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• Efficient questions

  - by rayman

  Hi, I have to manage xml's and Strings in my app. by efficenty and memory saving, is collection(ArrayList) will be much more 'expensive' then array of Strings? another issue is: i could use the content as regular String, or XML.. is working with XML also makes it more 'expensive' ? when i say i expensive i talk about taking system sources. please tell me by any of your exprience if the diffrences are significant? thanks, ray.

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• iphone best practice, how to load multiple high quality images

  - by bennythemink

  Hi guys and girls, I have about 20-ish high quality images (~3840x5800 px) that I need to load in a simple gallery type app. The user clicks a button and the next image is loaded into the UIImageView. I currently use [UIImage imageWithContentsOfFile:] which takes about 6 seconds to load each image in the simulator :( if I use [UIImage imageNamed:] it takes even longer to load but caches the images which means its quicker if the user wishes to see the same images again. But it may cause memory problems later with all that caching crashing my app. I want to know whats the best practice for loading these? I'm experimenting with reducing image file size as much as is possible but I really need them to be high quality image for the purpose of the app (zoomable, etc.). Thanks for any advice

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• Quick way to get an NSDictionary from an XML NSData representation?

  - by dontWatchMyProfile

  I've loaded an XML file as NSData into memory and parse over the elements using NSXMLParser. Although it works, it's a very ugly and hard to maintain code since there are about 150 different elements to parse. I know there are nice third-party solutions, but I want to keep it with the iPhone SDK for purpose of practice and fun. So I thought: Why not convert that XML file into an NSDictionary? Having this, I could use fast enumeration to go over the elements. Or is it just the same amount of ugly code needed to parse and process an XML right away with NSXMLParser? Would I build up an NSDictionary for every found node in the XML and create a huge one, containing the whole structure and data? Or is there an even simpler way?

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• How to access controls collection of dynamically loaded aspx page?

  - by Naasir

  Let's say I have two webforms, A.aspx and B.aspx, where B.aspx contains some simple web controls such as a textbox and a button. I'm trying to do the following: When A.aspx is requested, I want to dynamically call and load B.aspx into memory and output details of all the controls contained in B.aspx. Here is what I tried in the codebehind for A.aspx: var compiledType = BuildManager.GetCompiledType("~/b.aspx"); if (compiledType != null) { var pageB = (Page)Activator.CreateInstance(compiledType); } foreach (var control in pageB.Controls) { //output some details for each control, like it's name and type... } When I try the code above, the controls collection for pageB is always empty. Any ideas on how I can get this to work? Some other important details: both webforms utilize a master page (so the web controls in b.aspx are actually placed within a "content" tag) I've also tried using BuildManager.CreateInstanceFromVirtualPath. No luck.

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• Volatile keyword

  - by Tiyoal

  Say I have two threads and an object. One thread assigns the object: public void assign(MyObject o) { myObject = o; } Another thread uses the object: public void use() { myObject.use(); } Does the variable myObject have to be declared as volatile? I am trying to understand when to use volatile and when not, and this is puzzling me. Is it possible that the second thread keeps a reference to an old object in its local memory cache? If not, why not? Thanks a lot.

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• Programatically determining file "size on disk" in advance

  - by porkchop

  I need to know how big a given in-memory buffer will be as an on-disk (usb stick) file before I write it. I know that unless the size falls on the block size boundary, its likely to get rounded up, e.g. a 1 byte file takes up 4096 bytes on-disk. I'm currently doing this using GetDiskFreeSpace() to work out the disk block size, then using this to calculate the on-disk size like this: GetDiskFreeSpace(szDrive, &dwSectorsPerCluster, &dwBytesPerSector, NULL, NULL); dwBlockSize = dwSectorsPerCuster * dwBytesPerSector; if (dwInMemorySize % dwBlockSize != 0) { dwSizeOnDisk = ((dwInMemorySize / dwBlockSize) * dwBlockSize) + dwBlockSize; } else { dwSizeOnDisk = dwInMemorySize; } Which seems to work fine, BUT GetDiskFreeSpace() only works on disks up to 2GB according to MSDN. GetDiskFreeSpaceEx() doesn't return the same information, so my question is, how else can I calculate this information for drives 2GB? Is there an API call I've missed? Can I assume some hard values depending on the overall disk size?

