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  • what is value of x for load and store

    - by Kevinniceguy
    This is some challenge On a single processor system, in which load and store are assumed to be atomic, what are all the possible values for x after both threads have completed in the following execution, assuming that x is initialised to O? Hint: you need to consider how this code might be compiled into machine language. for (int i = 0; i < 5; i++) : x = x + 1; for (int j = 0; j < 5; j++) : x = x + 1;

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  • Stopping looping thread in Java

    - by halfwarp
    I'm using a thread that is continuously reading from a queue. Something like: public void run() { Object obj; while(true) { synchronized(objectsQueue) { if(objectesQueue.isEmpty()) { try { objectesQueue.wait(); } catch (InterruptedException e) { e.printStackTrace(); } obj = objectesQueue.poll(); } } // Do something with the Object obj } } What is the best way to stop this thread? I see two options: 1 - Since Thread.stop() is deprecated, I can implement a stopThisThread() method that uses a n atomic check-condition variable. 2 - Send a Death Event object or something like that to the queue. When the thread fetches a death event it exists. I prefer the 1st way, however, I don't know when to call the stopThisThread() method, as something might be on it's way to the queue and the stop signal can arrive first (not desirable). Any suggestions?

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  • perl script grabbing environment vars from "someplace else"

    - by Michael Wilson
    On a Solaris box in a "mysterious production system" I'm running a perl script that references an environment variable. No big deal. The contents of that variable from the shell both pre and post execution are what I expect. However, when reported by the script, it appears as though it's running in some other sub-shell which is clobbering my vars with different values for the duration of the script. Unfortunately I really can't paste the code. I'm trying to get an atomic case, but I'm at my wit's end here. Thoughts?

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  • Arguments to convince to switch from CVS to SVN

    - by ereOn
    Hi, The UNIX department of my company currently uses CVS as source-version control system. They use it in a very strange way: different repositories for development/testing/production code (for the same project), no one tags anything, weird directory architecture, and so on. The system has been set for ages but now, I have an opportunity to organize a meeting where I have to suggest changes. I'd like to make them change from CVS to SVN (Mercurial or Git might be even better, however I can't really recommand using a system I don't know well, and switching to SVN will already be a great step forward). I don't have much experience with CVS so I can't compare them efficiently: I just know it doesn't support atomic operations and that it is deprecated. What killer arguments would you use to convince my collegues to do the switch ? Thank you very much.

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  • Do Managers in Python Multiprocessing module lock the shared data?

    - by AnonProcess
    This Question has been asked before: http://stackoverflow.com/questions/2936626/how-to-share-a-dictionary-between-multiple-processes-in-python-without-locking However I have several doubts regarding the program given in the answer: The issue is that the following step isn't atomic d['blah'] += 1 Even with locking the answer provided in that question would lead to random results. Since Process 1 read value of d['blah'] saves it on the stack increments it and again writes it. In Between a Process 2 can read the d['blah'] as well. Locking means that while d['blah'] is being written or read no other process can access it. Can someone clarify my doubts?

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  • What's a unit test? [closed]

    - by Tyler
    Possible Duplicates: What is unit testing and how do you do it? What is unit testing? I recognize that to 95% of you, this is a very WTF question. So. What's a unit test? I understand that essentially you're attempting to isolate atomic functionality but how do you test for that? When is it necessary? When is it ridiculous? Can you give an example? (Preferably in C? I mostly hear about it from Java devs on this site so maybe this is specific to Object Oriented languages? I really don't know.) I know many programmers swear by unit testing religiously. What's it all about? EDIT: Also, what's the ratio of time you typically spend writing unit tests to time spent writing new code?

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  • Express XPath as an expression tree

    - by 47d_
    If I have an XPath query like NodeA/NodeB[@WIDTH and not(@WIDTH="20")] | NodeC[@WIDTH and not(@WIDTH="20")]/NodeD Is there any API available to visualize this XPath query as a stack of atomic expressions, something like (following is generic) Get results of NodeA, call it "first set" Get results of NodeB from "first set" Filter where [@WIDTH and not(@WIDTH="20")] Filter NodeD, call this "node d for B" Get results of NodeC from "first set" Filter where [@WIDTH and not(@WIDTH="20")] Filter NodeD, call this "node d for C" Combine "node d for B" and "node d for C" I am trying to see if we can convert the XPath expression into custom expression which is close to english and vice versa. If no API is available, what would be the best approach? Thanks in advance.

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  • Is my Perl script grabbing environment variabless from "someplace else"?

    - by Michael Wilson
    On a Solaris box in a "mysterious production system" I'm running a Perl script that references an environment variable. No big deal. The contents of that variable from the shell both pre- and post-execution are what I expect. However, when reported by the script, it appears as though it's running in some other sub-shell which is clobbering my vars with different values for the duration of the script. Unfortunately I really can't paste the code. I'm trying to get an atomic case, but I'm at my wit's end here.

