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  • How to synchronize static method in java.

    - by Summer_More_More_Tea
    Hi there: I come up with this question when implementing singleton pattern in Java. Even though the example listed blow is not my real code, yet very similar to the original one. public class ConnectionFactory{ private static ConnectionFactory instance; public static synchronized ConnectionFactory getInstance(){ if( instance == null ){ instance = new ConnectionFactory(); } return instance; } private ConnectionFactory(){ // private constructor implementation } } Because I'm not quite sure about the behavior of a static synchronized method, I get some suggestion from google -- do not have (or as less as possible) multiple static synchronized methods in the same class. I guess when implementing static synchronized method, a lock belongs to Class object is used so that multiple static synchronized methods may degrade performance of the system. Am I right? or JVM use other mechanism to implement static synchronized method? What's the best practice if I have to implement multiple static synchronized methods in a class? Thank you all! Kind regards!

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  • Android add image to button

    - by Christiaan de Jong
    I want to add an image to a Button (no imagebutton, as the particular button can either contain text or an image; plus the imagebutton has the same problem), while still retaining the original android-style button. So adding android:background in the XML doesn't cut it, as that will remove the android default button with rounded corners etc. (android.R.drawable.btn_default) Is this in any way possible? I think one way is to make a 9patch image for the button pressed (one for up and one for down) and onTouch Action_DOWN make a layered background drawable and put that onto the button, and doing the same thing but with another 9patch for onTouch Action_UP, but I think that will decrease the performance of the application substantially, as that will require quite a lot of resource reading and layer merging for all the button clicks (and for my application, that will be quite a lot). Is what I state above correct?

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  • How does Core Data determine if an NSObjects data can be dropped?

    - by Kevin
    In the app I am working on now I was storing about 500 images in Core Data. I have since pulled those images out and store them in the file system now, but in the process I found that the app would crash on the device if I had an array of 500 objects with image data in them. An array with 500 object ids with the image data in those objects worked fine. The 500 objects without the image data also worked fine. I found that I got the best performance with both an array of object ids and image data stored on the filesystem instead of in core data. The conclusion I came to was that if I had an object in an array that told Core Data I was "using" that object and Core Data would hold on to the data. Is this correct?

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  • when to use StringBuilder in java

    - by kostja
    It is supposed to be generally preferable to use a StringBuilder for String concatenation in Java. Is it always the case? What i mean is : Is the overhead of creating a StringBuilder object, calling the append() method and finally toString() smaller then concatenating existing Strings with + for 2 Strings already or is it only advisable for more Strings? If there is such a threshold, what does it depend on (the String length i suppose, but in which way)? And finally - would you trade the readability and conciseness of the + concatenation for the performance of the StringBuilder in smaller cases like 2, 3, 4 Strings?

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  • Play a video with flash (with no controls, pause, etc) and stretch to full width and height of page.

    - by Tim
    Hi, I've managed this so far: [removed url] The plan is to have that video stretch across the whole page (the flash does, the video itself does not). Firstly: well aware of the issues - bad performance, horribly stretched/pixelated video. I know this. However a client wants it so we have to do it, simple as that. Does anyone have any ideas on how this can be achieved? I've been in touch with the creators of the flash video player I'm currently using and they've confirmed it isn't possible with that flash video player. Anyone know of any players where it is possible? Thanks, Tim

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  • Is both approach same ?

    - by Harikrishna
    I have one datatable which is not bindided and records are coming from the file by parsing it in the datatable dynamically every time. Now there is three columns in the datatable Marks1,Marks2 and FinalMarks. And their types is decimal. Now for making addition of columns Marks1 and Marks2 's records and store it into FinalMarks column,For that what I do is : datatableResult.Columns["FinalMarks"].Expression="Marks1+Marks2"; It's works properly. It can be done in other way also is foreach (DataRow r in datatableResult.Rows) { r["FinalMarks"]=Convert.ToDecimal(r["Marks1"])+Convert.ToDecimal(r["Marks2"]); } Now I don't know that which is the best way to do this means performance wise. Is first approach same as second approach in background means is both approach same or what?

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  • Detect numbers and process them ?

