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  • Atomic Instructions and Variable Update visibility

    - by dsimcha
    On most common platforms (the most important being x86; I understand that some platforms have extremely difficult memory models that provide almost no guarantees useful for multithreading, but I don't care about rare counter-examples), is the following code safe? Thread 1: someVariable = doStuff(); atomicSet(stuffDoneFlag, 1); Thread 2: while(!atomicRead(stuffDoneFlag)) {} // Wait for stuffDoneFlag to be set. doMoreStuff(someVariable); Assuming standard, reasonable implementations of atomic ops: Is Thread 1's assignment to someVariable guaranteed to complete before atomicSet() is called? Is Thread 2 guaranteed to see the assignment to someVariable before calling doMoreStuff() provided it reads stuffDoneFlag atomically? Edits: The implementation of atomic ops I'm using contains the x86 LOCK instruction in each operation, if that helps. Assume stuffDoneFlag is properly cleared somehow. How isn't important. This is a very simplified example. I created it this way so that you wouldn't have to understand the whole context of the problem to answer it. I know it's not efficient.

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  • Cocoa/Objective-C - Child window with text input without main window becoming inactive

    - by Josh
    Hello All, I have a need to spawn a window that will hover just above my main window in a cocoa application. I want this main window to allow the user to enter some text in an input box. All is well until the text input box actually gains focus. The main window becomes "deactivated." This window is borderless and is a slightly custom shape -- its more like a hover card than anything else, I suppose. Basically, I'd like this thing to work almost exactly like Spotlight (Apple + Space) -- you can enter text, but this is such an an ancillary operation that in the context of the greater UX, you don't want the jarring effect of the main window graying out (becoming inactive). You'll notice when you have some application open and in-focus, spotlight will not cause the window of that application to become inactive. This problem arises because text input seems to REQUIRE that the child window become the key window (it will not let you place the cursor in the text input field). When it becomes key, the main window becomes inactive. So far I've tried: Subclassing NSWindow for my main application and overriding isKeyWindow such that it only loses key when the application is no longer the users focus (as opposed to the window). This had the unintended effect of colliding with key status of the child window and having very strange effects on the keyboard input (some keys are not captured, like delete) Creating a view instead of a window. Doesn't work because of this problem -- you cannot draw over a Webkit WebView these days. Anybody Cocoa/OSX wizards have any ideas? I've become a little obsessed with this one. An itch I can't scratch.

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  • Supressing GUI?

    - by Legend
    I am trying to run a plugin designed for Vuze using Java. For this I am using a command like this: /home/x/jre1.6.0_14/bin/java -Dazureus.config.path=/home/x/plugin_directory -Dfile.encoding=ANSI_X3.4-1968 -classpath /home/x/P/lib/swtgraphics2d.jar:/home/x/P/lib/Azureus2.jar:/home/x/P/lib/swt.jar org.gudy.azureus2.ui.swt.Main The problem with this is that the launch is failing with an error: changeLocale: *Default Language* != English (United States). Searching without country.. changeLocale: Searching for language English in *any* country.. changeLocale: no message properties for Locale 'English (United States)' (en_US), using 'English (default)' Invoking main failed java.lang.reflect.InvocationTargetException at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) at java.lang.reflect.Method.invoke(Unknown Source) at com.aelitis.azureus.launcher.MainExecutor$1.run(MainExecutor.java:37) at java.lang.Thread.run(Unknown Source) Caused by: org.eclipse.swt.SWTError: No more handles [gtk_init_check() failed] at org.eclipse.swt.SWT.error(SWT.java:3910) at org.eclipse.swt.widgets.Display.createDisplay(Display.java:863) at org.eclipse.swt.widgets.Display.create(Display.java:851) at org.eclipse.swt.graphics.Device.<init>(Device.java:152) at org.eclipse.swt.widgets.Display.<init>(Display.java:479) at org.eclipse.swt.widgets.Display.<init>(Display.java:470) at org.gudy.azureus2.ui.swt.mainwindow.SWTThread.<init>(SWTThread.java:84) at org.gudy.azureus2.ui.swt.mainwindow.SWTThread.createInstance(SWTThread.java:59) at org.gudy.azureus2.ui.swt.mainwindow.Initializer.<init>(Initializer.java:110) at org.gudy.azureus2.ui.swt.Main.<init>(Main.java:88) at org.gudy.azureus2.ui.swt.Main.main(Main.java:255) ... 6 more Exception in thread "MainRunner" java.lang.SecurityException: VM exit operation prohibited at org.gudy.azureus2.core3.security.impl.SESecurityManagerImpl$2.checkExit(SESecurityManagerImpl.java:274) at java.lang.Runtime.exit(Unknown Source) at java.lang.System.exit(Unknown Source) at com.aelitis.azureus.launcher.MainExecutor$1.run(MainExecutor.java:42) at java.lang.Thread.run(Unknown Source) I am sure that this is happening because I am running the program on a terminal. Is there a way to supress the GUI or let the program think that the GUI was spawned successfully? Any suggestions?

