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  • Are indivisible operations still indivisible on multiprocessor and multicore systems?

    - by Steve314
    As per the title, plus what are the limitations and gotchas. For example, on x86 processors, alignment for most data types is optional - an optimisation rather than a requirement. That means that a pointer may be stored at an unaligned address, which in turn means that pointer might be split over a cache page boundary. Obviously this could be done if you work hard enough on any processor (picking out particular bytes etc), but not in a way where you'd still expect the write operation to be indivisible. I seriously doubt that a multicore processor can ensure that other cores can guarantee a consistent all-before or all-after view of a written pointer in this unaligned-write-crossing-a-page-boundary situation. Am I right? And are there any similar gotchas I haven't thought of?

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  • Resetting Objects vs. Constructing New Objects

    - by byronh
    Is it considered better practice and/or more efficient to create a 'reset' function for a particular object that clears/defaults all the necessary member variables to allow for further operations, or to simply construct a new object from outside? I've seen both methods employed a lot, but I can't decide which one is better. Of course, for classes that represent database connections, you'd have to use a reset method rather than constructing a new one resulting in needless connecting/disconnecting, but I'm talking more in terms of abstraction classes. Can anyone give me some real-world examples of when to use each method? In my particular case I'm thinking mostly in terms of ORM or the Model in MVC. For example, if I would want to retrieve a bunch of database objects for display and modify them in one operation.

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  • Linux and I/O completion ports?

    - by someguy
    Using winsock, you can configure sockets or seperate I/O operations to "overlap". This means that calls to perform I/O are returned immediately, while the actual operations are completed asynchronously by separate worker threads. Winsock also provides "completion ports". From what I understand, a completion port acts as a multiplexer of handles (sockets). A handle can be demultiplexed if it isn't in the middle of an I/O operation, i.e. if all its I/O operations are completed. So, on to my question... does linux support completion ports or even asynchronous I/O for sockets?

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  • HSQLDB and in-memory files

    - by lewap
    Is it possible to setup HSQLDB in a way, so that the files with the db information are written into memory instead of using actual files? I want to use hsqldb to export some data structures together with hibernate mappings. Is is, however, not possible to write temporary files, so that I need to generate the files in-memory and return a stream with their contents as a response. Setting hsqldb to use nio seems not to be a solution, because there is no way to get hold of those files before they get written onto the filesystem. What I'm thinking of is a protocol handler for hsqldb, but I didn't find a suitable solution yet. Just to describe in other words: A hack solution would be to pass hsqldb a stream or several streams. It would then during its operation write data into those streams. After all data is written, the user of the db could then use those streams to send it back over the network.

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  • About the fix for the interference between Company mode and Yasnippet

    - by janoChen
    Emacs wiki says: Company does interfere with Yasnippet’s native behaviour. Here’s a quick fix: http://gist.github.com/265010 The code is the following: (define-key company-active-map "\t" 'company-yasnippet-or-completion) (defun company-yasnippet-or-completion () (interactive) (if (yas/expansion-at-point) (progn (company-abort) (yas/expand)) (company-complete-common))) (defun yas/expansion-at-point () "Tested with v0.6.1. Extracted from `yas/expand-1'" (first (yas/current-key))) I placed that code in my .emacs and the following message appeared: Warning (initialization): An error occurred while loading `c:/Documents and Settings/Alex.AUTOINSTALL.001/Application Data/.emacs.elc': Symbol's value as variable is void: company-active-map To ensure normal operation, you should investigate and remove the cause of the error in your initialization file. Start Emacs with the `--debug-init' option to view a complete error backtrace. Do I have to place the fix code inside a YASnippet's .el file? or in my .emacs (which throws me an error)?

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  • How do I prevent an ASP.NET MVC deployment on IIS 6.0, using wildcard mapping, from attempting to ha

