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• Reverse massive text file in Java

  - by DanJanson

  What would be the best approach to reverse a large text file that is uploaded asynchronously to a servlet that reverses this file in a scalable and efficient way? text file can be massive (gigabytes long) can assume mulitple server/clustered environment to do this in a distributed manner. open source libraries are encouraged to consider I was thinking of using Java NIO to treat file as an array on disk (so that I don't have to treat the file as a string buffer in memory). Also, I am thinking of using MapReduce to break up the file and process it in separate machines. Any input is appreciated. Thanks. Daniel

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• MEMORY(HEAP) vs. InnoDB in a Read and Write Environment

  - by Johannes

  I want to program a real-time application using MySQL. It needs a small table (less than 10000 rows) that will be under heavy read (scan) and write (update and some insert/delete) load. I am really speaking of 10000 updates or selects per second. These statements will be executed on only a few (less than 10) open mysql connections. The table is small and does not contain any data that needs to be stored on disk. So I ask which is faster: InnoDB or MEMORY (HEAP)? My thoughts are: Both engines will probably serve SELECTs directly from memory, as even InnoDB will cache the whole table. What about the UPDATEs? (innodb_flush_log_at_trx_commit?) My main concern is the locking behavior: InnoDB row lock vs. MEMORY table lock. Will this present the bottleneck in the MEMORY implementation? Thanks for your thoughts!

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• Emulating a transaction-safe SEQUENCE in MySQL

  - by Michael Pliskin

  We're using MySQL with InnoDB storage engine and transactions a lot, and we've run into a problem: we need a nice way to emulate Oracle's SEQUENCEs in MySQL. The requirements are: - concurrency support - transaction safety - max performance (meaning minimizing locks and deadlocks) We don't care if some of the values won't be used, i.e. gaps in sequence are ok. There is an easy way to archieve that by creating a separate InnoDB table with a counter, however this means it will take part in transaction and will introduce locks and waiting. I am thinking to try a MyISAM table with manual locks, any other ideas or best practices?

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• data between pages: $_SESSION vs. $_GET ?

  - by Haroldo

  Ok, firstly this is not about forms this is about consistent layout as a user explores a site. let me explain: If we imagine a (non-ajax) digital camera online store, say someone was on the DSLR section and specified to view the cameras in Gallery mode and order by price. They then click onto the Compact camera's page. It would be in the users interests if the 'views' they selected we're carried over to this new page. Now, i'd say use a session - am i wrong? are there performance issues i should be aware of for a few small session vars ( ie view=1 , orderby=price) ?

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• Has Object in VB 2010 received the same optimalization as dynamic in C# 4.0?

  - by Abel

  Some people have argued that the C# 4.0 feature introduced with the dynamic keyword is the same as the "everything is an Object" feature of VB. However, any call on a dynamic variable will be translated into a delegate once and from then on, the delegate will be called. In VB, when using Object, no caching is applied and each call on a non-typed method involves a whole lot of under-the-hood reflection, sometimes totaling a whopping 400-fold performance penalty. Have the dynamic type delegate-optimization and caching also been added to the VB untyped method calls, or is VB's untyped Object still so slow?

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• Should I use a hosted version of JQuery? Which one?

  - by ataylor

  Should I use a local copy of jquery, or should I link to a copy provided by Google or Microsoft? I'm primarily concerned about speed. I've heard that just pulling content from other domains can have performance advantages related to how browsers limit connections. In particular, has anyone benchmarked the speed and latency of Google vs. Microsoft vs. local? Also, do I have to agree to any conditions or licenses to link from a third-party?

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• designing data structures for an address book in C program??

  - by osabri

  i want that the number of address book item is not known in advance, i am thinking to use linked list is it the right choice?? "the user can enter new person data, or print the data for a given name, the asking data need not be a name but also an address on a telephone number, the program prints the whole information about a person, print the content of the book in alphabetical order. Store some data in a file; retrieve it and safe it after modification Program should write a file to the disk and retrieve the file from it. Program should be called with arguments. i will use malloc but i don't know when and how? somebody did similar task or have an idea can help me plz

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• Multimedia content in REST responce(XML/JSON)

  - by Koushik

  In my thesis I need to test different architectures. A request to a REST web service developed using Apache CXF and Spring MVC with MySQL as back end serving references(a field in database) to images,audio and video files stored in file system. In the response message, what is the best method to send the content to the client(another application using the service which I developed). URI: http://www.filmservices.com/film/{id} A client here is not the end user. Send the encoded hyperlink's(where the content is stored in the file system) to the client, so that the client renders the response and displays it to the browser. Use Base64 to encode the message(image,audio,video) and send it to the client. Main concern is performance.

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• How can I measure TForm deserialization time in Delphi?

  - by mjustin

  For performance tests I need a way to measure the time needed for a form to load its definition from the DFM. All existing forms inherit a custom form class. To capture the current time, this base class needs overriden methods as "extension points": before the beginning of the deserialization process after the completion of deserialization (can be implemented by overriding the Loaded procedure) the moment just before the execution of the OnFormCreate event Which TObject (or TComponent) methods are best suited? Maybe there are other extension points in the form creation process, please feel free to make suggestions.