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  • SPPersistedObject and List<T>

    - by Sam
    Hi I want sharepoint to "persist" a List of object I wrote a class SPAlert wich inherit from SPPersistedObject : public class SMSAlert: SPPersistedObject { [Persisted] private DateTime _scheduledTime; [Persisted] private Guid _listId; [Persisted] private Guid _siteID; } Then I wrote a class wich inherit from SPJobDefinition an add a List of my previous object: public sealed class MyCustomJob: SPJobDefinition { [Persisted] private List<SMSAlert> _SMSAlerts; } The problem is : when I call the Update method of y MyCustomJob: myCustomJob.Update(); It throw an exception : message : An object in the SharePoint administrative framework, depends on other objects which do not exist. Ensure that all of the objects dependencies are created and retry this operation. stack at Microsoft.SharePoint.Administration.SPConfigurationDatabase.StoreObject(SPPersistedObject obj, Boolean storeClassIfNecessary, Boolean ensure) at Microsoft.SharePoint.Administration.SPConfigurationDatabase.PutObject(SPPersistedObject obj, Boolean ensure) at Microsoft.SharePoint.Administration.SPPersistedObject.Update() at Microsoft.SharePoint.Administration.SPJobDefinition.Update() at Sigi.Common.AlertBySMS.SmsAlertHandler.ScheduleJob(SPWeb web, SPAlertHandlerParams ahp) inner exception An object in the SharePoint administrative framework depends on other objects which do not exist. The INSERT statement conflicted with the FOREIGN KEY constraint "FK_Dependencies1_Objects". The conflict occurred in database "SharePoint_Config, table "dbo.Objects", column 'Id'. The statement has been terminated. Can anyone help me with that??

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  • i m trying to return list<object> from webmethod but gives error

    - by girish
    System.InvalidOperationException: There was an error generating the XML document. --- System.InvalidOperationException: The type WebService.Property.Property_Users was not expected. Use the XmlInclude or SoapInclude attribute to specify types that are not known statically. at System.Xml.Serialization.XmlSerializationWriter.WriteTypedPrimitive(String name, String ns, Object o, Boolean xsiType) at Microsoft.Xml.Serialization.GeneratedAssembly.XmlSerializationWriter1.Write1_Object(String n, String ns, Object o, Boolean isNullable, Boolean needType) at Microsoft.Xml.Serialization.GeneratedAssembly.XmlSerializationWriter1.Write8_ArrayOfAnyType(Object o) at Microsoft.Xml.Serialization.GeneratedAssembly.ListOfObjectSerializer.Serialize(Object objectToSerialize, XmlSerializationWriter writer) at System.Xml.Serialization.XmlSerializer.Serialize(XmlWriter xmlWriter, Object o, XmlSerializerNamespaces namespaces, String encodingStyle, String id) --- End of inner exception stack trace --- at System.Xml.Serialization.XmlSerializer.Serialize(XmlWriter xmlWriter, Object o, XmlSerializerNamespaces namespaces, String encodingStyle, String id) at System.Xml.Serialization.XmlSerializer.Serialize(TextWriter textWriter, Object o, XmlSerializerNamespaces namespaces) at System.Xml.Serialization.XmlSerializer.Serialize(TextWriter textWriter, Object o) at System.Web.Services.Protocols.XmlReturnWriter.Write(HttpResponse response, Stream outputStream, Object returnValue) at System.Web.Services.Protocols.HttpServerProtocol.WriteReturns(Object[] returnValues, Stream outputStream) at System.Web.Services.Protocols.WebServiceHandler.WriteReturns(Object[] returnValues) at System.Web.Services.Protocols.WebServiceHandler.Invoke() public List<object> GetDataByModuleName(string ModuleName) { List<Property_Users> obj_UserList = new List<Property_Users>(); // performing some operation that add data to obj_UserList List < Object > myList = new List<object>(); return ConvertToObjectList<Property_Users>(obj_UserList); } public List<Object> ConvertToObjectList<N>(List<N> sourceList) { List<Object> result = new List<Object>(); foreach (N item in sourceList) { result.Add(item as Object); } return result; } [WebMethod] public List<object> GetDataByModuleName(string ModuleName) { List<object> obj_list = new List<object>(); obj_list = BAL_GeneralService.GetDataByModuleName(ModuleName); return obj_list; }

