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• [java] Efficiency of while(true) ServerSocket Listen

  - by Submerged

  I am wondering if a typical while(true) ServerSocket listen loop takes an entire core to wait and accept a client connection (Even when implementing runnable and using Thread .start()) I am implementing a type of distributed computing cluster and each computer needs every core it has for computation. A Master node needs to communicate with these computers (invoking static methods that modify the algorithm's functioning). The reason I need to use sockets is due to the cross platform / cross language capabilities. In some cases, PHP will be invoking these java static methods. I used a java profiler (YourKit) and I can see my running ServerSocket listen thread and it never sleeps and it's always running. Is there a better approach to do what I want? Or, will the performance hit be negligible? Please, feel free to offer any suggestion if you can think of a better way (I've tried RMI, but it isn't supported cross-language. Thanks everyone

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• Optimising local image loading/rendering on iPhone

  - by Tricky

  Hi, I'm looking to create an interface where the user can navigate through large volumes of images. Each image has a thumbnail of 128x128 that I wish to display and will be kind of similar to coverflow in operation. I have this all working in principle but am becoming stuck when navigating through content at speed. The interface begins to stutter and becoming jerky. I believe this is primarily because of disk i/o and the cost of rendering each image. Is there anyway this can be handed over to a seperate thread simply? Defaulting to a greyed out thumbnail until the image has loaded? How have Apple managed to achieve this in coverflow? Many thanks,

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• how does NTFS actually work with B-tree ?

  - by bakra

  To improve performance, NTFS directories use a special data management structure called a B-tree. "B-tree" concept here refers to a "tree of storage units" that hold the contents of an individual directory. What I don't understand is where on the disk is this tree stored? Its surely not created every-time we reboot...that would take lots of time. and since its a tree(dynamic Data structure) unlike arrays it will grow. so space needs to be allocated every-time it grows. so how is this "dynamic meta-data" stored ?

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• Best way to handle SQL Server fulltext index updates

  - by tlianza

  Hi all, I have a fulltext index which doesn't need to be immediately up-to-date, I'd like to spare myself the I/O (when I do bulk updates, I see a ton of I/O related to the index) and do the index updates during low usage times (nightly, perhaps even weekly). It seems there are two ways to go about this: Turn off change tracking (SET CHANGE_TRACKING OFF) and add a timestamp field to the indexed table, so that you can run alter fulltext index on <table> start INCREMENTAL population, or Enable change tracking, but set it to MANUAL, so that you can run alter fulltext index on <table> start UPDATE population when you need it updated. Is there a preferred method? I couldn't tell from this overview if there was a performance benefit one way or the other. Tom

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• How to SET ARITHABORT ON for connections in Linq To SQL

  - by Laurence

  By default, the SQL connection option ARITHABORT is OFF for OLEDB connections, which I assume Linq To SQL is using. However I need it to be ON. The reason is that my DB contains some indexed views, and any insert/update/delete operations against tables that are part of an indexed view fail if the connection does not have ARITHABORT ON. Even selects against the indexed view itself fail if the WITH(NOEXPAND) hint is used (which you have to use in SQL Standard Edition to get the performance benefit of the indexed view). Is there somewhere in the data context I can specify I want this option ON? Or somewhere in code I can do it?? I have managed a clumsy workaround, but I don't like it .... I have to create a stored procedure for every select/insert/update/delete operation, and in this proc first run SET ARITHABORT ON, then exec another proc which contains the actual select/insert/update/delete. In other words the first proc is just a wrapper for the second. It doesn't work to just put SET ARITHABORT ON above the select/insert/update/delete code.

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• Can I get the stack traces of all threads in my c# app?

  - by Drew Shafer

  I'm debugging an apparent concurrency issue in a largish app that I hack on at work. The bug in question only manifests on certain lower-performance machines after running for many (12+) hours, and I have never reproduced it in the debugger. Because of this, my debugging tools are basically limited to analyzing log files. C# makes it easy to get the stack trace of the thread throwing the exception, but I'd like to additionally get the stack traces of every other thread currently executing in my AppDomain at the time the exception was thrown. Is this possible?

