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• Giving Users an Option Between UDP & TCP?

  - by cam

  After studying TCP/UDP difference all week, I just can't decide which to use. I have to send a large amount of constant sensor data, while at the same time sending important data that can't be lost. This made a perfect split for me to use both, then I read a paper (http://www.isoc.org/INET97/proceedings/F3/F3_1.HTM) that says using both causes packet/performance loss in the other. Is there any issue presented if I allow the user to choose which protocol to use (if I program both server side) instead of choosing myself? Are there any disadvantages to this? The only other solution I came up with is to use UDP, and if there seems to be too great of loss of packets, switch to TCP (client-side).

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• How to save multiple UIImage to a file iPad

  - by aron

  I have a PDF reader that displays pages of the document. What I want to do is allow the user to draw over the PDF in a transparent view. Then I want to save the drawing (UIImage) to disk. If at all possible, I don't want to have the documents folder filled with files like documentName_page01.png, documentName_page02.png for every page that is drawn over. However, I can't figure out how to store these UIImages into a single file without it becoming unwieldy and memory intensive. Any ideas appreciated.

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• Is it better to alloc/dealloc new UIBarButtonItems when toggling Edit/Done? Why?

  - by cambria

  Apple's documentation implies that for a UITableView editable with an "Edit/Done" button, you should create and destroy the button each time it's toggled. Here's a snippet of code "BonjourWeb" sample code project that does this: if (editing) { // Add the "done" button to the navigation bar UIBarButtonItem *doneButton = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemDone target:self action:@selector(doneAction:)]; self.navigationItem.leftBarButtonItem = doneButton; [doneButton release]; [self addAddButton:YES]; } else { if ([self.customs count]) { // Add the "edit" button to the navigation bar UIBarButtonItem *editButton = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemEdit target:self action:@selector(editAction:)]; self.navigationItem.leftBarButtonItem = editButton; [editButton release]; } Is this really better than just editing the title of the button? Is there some performance optimisation that I'm not seeing? Or is this just bad example source?

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• How to Get the Method/Function Call Trace for a Specific Run?

  - by JackWM

  Given a Java or JavaScript program, after its execution, print out a sequence of calls. The calls are in invocation order. E.g. main() { A(); } A() { B(); C(); } Then the call trace should be: main -> A() -> B() -> C() Is there any tool that can profile and output this kind of information? It seems this is common a need for debugging or performance tuning. I noticed that some profilers can do this, but I prefer a simpler/easy-to-use one. Thanks!

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• Apache2 on Ubuntu Server w/ CGI, FastCGI, mod_php

  - by illegal3alien

  I've looked at various websites on configuring Apache with cgi and can't get mod_fcgid to work. It works fine using mod_php5, but I wanted to compare performance using cgi and fastcgi. I tried methods using FGCIWrapper among various other techniques and the only one that didn't result in an unlogged 403 or download of the file was using "Action application/x-httpd-php /usr/bin/php-cgi" When trying to configure mod_fcgid the file normally just started a download of an unprocessed file. I used wget to check headers and type was "application/x-httpd-php" At one point I was able to get to the page, but it resulted in a 403, which was listed in access.log, but not error.log (I was told it should be in there too) I tried to get it working on a fresh install of Ubuntu Server 10.04 LTS and 10.10 and had the same results on both, so I'm not doing something correctly in terms of configuration. I tried virtualmin and could only get mod_php to work. The page just prompted a download when selecting cgi or fcgi from the control panel.

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• A non-blocking server with java.io

  - by Jon

  Everybody knows that java IO is blocking, and java NIO is non-blocking. In IO you will have to use the thread per client pattern, in NIO you can use one thread for all clients. Now my question follows: is it possible to make a non-blocking design using only the Java IO api. (not NIO) I was thinking about a pattern like this (obviously very simplified); List<Socket> li; for (Socket s : li) { InputStream in = s.getInputStream(); byte[] data = in.available(); in.read(data); // processData(data); (decoding packets, encoding outgoing packets } Also note that the client will always be ready for reading data. What are your opinions on this? Will this be suitable for a server that should at least hold a few hundred of clients without major performance issues?