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  • MySQL table data transformation -- how can I dis-aggregate MySQL time data?

    - by lighthouse65
    We are coding for a MySQL data warehousing application that stores descriptive data (User ID, Work ID, Machine ID, Start and End Time columns in the first table below) associated with time and production quantity data (Output and Time columns in the first table below) upon which aggregate (SUM, COUNT, AVG) functions are applied. We now wish to dis-aggregate time data for another type of analysis. Our current data table design: +---------+---------+------------+---------------------+---------------------+--------+------+ | User ID | Work ID | Machine ID | Event Start Time | Event End Time | Output | Time | +---------+---------+------------+---------------------+---------------------+--------+------+ | 080025 | ABC123 | M01 | 2008-01-24 16:19:15 | 2008-01-24 16:34:45 | 2120 | 930 | +---------+---------+------------+---------------------+---------------------+--------+------+ Reprocessing dis-aggregation that we would like to do would be to transform table content based on a granularity of minutes, rather than the current production event ("Event Start Time" and "Event End Time") granularity. The resulting reprocessing of existing table rows would look like: +---------+---------+------------+---------------------+--------+ | User ID | Work ID | Machine ID | Production Minute | Output | +---------+---------+------------+---------------------+--------+ | 080025 | ABC123 | M01 | 2010-01-24 16:19 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:20 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:21 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:22 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:23 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:24 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:25 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:26 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:27 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:28 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:29 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:30 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:31 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:22 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:33 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:34 | 133 | +---------+---------+------------+---------------------+--------+ So the reprocessing would take an existing row of data created at the granularity of production event and modify the granularity to minutes, eliminating redundant (Event End Time, Time) columns while doing so. It assumes a constant rate of production and divides output by the difference in minutes plus one to populate the new table's Output column. I know this can be done in code...but can it be done entirely in a MySQL insert statement (or otherwise entirely in MySQL)? I am thinking of a INSERT ... INTO construction but keep getting stuck. An additional complexity is that there are hundreds of machines to include in the operation so there will be multiple rows (one for each machine) for each minute of the day. Any ideas would be much appreciated. Thanks.

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  • Using Qt signals/slots instead of a worker thread

    - by Rob
    I am using Qt and wish to write a class that will perform some network-type operations, similar to FTP/HTTP. The class needs to connect to lots of machines, one after the other but I need the applications UI to stay (relatively) responsive during this process, so the user can cancel the operation, exit the application, etc. My first thought was to use a separate thread for network stuff but the built-in Qt FTP/HTTP (and other) classes apparently avoid using threads and instead rely on signals and slots. So, I'd like to do something similar and was hoping I could do something like this: class Foo : public QObject { Q_OBJECT public: void start(); signals: void next(); private slots: void nextJob(); }; void Foo::start() { ... connect(this, SIGNAL(next()), this, SLOT(nextJob())); emit next(); } void Foo::nextJob() { // Process next 'chunk' if (workLeftToDo) { emit next(); } } void Bar::StartOperation() { Foo* foo = new Foo; foo->start(); } However, this doesn't work and UI freezes until all operations have completed. I was hoping that emitting signals wouldn't actually call the slots immediately but would somehow be queued up by Qt, allowing the main UI to still operate. So what do I need to do in order to make this work? How does Qt achieve this with the multitude of built-in classes that appear to perform lengthy tasks on a single thread?

