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• Would using a MemoryMappedFile for IPC across AppDomains be faster than WCF/named pipes?

  - by Morten Mertner

  Context: I am loading and executing untrusted code in a separate AppDomain and am currently communicating between the two using WCF (using named pipes as the underlying transport). I am exchanging relatively simple object graphs using a reasonably coarse-grained API, but would like to use a more fine-grained API if it does not cost me performance-wise. I've noticed that 4.0 adds a MemoryMappedFile class (which doesn't need a physical file, so could be entirely memory based). What kind of performance gains could I expect to see (if any) by using this new class? I know that it would take some "infrastructure code" to get the request/response behavior of WCF, but for now I'm only interested in the performance difference.

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• Calling assembly in GCC????

  - by rbr200

  include static inline uint xchg(volatile unsigned int *addr, unsigned int newval) { uint result; asm volatile("lock; xchgl %0, %1" : "+m" (*addr), "=a" (result) : "1" (newval) : "cc"); return result; } Can some one tell me what this code does exactly. I mean I have an idea or the parts of this command. "1" newval is the input, "=a" is to flush out its previous value and update it. "m" is for the memory operation but I am confused about the functionality of this function. What does the "+m" sign do? Does this function do sumthing like m=a; m = newval; return a

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• iphone threading speed up startup of app

  - by BahaiResearch.com

  I have an app that must get data from the Sqlite database in order to display the first element to the User. I have created a domain object which wraps the DB access and is a thread safe singleton. Is this following strategy optimal to ensure the fastest load given the iPhone's file access and memory management capabilities in threaded apps: 1) In the AppDelegate's FinishedLaunching event the very first thing I do is create the domain singleton within a new thread. This will cause the domain object to go to Sqlite and get the data it needs without locking the UI thread. 2) I then call the standard Window methods to add the View and MakeKeyAndVisible etc. Is there an earlier stage in the AppDelegate where I should fire off the thread that creates the Domain Object and accesses Sqlite?

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• Why does UITableViewCell have a contentView property?

  - by mystify

  What's the point of this contentView property? I mean: Why aren't all the subviews just added to self? Let me get that right: Every cell is a view (UITabvleViewCell is a UIView subclass). And this fat view has another fat view with same bounds sitting on top of it, called contentView. That contentView then carries all those other subviews. Now why didn't they save that extra chunk of memory? Is there any genius logic behind this decision? Would love to understand the reason for this.

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• Good Silverlight 4.0 chart / graph component?

  - by Duncan Bayne

  I've been using the Silverlight Toolkit but I'm finding the quality lacking; in particular this memory leak / phantom point bug renders the Chart component completely unusable. Can anyone recommend a good chart / graph component for Silverlight 4.0? I'm looking for one that provides: multiple simultaneous series, both scatter and line multi-select of points configurable tool-tips automatic axis scaling real-time update of data That last point sounds trivial but is tripping up the Silverlight Toolkit Chart; if you rapidly change the axis range, it sometimes leaves phantom points behind in addition to the points it should be displaying.

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• How does Photoshop (Or drawing programs) blit?

  - by user146780

  I'm getting ready to make a drawing application in Windows. I'm just wondering, do drawing programs have a memory bitmap which they lock, then set each pixel, then blit? I don't understand how Photoshop can move entire layers without lag or flicker without using hardware acceleration. Also in a program like Expression Design, I could have 200 shapes and move them around all at once with no lag. I'm really wondering how this can be done without GPU help. I don't think super efficient algorithms could justify that? Thanks

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• segmentation fault

  - by gcc

  int num_arrays; char *p[20]; char tempc; int i=0; do { p[i]=malloc(sizeof(int)); scanf("%s",p[i]); tempc=p[i]; ++i; }while(tempc=='x'); num_arrays=atoi(p[0]); When i write num_arrays=atoi(..),gcc give me segmentation fault or memory stack is exceeded, I don't understand why it behaves like that can anyone explain, why?

