runtime, while javac compiles sources to bytecode,is that right?

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  • Correct way to read configuration file and using configuration values

    - by Harza
    I'm reading applications .config file using .NET ConfigurationManager like it should be done, but .... Which one is most preferred option: Read config and store instance of (build in or custom) ConfigurationElement for later use Read config and store only needed values (but not instances of ConfigrationElement classes) for later use Read ConfigurationElement from config always when configuration values are needed These two things are in my mind: Performance impact in case 3 when reading config all the time Problems occuring in case 1 when using cached instances of ConfigurationElements

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  • What was the most refreshingly honest non-technical comment you saw?

    - by DVK
    OK, so we all saw the lists of "funny" or "bad" comments. However, today, when maintaining an old stored procedure, I stumbled upon a comment which I couldn't classify other than "refreshingly brutally honest", left by a previous maintainer around a really freakish (both performance and readability-wise) page-long query: -- Feel free to optimize this if you can understand what it means So, in the first (and hopefully only) poll type question in my history of Stack Overflow, I'd like to hear some other "refreshingly brutally honest" code comments you encountered or written.

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  • Is it possible to use Boehm garbage collector only for the part of the program?

    - by bialix
    I've read article in LinuxJournal about Boehm-Demers-Weiser garbage collector library. I'm interesting to use it in my library instead of my own reference counting implementation. I have only one question: is it possible to use gc only for my shared library and still use malloc/free in the main application? I'm not quite understand how gc checks the heap so I'm worrying about performance of gc in that case and possible side effects.

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