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  • Even lighter than SQLite

    - by Richard Fabian
    I've been looking for a C++ SQL library implementation that is simple to hook in like SQLite, but faster and smaller. My projects are in games development and there's definitely a cutoff point between needing to pass the ACID test and wanting some extreme performance. I'm willing to move away from SQL string style queries, allowing it to be code driven, but I haven't found anything out there that provides SQL like flexibility while also preferring performance over the ACID test. I don't want to go reinventing the wheel, and the idea of implementing an SQL library on my own is quite daunting, even if it's only going to be simple subset of all the calls you could make. I need the basic commands (SELECT, MODIFY, DELETE, INSERT, with JOIN, and WHERE), not data operations (like sorting, min, max, count) and don't need the database to be atomic, or even enforce consistency (I can use a real SQL service while I'm testing and debugging).

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  • Faking a Single Address Space

    - by dsimcha
    I have a large scientific computing task that parallelizes very well with SMP, but at too fine grained a level to be easily parallelized via explicit message passing. I'd like to parallelize it across address spaces and physical machines. Is it feasible to create a scheduler that would parallelize already multithreaded code across multiple physical computers under the following conditions: The code is already multithreaded and can scale pretty well on SMP configurations. The fact that not all of the threads are running in the same address space or on the same physical machine must be transparent to the program, even if this comes at a significant performance penalty in some use cases. You may assume that all of the physical machines involved are running operating systems and CPU architectures that are binary compatible. Things like locks and atomic operations may be slow (having network latency to deal with and all) but must "just work".

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  • MySQL transaction conundrum

    - by David Faitelson
    I need to perform several inserts in a single atomic transaction. For example: start transaction; insert ... insert ... commit; However when MySQL encounters an error it aborts only the particular statement that caused the error. For example, if there is an error in the second insert statement the commit will still take place and the first insert statement will be recorded. Thus, when errors occur a MySQL transaction is not really a transaction. To overcome this problem I have used an error exit handler where I rollback the transaction. Now the transaction is silently aborted but I don't know what was the problem. So here is the conundrum for you: How can I both make MySQL abort a transaction when it encounters an error, and pass the error code on to the caller?

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  • Is a Critical Section around an integer getter and setter redundant?

    - by Tim Gradwell
    Do critical sections inside trivial int accessors actually do anything useful? int GetFoo() { CriticalSection(crit_id); return foo; } void SetFoo(int value) { CriticalSection(crit_id); foo = value; } Is it possible for two threads to be attempting to read and write foo simultaneously? I'd have thought 'no' unless integers are written byte-at-a-time, in which case I can see the use. But I'd have though modern cpus would read/write integers in a single atomic action...

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  • db2 stored procedure. locking / releasing table

    I use a stored procedure to read/update/return certain fields in a journaled as400 table. I want to lock the table first and then release it after the record is updated. I tried tons of stuff, but releasing table is a problem. SP defines and opens cursor, selects record into variables and updates the record. I tried 'begin atomic', then lock table in exclusive mode and then when it's over, it doesn't release. Is there any statement i missing or do i need to compile it with certain parameters? I use a simple create procedure statement in AS400 navigator's sql panel to compile it. Will very appreciate some help with example. Thanks.

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  • Javascript newbie, how to choose between window.URL.createObjectURL() and window.webkitURL.createObjectURL() based on browser

    - by Rohith Raveendran
    From the firefox developer website I know that firefox use objectURL = window.URL.createObjectURL(file); to get url of file type, but in chrome and other webkit browsers we have window.webkitURL.createObjectURL() for detecting url. I don't know how to swap this functions based on browser engines, and I need it to be worked on both browsers (Chrome and firefox) https://developer.mozilla.org/en/DOM/window.URL.createObjectURL

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  • Can we use JCR API over MySQL?

    - by n_mysql
    Apache Jackrabbit (or the JCR API) helps you separate the data store from the data management system. This would mean that every data store provider would have to implement the JCR API for his own data store. The question is JCR implemented for MySQL? Can we use the JCR API over MySQL? I want to truly abstract out where i store my content, so that tomorrow if i don't want to use a relational DB i can swap it out with the file system with ease.