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• How do I view how many concurrent long polling requests there are on my server?

  - by Pascal

  My host is Joyent. My host says I have 15 process limit and prstat -J shows those processes but that doesn't tell me how many long polling requests are currently being served. I could record it myself but that would add alot of performance overhead. I need to know when the server is at its long polling limits. I know this limit occurs far before the memory or CPU is used up. From experimentation, I've already verified that the number of long polls open is NOT equivalant to the number of processes running, probably because each process has multiple threads, each serving a request. thanks.

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• accesing local exe file from asp.net application

  - by sansknwoledge

  hi, i am having a intranet asp.net application , all the clients connected to it is having a specific .exe file in their local disk, now i want to execute the .exe file from the .net application hosted in a intranet server. i used this code to do that Dim psi As New System.Diagnostics.ProcessStartInfo() psi.WorkingDirectory = "C:\\" psi.FileName = "c:\\Project1.exe" '"file:///c:/Project1.exe" psi.Arguments = iApqpId 'cTimeMaster.APQPID psi.UseShellExecute = False System.Diagnostics.Process.Start(psi) but it is throwing a error the system cannot find the file specified. is it having a permission issue on local system or any thing else, any help would be greatly appriciated. thanks and regards

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• How do I calculate a good hash code for a list of strings?

  - by Ian Ringrose

  Background: I have a short list of strings. The number of strings is not always the same, but are nearly always of the order of a “handful” In our database will store these strings in a 2nd normalised table These strings are never changed once they are written to the database. We wish to be able to match on these strings quickly in a query without the performance hit of doing lots of joins. So I am thinking of storing a hash code of all these strings in the main table and including it in our index, so the joins are only processed by the database when the hash code matches. So how do I get a good hashcode? I could: Xor the hash codes of all the string together Xor with multiply the result after each string (say by 31) Cat all the string together then get the hashcode Some other way So what do people think? (If you care we are using .NET and SqlServer)

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• Trying to right click on code in VS2008 causes lockup.

  - by Adam Haile

  Working on a Win32 DLL using Visual Studio 2008 SP1 and, since yesterday, whenever I try to right click on code, to go to a variable definition for example, VS completely locks up and I have to manually kill the process. To make it even weirder, whenever this happens the devenv.exe process uses exactly 25% of the CPU. And I mean exactly, never 24%, never 26%, always 25% Also, I've run ProcMon to see if devenv is actually doing something, but it's doing absolutely nothing external of the process. No disk, network, registry access. Nothing. This is getting really aggravating because I have a large code base to deal with and the only other way of jumping to the definition is to first search for it. Has anyone run into a similar issue? And, better yet, know a fix?

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• Alternative to NOT EXISTS

  - by Dave Colwell

  Hi all, I have two tables linked by an ID column, lets call them Table A and table B. My goal is to find all the records in table A that have no record in table B. For instance: Table A: ID----Value 1-----value1 2-----value2 3-----value3 4-----value4 Table B ID----Value 1-----x 2-----y 4-----z 4-----l As you can see, record with ID = 3 does not exist in table B, so i want a query that will give me record 3 from table A. the way i am currently doing this is by saying AND NOT EXISTS (SELECT ID FROM TableB) but since the tables are huge, the performance on this is terrible. Also, when i tried using a Left Join where TableB.ID is null, it didnt work. Can anyone suggest an alternative?

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• Should we use a CSS frame work ? Are they worth it ?

  - by Gaurav M

  CSS frameworks have nice styles inbuilt and ask you to focuses on the grids but still there is a bit of dependency and lack of freedom it provide.. If I need to generate a webpage by looking on a PSD based mockup screen ..either i will use the classes provided by the framework but if that actual measurements does not exist I need to again specify my own rules that will add upto my CSS filesize and if performance is a constraint as always it is...you need not a big size file..though its in kb but every drop counts. Any comments and suggestions to use the framework in a best possible way.

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• Seeking tutorial: introduction to ODBC with Delphi

  - by mawg

  I have a lot of embedded C/C++/Ada experience and an outdated smattering of Delphi plus some database stuff. Now I have to implement an app in Delphi which can manipulate MySql, Oracle, maybe MS Access. In short, I need ODBC. I need to programmatically created a database, define its structure and populate its contents, then later query its existence and programmatically search. I would prefer not to use 3rd party components, unless there is a compelling reason to do so (performance ought not to be an issue for the app, it won't have much data or be run often, at least not in v1.0) . Can anyone point me at a tutorial which can get me up to speed? Thanks

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• Rails/mysql SUM distinct records - optimization

  - by pepernik

  Hey. How would you optimize this SQL SELECT SUM(tmp.cost) FROM ( SELECT DISTINCT clients.id as client, countries.credits_cost AS cost FROM countries INNER JOIN clients ON clients.country_id = countries.id INNER JOIN clients_groups ON clients_groups.client_id=clients.id WHERE clients_groups.group_id IN (1,2,3,4,5,6,7,8,9) GROUP BY clients.id ) AS tmp; I'm using this example as part of my Ruby on Rails project. Note that my nested SQL (tmp) can have more then 10 milion records. You can split that in more SQLs if the performance is better. Should I add any indexes to make it quicker (i have it on IDs)?