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• Implementing ma? osx loop device driver.

  - by Inso Reiges

  Hello, I am aware that there is a native implementation of loop device system on osx, the hdiutil/hdix driver. But due to a number of reasons i need to roll out my own custom loop driver. Since hdix is closed-source can anyone give some starting pointers, links, advises, etc. on the subject? I had expirience implementing loop drivers on linux and windows but i don't really have a clue where to start from on osx. The basic functionality i need to implement is the same: given any file on disk, simulate a virtual block device interface for it. I also would like my loop driver to use all the native partition filter stacking available for real and hdix virtual block devices on osx.

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• setting up/installing/configuring nginx LEMP stack on fresh VPS server

  - by grant tailor

  I need some help in settingup/installing and configuring nginx LEMP stack on a fresh new VPS i have. The specs of the CentOS 5.7 VPS are 2GB DDR3 ECC RAM(4GB burst), 1 core 1.5Ghz(3Ghz burst) and 100GB RAID 10 storage, unmetered bandwidth @ 100Mpbs all for a whopping $25/month(unbeatable, yeah i know :) Anyways i have followed this LEMP(will also need MySQL and PHP) stack guide on linode http://library.linode.com/lemp-guides/centos-5 but basically what i want is to be able to host multiple website on this webserver after everything is setup. I am used to using DirectAdmin control panel on other server and want to have things setup so i can host multiple websites...mostly wordpress and drupal themes. Lets say 10 websites on this nginx web server. So can someone please help me on what i need to do to take "full" advantage of nginx power and performance, while been able to easily manage these multiple websites (wordpress and drupal themes)? Thanks.

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• Java Swing: how to add an image to a JPanel ?

  - by Leonel

  I have a JPanel to which I'd like to add JPEG and PNG images that I generate on the fly. All the examples I've seen so far in the Swing Tutorials, specially in the Swing examples use ImageIcons. I'm generating these images as byte arrays, and they are usually larger than the common icon they use in the examples, at 640x480. Is there any (performance or other) problem in using the ImageIcon class to display an image that size in a JPanel ? What's the usual way of doing it ? How to add an image to a JPanel without using the ImageIcon class ? Edit: A more careful examination of the tutorials and the API shows that you cannot add an ImageIcon directly to a JPanel. Instead, they achieve the same effect by setting the image as an icon of a JLabel. This just doesn't fill right...

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• Sql server indexed view

  - by Jose

  OK, I'm confused about sql server indexed views(using 2008) I've got an indexed view called AssignmentDetail when I look at the execution plan for select * from AssignmentDetail it shows the execution plan of all the underlying indexes of all the other tables that the indexed view is supposed to abstract away. I would think that the execution plan woul simply be an clustered index scan of PK_AssignmentDetail(the name of the clustered index for my view) but it doesn't. There seems to be no performance gain with this indexed view what am I supposed to do? Should I also create a non-clustered index with all of the columns so that it doesn't have to hit all the other indexes? Any insight would be greatly appreciated

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• Stream (.NET) handling best-practices

  - by Jader Dias

  The question is entitled with the word "Stream" because the question below is a concrete example of a more generic doubt I have about Streams: I have a problem that accepts two solutions and I want to know the best one: I download a file, save it to disk (2 min), read it and write the contents to the DB (+ 2 min). I download a file and write the contents directly to the DB (3 min). If the write to DB fails I'll have to download again in the second case, but not in the first case. Which is best? Which would you use?

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• Dispelling the UIImage imageNamed: FUD

  - by Roger Nolan

  I see a lot of people saying imageNamed is bad but equal numbers of people saying the performance is good - especially when rendering UITableViews. See this SO question for example or this article on iPhoneDeveloperTips.com UIImage's imageNamed method used to leak so it was best avoided but has been fixed in recent releases. I'd like to understand the caching algorithm better in order to make a reasoned decision about where I can trust the system to cache my images and where I need to go the extra mile and do it myself. My current basic understanding is that it's a simple NSMutableDictionary of UIImages referenced by filename. It gets bigger and when memory runs out it gets a lot smaller. For example, does anyone know for sure that the image cache behind imageNamed does not respond to didReceiveMemoryWarning? It seems unlikely that Apple would not do this. If you have any insight into the caching algorithm, please post it here.