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  • Create a screen like the iPhone home screen with Scrollview and Buttons

    - by Anthony Chan
    Hi, I'm working on a project and need to create a screen similar to the iPhone home screen: A scrollview with multiple pages A bunch of icons When not in edit mode, swipe through different pages (even I started the touch on an icon) When not in edit mode, tap an icon to do something When in edit mode, drag the icon to swap places, and even swap to different pages When in edit mode, tap an icon to remove it Previously I read from several forums that I have to subclass UIScrollview in order to have touch input for the UIViews on top of it. So I subclassed it overriding the methods to handle touches: - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event { //If not dragging, send event to next responder if (!self.dragging) [self.nextResponder touchesBegan:touches withEvent:event]; else [super touchesBegan:touches withEvent:event]; } In general I've override the touchesBegan:, touchesMoved: and touchesEnded: methods similarly. Then in the view controller, I added to following code: - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event { UITouch *touch = [touches anyObject]; UIView *hitView = (UIView *)touch.view; if ([hitView isKindOfClass:[UIView class]]) { [hitView doSomething]; NSLog(@"touchesBegan"); } } - (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event { // Some codes to move the icons NSLog(@"touchesMoved"); } - (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event { NSLog(@"touchesEnded"); } When I run the app, I have the touchesBegan method detected correctly. However, when I tried to drag the icon, the icon just moved a tiny bit and then the page started to scroll. In console, it logged with 2 or 3 "touchesMoved" message only. However, I learned from another project that it should logged tonnes of "touchesMoved" message as long as I'm still dragging on the screen. (I'm suspecting I have the delaysContentTouches set to YES, so it delays a little bit when I tried to drag the icons. After that minor delay, it sends to signal back to the scrollview to scroll through the page. Please correct me if I'm wrong.) So if any help on the code to perform the above tasks would be greatly appreciated. I've stuck in this place for nearly a week with no hope. Thanks a lot.

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  • ggplot2 heatmap : how to preserve the label order ?

    - by Tg
    I'm trying to plot heatmap in ggplot2 using csv data following casbon's solution in http://biostar.stackexchange.com/questions/921/how-to-draw-a-csv-data-file-as-a-heatmap-using-numpy-and-matplotlib the problem is x-label try to re-sort itself. For example, if I swap label COG0002 and COG0001 in that example data, the x-label still come out in sort order (cog0001, cog0002, cog0003.... cog0008). Is there anyway to prevent this ? I want to it to be ordered as in csv file thanks pp

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  • jQuery - Shadowbox rebinding

    - by teepusink
    Hi, How do I bind / initialize Shadowbox to content loaded by jQuery using AJAX? Right now shadowbox works when I first come into the site. However, when I swap the content with a new one loaded through AJAX, these new batch of content doesn't do the shadowbox popup, instead it just redirect to the content. I have Shadowbox.init(shadowbox_conf); in the success but it doesn't seem to do the trick. Thanks, Tee

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  • Single-Stage vs Two-Stage Animation for iPhone Apps?

    - by Devoted
    What are single-state and two-stage animation for rotating an iPhone window? This is the "error" message I get in the Debugger Console (nothing crashes): Using two-stage rotation animation. To use the smoother single-stage animation, this application must remove two-stage method implementations. I was working through the book "Beginning iPhone Development: Exploring the iPhone SDK" by Apress (Dave Mark, Jeff LaMarche) on the Swap Project.

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  • javascript: why to "sign-prefix" a variable?

    - by harald
    hello, i'm currently looking at a little 3rd-party javascript library and i see a lot of "sign-prefixed" variables in it: function_call(+value); i know, that you can swap the sign, if you prefix a variable with '-', but why to prefix something with a '+' -- it doesn't do anything to the value, no? thanks in advance!

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  • Marshal.PtrToStructure (and back again) and generic solution for endianness swapping

    - by cgyDeveloper
    I have a system where a remote agent sends serialized structures (from and embedded C system) for me to read and store via IP/UDP. In some cases I need to send back the same structure types. I thought I had a nice setup using Marshal.PtrToStructure (receive) and Marshal.StructureToPtr (send). However, a small gotcha is that the network big endian integers need to be converted to my x86 little endian format to be used locally. When I'm sending them off again, big endian is the way to go. Here are the functions in question: private static T BytesToStruct<T>(ref byte[] rawData) where T: struct { T result = default(T); GCHandle handle = GCHandle.Alloc(rawData, GCHandleType.Pinned); try { IntPtr rawDataPtr = handle.AddrOfPinnedObject(); result = (T)Marshal.PtrToStructure(rawDataPtr, typeof(T)); } finally { handle.Free(); } return result; } private static byte[] StructToBytes<T>(T data) where T: struct { byte[] rawData = new byte[Marshal.SizeOf(data)]; GCHandle handle = GCHandle.Alloc(rawData, GCHandleType.Pinned); try { IntPtr rawDataPtr = handle.AddrOfPinnedObject(); Marshal.StructureToPtr(data, rawDataPtr, false); } finally { handle.Free(); } return rawData; } And a quick example structure that might be used like this: byte[] data = this.sock.Receive(ref this.ipep); Request request = BytesToStruct<Request>(ref data); Where the structure in question looks like: [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi, Pack = 1)] private struct Request { public byte type; public short sequence; [MarshalAs(UnmanagedType.ByValArray, SizeConst = 5)] public byte[] address; } What (generic) way can I swap the endianness when marshalling the structures? My need is such that the locally stored 'public short sequence' in this example will be little-endian for displaying to the user. I don't want to have to swap the endianness on a structure-specific way. My first thought was to use Reflection, but I'm not very familiar with that feature. Also, I hoped that there would be a better solution out there that somebody could point me towards. Thanks in advance :)