    - by Madhup
    Hi, I am trying to detect the numbers written on a grid and then process them using the iPhone camera. What i have found till yet are some good examples like: http://blog.damiles.com/?p=93 http://cmgresearch.blogspot.com/2010/01/augmented-reality-on-iphone-how-to_01.html Although I am able to draw the numbers on the overlay view to a good extent but still not able to detect what these numbers are. What I don't wanna do is to go through the whole AI process: training the system, providing the system whole set of values and then process them, because this is so much troublesome for me as well for the performance of my application. So guys having any idea or work arround for this please help. Thanks, Madhup

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  • Hit Testing with CALayer using the alpha properties of the CALayer contents.

    - by Charliehorse
    I'm writing a game for Mac using Cocoa. I'm currently implementing hit testing and have founds that CALayer offers hit testing, but does not seem to implement the alpha properties. As I have at times many CALayers stacked on top of each other, I really need to find a way to determine what the user actually meant to click on. I'm thinking if I could somehow get an array that contains pointers to all of the CALayers that contain the click point, I could filter through them some how. However the only way I've got so far to create the array is: NSMutableArray* anArrayOfLayers = [NSMutableArray array]; for (CALayer* aLayer in mapLayer.sublayers) { if ([aLayer containsPoint:mouseCoord]) [anArrayOfLayers addObject:aLayer]; } Then sort the array by the CALayer's z-values then go through checking if the pixel at location is alpha or not. However, between the sort and the alpha check this seems to be an incredible performance hog. (How would you even check the alpha?) Is there any way to do this?

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  • [Symfony] Admin generator and i18n

    - by David
    I have read lots of questions about i18n, but I haven't found any about performance. I have a simple backend app listing the contents of an ads table. These ads have a category, that is translated in some languages (it's defined as i18n in the Doctrine schema). So, when I add a "table_method" in my generator.yml to include de Category table, it reduces the number of queries, but there are yet some of them referencing i18n translation tables. So, if I add the category Translation table to the query, it reduces even more the queries BUT it increases the processing time considerably. Why this time penalty? Just because of the translation table? And why isn't the filter using this method to avoid so many translation queries as well? I mean, if I want to filter by category, it is making one query per category to include the translation table. Why??

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  • How to handle images folder with many images

    - by Billy
    I'm developing a new aspnet website with 200k images in a /Images/ -folder. Many operations in Visual Studio is slow because it access the folder, adding a web service takes 10 minutes. The images is not checked into scm (svn). How should I structure the tree of code, to improve performance in VS? It would also be neat if not all developers needed to copy 200k images to their local disk to be able to develop on the site. Images as DB blobs is not an option.

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  • What FIX implementation do you recommend for use with .NET

    - by Ajaxx
    I am reviewing implementation choices for FIX when using .NET. A few obvious choices come to mind, but I want to know if there are other options, better choices or if we've made the same decision as a lot of you. QuickFIX - Stable, C++ implementation - so you've got unmanaged code to interop with. FIX4NET - C# implementation - seems to have some gaps in its implementation. DIY - Chime in here if you've made your own FIX engine Let me throw in some caveats here. I'm not looking for sub 100 microsecond processing. Performance is a requirement, but not so much that it's driving my decisions. A solid product that is stable, performs well and is flexible enough to deal with vendor specific dialects is the sweet spot. The more we can do in .NET the better.

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  • Is there a library / tool to query MySQL data files (MyISAM / InnoDB) without the server? (the SQLit

    - by MGW
    Oftentimes I want to query my MySQL data directly without a server running or without having access to the server (but having read / write rights to the files). Is there a tool or maybe even a library around to query MySQL data files like it is possible with SQLite? I'm specifically looking for InnoDB and MyISAM support. Performance is not a factor. I don't have any knowledge about MySQL internals, but I presume it should be possible to do and not too hard to get the specific code out? Thank you for any suggestions!

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  • how to pass in a reference to a string in javascript?

    - by ijjo
    maybe a closure is my solution? not exactly sure how to pull it off though. the code is set up like so: var globalVar = ''; var globalVar2 = ''; function func() { if (condition) func2(globalVar) else func2(globalVar2) } in func2() i cache some HTML in a main container into the appropriate global variable that i pass to it. basically i have a main container that holds different pages depending on what tab they choose. for performance i want to cache the page into global vars so i need to know what tab is active to figure out which global var to assign the html to.