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• Using locks inside a loop

  - by Xaqron

  // Member Variable private readonly object _syncLock = new object(); // Now inside a static method foreach (var lazyObject in plugins) { if ((string)lazyObject.Metadata["key"] = "something") { lock (_syncLock) { if (!lazyObject.IsValueCreated) lazyObject.value.DoSomething(); } return lazyObject.value; } } Here I need synchronized access per loop. There are many threads iterating this loop and based on the key they are looking for, a lazy instance is created and returned. lazyObject should not be created more that one time. Although Lazy class is for doing so and despite of the used lock, under high threading I have more than one instance created (I track this with a Interlocked.Increment on a volatile shared int and log it somewhere). The problem is I don't have access to definition of Lazy and MEF defines how the Lazy class create objects. My questions: 1) Why the lock doesn't work ? 2) Should I use an array of locks instead of one lock for performance improvement ?

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• Question About Eclipse Java Debugger Conditional Breakpoints Inefficiency

  - by Personman

  I just set a conditional breakpoint in Eclipse's debugger with a mildly inefficient condition by breakpoint standards - checking whether a HashMap's value list (8 elements) contains Double.NaN. This resulted in an extremely noticeable slowdown in performance - after about five minutes, I gave up. Then I copy pasted the condition into an if statement at the exact same line, put a noop in the if, and set a normal breakpoint there. That breakpoint was reached in the expected 20-30 seconds. Is there something special that conditional breakpoints do that is different from this, or is Eclipse's implementation just kinda stupid? It seems like they could fairly easily just do exactly the same thing behind the scenes.

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• Does Oracle 11g automatically index fields frequently used for full table scans?

  - by gustafc

  I have an app using an Oracle 11g database. I have a fairly large table (~50k rows) which I query thus: SELECT omg, ponies FROM table WHERE x = 4 Field x was not indexed, I discovered. This query happens a lot, but the thing is that the performance wasn't too bad. Adding an index on x did make the queries approximately twice as fast, which is far less than I expected. On, say, MySQL, it would've made the query ten times faster, at the very least. I'm suspecting Oracle adds some kind of automatic index when it detects that I query a non-indexed field often. Am I correct? I can find nothing even implying this in the docs.

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• Organizing PHP includes in your development environment

  - by Andrew Heath

  I'm auditing my site design based on the excellent Essential PHP Security by Chris Shiflett. One of the recommendations I'd like to adopt is moving all possible files out of webroot, this includes includes. Doing so on my shared host is simple enough, but I'm wondering how people handle this on their development testbeds? Currently I've got an XAMPP installation configured so that localhost/mysite/ matches up with D:\mysite\ in which includes are stored at D:\mysite\includes\ In order to keep include paths accurate, I'm guess I need to replicate the server's path on my local disk? Something like D:\mysite\public_html\ Is there a better way?

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• Codeigniter - Is it ok to add functionality to the constructor in controllers?

  - by Irro

  I'm making a project where I want the user to search for shops in different cities and would like the url to be like this: domain/shop/city/name. So I created a controller in codeigniter called Shop. But I cant create a city function since the city part of the url changes dependent on city name. One easy way to do it would be to add a function called "search" and add the functionality there but then I get url's like: domain/shop/search/city/name which I really would like to avoid. So my question is if it's ok to add my functionality directly into the constructor to avoid that extra "search" part in the url? I'm afraid that there might be some performance tricks involved that potentially keeps the class in memory so the constructor will not be called every time.

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• MVC framework for huge JEE application

  - by chaKa

  Which MVC-framework is the best option (performance/ease of development) for a web application, that will have + 2 million visits per week. Basically the site is a search engine,but also there will be large amounts of xml parsing, and high db traffic. We are using Java, over Jboss 4.2.3x, with PG as DB, and Solr for the searches. We were thinking on code JSPs with taglibs, and Servlets, but we were feeling like there would be a better alternative, which don't know yet, as we are starting on the Java Web applications world. Any opinions, and shares of your experience will be appreciated! Thanks in advance!

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• When is BIG, big enough for a database?

  - by David ???

  I'm developing a Java application that has performance at its core. I have a list of some 40,000 "final" objects, i.e., I have an initialization input data of 40,000 vectors. This data is unchanged throughout the program's run. I am always preforming lookups against a single ID property to retrieve the proper vectors. Currently I am using a HashMap over a sub-sample of a 1,000 vectors, but I'm not sure it will scale to production. When is BIG, actually big enough for a use of DB? One more thing, an SQLite DB is a viable option as no concurrency is involved, so I guess the "threshold" for db use, is perhaps lower.