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• Running multiple jvms for different applications in same machine

  - by Rajesh

  We are getting frequent out of memory errors in our dev. machines We are running webshpere, eclipse, soap UI and maven in it. Our server gets down due to this "out of memory errors" when we restart our applications in websphere 2/3 times, We already increased the virtual memory setting in wesphere to 1GB. So what i did was copied the jre we use in eclipse and maven folders so that each of these uses individual jvms. But the performance of websphere is same. 2/3 restarts and out of memory errors. Is there any may of making eclipse and maven use different jvms other than websphere's?

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• Is it possible to find out what FlashBuilder is doing during compilation?

  - by justkevin

  I've found that Flash Builder 4 (formerly Flex Builder) has trouble working with large projects. After a certain point, builds seem to take longer and longer. I've tried many different ways of improving build time including: Moving embedded resources into externally linked projects. Using -incremental. Tweaking the .ini jvm settings including memory and -server. Turning off automatic build (I'd prefer not to have to do this, because one of the main reasons for using an IDE is to be told about errors as you make them). Deleting the project and re-checking out from the repository. While some of these may help a bit, the performance is still annoyingly slow. I feel if I knew what was taking so long I could refactor my projects to build faster. Is there some setting that tells FlashBuilder to let me see what parts of the build process take so much time?

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• ContextSwitchDeadlock Was Detected error in C#

  - by assassin

  Hi, I am running a C# application, and during run-time I get the following error: The CLR has been unable to transition from COM context 0x20e480 to COM context 0x20e5f0 for 60 seconds. The thread that owns the destination context/apartment is most likely either doing a non pumping wait or processing a very long running operation without pumping Windows messages. This situation generally has a negative performance impact and may even lead to the application becoming non responsive or memory usage accumulating continually over time. To avoid this problem, all single threaded apartment (STA) threads should use pumping wait primitives (such as CoWaitForMultipleHandles) and routinely pump messages during long running operations. Can anyone please help me out with the problem here? Thanks a lot.

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• How to correct this glitch

  - by Rebol Tutorial

  I removed background: url(none); in my stylesheet because of load performance http://stackoverflow.com/questions/2577422/why-firebug-pretends-that-my-stylesheet-is-calling-my-xmlrpc The problem is that it now causes some glitch on css list. Any idea how to fix this ? Thanks. Update: picture below Tried to put background: none as suggested but didn't solve the problem/ ul.sidebar_list li ul li ul { margin: 0px; padding: 0px!important; float: left; width: 100%; list-style-type: none; background: none; }

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• Morfik - suitability for medium-scale web enterprise applications

  - by MaikB

  I'm investigating technologies with which to develop a medium-scale (up to 100 or 200 simultaneous users) database-driven web application, and someone suggested Morfik. However, outside of the Morfik company I can find practically zero community support - no active blogs, no tutorials, no videos, no books - and this is of some concern (especially when compared to C# / ASP.NET / nHibernate etc support). Deciding between Morfik (untried and not used widely AFAIK) and the other technologies I mentioned (tried, tested, used widely) is becoming a critical issue for my company. Has anyone had success using Morfik in these kind of circumstances? What kind of performance did you achieve?

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• dotTrace cant create deploy folder on Windows Azure Web Sites (WAWS)

  - by Orhan Maden

  I get the error message 'Can't create deploy folder.' when I try to profile a remote websites on WAWS. Actions taken: Downloaded and installed the dotTrace Profiler 5.5 from the JetBrains website Downloaded the dotTrace.Performance.Remote version 5.5.0 from Nuget Published the website to WAWS via Visual Studio 2013 Started the dotTrace application as Administrator Connected to the remote _https://subdomain.azurwebsites.net/AgentService.asmx. See image: http://1drv.ms/1nF5Cyh Selected the w3wp process and pressed Run Got the error message 'Can't create deploy folder'. See image: http://1drv.ms/U5h35A I'm running dotTrace in trial mode at the moment. Swift help is much appreciated. Orhan

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• Read and Write in the same file with different process

  - by muruga

  I have written the two program. One program is write the content to the text file simultaneously. Another program is read that content simultaneously. But both the program should run at the same time. For me the program is write the file is correctly. But another program is not read the file. I know that once the write process is completed than only the data will be stored in the hard disk. Then another process can read the data. But I want both read and write same time with different process in the single file. How can I do that? Please help me.

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• Reading ResultSet from multiple threads

  - by superdario

  Hello, In the database, I have a definition table that is read from the application once upon starting. This definition table rarely changes, so it makes sense to read it once and restart the application every time it changes. However, after the table is read (put into a ResultSet), it will be read by multiple handlers running in their own threads. How do you suggest to accomplish this? My idea was to populate a CachedRowSet, and then create a copy of this set (through the createCopy() method) for each handler every time a new request comes. Do you think this is wise? Does this offer a good performance? Thanks.

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