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  • Collection wrapping a array is read-only. Possible to make it writeable without casting?

    - by Brian Triplett
    I have a Collection<T> property that wraps a array like T[] array; public Collection<T> Items { get { return new Collection<T>(array); } } When I attempt to assign to the collection via: T variable; Items[i] = variable; I get a NotSupportedException because the colleciton's IsReadOnly property is true. Turns out that this is a design choice by Microsoft. Does anyone know a workaround that does NOT involve enumeration? It could be done if the underlying data is not an array but I enjoy the performance gains because the data is fixed length.

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  • Database structure for storing Bank-like accounts and transactions

    - by user1241320
    We're in the process of adding a bank-like sub-system to our own shop. We already have customers, so each will be given a sort of account and transactions of some kind will be possible (adding to the account or subtracting from it). So we at least need the account entity, the transaction one and operations will then have to recalculate overall balances. How would you structure your database to handle this? Is there any standard bank system have to use that I could mock? By the way, we're on mysql but will also look at some nosql solution for performance boost.

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  • .Net Logger (Write your own vs log4net/enterprise logger/nlog etc.)

    - by Jack
    I work for an IT department with about 50+ developers. It used to be about 100+ developers but was cut because of the recession. When our department was bigger there was an ambitious effort made to set up a special architecture group. One thing this group decided to do was create our own internal logger. They thought it was such a simple task that we could spend recources and do it ourselves. Now we are having issues with performance and difficulty viewing the logs generated and some employees are frustrated that we are spending recources on infrastructure stuff like this instead of focusing on serving our business and using stuff that already exists like log4net or Enterprise Logger. Can you assist me in listing up reasons why you should not create your own .net logger. Also reasons for why you should are welcome to get a fair point of view :)

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  • XmlDocument caching memory usage

    - by mdsharpe
    We are seeing very high memory usage in .NET web applications which use XmlDocument. A small (~5MB) XML document is loaded into an XmlDocument object and stored in HttpContext.Cache for easy querying and XSLT transformation on each page load. The XML is modified on disk periodically so a cache has a dependency on the file. Such an application appears to be using hundreds of megabytes of RAM. I have experimented with requesting garbage collection on each request start, and this keeps the RAM usage far lower but I cannot imagine this is good practise. Does anyone have any suggestions as to how we can achieve the same goal but with lower RAM usage?

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  • How to reliably measure available memory in Linux?

    - by Alex B
    Linux /proc/meminfo shows a number of memory usage statistics. MemTotal: 4040732 kB MemFree: 23160 kB Buffers: 163340 kB Cached: 3707080 kB SwapCached: 0 kB Active: 1129324 kB Inactive: 2762912 kB There is quite a bit of overlap between them. For example, as far as I understand, there can be active page cache (belongs to "cached" and "active") and inactive page cache ("inactive" + "cached"). What I want to do is to measure "free" memory, but in a way that it includes used pages that are likely to be dropped without a significant impact on overall system's performance. At first, I was inclined to use "free" + "inactive", but Linux's "free" utility uses "free" + "cached" in its "buffer-adjusted" display, so I am curious what a better approach is. When the kernel runs out of memory, what is the priority of pages to drop and what is the more appropriate metric to measure available memory?

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  • How to save objects using Multi-Threading in Core Data?

    - by Konstantin
    I'm getting some data from the web service and saving it in the core data. This workflow looks like this: get xml feed go over every item in that feed, create a new ManagedObject for every feed item download some big binary data for every item and save it into ManagedObject call [managedObjectContext save:] Now, the problem is of course the performance - everything runs on the main thread. I'd like to re-factor as much as possible to another thread, but I'm not sure where I should start. Is it OK to put everything (1-4) to the separate thread?

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  • Good reasons why to not use XIB files?

    - by mystify
    Are there any good reasons why I should not use XIB / NIB files with an highly customized UI and extensive animations and super low memory footprint needs? As a beginner I started with XIB. Then I figured out I couldn't do just about everything in them. It started to get really hard to customize things the way I wanted them to be. So at the end, I threw all my XIBs away and did it all programmatically. So when someone asks me if XIB is good, I generally say: Yeah, if you want to make crappy boring interfaces and don't care too much about performance, go ahead. But what else could be a reason not to use XIB? Am I the only iPhone developer who prefers doing everything programmatically for this reasons?

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  • HSM - cryptoki - opening sessions overhead

    - by Raj
    I am having a query regarding sessions with HSM. I am aware that there is an overhead if you initialise and finalise the cryptoki api for every file you want to encrypt/decrypt. My queries are, Is there an overhead in opening and closing individual sessions for every file, you want to encrypt/decrypt.(C_Initialize/C_Finalize) How many maximum number of sessions can i have for a HSM simultaneously, with out affecting the performance? Is opening and closing the session for processing individual files the best approach or opening a session and processing multiple files and then closing the session the best approach? Thanks

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  • URL encoded POST bad practice?

