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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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• Why would you want a case sensitive database?

  - by Khorkrak

  What are some reasons for choosing a case sensitive collation over a case insensitive one? I can see perhaps a modest performance gain for the DB engine in doing string comparisons. Is that it? If your data is set to all lower or uppercase then case sensitive could be reasonable but it's a disaster if you store mixed case data and then try to query it. You have then apply a lower() function on the column so that it'll match the corresponding lower case string literal. This prevents index usage in every dbms. So wondering why anyone would use such an option.

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• Optimizing for speed - 4 dimensional array lookup in C

  - by Tiago

  I have a fitness function that is scoring the values on an int array based on data that lies on a 4D array. The profiler says this function is using 80% of CPU time (it needs to be called several million times). I can't seem to optimize it further (if it's even possible). Here is the function: unsigned int lookup_array[26][26][26][26]; /* lookup_array is a global variable */ unsigned int get_i_score(unsigned int *input) { register unsigned int i, score = 0; for(i = len - 3; i--; ) score += lookup_array[input[i]][input[i + 1]][input[i + 2]][input[i + 3]]; return(score) } I've tried to flatten the array to a single dimension but there was no improvement in performance. This is running on an IA32 CPU. Any CPU specific optimizations are also helpful. Thanks

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• writing a fast parser in python

  - by panzi

  I've written a hands-on recursive pure python parser for a some file format (ARFF) we use in one lecture. Now running my exercise submission is awfully slow. Turns out by far the most time is spent in my parser. It's consuming a lot of CPU time, the HD is not the bottleneck. I wonder what performant ways are there to write a parser in python? I'd rather not rewrite it in C. I tried to use jython, but that decreased performance a lot! The files I parse are partially huge ( 150 MB) with very long lines. My current parser only needs a look-ahead of one character. I'd post the source here but I don't know if that's such a good idea. After all the submission deadline has not jet ended. But then, the focus in this exercise is not the parser. You can choose whatever language you want to use and there already is a parser for Java.

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• nHibernate multiple classes pointing to same table?

  - by Amitabh

  Is it a good idea to create a lighter version of an Entity in some cases just for performance reason pointing to same table but with fewer columns mapped. E.g If I have a Contact Table which has 50 Columns and in few of the related entities I might be interested in FirstName and LastName property is it a good idea to create a lightweight version of Contact table. E.g. public class LightContact { public int Id {get; set;} public string FirstName {get; set;} public string LastName {get; set;} } Also is it possible to map multiple classes to same table?

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• New to AVL tree implementation.

  - by nn

  I am writing a sliding window compression algorithm (LZ77) that searches for phrases in a "moving" dictionary. So far I have written a BST where each node is stored in an array and it's index in the array is also the value of the starting position in the window itself. I am now looking at transforming the BST to an AVL tree. I am a little confused at the sample implementations I have seen. Some only appear to store the balance factors whereas others store the height of each tree. Are there any performance advantage/disadvantages of storing the height and/or balance factor for each node? Apologies if this is a very simple question, but I'm still not visualizing how I want to restructure my BST to implement height balancing. Thanks.

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• Remove first 'n' elements from list without itterating

  - by Eldhose M Babu

  I need an efficient way of removing items from list. If some condition happens, I need to remove first 'n' elements from a list. Can some one suggest the best way to do this? Please keep in mind: performance is a factor for me, so I need a faster way than itterating. Thanks. I'm thinking of a way through which the 'n'th item can be made as the starting of the list so that the 0-n items will get garbage collected. Is it possible?

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• How to improve INSERT INTO ... SELECT locking behavior

  - by Artem

  In our production database, we ran the following pseudo-code SQL batch query running every hour: INSERT INTO TemporaryTable (SELECT FROM HighlyContentiousTableInInnoDb WHERE allKindsOfComplexConditions are true) Now this query itself does not need to be fast, but I noticed it was locking up HighlyContentiousTableInInnoDb, even though it was just reading from it. Which was making some other very simple queries take ~25 seconds (that's how long that other query takes). Then I discovered that InnoDB tables in such a case are actually locked by a SELECT! http://www.mysqlperformanceblog.com/2006/07/12/insert-into-select-performance-with-innodb-tables/ But I don't really like the solution in the article of selecting into an OUTFILE, it seems like a hack (temporary files on filesystem seem sucky). Any other ideas? Is there a way to make a full copy of an InnoDB table without locking it in this way during the copy. Then I could just copy the HighlyContentiousTable to another table and do the query there.

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• Best way to store large dataset in SQL Server?

  - by gary

  I have a dataset which contains a string key field and up to 50 keywords associated with that information. Once the data has been inserted into the database there will be very few writes (INSERTS) but mostly queries for one or more keywords. I have read "Tagsystems: performance tests" which is MySQL based and it seems 2NF appears to be a good method for implementing this, however I was wondering if anyone had experience with doing this with SQL Server 2008 and very large datasets. I am likely to initially have 1 million key fields which could have up to 50 keywords each. Would a structure of keyfield, keyword1, keyword2, ... , keyword50 be the best solution or two tables keyid keyfield | 1 | | M keyid keyword Be a better idea if my queries are mostly going to be looking for results that have one or more keywords?

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• Multiple Socket Connections

  - by BSchlinker

  I need to write a server which accepts connections from multiple client machines, maintains track of connected clients and sends individual clients data as necessary. Sometimes, all clients may be contacted at once with the same message, other times, it may be one individual client or a group of clients. Since I need confirmation that the clients received the information and don't want to build an ACK structure for a UDP connection, I decided to use a TCP streaming method. However, I've been struggling to understand how to maintain multiple connections and keep them idle. I seem to have three options. Use a fork for each incoming connection to create a separate child process, use pthread_create to create an entire new thread for each process, or use select() to wait on all open socket IDs for a connection. Recommendations as to how to attack this? I've begun working with pthreads but since performance will likely not be an issue, multicore processing is not necessary and perhaps there is a simpler way.