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• How to handle huge table ?

  - by misha-moroshko

  I would like to display to user a table which contains ~500,000 rows. The table should be calculated based on a file (i.e. the table is known at the beginning, and does not change). I guess that building the HTML text of this table is not a good idea in terms of memory performance. So how can I build such table ? I would like user to be able to scroll the table using a vertical scroll bar. Is it possible to build on the fly only the visible part of the table ? I'm afraid to see delays because of this. Is it a better idea to use server side programming rather than Javascript ? Any advise would be appreciated.

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• Will Emacs --batch run in cron will hang when require user input?

  - by J Spen

  I have a job in crontab that requires emacs --batch but if the file is currently open it requests (s, p, q) to (steal, quit, etc...) which is fine if this file is being edited to not run the script but I want to make sure it kills the cron running script so it's not sitting in the background taking up memory. I have the output set to go to a log file so I can see this happening but no way to tell whether the script was terminated even though asked for user input. Does cron terminate these scripts and how to check the PID to make sure?

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• PHP+MYSQL Server Config

  - by Matias

  Hi guys, I am parsing an XML file with PHP and inserting the rows in a MYSQL database. I am using PHP simplexml_load_files to load the XML and a foreach to loop through the array and insert the rows into my database. It works perfectly fine with small files i am testing, but it comes to reality I need to parse a large 500mb XML file and nothing happens. I was wondering what was the right Php.ini config for this case ? I have a VPS Linux Cent OS, with 256 mb of dedicated Memory and MYSQL 5.0.5. I have also set php memory_limit = 256M (maximum of my server) Any suggestions, similar experiences will be greatly appreciated Thanks

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• Backbone JS central model where all views can use

  - by chchrist

  I am new to backbone js and require js. I use requirejS to organize my backbone code into modules. I don't know if this has any importance to what I want though. I want to have a central model where all my views will have access to. They should be able to get and set values. I don't want to use it as each view model though. I need to keep in memory search options, user status (logged in/out) etc. Any ideas? EDIT Maybe the answer is here? Share resources across different amd modules

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• How can one use multi threading in php applications

  - by Steve Obbayi

  Is there a realistic way of implementing a multi-threaded model in php whether truly or just simulating it. Some time back it was suggested that you can force the operating system to load another instance of the php executable and handle other simultaneous processes. The problem with this is that when the php code finished executing the php instance remains in memory because there is no way to kill it from within php. so if you are simulating several threads you can imagine whats going to happen. So am still looking for a way multi-threading can be done or simulated effectively from within php. Any ideas?

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• Load python module not from a file

  - by user575061

  Hello, I've got some python code in a library that attempts to load a simple value from a module that will exist for the applications that use this library from somemodule import simplevalue Normally, the application that uses the library will have the module file and everything works fine. However, in the unit tests for this library the module does not exist. I know that I can create a temporary file and add that file to my path at runtime, but I was curious if there is a way in python to load something in to memory that would allow the above import to work. This is more of a curiosity, saying "add the module to your test path" is not helpful :P

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• What is the best way to pass server side variables to JavaScript on the client side?

  - by steve_c

  Our application uses a lot of configuration options. Those options need to be reflected on the client side in the form of User preferences, site wide preferences, etc. Currently, we pass server side settings down to the client side in the form of JSON that is stored in custom attributes in the markup for a specific element (and no, our application currently doesn't worry about W3C validation). We then retrieve the data from the custom attribute, and parse it into a JSON object for use in script using jQuery. One drawback to this is referencing attributes on elements from within event handlers. I know this is frowned upon, as it can create circular references, and subsequently memory leaks. I would much prefer to use jQuery's data function, but you can't invoke this from the server side at page render time. What does everyone else do in this type of scenario?