    - by StackedCrooked
    I am (just for fun) trying to implement a High Score web-service. I would like it be compatible with REST principles. I want to be able to add a new highscore using url parameters like this http://mydomain.com/hs/add&name=John&score=987. According to REST this must be done using a POST request. Which leads to empty POST request with all data contained in the URL parameters. Would this be considered a bad practice? Update Security is currently not a big concern.

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  • Linux, how to capture screen, and simulate mouse movements.

    - by 2di
    Hi All I need to capture screen (as print screen) in the way so I can access pixel color data, to do some image recognition, after that I will need to generate mouse events on the screen such as left click, drag and drop (moving mouse while button is pressed, and then release it). Once its done, image will be deleted. Note: I need to capture whole screen everything that user can see, and I need to simulate clicks outside window of my program (if it makes any difference) Spec: Linux ubuntu Language: C++ Performance is not very important,"print screen" function will be executed once every ~10 sec. Duration of the process can be up to 24 hours so method needs to be stable and memory leaks free (as usuall :) I was able to do in windows with win GDI and some windows events, but I'ev no idea how to do it in Linux. Thanks a lot

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  • What are the main benefits of implementing a virtual machine as part of an application?

    - by Marplesoft
    Several databases I've been looking at recently implement a virtual machine internally to perform the respective data reads and writes. For an example, check out this article on SQLite's virtual machine they call the 'VDBE'. I'm curious as to what the benefits of such an architecture are. I would assume performance is one but why would a virtual machine like this run faster? In fact, it seems to be that this extra layer could cause it to run slower. So perhaps it's for security? Or portability? Anyway, just curious about this.

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  • Avoiding Nested Queries

    - by Midhat
    How Important is it to avoid nested queries. I have always learnt to avoid them like a plague. But they are the most natural thing to me. When I am designing a query, the first thing I write is a nested query. Then I convert it to joins, which sometimes takes a lot of time to get right. And rarely gives a big performance improvement (sometimes it does) So are they really so bad. Is there a way to use nested queries without temp tables and filesort

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  • Maximizing the number of threads to fully utilize all available resources without hindering overall

    - by Matt
    Let's say I have to generate a bunch of result files, and I want to make it as fast as possible. Each result file is generated independently of any other result file; in fact, one could say that each result file is agnostic to every other result file. The resources used to generate each result file is also unique to each. How can I dynamically decide the optimal number of threads to run simultaneously in order to minimize the overall run time? Is my only option to write my own thread manager that watches performance counters and adjust accordingly or does there exists some solid classes that already accomplish this?

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  • Silverlight/Web Service Serializing Interface for use Client Side

    - by Steve Brouillard
    I have a Silverlight solution that references a third-party web service. This web service generates XML, which is then processed into objects for use in Silverlight binding. At one point we the processing of XML to objects was done client-side, but we ran into performance issues and decided to move this processing to the proxies in the hosting web project to improve performance (which it did). This is obviously a gross over-simplification, but should work. My basic project structure looks like this. Solution Solution.Web - Holds the web page that hosts Silverlight as well as proxies that access web services and processes as required and obviously the references to those web services). Solution.Infrastructure - Holds references to the proxy web services in the .Web project, all genned code from serialized objects from those proxies and code around those objects that need to be client-side. Solution.Book - The particular project that uses the objects in question after processed down into Infrastructure. I've defined the following Interface and Class in the Web project. They represent the type of objects that the XML from the original third-party gets transformed into and since this is the only project in the Silverlight app that is actually server-side, that was the place to define and use them. //Doesn't get much simpler than this. public interface INavigable { string Description { get; set; } } //Very simple class too public class IndexEntry : INavigable { public List<IndexCM> CMItems { get; set; } public string CPTCode { get; set; } public string DefinitionOfAbbreviations { get; set; } public string Description { get; set; } public string EtiologyCode { get; set; } public bool HighScore { get; set; } public IndexToTabularCommandArguments IndexToTabularCommandArgument { get; set; } public bool IsExpanded { get; set; } public string ManifestationCode { get; set; } public string MorphologyCode { get; set; } public List<TextItem> NonEssentialModifiersAndQualifyingText { get; set; } public string OtherItalics { get; set; } public IndexEntry Parent { get; set; } public int Score { get; set; } public string SeeAlsoReference { get; set; } public string SeeReference { get; set; } public List<IndexEntry> SubEntries { get; set; } public int Words { get; set; } } Again; both of these items are defined in the Web project. Notice that IndexEntry implments INavigable. When the code for IndexEntry is auto-genned in the Infrastructure project, the definition of the class does not include the implmentation of INavigable. After discovering this, I thought "no problem, I'll create another partial class file reiterating the implmentation". Unfortunately (I'm guessing because it isn't being serialized), that interface isn't recognized in the Infrastructure project, so I can't simply do that. Here's where it gets really weird. The BOOK project CAN see the INavigable interface. In fact I use it in Book, though Book has no reference to the Web Service in the Web project where the thing is define, though Infrastructure does. Just as a test, I linked to the INavigable source file from indside the Infrastructure project. That allowed me to reference it in that project and compile, but causes havoc in the Book project, because now there's a conflick between the one define in Infrastructure and the one defined in the Web project's web service. This is behavior I would expect. So, to try and sum up a bit. Web project has a web service that process data from a third-party service and has a class and interface defined in it. The class implements the interface. The Infrastructure project references the web service in the Web Project and the Book project references the Infrastructure project. The implmentation of the interface in the class does NOT serialize down, so the auto-genned code in INfrastructure does not show this relationship, breaking code further down-stream. The Book project, whihc is further down-stream CAN see the interface as defined in the Web Project, even though its only reference is through the Infrastructure project; whihc CAN'T see it. Am I simple missing something easy here? Can I apply an attribute to either the Interface definition or to the its implmentation in the class to ensure its visibility downstream? Anything else I can do here? I know this is a bit convoluted and anyone still with me here, thanks for your patience and any advice you might have. Cheers, Steve