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  • Capturing Set Behavior with Mutating Elements

    - by Carl
    Using the Guava library, I have the following situation: SetMultimap<ImmutableFoo, Set<Foo>> setMM = HashMultimap.create(); Set<Foo> mask = Sets.newHashSet(); // ... some iteration construct { setMM.put(ImmutableFoo1, Sets.difference(SomeSetFoo1,mask)); setMM.put(ImmutableFoo1, Sets.difference(SomeSetFoo2,mask)); mask.add(someFoo); } that is, the same iteration to create the setMM is also used to create the mask - this can of course result in changes to hashCode()s and create duplicates within the SetMultimap backing. Ideally, I'd like the duplicates to drop without me having to make it happen, and avoid repeating the iteration to separately construct the multimap and mask. Any easy libraries/Set implementations to make that happen? Alternatively, can you identify a better way to drop the duplicates than: for (ImmutableFoo f : setMM.keySet()) setMM.putAll(f,setMM.removeAll(f)); revisiting the elements is probably not a performance problem, since I could combine a separate filter operation that needs to visit all the elements anyway.

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  • Ordered delivery with NetNamedPipeBinding using oneWay calls

    - by Aseem Bansal
    Is it possible to guarantee ordered delivery with oneWay calls using namedPipe binding? I have a WCF service/client communicating using namedPipe binding. The client is exposing a callback contract in which all the methods in the callback are marked as OneWay. Something like this [ServiceContract(CallbackContract = typeof(IMyServiceCallback))] public interface IMyService { [OperationContract] void MyOperation(); } public interface IMyServiceCallback { [OperationContract(IsOneWay=true)] void MyCallback1(); [OperationContract(IsOneWay=true)] void MyCallback2(); } At the server side, the implementation of MyOperation method always calls MyCallback1 first and then MyCallback2 but I am observing that sometimes the client receives the calls in the incorrect order (MyCallback2 first and then MyCallback1). On searching the internet I found that the order is not guaranteed with oneway operation as mentioned here and also there is something called reliableSession which ensure message ordering. All the examples on the internet for reliable session are with TCP binding (and not a single one with NamedPipeBinding) and the tcpBinding also has a property called ReliableSession which is not present on the NetNamedPipeBinding. So I am not sure whether reliable session is expected to work with NetNamedPipeBinding or not. Question: Does reliable session work with namedPipeBinding? If yes, how? If no, Is there any other approach with which I can guarantee ordered delivery?

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  • Can I use Ninject ConstructorArguments with strong naming?

    - by stiank81
    Well, I don't know if "strong naming" is the right term, but what I want to do is as follows. Currently I use ConstructorArgument like e.g. this: public class Ninja { private readonly IWeapon _weapon; private readonly string _name; public Ninja(string name, IWeapon weapon) { _weapon = weapon; _name = name; } // ..more code.. } public void SomeFunction() { var kernel = new StandardKernel(); kernel.Bind<IWeapon>().To<Sword>(); var ninja = ninject.Get<Ninja>(new ConstructorArgument("name", "Lee")); } Now, if I rename the parameter "name" (e.g. using ReSharper) the ConstructorArgument won't update, and I will get a runtime error when creating the Ninja. To fix this I need to manually find all places I specify this parameter through a ConstructorArgument and update it. No good, and I'm doomed to fail at some point even though I have good test coverage. Renaming should be a cheap operation. Is there any way I can make a reference to the parameter instead - such that it is updated when I rename the parameter?

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  • Generate colors between red and green for a power meter?