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• Android / Java rare and seemingly impossible exception causing force close

  - by Guzba

  Hello all, I have an interesting problem being reported to me from an android application I have published. I have a two-dimensional array that I am iterating through using two for loops like so: for (int i = 0; i < arr.length; ++i) { for (int j = 0; j < arr[i].length; ++j) { if (arr[i][j] != 0) // does stuff } } The problem is, somehow arr[i][j] != 0 is throwing an ArrayIndexOutOfBoundsException. But very rarely. I have thousands of people use the app on a daily basis and get maybe twenty force close reports. Is this something I can't avoid, maybe a problem with the phones memory, etc. or is there something I can do that I haven't thought of yet? Thanks.

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• Garbage Collection Java

  - by simion

  On the slides i am revising from it says the following; Live objects can be identified either by maintaining a count of the number of references to each object, or by tracing chains of references from the roots. Reference counting is expensive – it needs action every time a reference changes and it doesn’t spot cyclical structures, but it can reclaim space incrementally. Tracing involves identifying live objects only when you need to reclaim space – moving the cost from general access to the time at which the GC runs, typically only when you are out of memory. I understand the principles of why reference counting is expensive but do not understand what "doesn’t spot cyclical structures, but it can reclaim space incrementally." means. Could anyone help me out a little bit please? Thanks

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• Simplest one-to-many Map case in Hibernate doesn't work in MySQL

  - by Malvolio

  I think this is pretty much the simplest case for mapping a Map (that is, an associative array) of entities. @Entity @AccessType("field") class Member { @Id protected long id; @OneToMany(cascade = CascadeType.ALL, fetch=FetchType.LAZY) @MapKey(name = "name") private Map<String, Preferences> preferences = new HashMap<String, Preferences>(); } @Entity @AccessType("field") class Preferences { @ManyToOne Member member; @Column String name; @Column String value; } This looks like it should work, and it does, in HSQL. In MySQL, there are two problems: First, it insists that there be a table called Members_Preferences, as if this were a many-to-many relationship. Second, it just doesn't work: since it never populates Members_Preferences, it never retrieves the Preferences. [My theory is, since I only use HSQL in memory-mode, it automatically creates Members_Preferences and never really has to retrieve the preferences map. In any case, either Hibernate has a huge bug in it or I'm doing something wrong.]

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• OpenGL texture not showing up on some computers, problem with auxDIBImageLoad?

  - by CptanPanic

  I have a simple openGL GUI that has uses a bmp as a texture. The problem is on some computers the texture doesn't show up. But on ones with newer OpenGL drivers it works. How can I make it more compatible. I think the problem may be with auxDIBImageLoad. When I inspect the result, I see the x,y correct, but the data pointer points to memory bank with all zeros. What could be wrong?

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• Get license file from a folder in C# project

  - by daft

  I have a license file that I need to access at runtime in order to create pdf-files. After I have created the in memory pdf, I need to call a method on that pdf to set the license, like this: pdf.SetLicense("pathToLicenseFileHere"); The license file is located in the same project as the.cs-file that creates the pdf, but is in a separate folder. I cannot get this simple thing to behave correctly, which makes me a bit sad, since it really shouldn't be that hard. :( I try to set the path like this: string path = @"\Resources\File.lic"; But it just isn't working out for me.

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• How can I avoid setting some columns if others haven't changed, when working with Linq To SQL?

  - by Patrick Szalapski

  In LINQ to SQL, I want to avoid setting some columns if others haven't changed? Say I have dim row = (From c in dataContext.Customers Where c.Id = 1234 Select c).Single() row.Name = "Example" ' line 3 dataContext.SubmitChanges() ' line 4 Great, so LINQ to SQL fetches a row, sets the name to "Example" in memory, and generates an update SQL query only when necessary--that is, no SQL will be generated if the customer's name was already "Example". So suppose on line 3, I want to detect if row has changed, and if so, set row.UpdateDate = DateTime.Now. If row has not changed, I don't want to set row.UpdateDate so that no SQL is generated. Is there any good way to do this?