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  • Java multiline string

    - by skiphoppy
    Coming from Perl, I sure am missing the "here-document" means of creating a multi-line string in source code: $string = <<"EOF" # create a three line string text text text EOF In Java I have to have cumbersome quotes and plus signs on every line as I concatenate my multiline string from scratch. What are some better alternatives? Define my string in a properties file? Edit: Two answers say StringBuilder.append() is preferable to the plus notation. Could anyone elaborate as to why they think so? It doesn't look more preferable to me at all. I'm looking for away around the fact that multiline strings are not a first-class language construct, which means I definitely don't want to replace a first-class language construct (string concatenation with plus) with method calls. Edit: To clarify my question further, I'm not concerned about performance at all. I'm concerned about maintainability and design issues.

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  • General zoom algorithm for drawing program

    - by Steven Sproat
    My GUI toolkit, wxPython provides some methods for implementing a user zoom factor, however the quality isn't too good. I'm looking for ideas on how to create a zooming feature, which I know is complicated. I have a bitmap representing my canvas which is drawn to. This is displayed inside a scrolled window. Problems I forsee: - performance when zoomed in and panning around the canvas - difficulties with "real" coordinates and zoomed in coordinates - image quality not degrading with the zoom Using wxPython's SetUserScale() on its device contexts presents image quality like this - this is with a 1px line, at 30% zoomed in. I'm just wondering the general steps I'll need to take and the challenges I'll encounter. Thanks for any suggestions

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  • checking if records exists in DB, in single step or 2 steps?

    - by Sinan
    Suppose you want to get a record from database which returns a large data and requires multiple joins. So my question would be is it better to use a single query to check if data exists and get the result if it exists. Or do a more simple query to check if data exists then id record exists, query once again to get the result knowing that it exists. Example: 3 tables a, b and ab(junction table) select * from from a, b, ab where condition and condition and condition and condition etc... or select id from a, b ab where condition then if exists do the query above. So I don't know if there is any reason to do the second. Any ideas how this affects DB performance or does it matter at all?

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  • Why should I reuse XmlHttpRequest objects?

    - by Xavi
    From what I understand, it's a best practice to reuse XmlHttpRequest objects whenever possible. Unfortunately, I'm having a hard time understanding why. It seems like trying to reuse XHR objects can increase code complexity, introduce possible browser incompatibilities, and lead to other subtle bugs. After researching this question for a while, I did come up with a list of possible explanations: Fewer objects created means less garbage collecting Reusing XHR objects reduces the chance of memory leaks The overhead of creating a new XHR object is high The browser is able to perform some sort of network optimization under hood But I'm not sure if any of these reasons are actually valid. Any light you can shed on this question would be much appreciated.

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  • MySQL triggers cannot update rows in same table the trigger is assigned to. Suggested workaround?

    - by Cory House
    MySQL doesn't currently support updating rows in the same table the trigger is assigned to since the call could become recursive. Does anyone have suggestions on a good workaround/alternative? Right now my plan is to call a stored procedure that performs the logic I really wanted in a trigger, but I'd love to hear how others have gotten around this limitation. Edit: A little more background as requested. I have a table that stores product attribute assignments. When a new parent product record is inserted, I'd like the trigger to perform a corresponding insert in the same table for each child record. This denormalization is necessary for performance. MySQL doesn't support this and throws: Can't update table 'mytable' in stored function/trigger because it is already used by statement which invoked this stored function/trigger. A long discussion on the issue on the MySQL forums basically lead to: Use a stored proc, which is what I went with for now. Thanks in advance!