    - by Simucal
    I'm writing a java game and I want to implement a power meter for how hard you are going to shoot something. I need to write a function that takes a int between 0 - 100, and based on how high that number is, it will return a color between Green (0 on the power scale) and Red (100 on the power scale). Similar to how volume controls work: What operation do I need to do on the Red, Green, and Blue components of a color to generate the colors between Green and Red? So, I could run say, getColor(80) and it will return an orangish color (its values in R, G, B) or getColor(10) which will return a more Green/Yellow rgb value. I know I need to increase components of the R, G, B values for a new color, but I don't know specifically what goes up or down as the colors shift from Green-Red. Progress: I ended up using HSV/HSB color space because I liked the gradiant better (no dark browns in the middle). The function I used was (in java): public Color getColor(double power) { double H = power * 0.4; // Hue (note 0.4 = Green, see huge chart below) double S = 0.9; // Saturation double B = 0.9; // Brightness return Color.getHSBColor((float)H, (float)S, (float)B); } Where "power" is a number between 0.0 and 1.0. 0.0 will return a bright red, 1.0 will return a bright green. Java Hue Chart: Thanks everyone for helping me with this!

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  • How make this special many2many fields validation using Django ORM?

    - by e-satis
    I have the folowing model: class Step(models.Model): order = models.IntegerField() latitude = models.FloatField() longitude = models.FloatField() date = DateField(blank=True, null=True) class Journey(models.Model): boat = models.ForeignKey(Boat) route = models.ManyToManyField(Step) departure = models.ForeignKey(Step, related_name="departure_of", null=True) arrival = models.ForeignKey(Step, related_name="arrival_of", null=True) I would like to implement the following check: # If a there is less than one step, raises ValidationError. routes = tuple(self.route.order_by("date")) if len(routes) <= 1: raise ValidationError("There must be at least two setps in the route") # save the first and the last step as departure and arrival self.departure = routes[0] self.arrival = routes[-1] # departure and arrival must at least have a date if not (self.departure.date or self.arrival.date): raise ValidationError("There must be an departure and an arrival date. " "Please set the date field for the first and last Step of the Journey") # departure must occurs before arrival if not (self.departure.date > self.arrival.date): raise ValidationError("Departure must take place the same day or any date before arrival. " "Please set accordingly the date field for the first and last Step of the Journey") I tried to do that by overloading save(). Unfortunately, Journey.route is empty in save(). What's more, Journey.id doesn't exists yet. I didn't try django.db.models.signals.post_save but suppose it will fail because Journey.route is empty as well (when does this get filled anyway?). I see a solution in django.db.models.signals.m2m_changed but there are a lot of steps (thousands), and I want to avoid to perform an operation for every single of them.

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  • WPF, C# - Making Intellisense/Autocomplete list, fastest way to filter list of strings

    - by user559548
    Hello everyone, I'm writing an Intellisense/Autocomplete like the one you find in Visual Studio. It's all fine up until when the list contains probably 2000+ items. I'm using a simple LINQ statement for doing the filtering: var filterCollection = from s in listCollection where s.FilterValue.IndexOf(currentWord, StringComparison.OrdinalIgnoreCase) >= 0 orderby s.FilterValue select s; I then assign this collection to a WPF Listbox's ItemSource, and that's the end of it, works fine. Noting that, the Listbox is also virtualised as well, so there will only be at most 7-8 visual elements in memory and in the visual tree. However the caveat right now is that, when the user types extremely fast in the richtextbox, and on every key up I execute the filtering + binding, there's this semi-race condition, or out of sync filtering, like the first key stroke's filtering could still be doing it's filtering or binding work, while the fourth key stroke is also doing the same. I know I could put in a delay before applying the filter, but I'm trying to achieve a seamless filtering much like the one in Visual Studio. I'm not sure where my problem exactly lies, so I'm also attributing it to IndexOf's string operation, or perhaps my list of string's could be optimised in some kind of index, that could speed up searching. Any suggestions of code samples are much welcomed. Thanks.

