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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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• 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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• 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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• Returning the address of local or temporary variable

  - by Dave18

  #include <iostream> int& foo() { int i = 6; std::cout << &i << std::endl; return i; } int main() { int i = foo(); std::cout << &i << std::endl; } I know it doesn't return the address of local variable so that is why the warning but why does it still works and assign the variable i in main() to '6'? How does it only return the value if the variable the was removed from stack memory?

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• Differences between extension methods in C#3 & 4

  - by Buh Buh

  I think I remember reading a long time ago that in C#3 extension methods could only be applied to primitive types and interfaces; and that in C#4 they could be used to extend any type. This doesn't seam to match up with what I am seeing now and I am finding it difficult to find this documented. Is there any truth to this or did my memory make it all up? What are the rules relating to which types can be extended? Are there any differences between C# 3 and 4?

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• C++ DWORD* to BYTE*

  - by NomeSkavinski

  My issue, i am trying to convert and array of dynamic memory of type DWORD to a BYTE. Fair enough i can for loop through this and convert the DWORD into a BYTE per entry. But is their a faster way to do this? to take a pointer to DWORD data and convert the whole piece of data into a pointer to BYTE data? such as using a memcpy operation? I feel this is not possible, im not requesting an answer just an experienced opinion on my approach, as i have tried testing both approaches but seem to fail getting to a solution on my second solution. Thanks for any input, again no answers just a point in the right direction. Nor is this a homework question, i felt that had to be mentioned.

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• Forcing an app to run single core only?

  - by Kevin

  I have this strange issue with some third party DLL's. The third party provider references some open source DLL's that have a memory exception whenever I try to use a certain method. This issue does not appear when the app is run on a single core machine, but obviously we cannot assume a user will have that. Is there a way to force an app, or even better yet a referenced DLL to run on a single core? Any other way to possibly fix this? Getting the third party to rebuild the OS dll's is apparently out of the question (its a bit of a sore spot with me currently :) ) so I have to handle it myself or just forget about providing this functionality.

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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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• How does the WP7 Pivot control dynamically load pivot items?

  - by mztan

  IIRC, the Pivot control only loads a child PivotItem if it is the currently shown child. I would then guess that the previously seen child is also somehow unloaded, presumably still stored in memory, but hidden from the UI. What I'm wondering is, how does the Pivot control dynamically load/unload a child control, and can that behavior be imitated within a custom UserControl? As for unloading, is it as simple as collapsing the previous child's visibility, or is something trickier going on? That is to say, supposing I use my own UserControl like: <my:CustomUserControl> <TextBlock x:Name="_textBlock" Text="wait for it ..." /> </my:CustomUserControl> Normally, the child TextBlock is instantiated when the surrounding PhoneApplicationPage is instantiated, via InitializeComponent and all that. Is there any way to postpone this behavior and load the child programmatically?

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• Intercommunication between Java Chat Servers

  - by Pravingate

  I have a application in which I am using socket programming , having this(image) scenario. Where number of clients will try to connect Broadcast server. Now here I am managing load through LVS(Load balancer). so as a example shown in image, suppose 200 clients will wish to login for broadcast they will be distributed as 100 users on server 1 and another 100 users on server 2.clients will get connected to servers using TCP connection. Now I am maintaining user information on server side in arraylist which will be stored in heap memory,Now the problem is if client wish to broadcast to all logged in users, but that particular client is logged in server 1. and so client will not be able to broadcast another 100 users from server 2. Because both ther servers are unaware about each others state. please suggest to solve this scenario by whatever means you want.

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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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• 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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• 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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• 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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• Efficient way to access a mapping of identifiers in Python

  - by sixbelo

  I am writing an app to do a file conversion and part of that is replacing old account numbers with a new account numbers. Right now I have a CSV file mapping the old and new account numbers with around 30K records. I read this in and store it as dict and when writing the new file grab the new account from the dict by key. My question is what is the best way to do this if the CSV file increases to 100K+ records? Would it be more efficient to convert the account mappings from a CSV to a sqlite database rather than storing them as a dict in memory?