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• Need a Concatenating VBA code to prevent memory issue workaround

  - by doharr

  My set up: Have 50,000 rows of data. ( My row count will increase in the future. So might as well say I have a full worksheet of 64000+ rows.) All Data is TEXT, no formulas, etc. Column A is open Columns B thru AC contain the Data that needs to be concatenated The Data in the rows once concatenated to Column A will contain 60,000 digits or 6kb in file size. After additional maniuplation each cell will become a file. I have tried concatenating in Excel and I run into memory issues. The memory issue is when I Select and fill down the concatenating function into the worksheet. It crashes at the 8200 +/-row. My system is 2gb of ram, windows xp professional and Excel 2003. Have 4GB of disk space Hoping to find a VBA code that will conserve memory, and not crash like it does in excel. Thank you

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• What's a good way to set up a development environment on OS X for ruby, rails, and git?

  - by Ein2015

  I'm going to start development on a web app using ruby, rails, probably either postgres or mysql, and most likely apache. I'll be using a git repository with the master repo on another server. I've searched through stackoverflow and done some Googling... so here's what I have so far... What are your opinions on what's described on this page?: http://robots.thoughtbot.com/post/159805668/2009-rubyists-guide-to-a-mac-os-x-development What about this one?: http://www.buildingwebapps.com/articles/79197-setting-up-rails-on-leopard-mac I don't need helping finding an editor, there's plenty out there (TextMate, TextWrangler, MacVim), but I do need help to make sure I'm setting things up correctly to code, build, and run the web app from my mac. Here's a specific set of scenarios I could use some help on: Testing various versions of rails and/or ruby. Testing performance, vulnerabilities, monitoring queries, etc. Testing different versions of gems. Working on other projects on this same machine.

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• IF/ELSE makes stored procedure not return a result set

  - by Brendan Long

  I have a stored procedure that needs to return something from one of two databases: IF @x = 1 SELECT @y FROM Table_A ELSE IF @x = 2 SELECT @y FROM Table_B Either SELECT alone will return what I want, but adding the IF/ELSE makes it stop returning anything. I tried: IF @x = 1 RETURN SELECT @y FROM Table_A ELSE IF @x = 2 RETURN SELECT @y FROM Table_B But that causes a syntax error. The two options I see are both horrible: Do a UNION and make sure that only one side has any results: SELECT @y FROM Table_A WHERE @x = 1 UNION SELECT @y FROM Table_B WHERE @x = 2 Create a temporary table to store one row in, and create and delete it every time I run this procedure (lots). Neither solution is elegant, and I assume they would both be horrible for performance (unless MS SQL is smart enough not to search the tables when the WHERE class is always false). Is there anything else I can do? Is option 1 not as bad as I think?

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• how to protect an imported win32 dll into a .net application from memory issues

  - by Eric

  I have a c# application that needs to use a legacy win32 dll. The dll is almost its own app, it has dialogs, operations with hardware, etc. When this dll is imported and used, there are a couple of problems that occur: Dragging a dialog (not a windows system dialog, but one created by the dll) across the managed code app causes the UI to not repaint. Further it generates a system out of memory exception from various ui controls. The performance is incredibly slow. There seems to be no way to unload the dll so the memory never gets cleaned up. When we close our managed app, we get another memory exception. At the moment we import each method call as such: [DllImport("dllname.dll", EntryPoint = "MethodName", SetLastError = true, CharSet = CharSet.Auto, ExactSpelling = true, CallingConvention = CallingConvention.StdCall)]

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• PCI function number for SATA AHCI controller

  - by Look Alterno

  I'm debugging a second stage boot loader for a PC with SATA AHCI controller. I'm able to enumerate the PCI bus and find the hard disk. So far, so good. Now, lspci in my notebook (Dell Inspiron 1525) show me: -[0000:00]-+-1f.0 Intel Corporation 82801HEM (ICH8M) LPC Interface Controller +-1f.1 Intel Corporation 82801HBM/HEM (ICH8M/ICH8M-E) IDE Controller +-1f.2 Intel Corporation 82801HBM/HEM (ICH8M/ICH8M-E) SATA AHCI Controller \-1f.3 Intel Corporation 82801H (ICH8 Family) SMBus Controller My question: Is SATA AHCI Controller always function 2 in any PC? If not, how I found? I don't pretend to be general; booting my notebook will be good enough, without compromise further refinements.