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  • Rails: getting logic to run at end of request, regardless of filter chain aborts?

    - by JSW
    Is there a reliable mechanism discussed in rails documentation for calling a function at the end of the request, regardless of filter chain aborts? It's not after filters, because after filters don't get called if any prior filter redirected or rendered. For context, I'm trying to put some structured profiling/reporting information into the app log at the end of every request. This information is collected throughought the request lifetime via instance variables wrapped in custom controller accessors, and dumped at the end in a JSON blob for use by a post-processing script. My end goal is to generate reports about my application's logical query distribution (things that depend on controller logic, not just request URIs and parameters), performance profile (time spent in specific DB queries or blocked on webservices), failure rates (including invalid incoming requests that get rejected by before_filter validation rules), and a slew of other things that cannot really be parsed from the basic information in the application and apache logs. At a higher level, is there a different "rails way" that solves my app profiling goal?

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  • CAD/CAM without C++

    - by zaladane
    Hello, Is it possible to do CAD/CAM software without having to use C++? My company developed their software with c/C++ but that was more than 10 years ago. Today,there is a lot of legacy code that switching would force us to get rid of but i was wondering what the actual risks are. We have a lot of mathematical algorithms for toolpath calculations, feature recognition and simulation and 3D Rendering and i was wondering if C# can handles all of that without great performance loss. Is it a utopia to rewrite such algorithms in c# or should that language only deal with UI. We are not talking about game development here (Halo 3 or Call Of Duty) so how much processing does CAD/CAM really need? Can anybody enlighten me on this matter? Most of my colleagues are hardcore C++ programmers and although i program in c++ i love .NET but i am having a hard time selling .NET to them other than basic UI. Does it make sense to consider switching to .NET in such a field, or is it just not a wise idea? Thank you

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  • Ternary operators and variable reassignment in PHP

    - by TomcatExodus
    I've perused the questions on ternary operators vs. if/else structures, and while I understand that under normal circumstances there is no performance loss/gain in using ternary operators over if/else structures, I've not seen any mention of this situation. Language specific to PHP (but any language agnostic details are welcome) does the interpreter reassign values in situations like this: $foo = 'bar' $foo = strlen($foo) > 3 ? substr($foo, 0, 3) : $foo; Since this would evaluate to $foo = $foo; is this inefficient, or does the interpreter simply overlook/discard this evaluation? On a side note, what about: !defined('SECURE') ? exit : null;

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  • What are some Servlet Container pros and cons for a Solr installation?

    - by danieltalsky
    The SolrInstall wiki page lists seven different server / Servlet Containers compatible with Solr: Tomcat Jetty Resin JBoss WebSphere Weblogic Glassfish I'm sure that "best" is subjective, so I'll just say my criteria are: easiest to set up, best for search performance with a smallish, infrequently-updated dataset, and with the fewest number of gotchas. Jetty and Tomcat both have apt-get solr packages, so they're clearly the frontrunners for some. Jetty is used in the demo install, but there's some notes that Jetty has some difficulties handling Unicode in some cases. Tomcat is a common choice but my understanding is that it's not as lightweight and has a lot of features not needed by Solr. Is it worth considering any of the others? Are there some important pro's and cons I should be aware of?

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  • Stored Procedure or calculations via IQueryable?

    - by Shawn Mclean
    This is a question that is based on choosing performance over design practices. If I have a method that will be executed many times a second; public static IQueryable<IPerson> InRadius(this IQueryable<IPerson> query, Coordinate center, double radius) { return (from u in query where CallHeavyMathFormula(u, center, radius) select u); } This extension method for IQueryable generates a SQL that does some heavy maths calculation (Cosine, Sine, etc). This would mean the application sends 1-2KB of sql to the server per call. I've heard of placing all application logic, in your application. I also would like to change to a database such as azure or one of those scalable databases in the future. How do I handle something like this? Should I leave it as it is now or write stored procedures? How do applications like twitter or facebook do it?

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  • Is select() Ok to implement single socket read/write timeout ?