    - by Rob
    As noted by the title, what is the best way to configure an IIS 6.0 deployment of an ASP.NET MVC application such that connections to hidden shares are ignored? The application in question is using wildcard mapping to allow for clean URLs since we are planning on upgrading to IIS 7.0 in the near future and we are also handling the caching and compression issues with a custom library so we would like to avoid turning wildcard mapping off unless absolutely necessary. Below is a one of the errors from the application to give you an example of what we are seeing. -------------------------------------------------------------------------------- System.Web.HttpException -------------------------------------------------------------------------------- Time Stamp - 03 Mar 2010, 08:11:44 Path - N/A, Internal Server Operation Message - The controller for path '/C$' could not be found or it does not implement IController. Target Site - System.Web.Mvc.IController GetControllerInstance(System.Type) Stack Trace - at System.Web.Mvc.DefaultControllerFactory.GetControllerInstance(Type controllerType) at System.Web.Mvc.DefaultControllerFactory.CreateController(RequestContext requestContext, String controllerName) at System.Web.Mvc.MvcHandler.ProcessRequest(HttpContextBase httpContext) at System.Web.Mvc.MvcHandler.ProcessRequest(HttpContext httpContext) at System.Web.Mvc.MvcHandler.System.Web.IHttpHandler.ProcessRequest(HttpContext httpContext) at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) --------------------------------------------------------------------------------

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  • PHP: deleting files – permission denied – chmod?

    - by mathiregister
    hi guys, i want to delete files from a directory via php. Somehow my php_errorlog always tells me: [06-Jun-2010 19:38:46] PHP Warning: chmod() [function.chmod]: Operation not permitted in /Users/myname/htdocs/ if ($_POST) { echo "yeah!!!"; print count($_POST['deletefiles']); chmod($path, 0777); //server rights foreach ($_POST['deletefiles'] as $value) { print $value; unlink($path .'/' . $value); } //chmod($path, 0666); //server rights } what am I doing wrong? Thank you

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  • c# multi threaded file processing

    - by user177883
    There is a folder that contains 1000 of small text files. I aim to parse and process all of them while more files are being populated in to the folder. My intention is to multithread this operation as the single threaded prototype took 6 minutes to process 1000 files. I like to have reader and writer thread(s) as following : while the reader thread(s) are reading the files, I d like to have writer thread(s) to process them. Once the reader is started reading a file, I d like to mark it as being processed, such as by renaming it, once it s read, rename it to completed. How to approach such multithreaded application ? Is it better to use a distributed hash table or a queue? Which data structure to use that would avoid locks? Would you have a better approach to this scheme that you like to share?

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  • TSQL ID generation

    - by Markus
    Hi. I have a question regarding locking in TSQL. Suppose I have a the following table: A(int id, varchar name), where id is the primary key, but is NOT an identity column. I want to use the following pseudocode to insert a value into this table: lock (A) uniqueID = GenerateUniqueID() insert into A values (uniqueID, somename) unlock(A) How can this be accomplished in terms of TSQL? The computation of the next id should be done with the table A locked in order to avoid other sessions to do the same operation at the same time and get the same id.

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  • Merging MySQL Structure and Data

    - by Shahid
    I have a MySQL database running on a deployment machine which also contains data. Then I have another MySQL database which has evolved in terms of STRUCTURE + DATA for some time. I need a way to merge the changes (ONLY) for both structure and data to the DB in deployment machine without disturbing the existing data. Does anyone know of a tool available which can do this safely. I have had a look at a few comparison tools but I need a tool which can automate the merge operation. Note also that most of the data in the tables is in BINARY so I can't use many file comparison tools. Does any one know of a solution to this? thanks

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  • How to correctly stop thread which is using Control.Invoke

    - by codymanix
    I tried the following (pseudocode) but I always get a deadlock when Iam trying to stop my thread. The problem is that Join() waits for the thread to complete and a pending Invoke() operation is also waiting to complete. How can I solve this? Thread workerThread = new Thread(BackupThreadRunner); volatile bool cancel; // this is the thread worker routine void BackupThreadRunner() { while (!cancel) { DoStuff(); ReportProgress(); } } // main thread void ReportProgress() { if (InvokeRequired) { Invoke(ReportProgress); } UpdateStatusBarAndStuff(); } // main thread void DoCancel() { cancel=true; workerThread.Join(); }

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  • Problems crossing the boundary between protected greasemonkey execution space and the unsafeWindow l

    - by Chilly
    Hi guys. Here is my problem: I've registered some callbacks into a Yahoo event driven webpage (betfair.com market views) and am trapping the betsPlaced events with a handler. So far so simple. Next stage is to get the event back into greasemonkey land, and while I know that from greasemoney space you can call unsafeWindow.stuff, there is no reverse operation (by design). So if I want to send the contents of the event over, say, a cometd queue, my carefully set up jquery, greasemonkey, YUI2, betfair environment fails by telling me that unsafeWindow processes cant call GM_ajax stuff. This is obviously safe and sane, but it basically stops me doing what I want to do. Has anyone tried doing this (ignore the cometd stuff, just general ajax calls) and succeeded? I've had a look at pages like this: http://wiki.greasespot.net/0.7.20080121.0%2B_compatibility but it doesnt appear to work for all the calls.