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• Help choosing the right data structure

  - by devoured elysium

  I need a data structure with the following requirements: Needs to be able to get elements by index (like a List). I will always just add / remove elements from the end of the structure. I am inclined to use an ArrayList. In this situation, it seems to be O(1) both to read elements (they always are?), remove elements (I only need to remove them at the end of the list) and to add(I only add to the end of the list). There is only the problem that time to time the ArrayList will have a performance penalty when it's completly full and I need to add more elements to it. Is there any other better idea? I don't think of a data structure that'd beat the ArrayList here. Thanks

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• How to add an existing folder to a Visual Studio project?

  - by Earlz

  I have a web application project made in Visual Studio 2008. Well, I added a jquery folder and added it to source control and other such things. I forgot to add it to the visual studio project though. How do I add the existing folder now? I've tried just creating a new folder and naming it jquery but it gave me a cryptic error "the directory is already on the disk ... if you want to see this directory then check the Show All Files option in the project file" Yet I looked and saw no such option. Is the only way around this to rename jquery to jquery2 and then create a new folder via visual studio named jquery and copy all my files into it?

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• Tips for measuring the parallelism speed-up in multi-core development.

  - by fnCzar

  I have read many of the good questions and answers around multi-core programming how-tos etc. I am familiar with concurrency, IPC, MPI etc but what I need is advice on how to measure speed-up which will help in making a business case of spending the time to write such code. Please don't answer with "well run it with single-core code then multi-core code and figure out the difference". This is neither a scientific nor a reliable way to measure performance improvement. If you know of tools that will do some of the heavy lifting please mention them. Answers pertaining to methodology will be more fitting but listing tools is ok as well.

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• Visual C++ 9 Linker file size limitation.

  - by Raindog

  It appears that the visual C++ 9 linker has a file allocation algorithm that doubles the size of the file every allocation, so you get 512mb, 1024mb, 2048mb, 4096mb. The problem is that it is using a library that cannot handle files larger 2048MB, and as such crashes with an error such as "cannot read file at is the disk full or write protected". Is there a way to bypass this limitation or otherwise replace the linker with something else that works? A bit of background, I have a code generator that generates a large number of files, ~15k cpp files, I've managed to reduce the number of files to something about 6k to get something that at least completes the linking process, I would like to be able to include all 15k without having to create multiple libs.

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• Does a Perl module know where it is installed?

  - by CoffeeMonster

  Hi Perl programmers, I have started creating a Perl package that contains a default email template. The MANIFEST looks something like: SendMyEmail.pm SendMyEmail/defualt_email.tt Currently I know where the module (and the template) are - but does the module itself know where on disk it is? So could the module find the default template without my help? # This is what I would like to do. package SendMyEmail; sub new { my ($self, $template) = @_; $template ||= $dir_of_SendMyEmail .'/SendMyEmail/default_email.tt'; # ?? } Is there a better way of including a templates text, or a better place to put the template? Any references to CPAN modules that do something similar would be welcome. Thanks in advance.

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• Apache Axis web service clients vs plain SOAP requests.

  - by Andy Pryor

  I'm looking for the best way to consume a Java web service that returns rather large and complex objects. I am currently using Apache Axis clients generated from the wsdl, (using eclipse "generate web service client" tool). We have concerns about performance of this. The service proxy objects are not thread safe, and they are rather heavy to instantiate, 2-3 MB on the JVM. The other alternative is making HTTP connections and building a String SOAP requests. I would have to interpret the response, and build objects from the XML. Would this be a better alternative to the heavy axis objects? I searched for good reading on this, if any one had any links I would greatly appreciate it.

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• Design guidelines for cache mechanism

  - by Delashmate

  Hi All, I got assignment to write design for cache mechanism (this is work assignment, not homework), This is my first time writing a design document, Our program display images for doctors, and we want to reduce the parsing time of the images So we want to save the parsed data in advance (in files or inside database) Currently I have several design key ideas: Handle locks - each shared data structure should be handled, also files Test - add test to verify the data from the cache is equal to the data from the files To decouple the connection to the database- not to call directly to the database Cleanup mechanisem- to delete old files if the cahce directory exceed configurable threshold Support config file Support performance tool in the feature I will also add class diagram, data flow charts, and workflow What do you think I should add to the key ideas? Do you know good link to atricales about design? Thanks in advance, Dan

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