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• Implementing Transparent Persistence

  - by Jules

  Transparent persistence allows you to use regular objects instead of a database. The objects are automatically read from and written to disk. Examples of such systems are Gemstone and Rucksack (for common lisp). Simplified version of what they do: if you access foo.bar and bar is not in memory, it gets loaded from disk. If you do foo.bar = baz then the foo object gets updated on disk. Most systems also have some form of transactions, and they may have support for sharing objects across programs and even across a network. My question is what are the different techniques for implementing these kind of systems and what are the trade offs between these implementation approaches?

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• Where is the chink in Google Chrome's armor?

  - by kudlur

  While browsing with Chrome, I noticed that it responds extremely fast (in comparison with IE and Firefox on my laptop) in terms of rendering pages, including JavaScript heavy sites like gmail. This is what googlebook on Chrome has to say tabs are hosted in process rather than thread. compile javascript using V8 engine as opposed to interpreting. Introduce new virtual machine to support javascript heavy apps introduce "hidden class transitions" and apply dynamic optimization to speed up things. Replace inefficient "Conservative garbage colllection" scheme with more precise garbage collection scheme. Introduce their own task scheduler and memory manager to manage the browser environment. All this sounds so familiar, and Microsoft has been doing such things for long time.. Windows os, C++, C# etc compilers, CLR, and so on. So why isn't Microsoft or any other browser vendor taking Chrome's approach? Is there a flaw in Chrome's approach? If not, is the rest of browser vendor community caught unaware with Google's approach?

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• Problem with running a program from flashdrive

  - by rajivpradeep

  I have a USB drive with two partitions in it, one hidden and one normal. I have an application which swaps the memory and runs the flash application in hidden zone. The problem is that the application works fine on Windows 7 and when run on Win XP, it swaps the partitions but doesn't run the flash applications but just keeps running in the background. I can see it in task manager. But, when I copy the application to desktop and run, it runs with no glitch. I was facing the same problem on Win 7 too, but it was running as required when I ran it using "Run in XP mode" and then I applied a SHIM and is running since then as required. The application is built using VC++ 2008. does anyone know the solution?

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• .net Compiler Optimizations

  - by Dested

  I am writing an application that I need to run at incredibly low speeds. The application creates and destroys memory in creative ways throughout its run, and it works just fine. I am wondering what compiler optimizations occur so I can try to build to that. One trick off hand is that the CLR handles arrays much faster than lists, so if you need to handle a ton of elements in a List, you may be better off calling ToArray() and handling it rather than calling ElementAt() again and again. I am wondering if there is any sort of comprehensive list for this kind of thing, or maybe the SO community can create one :-)

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• What is the '^' in Objective-C

  - by Chris Paterson

  What does the '^' mean in the code below? @implementation AppController - (IBAction) loadComposition:(id)sender { void (^handler)(NSInteger); NSOpenPanel *panel = [NSOpenPanel openPanel]; [panel setAllowedFileTypes:[NSArray arrayWithObjects: @"qtz", nil]]; handler = ^(NSInteger result) { if (result == NSFileHandlingPanelOKButton) { NSString *filePath = [[[panel URLs] objectAtIndex:0] path]; if (![qcView loadCompositionFromFile:filePath]) { NSLog(@"Could not load composition"); } } }; [panel beginSheetModalForWindow:qcWindow completionHandler:handler]; } @end === I've searched and searched - is it some sort of particular reference to memory?

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• Anyway to find out the current Windows is in lock mode?

  - by David.Chu.ca

  I have a windows application written in VS 2005. The application makes queries against to sql database in a timer cycle every 2 minutes. If there any data changes, the window will be refreshed with new data. If the user leaves the window, the windows will be automatically locked after a while. There is no sense to keep querying data in ever 2 minutes when the windows is locked; therefore I would like to stop the query when lock is on so that the network data trafic will be reduced and also saves the current windows resources such as memory and CPUs. I am not sure if there is any way to find out the current windows is locked? Not sure if there is any Windows APIs for this purpose if no .Net classes available? My project is in .Net 2.0 and all users are in Windows XP.