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• C#, WinForms: Which view type for periodically updated list?

  - by rdoubleui

  I'm having an application, that periodically polls a web service (about every 10 seconds). In my application logic I'm having a List<Message> holding the messages. All messages have an id, and might be received out of order. Therefore the class implements the Comparable Interface. What WinForm control would fit to be regurarly updated (with the items in order). I plan to hold the last 500 messages. Should I sort the list and then update the whole form? Or is data binding approriate (concerning performance)?

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• Why might SQL execute more quickly on SQL Server 2000 when NOT using a stored procedure?

  - by Kofi Sarfo

  I could see nothing wrong with the execution plan. Besides, as I understand it, SQL Server 2000 extended many of the performance benefits of stored procedures to all SQL statements by recognising new T-SQL statements against T-SQL statements of existing execution plans (by retaining execution plans for all SQL statements in the procedure cache, not just stored procedure execution plans) It's a fairly straight forward SELECT statement with sensible table joins, no transactions included or linked servers being referenced within the query and WITH (NOLOCK) table hints applied. The stored procedure was created by dbo and the user has all the necessary permissions. So my question is this: What are the likely reasons for a query to take only a few seconds to run but then take several minutes when identical T-SQL is run via a stored procedure?

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• What are the best options for a root filesystem hosted on SSD under Linux

  - by stsquad

  I'm working on an embedded system which is going to be booting and hosting it's rootfs on an SSD disk. We are currently looking at using Intel X-18M SSDs. The file system structure will have a fairly static /usr section (modulo software upgrades) and an active /var and /var/log for maintaining state and logging. Given the wear-levelling done by the underlying flash does having separate partitions help or hinder? As modern SSDs appear as straight block devices and hide their mapping magic behind their firmware is there any point trying to optimise the choice of file-system that sits on-top of the SSD? Finally does enable SMART monitoring make any sense in this context or are their SSD specific ways of determining the underlying health of the storage hardware?

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• How to create a delayed queue in RabbitMQ?

  - by eandersson

  What is the easiest way to create a delay (or parking) queue with Python, Pika and RabbitMQ? I have seen an similar questions, but none for Python. I find this an useful idea when designing applications, as it allows us to throttle messages that needs to be re-queued again. There are always the possibility that you will receive more messages than you can handle, maybe the HTTP server is slow, or the database is under too much stress. I also found it very useful when something went wrong in scenarios where there is a zero tolerance to losing messages, and while re-queuing messages that could not be handled may solve that. It can also cause problems where the message will be queued over and over again. Potentially causing performance issues, and log spam.

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• Looking for the most painless non-RDBMS storage method in C#

  - by NateD

  I'm writing a simple program that will run entirely client-side. (Desktop programming? do people still do that?) and I need a simple way to store trivial amounts of data in a structured form, but really don't see any need to use a database system. What's more, some of the data needs to be serialized and passed around to different users, like some kind of "file" or perhaps a "document". (has anyone ever done that before?) So, I've looked at using .Net DataSets, LINQ, direct XML manipulation, and they all seem like they would get the job done, but I would like to know before I dive into any of them if there's one method that is generally regarded as easier to code than others. As I said, the amount of data to be stored is trivial, even if one hundred people all used the same machine we're not talking about more than 10 MB, so performance is not as large a concern as is codeability/maintainability. Thank you all in advance!

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• Best Way to transfer data From one page to another In asp.net.

  - by Anish Karunakaran

  In my scenario am using java script popup that popups another form Which is an address Entry form of merely 20 Controls in it. Now am retrieving data from address page to main page by using a session variable which stores a data table of values. Two different Session variables are this way used for permanent and temporary addresses.. Using session variable degrades the performance i know.. What is the best way to transfer value from one page to another. Regards anish.