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• Retrieving Large Lists of Objects Using Java EE

  - by hallidave

  Is there a generally-accepted way to return a large list of objects using Java EE? For example, if you had a database ResultSet that had millions of objects how would you return those objects to a (remote) client application? Another example -- that is closer to what I'm actually doing -- would be to aggregate data from hundreds of sources, normalize it, and incrementally transfer it to a client system as a single "list". Since all the data cannot fit in memory, I was thinking that a combination of a stateful SessionBean and some sort of custom Iterator that called back to the server would do the trick. How have you successfully solved this problem in the past?

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• Reason for .Net UI Element Thread-restriction

  - by Charles Bretana

  We know that it is not possible to execute code that manipulates the properties of any UI element from any thread other than the thread the element was instantiated on... My question is why? I remember that when we used COM user interface elements, (in COM/VB6 days), that all UI elements were created using COM classes and co-classes that stored their resources using a memory model referred to as Thread-Local-Storage (TLS) , but as I recall, this was required because of something relaetd to the way COM components were constructed, and should not be relevant to .Net UI elements. Wha's the underlying reason why this restriction still exists? Is it because the underlying Operating System still uses COM-based Win32 API classes for all UI elements, even the ones manipulated in a managed .Net application ??

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• How to get "printer ready bytes" from a source in c#?

  - by luis_villase

  Hey everyone! I'm in a bit of trouble here, hoping you can help a fellow programmer out. I have an application that receives a pointer to raw bytes (plus length and stuff) and sends said raw data to a printer. This is important, I have no choice but to use this method to get any printing done. If I send a raw string, it will print with no problem. However, I need to be able to print formatted text, images, etc. So the thing is... I would like to be able to get printer ready bytes from a given source (maybe a pdf, or html, does not matter as long as it contains formatted text and/or images). It would be like "splitting" the print command like so: a) Open file and read data b) Load printer data into memory c) Send bytes to printer Obviously, I've got a) and c) covered, it's b) the one that's breaking my head. Any thoughts? Thanks in advance for your help.

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• Aptana Studio is opening but not ever closing a python.exe process

  - by SC Ghost

  I am developing a small testing website using Django 1.2 in Aptana Studio build 2.0.4.1268158907. I have a Django project that I test by running the command "runserver 8001" on my project. This command runs the project on a small server that comes with Django. However the problem arises that every time I run this command Aptana opens two instances of the process "python.exe". Upon terminating the command only one of these instances is ended. The other process continues to run and use memory. My server is not online, and the process doesn't seem to do anything that I can find. This happens every time i run the runserver command on my project and therefore more and more python.exe instances will open up through my development period. Any help discovering either the purpose of this extra python.exe or a way to prevent it from opening would be much appreciated.

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• Does a servlet-based stack have significant overheads?

  - by John

  I don't know if it's simply because page-loads take a little time, or the way servlets have an abstraction framework above the 'bare metal' of HTTP, or just because of the "Enterprise" in Jave-EE, but in my head I have the notion that a servlet-based app is inherently adding overhead compared to a Java app which simply deals with sockets directly. Forget web-pages, imagine instead a Java server app where you send it a question over an HTTP request and it looks up an answer from memory and returns the answer in the response. You can easily write a Java socket-based app which does this, you can also do a servlet approach and get away from the "bare metal" of sockets. Is there any measurable performance impact to be expected implementing the same approach using Servlets rather than a custom socket-based HTTP listening app? And yes, I am hazy on the exact data sent in HTTP requests and I know it's a vague question. It's really about whether servlet implementations have lots of layers of indirection or anything else that would add up to a significant overhead per call, where by significant I mean maybe an additional 0.1s or more.

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• Does the Internet make us less good programmers? [closed]

  - by stagas

  With all the information and code available nowadays on the Internet has that diminished our capability of remembering or learning stuff just because we know they're available somewhere out there, just a Google away or a StackOverflow question away? For example I find myself visiting php.net quite often to check the syntax of the same functions over and over again, not because my memory sucks, but I don't feel like keeping the information in me, since I know I'll find it again on the net. And about StackOverflow, isn't the process of figuring things out on your own supposed to improve your programming skills? If the answers are all just clicks away, do we actually learn something or just keep a pointer in our heads where to search for it again when we need it? Your thoughts are welcome. Hope it doesn't shut down as subjective or anything, the answers would be really interesting ;)

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• Windows XP: Have my program run in kernel mode?