    - by chmike
    I have an application processing network communication with blocking calls. Each thread manages a single connection. I've added a timeout on the read and write operation by using select prior to read or write on the socket. Select is known to be inefficient when dealing with large number of sockets. But is it ok, in term of performance to use it with a single socket or are there more efficient methods to add timeout support on single sockets calls ? The benefit of select is to be portable.

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  • "Single NSMutableArray" vs. "Multiple C-arrays" --Which is more Efficient/Practical?

    - by RexOnRoids
    Situation: I have a DAY structure. The DAY structure has three variables or attributes: a Date (NSString*), a Temperature (float), and a Rainfall (float). Problem: I will be iterating through an array of about 5000 DAY structures and graphing a portion of these onto the screen using OpenGL. Question: As far as drawing performance, which is better? I could simply create an NSMutableArray of DAY structures (NSObjects) and iterate on the array on each draw call -- which I think would be hard on the CPU. Or, I could instead manually manage three different C-Arrays -- One for the Date String (2-Dimensional), One for the temperature (1-Dimensional) and One for the Rainfall (1-Dimensional). I could keep track of the current Day by referencing the current index of the iterated C-Arrays.

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  • Virus - How much it can affect?

    - by Sarang
    In our daily life, we come across various Viruses. In this internet world, we do have lots of type of viruses come to visit us ! While for the beginners, Virus is a complicated matter to fight with. Please explain the way how the virus come flow across the PC using Internet. What are the ways to search for them in the Personal Computer ? Also, we do have various solutions available in the market of Anti-Viruses, but also have different comments available for different software. Which is actually, really a useful Anti-Virus in the market that can give reliable performance ? Every Personal Computer connected to internet has to face against the viruses. Isn't there any general solution using Internet itself through which all networked computers get protected against Viruses ? Please give any solution.

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  • (NOT) NULL for NVARCHAR columns

    - by Anders Abel
    Allowing NULL values on a column is normally done to allow the absense of a value to be represented. When using NVARCHAR there is aldready a possibility to have an empty string, without setting the column to NULL. In most cases I cannot see a semantical difference between an NVARCHAR with an empty string and a NULL value for such a column. Setting the column as NOT NULL saves me from having to deal with the possibility of NULL values in the code and it feels better to not have to different representations of "no value" (NULL or an empty string). Will I run into any other problems by setting my NVARCHAR columns to NOT NULL. Performance? Storage size? Anything I've overlooked on the usage of the values in the client code?

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  • how to handle db concurrency in client-server application in C#?

    - by RAJ K
    I am developing an application in C# WPF which will have Client-Server architecture (Client will do products sales billing). I am novice in this area and I asked this question to start my development process. Click here to view question. So, ultimately I have selected MySQl, WCf & WPF. Now I have one silly question. Do i need to handle DB concurrency explicitly in my application (like 3 clients inserting data same time) or MySQl will handle this without any conflict? To accomplish my project i thought, I will create a service in WCf which will do DB queries from client application. Do you have any suggestion to improve my application performance.

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  • Should I use "id" or "unique username"?

    - by roa3
    I am using PHP, AS3 and mysql. I have a website. A flash(as3) website. The flash website store the members' information in mysql database through php. In "members" table, i have "id" as the primary key and "username" as a unique field. Now my situation is: When flash want to display a member's profile. My questions: Should Flash pass the member "ID" or "username" to php to process the mysql query? Is there any different passing the "id" or "username"? Which one is more secure? Which one you recommend? I would like to optimize my website in terms of security and performance.

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  • Is it really wrong to version documents using CouchDB's behaviour?

    - by Tomas Sedovic
    This is one of those "I know I shouldn't do this but it's oh so convenient." questions. Sorry about that. I plan to use CouchDB for storing a bunch of documents and keeping their entire revision history. CouchDB does the versioning automatically, but it is strongly discouraged for programmer's use: "You cannot rely on document revisions for any other purpose than concurrency control." From what I've found on the CouchDB wiki, the versions can get deleted either during compaction or during replication. As far as I can tell, Compaction must always be triggered manually and Replication occurs only when there's more than one database server. The question is: if I won't run compaction and will use only single database instance for my documents, can I just use CouchDB's document versioning and expect it to work? What other problems I might run into? E.g. does not running compaction hurt the performance or consume significantly more disk space (than if I did handle the versioning manually)?

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