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• touches event handler for UIImageView

  - by madmik3

  I am just getting stated with iPhone development and can't seem to find the answer I am looking for what I want to do. It seems like I should be able to programmatically create a UIImageView and then set up an event handler for it's touch functions. in c# i would have something that looks like Button b = new Button(); b.Click+= my handler code right now I have this CGRect myImageRect = CGRectMake(0.0f, 0.0f, 141.0f, 151.0f); UIImageView *myImage = [[UIImageView alloc] initWithFrame:myImageRect]; myImage.userInteractionEnabled = YES; [myImage setImage:[UIImage imageNamed:@"myImage.png"]]; myImage.opaque = YES; // explicitly opaque for performance [self.view addSubview:myImage]; [myImage release]; What do I need to do to override the touch events? thanks

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• Need details about applications that are running on Windows Azure

  - by veda

  I have an application which requires large amount of data storage (say some PB) and computing resources. Instead of going for clusters, I am planning to propose to use Windows Azure Cloud for this application. I have gone through white papers of Windows Azure and have collected some details about Azure. But I feel that is not substantial. I need to do some case study about applications that are running on the azure and that uses azure storage efficiently. I looked for several research paper in related to performance of the applications in Windows Azure. But as Azure was quite new, I wasn't able to find any. Now, I am looking for some white papers/details regarding application that uses azure storage to substantiate my proposal. I also need to understand the windows azure storage architecture and virtual machine architecture. Do anyone know some research papers or details or blogs or something related to these topics.

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• arbitrary typed data in django model

  - by Dmitry Shevchenko

  I have a model, say, Item. I want to store arbitrary amount of attributes on it, like title, description, release_date. And i want them to be not just strings but have python type, so string, boolean, datetime etc. What are my options here? EAV pattern with separate name-value table won't work because of the same DB type across all values. JSONField can probably help, but it doesn't know about datetime, for example. Also i was looking at PickeField, it fits perfectly, but i'm a bit concerned about performance.

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• Are C++ meta-templates required knowledge for programmers?

  - by Robert Gould

  In my experience Meta-templates are really fun (when your compilers are compliant), and can give good performance boosts, and luckily I'm surrounded by seasoned C++ programmers that also grok meta-templates, however occasionally a new developer arrives and can't make heads or tails of some of the meta-template tricks we use (mostly Andrei Alenxandrescu stuff), for a few weeks until he gets initiated appropriately. So I was wondering what's the situation for other C++ programmers out there? Should meta-template programming be something C++ programmers should be "required" to know (excluding entry level students of course), or not? Edit: Note my question is related to production code and not little samples or prototypes

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• Cloud Agnostic Architecture?

  - by Dave

  Hi, I'm doing some architecture work on a new solution which will initially run in Windows Azure. However I'd like the solution (or at least the architecture/design) to be Cloud Agnostic (to whatever extent is realistic). Has anyone done any work on this front or seen any good white papers/blog posts? Our highlevel architecture will consist of a payload being sent to a web service (WCF for instance), this will be dumped on a queue (for arguments sake) and a worker process will grab messages off this queue and proccess them. There will be a database of customer information which we'd ideally like to keep out of the cloud however there are obvious performance considerations. Keen to hear other's thoughts. Cheers Dave

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• Multiple ParticleSystems in cocos2d

  - by Mattias Akerman

  I wonder about what road I should go with ParticleSystem. In this particular case I want to create 1-20 small explosions at the same time but with different positions. Right now I'm creating a new ParticleSystem for each explosion and then release it, but of course this is very punishing to the performance. My question is: Is there a way to create one ParticleSystem with multiple emitting sources. If not should I create an array of ParticleSystem in init and then use a free one when an explosion is needed? Or is there another approach I haven't thought of?

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• Concatenation Operator

  - by Chaitanya

  This might be a silly question but it struck me, and here i ask. <?php $x="Hi"; $y=" There"; $z = $x.$y; $a = "$x$y"; echo "$z"."<br />"."$a"; ?> $z uses the traditional concatenation operator provided by php and concatenates, conversely $a doesn't, My questions: by not using the concatenation operator, does it effect the performance? If it doesn't why at all have the concatenation operator. Why have 2 modes of implementation when one does the work?

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