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  • Append in Dom taking more time in IE than Firefox or any other browser.

    - by user307635
    Hi , I m working on .net framework 3.0 visual studio 08 and Testing it in IE8 and other browsers. Whenever I m inserting new elements in DOM (ex. 300 divs at one time) than I m getting the performance very slow in IE . Why?. If its a javascript debugging which is taking time or what else. Is it really true that IE Dom Append takes much time than any other browser. Please help me , I m stuck badly.

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  • how to implement unitofwork pattern when using subsonic 2.1(Repository pattern) ?

    - by ROHITH
    I am using subsonic repository pattern(2.1) for asp.net mvc application.In my application,there are many repositories like categoryRepository,Blogrepository etc.Inside each of this repository i am calling subsonic's DB.Select().From()...ExecuteReader() and then loading domain objects from those reader. In the controller action i make multiple calls from these repositories for e.g. List<IBlog> blogs=_blogRepository.GetHottestBlogs(); List<ICategory> categories=_categoryRepository.GetAll(); do i have to implement any unitofwork pattern for this ?.My doubt is that how subsonic performs each operation DB.Update/Insert/Select .Is a TransactionScope is enough for batch update or do i have to use SharedDbConnectionScope to get better performance?

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  • Audio processing in C# or C++

    - by melculetz
    Hi, I would like to create an application that uses AI techniques and allows the user to record a part of a song and then tries to find that song in a database of wav files. I would have liked to use some already existing libraries for the audio processing part. So, could you recommend any libraries in C# which can read a wav file, get input from microphone, have some audio filters (low pass, high pass, FFT etc) and maybe have the ability to plot the audio signal as well. I would prefer to develop in C#, but if there aren't good libraries for audio processing, I guess I could work in C++ as well. As far as I know, Mathlab already has the above mentioned functionalities, but I can't use it in my application.

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  • MySQL locking problem

    - by teehoo
    I have a simple setup of a set of writers and a set of readers working with a MySQL ISAM table. The writers are only inserting rows while the readers are only checking for new rows. OK, so I know that I don't need a lock in this situation, since I'm not modifying existing rows. However my Writers are accessing one more table that does need a lock. I piece of information seems irrelevant except for the following limitation stated in the MySQL documentation: A session that requires locks must acquire all the locks that it needs in a single LOCK TABLES statement. While the locks thus obtained are held, the session can access only the locked tables. For example, in the following sequence of statements, an error occurs for the attempt to access t2 because it was not locked in the LOCK TABLES statement: So to access the table I want to insert rows into, I NEED to lock it, which is causing me performance problems. Any suggestions of how to get around this?

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  • Site images don't refresh after setting expired headers on .htaccess

    - by Miguel Hernandez
    I have a site that uses a CSS sprite for all the images. I set the .htaccess file to set the expired headers to a future time as they recommend to improve site performance. However, when I updated the sprite image none of my browsers on two different computers seem to fetch the new image. I deleted the .htaccess serveral times but no luck. I am sure this must be easy as pie to fix but right now I am out of options. Here is the code inside my .htaccess file: # CONFIGURE media caching # Header unset ETag FileETag None <FilesMatch "(?i)^.*\.(ico|flv|jpg|jpeg|png|gif|js|css)$"> Header unset Last-Modified Header set Expires "Fri, 21 Dec 2012 00:00:00 GMT" Header set Cache-Control "public, no-transform" </FilesMatch> <IfModule mod_deflate.c> <FilesMatch "\.(js|css)$"> SetOutputFilter DEFLATE </FilesMatch> </IfModule> Thanks!

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  • Taking Responsibilites too early - danger or boon?

    - by narresh
    Just I am only six months experienced guy in software industry.Due to recession season,a large volume of employees from our company are asked to leave.This impact affects the new inexperienced guys. The problem is We have to interact with the client directly to gather the requirement We have to design all HLD and LLD ,use cases and DB Diagrams ,that should staisfy the customers who keeping the high software insdutry standards In this do or die situation (Client gives us narrow dead line),we spend most of time with interacting client (only less time is available for development and testing,even sit out for 24 X 7 won't help us to finish our task) If task will not be finished with in the expected time frame ,that will trigger poor performance ration to our profile There are two important questions flashing in our mind : (1) Quit the job and do other business (2) Face the challenge : (if the option is to face the challenge ,What are all the tools should we follow to automate requirement gathering,testing,DB diagram,Code review and the rest.(We are working on ASP.NET 3.5 with SQL Server 2005).

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