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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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• 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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• Which destructor is called when in C++?

  - by BastiBechtold

  I am hunting memory leaks in a program. I narrowed it down to some destructors not being called. However, I can't figure out why: class CMain : public CList { public: CMain(); virtual ~CMain(); ... } class CList : public CProc { public: CList(); virtual ~CList(); ... } CMain gets deallocated just fine, but ~CList() is never called. All parent classes of CList have virtual destructors, too. Do you have any hints about why the destructor for CList is never called?

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• Offline navigation software for Android - what is out there?

  - by Ted

  Im looking for navigation software for the Android platform and I have a few requirements: Offline maps. The maps should be stored on the device/memory card so no Internet-connection is required There should be some way to interact with the application "through code"; sending route requests, getting current location perhaps, bringing app to foreground/background, etc. An API so it can be controlled from another application. No monthly fees The only one I found so far to match the above is Sygic Navigation. However, I havent yet been able to communication with the app even though they say that it can be done. Still investigating that...

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• node.js storing gamestate, how?

  - by expressnoob

  I'm writing a game in javascript, and to prevent cheating, i'm having the game be played on the server (it's a board game like a more complicated checkers). Since the game is fairly complex, I need to store the gamestate in order to validate client actions. Is it possible to store the gamestate in memory? Is that smart? Should I do that? If so, how? I don't know how that would work. I can also store in redis. And that sort of thing is pretty familiar to me and requires no explanation. But if I do store in redis, the problem is that on every single move, the game would need to get the data from redis and interpret and parse that data in order to recreate the gamestate from scratch. But since moves happen very frequently this seems very stupid to me. What should I do?

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• C/C++ function definitions without assembly

  - by Jack

  Hi, I always thought that functions like printf() are in the last step defined using inline assembly. That deep into stdio.h is burried some asm code that actually tells CPU what to do. Something like in dos, first mov bagining of the string to some memory location or register and than call some int. But since x64 version of Visual Studio doesent support inline assembler at all, it made me think that there are really no assembler-defined functions in C/C++. So, please, how is for example printf() defined in C/C++ without using assembler code? What actually executes the right software interrupt? Thanks.

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• Speed of running a test suite in Rails

  - by Milan Novota

  I have 357 tests (534 assertions) for my app (using Shoulda). The whole test suite runs in around 80 seconds. Is this time OK? I'm just curious, since this is one of my first apps where I write tests extensively. No fancy stuff in my app. Btw.: I tried to use in memory sqlite3 database, but the results were surprisingly worse (around 83 seconds). Any clues here? I'm using Macbook with 2GB of RAM and 2GHz Intel Core Duo processor as my development machine.

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• C# array problem

  - by user208080

  Hi there. I am a newbie in C# and here are 2 questions: I have a 2d array a[3,3], how can I express one dimension as a new array and pass to some function. i.e. int[,] a = new int[3,3]; a[0,0] = 1; ... string b = concatenate(a[0]); // where concatenate is a function take a one dimension array as param Can I create a 65000x65000 array with C#? I got some "out of memory" error. Thanks in advance.

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• Heap Error in C++

  - by BobAlmond

  Dear all, I'm a beginner programmer in C++. Recently, I'm working on image processing thing using C++. but I have some problem that I want to ask. Suppose I have some code as follow: for (int i=0;i<100000;i++) { int * a = new int[10000]; //do something delete [] a; } When I executed that code, I receive runtime error, Heap Error... Is there anything wrong with that code, I mean, can I allocate memory and release it in the same loop? Thanks in advance...

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• How to kill slave kernel securely?

  - by Alexey Popkov

  Hello, LinkClose[link] "does not necessarily terminate the program at the other end of the connection" as it is said in the Documentation. Is there a way to kill the process of the slave kernel securely? EDIT: In really I need a function in Mathematica that returns only when the process of the slave kernel has already killed and its memory has already released. Both LinkInterrupt[link, 1] and LinkClose[link] do not wait while the slave kernel exits. At this moment the only such function is seemed to be killProc[procID] function I had showed in one of answers at this page. But is there a built-in analog?

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