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  • Atoms and references

    - by StackedCrooked
    According to the book Programming Clojure refs manage coordinated, synchronous changes to shared state and atoms manage uncoordinated, synchronous changes to shared state. If I understood correctly "coordinated" implies multiple changes are encapsulated as one atomic operation. If that is the case then it seems to me that coordination only requires using a dosync call. For example what is the difference between: (def i (atom 0)) (def j (atom 0)) (dosync (swap! i inc) (swap! j dec)) and: (def i (ref 0)) (def j (ref 0)) (dosync (alter i inc) (alter j dec))

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  • Where will this AsyncTask run?

    - by Binoy Babu
    Say I have this code in the AlertDialog.Builder(context) of my application. The question is in which Thread will it run? final Thread myPrettyOperation = new Thread() { @Override public void run() { //Do some really long operation. } }; class MyPrettyTask extends AsyncTask<Void, Integer, Boolean> { protected Boolean doInBackground( Void... voids) { myPrettyOperation.start(); return true; } protected void onProgressUpdate( Integer... progress) { } protected void onPostExecute(Boolean result) { } } new MyPrettyTask().execute();

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  • Can I override DropLocation target to avoid network latency?

    - by Chad
    In Team Build 2008, the Drop Location for a build is no longer specified in the .proj file, and instead is stored in the database and maintained in the GUI tool. The GUI tool only accepts a network path as a drop location (i.e. \\server\share) and will not accept a local path. Our build server also hosts the dropped files, so it seems that forcing a file copy operation to go through the network share introduces a lot of lag time when copying a large number of files. I would like to override this feature so that I can specify a local directory for drop location, but I can't figure out how.

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  • Problem with sendkeys in .NET

    - by AvidProgrammer
    I have a windows application, where I am using send keys to navigate from one window to another. My send key sequence is like activating another window with in my app, and sending key strokes to that window. But the key strokes I am sending is getting updated in the same window where I am activating the other window. But after few key strokes it is going to the other window. Seems like synchonization issue with send keys. Is there a way to specify the operation of the current send key is finished, before sending the next sendkey.

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  • How to Redirect a Python Console output to a QTextBox

    - by krishnanunni
    Hello, I'm working on developing a GUI for the recompilation of Linux kernel. For this I need to implement 4-5 Linux commands from Python. I use Qt as GUI designer. I have successfully implemented the commands using os.system() call. But the output is obtained at the console. The real problem is the output of command is a listing that takes almost 20-25 min continuous printing. How we can transfer this console output to a text box designed in Qt. Can any one help me to implement the setSource() operation in Qt using source as the live console outputs.

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  • When are dynamically loaded NIBs assigned frames and bounds data?

    - by thebossman
    In one of my UIViewControllers, I am calling initWithNibName:bundle: for several other UIViewControllers. I am grabbing the view property in each of those dynamically created controllers and placing them, one after the other, in my parent view. For instance, the y offset of viewControllerB should be equal to the height of viewControllerA. The y offset of viewControllerC should be equal to the height of viewControllerB, and so on. I am initalizing these nibs in viewDidLoad, yet none of them have any meaningful bounds or frame properties. The sizes and positions of each are all zero. Where is the 'correct' place to do this type of operation so that I can grab meaningful values from these properties?

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  • Binding a Java Integer to JavaScriptEngine doesn't work

    - by rplantiko
    To see how binding Java objects to symbols in a dynamic language works, I wrote the following spike test, binding a java.lang.Integer to the symbol i to be changed in JavaScript: @Test public void bindToLocalVariable() throws ScriptException { javax.script.ScriptEngineManager sem = new javax.script.ScriptEngineManager(); javax.script.ScriptEngine engine = sem.getEngineByName("JavaScript"); Integer i = new Integer(17); engine.put( "i", i ); engine.eval( "i++;" ); // Now execute JavaScript assertEquals( 18, i.intValue() ); } Unfortunately, I get a failure. java.lang.AssertionError: expected:<18> but was:<17> JavaScript knows the symbol i (otherwise it would have thrown a ScriptException which is not the case), but the increment operation i++ is not performed on the original Integer object. Any explanations?