  - by Kalamari

  I'm currently learning about the different modes the Windows operating system runs in (kernel mode vs. user mode), device drivers, their respective advantages and disadvantages and computer security in general. I would like to create a practical example of what a faulty device driver that runs in kernel mode can do to the system, by for example corrupting memory used for critical OS-processes. How can I execute my code in kernel mode instead of user mode, directly? Do I have to write a dummy device driver and install it to do this? Where can I read more about kernel and user mode in Windows? I know the dangers of this and will do all of the experiments on a virtual machine running Windows XP only

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• What is the difference between the * and the & operators in c programming?

  - by Wesley

  I am just making sure I understand this concept correctly. With the * operator, I make a new variable, which is allocated a place in memory. So as to not unnecessarily duplicate variables and their values, the & operator is used in passing values to methods and such and it actually points to the original instance of the variable, as opposed to making new copies...Is that right? It is obviously a shallow understanding, but I just want to make sure I am not getting them mixed up. Thanks!

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• Database Compression in Python

  - by user551832

  I have hourly logs like user1:joined user2:log out user1:added pic user1:added comment user3:joined I want to compress all the flat files down to one file. There are around 30 million users in the logs and I just want the latest user log for all the logs. My end result is I want to have a log look like user1:added comment user2:log out user3:joined Now my first attempt on a small scale was to just do a dict like log['user1'] = "added comment" Will doing a dict of 30 million key/val pairs have a giant memory footprint.. Or should I use something like sqllite to store them.. then just put the contents of the sqllite table back into a file?

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• Reason for different segments in Linux on x86

  - by anjruu

  Hey all, So, I know that Linux uses four default segments for an x86 processor (kernel code, kernel data, user code, user data), but they all have the same base and limit (0x00000000 and 0xfffff), meaning each segment maps to the same set of linear addresses. Given this, why even have user/kernel segments? I understand why there should be separate segments for code and data (just due to how the x86 processor deals with the cs and ds registers), but why not have a single code segment and a single data segment? Memory protection is done through paging, and the user and kernel segments map to the same linear addresses anyway. Thanks! anjruu

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• What could cause a returning function to crash? C++

  - by JeanOTF

  So I have been debugging this error for hours now. I writing a program using Ogre3d relevant only because it doesn't load symbols so it doesn't let me stack trace which made finding the location of the crash even harder. So, write before I call a specific function I print out "Starting" then I call the function and immediately after I print "Stopping". Throughout the function I print out letters A-F where F is printed right before the function returns (one line above the last '}') The weird thing is when the crash occurs it is after the 'F' is printed but there is no 'Stopping'. Does this mean that the crash is happening in between somewhere? The only thing I can think of is something going wrong during the deallocation of some of the memory allocated during the function. I've never had anything happen like this, I will keep checking to make sure it's going wrong where I think it is.

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• Strange "cache" effect between client and server

  - by mark

  I use a Socket-based connection between Client and server with ObjectOutputStream. The objects serialized and exchanged have this structure: public class RichiestaSalvataggioArticolo implements Serializable { private ArticoloDati articolo; public RichiestaSalvataggioArticolo(ArticoloDati articolo) { this.articolo = articolo; } @Override public void ricevi(GestoreRichieste gestore) throws Exception { gestore.interpreta(this); } public ArticoloDati getArticolo() { return articolo; } } the issue is that when I try to exchange messages between C/S with incapsulated content very similar (ArticoloDati whom differ only in 2 fields out of 10), the Client sends an ArticoloDati, but the Server receives the previous one. Does the ObjectOutputStream implement some kind of cache or memory between the calls, that fails to recognize that my 2 objects are different because they are very similar?

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