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• Unit testing with serialization mock objects in C++

  - by lhumongous

  Greetings, I'm fairly new to TDD and ran across a unit test that I'm not entirely sure how to address. Basically, I'm testing a couple of legacy class methods which read/write a binary stream to a file. The class functions take a serializable object as a parameter, which handles the actual reading/writing to the file. For testing this, I was thinking that I would need a serialization mock object that I would pass to this function. My initial thought was to have the mock object hold onto a (char*) which would dynamically allocate memory and memcpy the data. However, it seems like the mock object might be doing too much work, and might be beyond the scope of this particular test. Is my initial approach correct, or can anyone think of another way of correctly testing this? Thanks!

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• Application disappears after starting - C++ linking managed code dll

  - by Axarydax

  Hello, we have a problem with our applications. We have recently upgraded our toolchain to Visual Studio 2010 and friends, it all works fine on Windows Vista + Windows 7 developer machines and Windows 7 customer machines. (all x86) Today we did a first installation to a client PC running Windows XP SP3 x86, and all applications linking managed code dll do not work. After starting the .exe seemingly nothing happens, no window pops up, no memory gets eaten, no task shows in task manager, nothing, nada. Event log is empty, everything is just as if the application returned to the OS right after the start. I am at loss about this, I really don't know how should I start even debugging this problem. I don't want to install VS2010 and everything onto a Windows XP box, I'd like to try something less time intensive first. This all is happening just to native C++ apps that link managed c++ DLL. Pure managed C# apps do work. Pure native C++ apps do work.

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• C++ containers on classes, returning pointers

  - by otneil

  Hello, I'm having some trouble to find the best way to accomplish what I have in mind due to my inexperience. I have a class where I need to a vector of objects. So my first question will be: is there any problem having this: vector< AnyType container* and then on the constructor initialize it with new (and deleting it on the destructor)? Another question is: if this vector is going to store objects, shouldn't it be more like vector< AnyTipe* so they could be dynamically created? In that case how would I return an object from a method and how to avoid memory leaks (trying to use only STL)?

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• How to make a table view which is not the full width of the screen?

  - by mystify

  For some strange reason, UITableView resizes my cells to 320 width no matter how I set the frame for the UITableView object. Even if I go in later and resize the cell back to 250, UITableView seems to resize it again to 320 some time. Is there some property or method that must be set / called additionally to get that right? However, I can add my contents in a way that it looks like 250 width, but my whole layouting code is a big mess since I can't rely on the cell frame width which is "wrong". Also it seems like a big waste of memory since the bitmaps in the layer trees are nonsenseless 320 width instead of 250, even though the frame of the UITableView is not 320 width.

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• size of an image

  - by Mike

  From times to times I have to know the width and height of images. I am using the following code: UIImage *imageU = [UIImage imageWithContentsOfFile:[[[NSBundle mainBundle] resourcePath] stringByAppendingPathComponent:@"myImage.png"]]; CGFloat imageW = CGImageGetWidth(imageU.CGImage); CGFloat imageH = CGImageGetHeight(imageU.CGImage); My question is that if it is there any other way to know the width and height of an image, in pixels, without having to load the image on a variable, that's probably consuming memory. Can the dimensions be read from the file directly without loading the whole image? thanks.

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• Get a value from hashtable by a part of its key

  - by htf

  Hi. Say I have a Hashtable<String, Object> with such keys and values: apple => 1 orange => 2 mossberg => 3 I can use the standard get method to get 1 by "apple", but what I want is getting the same value (or a list of values) by a part of the key, for example "ppl". Of course it may yield several results, in this case I want to be able to process each key-value pair. So basically similar to the LIKE '%ppl%' SQL statement, but I don't want to use a (in-memory) database just because I don't want to add unnecessary complexity. What would you recommend?

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