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• Using one sqlconnection/sqlcommand through 2 DB-bound methods

  - by dotnetdev

  I have a class with a method which gets data from a database through a SELECT stored proc. This method uses a SqlDbReader by returning ExecuteReader() on a SqlCommand. The connection and everything is made in this method, with fields (such as connection string) set as class level fields. I now need to populate an array based on the results of this query (so the columns of each row will go into the array with its own index). However, this query will not select all of the data from one table which is involved. I can write the queries to get what I need, but how can I use one connection throughout the class? If I instantiate the connection object and call Open() in the constructor, I get an exception @ runtime. I'm hoping for something like this: // At class level: sqlconn.Open(); // sqlcommand set up Method() { // Fire stored proc // Insert results in a collection } Method2() { // Pass same collection in (use same one), // Add new row columns into same collection } How can I do this with strict performance in mind? Thanks

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• Tomcat - virtualhosting - name / ip / port - based

  - by lisak

  Hey, what are the usage scenarios for these kinds of virtual hosting ? Name Based - typical tomcat virtual hosting, one HOME instance with many contexts, each as an individual host IP based / port based - multiple instances of tomcat ( how is it with performance and memory consuption?) running on IP aliases (virtual IPs) for one network adapter, usually behind http apache server that can run name based virtual hostings. Otherwise I can't figure out how would I forward requests in iptables/firewall based on IP address, which is just one. How is IP based virtual hosting done as to Tomcat and multiple instances ? I'd like to hear some usage scenarios from your experience. How are you running your applications. Cause there are applications having it's own modified classloader and they are developed in a way to run alone withing a tomcat instance. Then there are trivial applications which can run within one instance without problems. Many thanks

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• Using Windows media foundation

  - by Martin Beckett

  Ok so my new gig is high performance video (think Google streetview but movies) - the hard work is all embedded capture and image processing but: I was looking at the new MS video offerings to display content = Windows Media Foundation. Is anyone actually using this ? There are no books on the topic. The only documentation is a developer team blog with a single entry 9 months old. I thought we had got past having to learn an MS api by spying on the com control messages! Is it just another wrapper around the same old activeX control?

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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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• How to achieve a palette effect on iPhone using OpenGL

  - by Joe

  I'm porting a 2d retro game to iPhone that has the following properties: targets OpenGL ES 1.1 entire screen is filled with tiles (textured triangle strip tile textured using a single 256x256 RGBA texture image the texture is passed to OpenGL once at the start of the game only 4 displayed colours are used one of the displayed colours is black The original game flashed the screen when time starts to run out by toggling the black pixels to white using an indexed palette. What is the best (i.e. most efficient) way to achieve this in OpenGL ES 1.1? My thoughts so far: Generate an alternative texture with white instead of black pixels, and pass to OpenGL when the screen is flashing Render a white poly underneath the background and render the texture with alpha on to display it Try and render a poly on top with some blending that achieves the effect (not sure this is possible) I'm fairly new to OpenGL so I'm not sure what the performance drawbacks of each of these are, or if there's a better way of doing this.

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• Are IoC containers about configuration files?

  - by Jader Dias

  Recently I developed a performance tester console application, with no UI, with the help of a IoC containter (Castle-Windsor-Microkernel). This library enabled me to let the user choose which test(s) to run, simply by changing the configuration file. Have I realized what IoC containers are about? I'm not sure. Even Joel said here on SO that IoC are difficult to understand. From my example, what do you conclude? Am I using IoC container for exactly what they were designed for? Or I am just using one of its secondary features?

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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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• Building a case for solr

  - by Midhat

  Our product consists of multiple applications, All using Lucene. 2 of the applications I am involved with have Lucene indexes of about 3 GB and 12GB. Another team is building an application, for which they estimate the LUCENE INDEX size to be close to 1 Terabyte. New documents are added to the indexes every 15 days approx. We do not have any apparent performance issues with the current applications. So my question is SHould we be using Solr now? When should one stop using Lucene and graduate to Solr? Any disadvantages/problems for using Solr? The client applications are made in ASP.Net, but I assume they will be able to use a solr server using solrnet

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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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• 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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• 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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• 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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• Compress components with gzip - J2EE

  - by Venkata Sirish

  I am looking to improve front-end performance of my application, so I used YSlow tool in Firefox. When I ran this tool for my app, in the YSlow grade tab it showed up a issue 'Grade F on Compress components with gzip'. Seems to be that we need to compress the files(js, css) while sending from the server to client to increase the server response time. My app is a Struts Java application. Can anyone let me know how to compress and send the front end UI files(JS,CSS) from server so that the response time increases and my pages lot fastly? What are the things that I need to do to compress these files in Java at server?

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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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• Python: split a list based on a condition?

  - by Parand

  What's the best way, both aesthetically and from a performance perspective, to split a list of items into multiple lists based on a conditional? The equivalent of: good = [x for x in mylist if x in goodvals] bad = [x for x in mylist if x not in goodvals] is there a more elegant way to do this? Update: here's the actual use case, to better explain what I'm trying to do: # files looks like: [ ('file1.jpg', 33L, '.jpg'), ('file2.avi', 999L, '.avi'), ... ] IMAGE_TYPES = ('.jpg','.jpeg','.gif','.bmp','.png') images = [f for f in files if f[2].lower() in IMAGE_TYPES] anims = [f for f in files if f[2].lower() not in IMAGE_TYPES]

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