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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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• Is writing to a socket an arbitrary limitation of the sendfile() syscall?

  - by Sufian

  Prelude sendfile() is an extremely useful syscall for two reasons: First, it's less code than a read()/write() (or recv()/send() if you prefer that jive) loop. Second, it's faster (less syscalls, implementation may copy between devices without buffer, etc...) than the aforementioned methods. Less code. More efficient. Awesome. In UNIX, everything is (mostly) a file. This is the ugly territory from the collision of platonic theory and real-world practice. I understand that sockets are fundamentally different than files residing on some device. I haven't dug through the sources of Linux/*BSD/Darwin/whatever OS implements sendfile() to know why this specific syscall is restricted to writing to sockets (specifically, streaming sockets). I just want to know... Question What is limiting sendfile() from allowing the destination file descriptor to be something besides a socket (like a disk file, or a pipe)?

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• ASP.NET Download All Files as Zip

  - by Ronnie Overby

  I have a folder on my web server that has hundreds of mp3 files in it. I would like to provide the option for a user to download a zipped archive of every mp3 in the directory from a web page. I want to compress the files programmatically only when needed. Because the zip file will be quite large, I am thinking that I will need to send the zip file to the response stream as it is being zipped, for performance reasons. Is this possible? How can I do it?

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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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• 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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• 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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• 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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• 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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• 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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• 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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• 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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• 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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• 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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• 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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• 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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• SDK for writing DVD's

  - by Matt Warren

  I need to add DVD writing functionality to an application I'm working on. However it needs to be able to write out files that are being grabbed "live" from a camera, over a long period of time. I can't wait until all the files are captured before I start writing them to the DVD, I need to write them out in chunks as I go along. I've looked at IMAPI v2, but the main problems seems to be that you need to point it to all the files you plan to write out to disk before you start the burning process. I know it has to concept of "sessions", which means you can write to the DVD in several parts, before you finally "close" it. But I was wondering if there were any other DVD writing SDK's that allow you to be constantly writing files to a DVD and in particular files that are only in memory. It would be more efficient if I didn't have to write the captured images out to hard before they are burned to DVD. The solution needs to work under .NET on Windows XP and vista

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• PostgreSQL 8.3 data types: xml vs varchar

  - by Sejanus

  There's xml data type in Postgres, I never used it before so I'd like to hear opinions. Downsides and upsides vs using regular varchar (or Text) column to store xml. The text I'm going to store is xml, well-formed, UTF-8. No need to search by it (I've read searching by xml is slow). This XML actually is data prepared for PDF generation with Apache FOP. XML can be generated dynamically from data found elsewhere (other Postgres tables), it's stored as is only so that I won't need to generate it twice. Kinda backup#2 for already generated PDF documents. Anything else to know? Good practices, performance, maintenance, etc?

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• Parametrize the WHERE clause?

  - by ControlFlow

  Hi, stackoverflow! I'm need to write an stored procedure for SQL Server 2008 for performing some huge select query and I need filter it results with specifying filtering type via procedure's parameters (parameterize where clause). I found some solutions like this: create table Foo( id bigint, code char, name nvarchar(max)) go insert into Foo values (1,'a','aaa'), (2,'b','bbb'), (3,'c','ccc') go create procedure Bar @FilterType nvarchar(max), @FilterValue nvarchar(max) as begin select * from Foo as f where case @FilterType when 'by_id' then f.id when 'by_code' then f.code when 'by_name' then f.name end = case @FilterType when 'by_id' then cast(@FilterValue as bigint) when 'by_code' then cast(@FilterValue as char) when 'by_name' then @FilterValue end end go exec Bar 'by_id', '1'; exec Bar 'by_code', 'b'; exec Bar 'by_name', 'ccc'; But it doesn't work when the columns has different data types... It's possible to cast all the columns to nvarchar(max) and compare they as strings, but I think it will cause a performance degradation... Is it possible to parameterize where clause in stored procedure without using things like EXEC sp_executesql (dynamic SQL and etc.)?

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• Does JavaME and/or Proguard reorder assignments?

  - by chrisdew

  This is a simplified example - I have two threads: Can JavaME and/Proguard ever reorder the obX = ... statements, such that thread_B will have a null pointer exception at ob2.someMethod? thread_A: Object ob1 = null; Object ob2 = null; ... ob1 = something1; ob2 = something2; thread_B: if (ob2 != null) { ob1.someMethod(); ... } P.S. I do realise that synchronising these will avoid the issue. Synchronisation has both a performance overhead, and more importantly, a chance to introduce deadlock.

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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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• 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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• How to monitor MySQL query errors, timeouts and logon attempts?

  - by Abel

  While setting up a third party closed source CMS (Sitefinity) the setup doesn't create all tables and procedures necessary to run it. The software lacks a logging system itself and it made me wonder: could I trace and monitor failing SQL statements from MySQL? This serves more than only the purpose of solving my issue with Sitefinity. More often I wonder what's send to the MySQL server, not wanting to dive into the software products or setup a debugging environment etc. I tried JetProfiler (only performance) and looked through a few others, but although they monitor a lot, they don't monitor query failures, timeouts or logon attempts. Does anyone know a profiler, tracer, monitoring tool, commercial or free, that can show me this information?

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• Grand Central Strategy for Opening Multiple Files

  - by user276632

  I have a working implementation using Grand Central dispatch queues that (1) opens a file and computes an OpenSSL DSA hash on "queue1", (2) writing out the hash to a new "side car" file for later verification on "queue2". I would like to open multiple files at the same time, but based on some logic that doesn't "choke" the OS by having 100s of files open and exceeding the hard drive's sustainable output. Photo browsing applications such as iPhoto or Aperture seem to open multiple files and display them, so I'm assuming this can be done. I'm assuming the biggest limitation will be disk I/O, as the application can (in theory) read and write multiple files simultaneously. Any suggestions? TIA

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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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