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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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  • Generate a commutative hash based on three sets of numbers?

    - by DarkAmgine
    I need to generate a commutative hash based on three sets of "score" structs. Each score has a "start", an "end" and a "number". Both start and end are usually huge numbers (8-9 digits) but number is just from 1 to 4. I need them to be commutative so the order does not matter. I'm using XOR at the moment but it seems to be giving bad results. Since I'm working with large large datasets, I'd prefer a performance-friendly solution. Any suggestions? Thanks =] public static int getCustomHash(cnvRegion c1, cnvRegion c2, cnvRegion c3) { int part1 = (c1.startLocation * c2.startLocation * c3.startLocation); int part2 = (c1.endLocation * c2.endLocation * c3.endLocation); int part3 = (c1.copyNumber + c2.copyNumber + c3.copyNumber)*23735160; return part1 ^ part2 ^ part3; }

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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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  • 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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  • Does Python Django support custom SQL and denormalized databases with no Foreign Key relationships?

    - by Jay
    I've just started learning Python Django and have a lot of experience building high traffic websites using PHP and MySQL. What worries me so far is Python's overly optimistic approach that you will never need to write custom SQL and that it automatically creates all these Foreign Key relationships in your database. The one thing I've learned in the last few years of building Chess.com is that its impossible to NOT write custom SQL when you're dealing with something like MySQL that frequently needs to be told what indexes it should use (or avoid), and that Foreign Keys are a death sentence. Percona's strongest recommendation was for us to remove all FKs for optimal performance. Is there a way in Django to do this in the models file? create relationships without creating actual DB FKs? Or is there a way to start at the database level, design/create my database, and then have Django reverse engineer the models file?

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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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  • 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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  • How can i convert between F# List and F# Tuple?

    - by ksharp
    Is there some way to convert between F# List and F# Tuple? For example: [1;2;3] -> (1,2,3) (1,2,3,4) -> [1;2;3;4] I need two Functions to do that: let listToTuple list = ... let tupleToList tuple = ... Thank you in advance. I think reflection is necessary to this problem. I know the performance is not good. I have to pay the cost of breaking functional programming rule.

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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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  • 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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  • 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 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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  • 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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  • 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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  • 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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  • 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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  • 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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  • 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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  • (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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  • I would like to learn C++, what is the first step ?

    - by Cesar
    My actual experience comes from PHP and Delphi(Borland) and recently also from Obj-C (iPhone sdk). In the past I also used Java, Python, VB 6 and some other scripting language. I would like to learn C++ because i need a standard tool for write compiled applications with good performance but i have no idea about witch environment i have to choose (Ex: Borland, Microsoft, Eclipse+MinGW, ...). Based those parameters: Most useful more opensource project or work requests Most standard not a proprietary versions Biggest community documentation, manuals, tutorials, forums... Better IDE add-ons, highlight, debug, cross platform, autocomplete... Easy setup A simple setup, to focus on learning the basics Actually I'm on OSX but I can use a VM if needed. Advices about tutorial or books are welcome. I hope it's not too generic as question.

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  • When to use Hibernate?

    - by Ramo
    Hi All, I was asked in an interview this question so I answered with the following: -Better Performance: - Efficient queries. - 1st and 2nd level caching. - Good caching gives better scalability. - Good Database Portability: - Changing the DB is as easy as changing the dialect configuration. - Increased Developer Productivity: - Think only in object terms not in query language terms. But I also feel that systems fall in one of the below categories, and Hibernate may not be suited for all these cases, I'm interested in your thoughts about this, do you agree with me? please let me know when would use HB in the following case and why. Write Only Systems: Read Only Systems: Write Mostly Systems: Read Mostly Systems: Regards Ramo

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  • Android: Custom Clock widget Service work-around?

    - by Anthony Forloney
    I was interested in developing a clock widget for the homescreen and upon reading Home Screen Widgets tutorial, is there a pre-existing Service I could reference for updating the current time rather than re-inventing the wheel? I have currently Retro Clock on my android phone and noticed that when I click it, it pops up the Alarm Clock settings, but with the default Google Analog Clock widget, upon click does nothing. Is that because the Retro Clock widget implements the Alarm Clock service? If so, how can I go about referencing that service? Or do I have this all wrong and misunderstood? Any help is appreciated. EDIT: I believe implementing the service to update the clock would drain the battery life tremendously, any ideas on a work around or help shed some light on any performance issues with using Service?

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  • Is a PHP-only "cache engine" ever worth it?

    - by adsads
    I wrote a rather small skeleton for my web apps and thought that I would also add a small cache for it. It is rather simple: If the current page exists as a file in the cache and the file isn't too old, read it out and exit instead of rebuilding the page If the current page isn't cached/outdated recalc the page and save it However, the bad thing about it is: My performance tests with a page that receives 40 relatively long posts via a MySQL query said that with using the cache, it took even longer to handle a single request (1000 tests each) How can that happen? Should I just remove the complete raw-PHP cache and relieve on the availability of some PHP cache like memcached or so?

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  • iPhone , core data, whether NSManagedObject use lazy load mechanism when it was create ?

    - by Robin
    Hi, all, I have use core data in app, I have definite a class that most like as follows: @interface Master : NSManagedObject { } @property (nonatomic, retain) NSSet* Details; .... the entity Master contains a property 'Details' that is relate to another table, this is typical Master-Details relationship, I trace the app , but I find a issue that the property 'Details' value was construct even it never be invoked ..... but I consider that the core data 'should' use some lazy mechanism to improve performance, or maybe I miss some configure step ? because the Master entity contains at least five 'Child' table properties , I have to consider this problem before use the core data .... any help ? thanks for your time!

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