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  • Repeating a List in Scala

    - by Ralph
    I am a Scala noob. I have decided to write a spider solitaire solver as a first exercise to learn the language and functional programming in general. I would like to generate a randomly shuffled deck of cards containing 1, 2, or 4 suits. Here is what I came up with: val numberOfSuits = 1 (List["clubs", "diamonds", "hearts", "spades"].take(numberOfSuits) * 4).take(4) which should return List["clubs", "clubs", "clubs", "clubs"] List["clubs", "diamonds", "clubs", "diamonds"] List["clubs", "diamonds", "hearts", "spades"] depending on the value of numberOfSuits, except there is no List "multiply" operation that I can find. Did I miss it? Is there a better way to generate the complete deck before shuffling? BTW, I plan on using an Enumeration for the suits, but it was easier to type my question with strings. I will take the List generated above and using a for comprehension, iterate over the suits and a similar List of card "ranks" to generate a complete deck.

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  • C# socket blocking behavior

    - by Gearoid Murphy
    My situation is this : I have a C# tcp socket through which I receive structured messages consisting of a 3 byte header and a variable size payload. The tcp data is routed through a network of tunnels and is occasionally susceptible to fragmentation. The solution to this is to perform a blocking read of 3 bytes for the header and a blocking read of N bytes for the variable size payload (the value of N is in the header). The problem I'm experiencing is that occasionally, the blocking receive operation returns a partial packet. That is, it reads a volume of bytes less than the number I explicitly set in the receive call. After some debugging, it appears that the number of bytes it returns is equal to the number of bytes in the Available property of the socket before the receive op. This behavior is contrary to my expectation. If the socket is blocking and I explicitly set the number of bytes to receive, shouldn't the socket block until it recv's those bytes?, any help, pointers, etc would be much appreciated.

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  • For what purpose does java have a float primitive type?

    - by Roman
    I heard plenty times different claims about float type in java. The most popular issues typicaly regard to converting float value to double and vice versa. I read (rather long time ago and not sure that it's actual now with new JVM) that float gives much worse performance then double. And it's also not recommended to use float in scientific applications which should have certain accuracy. I also remember that when I worked with AWT and Swing I had some problems with using float or double (like using Point2D.Float or Point2D.Double). So, I see only 2 advantages of float over double: it needs only 4 bytes while double needs 8 bytes JMM garantees that assignment operation is atomic with float variables while it's not atomic with double's. Are there any other cases where float is better then double? Do you use float's in your applications? It seems to me that the only valuable reason java has float is backward compatibility.

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  • I/O Asynchronous Completion

    - by lockedscope
    In the following, it is said that an I/O handle must be associated with the thread pool but i could not find where in the given example an handle is associated with the thread. Which function or code helps to bind the file handle in that example? Using asynchronous I/O completion events, a thread from the thread pool processes data only when the data is received, and once the data has been processed, the thread returns to the thread pool. To make an asynchronous I/O call, an operating-system I/O handle must be associated with the thread pool and a callback method must be specified. When the I/O operation completes, a thread from the thread pool invokes the callback method. http://msdn.microsoft.com/en-us/library/aa720215(VS.71).aspx

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  • Amazon S3 copy request timeouts

    - by jean27
    We're uploading files to a temporary folder in a bucket. After that, we're trying to copy the uploaded files to its actual folder then delete the files in the temporary folder. It doesn't timeout when working with a single file. We're using the ThreeSharp API. Stack Trace: [WebException: The operation has timed out] System.Net.HttpWebRequest.GetRequestStream() +5322142 Affirma.ThreeSharp.Query.ThreeSharpQuery.GenerateAndSendHttpWebRequest(Request request) in C:\Consulting\Amazon\Amazon S3\Affirma.ThreeSharp\Affirma.ThreeSharp\Query\ThreeSharpQuery.cs:386 Affirma.ThreeSharp.Query.ThreeSharpQuery.Invoke(Request request) in C:\Consulting\Amazon\Amazon S3\Affirma.ThreeSharp\Affirma.ThreeSharp\Query\ThreeSharpQuery.cs:479

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  • "painting" one array onto another using python / numpy

    - by Nate
    I'm writing a library to process gaze tracking in Python, and I'm rather new to the whole numpy / scipy world. Essentially, I'm looking to take an array of (x,y) values in time and "paint" some shape onto a canvas at those coordinates. For example, the shape might be a blurred circle. The operation I have in mind is more or less identical to using the paintbrush tool in Photoshop. I've got an interative algorithm that trims my "paintbrush" to be within the bounds of my image and adds each point to an accumulator image, but it's slow(!), and it seems like there's probably a fundamentally easier way to do this. Any pointers as to where to start looking?

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