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  • JavaScript question -- onMouseOver event

    - by alex_wang
    Why doesn't this piece of code swap images on mouse-over as intended?: <a href="#" onMouseOver=" if (document.the_image.src == '01.jpg') { document.the_image.src = '02.jpg'; } else if (document.the_image.src == '02.jpg') { document.the_image.src = '03.jpg'; } else { document.the_image.src = '01.jpg'; } "> Some image</a><br>

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  • Would someone mind giving suggestions for this new assembly language?

    - by Noctis Skytower
    Greetings! Last semester in college, my teacher in the Computer Languages class taught us the esoteric language named Whitespace. In the interest of learning the language better with a very busy schedule (midterms), I wrote an interpreter and assembler in Python. An assembly language was designed to facilitate writing programs easily, and a sample program was written with the given assembly mnemonics. Now that it is summer, a new project has begun with the objective being to rewrite the interpreter and assembler for Whitespace 0.3, with further developments coming afterwards. Since there is so much extra time than before to work on its design, you are presented here with an outline that provides a revised set of mnemonics for the assembly language. This post is marked as a wiki for their discussion. Have you ever had any experience with assembly languages in the past? Were there some instructions that you thought should have been renamed to something different? Did you find yourself thinking outside the box and with a different paradigm than in which the mnemonics were named? If you can answer yes to any of those questions, you are most welcome here. Subjective answers are appreciated! hold N Push the number onto the stack copy Duplicate the top item on the stack copy N Copy the nth item on the stack (given by the argument) onto the top of the stack swap Swap the top two items on the stack drop Discard the top item on the stack drop N Slide n items off the stack, keeping the top item add Addition sub Subtraction mul Multiplication div Integer Division mod Modulo save Store load Retrieve L: Mark a location in the program call L Call a subroutine goto L Jump unconditionally to a label if=0 L Jump to a label if the top of the stack is zero if<0 L Jump to a label if the top of the stack is negative return End a subroutine and transfer control back to the caller exit End the program print chr Output the character at the top of the stack print int Output the number at the top of the stack input chr Read a character and place it in the location given by the top of the stack input int Read a number and place it in the location given by the top of the stack Question: How would you redesign, rewrite, or rename the previous mnemonics and for what reasons?

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  • awk or perl file editing & manipulation

    - by paul44
    I have a standard passwd file & a usermap file - which maps unix name (eg jbloggs) with AD account name (eg bloggsjoe) in the format: jbloggs bloggsjoe jsmith smithjohn ... etc. How can I edit the passwd file to swap the original unix name with the AD account name so each line of the passwd file has the AD account name instead. Appreciate any help for a perl learner.

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  • Problem implementing sorting algorithm in C with an array of structs

    - by dilog
    Well here is my little problem, first my code: struct alumn { char name[100]; char lastname[100]; int par; int nota; }; typedef struct alumn alumn; int bubble(alumn **arr, int length) { int i,j; alumn *temp; for (i=0; i<=length-2; i++) { for (j=i+1; j<=length-1;j++) { if ((*arr)[i].nota > (*arr)[j].nota) { temp = arr[i]; arr[i] = arr[j]; arr[j] = temp; } } } } int main(int argc, char **argv) { alumn *alumns; ... here goes some other code ... bubble(&alumns,totalAlumns); return 0; } My problem is that this algorith is not sorting anything. I'm having a hard time doing the swap, i tried everything but nothing works :( . Any help??? struct alumn { char name[100]; char lastname[100]; int par; int nota; }; typedef struct alumn alumn; int bubble(alumn **arr, int length) { int i,j; alumn *temp; for (i=0; i<=length-2; i++) { for (j=i+1; j<=length-1;j++) { if ((*arr)[i].nota > (*arr)[j].nota) { temp = arr[i]; arr[i] = arr[j]; arr[j] = temp; } } } } int main(int argc, char **argv) { alumn *alumns; ... here goes some other code ... bubble(&alumns,totalAlumns); return 0; } My problem is that this algorith is not sorting anything. I'm having a hard time doing the swap, i tried everything but nothing works :( . Any help???

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