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  • Create image from scratch with JMagick

    - by Michael IV
    I am using Java port of ImageMagick called JMagick .I need to be able to create a new image and write an arbitrary text chunk into it.The docs are very poor and what I managed to get so far is to write text into the image which comes from IO.Also , in all the examples I have found it seems like the very first operation ,before writing new image data , is always loading of an existing image into ImageInfo instance.How do I create an image from scratch with JMagick and then write a text into it? Here is what I do now : try { ImageInfo info = new ImageInfo(); info.setSize("512x512"); info.setUnits(ResolutionType.PixelsPerInchResolution); info.setColorspace(ColorspaceType.RGBColorspace); info.setBorderColor(PixelPacket.queryColorDatabase("red")); info.setDepth(8); BufferedImage img = new BufferedImage(512,512,BufferedImage.TYPE_4BYTE_ABGR); byte[] imageBytes = ((DataBufferByte) img.getData().getDataBuffer()).getData(); MagickImage mimage = new MagickImage(info,imageBytes); DrawInfo aInfo = new DrawInfo(info); aInfo.setFill(PixelPacket.queryColorDatabase("green")); aInfo.setUnderColor(PixelPacket.queryColorDatabase("yellow")); aInfo.setOpacity(0); aInfo.setPointsize(36); aInfo.setFont("Arial"); aInfo.setTextAntialias(true); aInfo.setText("JMagick Tutorial"); aInfo.setGeometry("+40+40"); mimage.annotateImage(aInfo); mimage.setFileName("text.jpg"); mimage.writeImage(info); } catch (MagickException ex) { Logger.getLogger(LWJGL_IDOMOO_SIMPLE_TEST.class.getName()).log(Level.SEVERE, null, ex); } It doesn't work , the JVM crashes with access violation as it probably expects for the input image from IO.

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  • Java operator overloading

    - by nimcap
    Not using operators makes my code obscure. (aNumber / aNother) * count is better than aNumber.divideBy(aNother).times(count) After 6 months of not writing a single comment I had to write a comment to the simple operation above. Usually I refactor until I don't need comment. And this made me realize that it is easier to read and perceive math symbols and numbers than their written forms. For example TWENTY_THOUSAND_THIRTEEN.plus(FORTY_TWO.times(TWO_HUNDERED_SIXTY_ONE)) is more obscure than 20013 + 42*261 So do you know a way to get rid of obscurity while not using operator overloading in Java? Update: I did not think my exaggeration on comments would cause such trouble to me. I am admitting that I needed to write comment a couple of times in 6 months. But not more than 10 lines in total. Sorry for that. Update 2: Another example: budget.plus(bonusCoefficient.times(points)) is more obscure than budget + bonusCoefficient * points I have to stop and think on the first one, at first sight it looks like clutter of words, on the other hand, I get the meaning at first look for the second one, it is very clear and neat. I know this cannot be achieved in Java but I wanted to hear some ideas about my alternatives.

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  • Implementing Operator Overloading with Logarithms in C++

    - by Jacob Relkin
    Hello my friends, I'm having some issues with implementing a logarithm class with operator overloading in C++. My first goal is how I would implement the changeBase method, I've been having a tough time wrapping my head around it. My secoond goal is to be able to perform an operation where the left operand is a double and the right operand is a logarithm object. Here's a snippet of my log class: // coefficient: double // base: unsigned int // number: double class _log { double coefficient, number; unsigned int base; public: _log() { base = rand(); coefficient = rand(); number = rand(); } _log operator+ ( const double b ) const; _log operator* ( const double b ) const; _log operator- ( const double b ) const; _log operator/ ( const double b ) const; _log operator<< ( const _log &b ); double getValue() const; bool changeBase( unsigned int base ); }; You guys are awesome, thank you for your time.

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  • Show me your Linq to SQL architectures!

    - by Brad Heller
    I've been using Linq to SQL for a new implementation that I've been working on. I have about 5000 lines of code and am a little ways from a solid demo. I've been pretty satisfied with Linq to SQL so far -- the tools are excellent and pretty painless and it allows you to get a DAL up and running quickly. That said, there are some major draw backs that I just keep hitting over and over again. Namely how to handle separation of concerns between my DAL and my business layer and juggling that with different data contexts. Here is the architecture I've been using: My repositories do all my data access and they return Linq to SQL objects. Each of my Linq to SQL objects implements an IDetachable interface. A typical implementation looks like this: partial class PaymentDetail : IDetachable { #region IDetachable Members public bool IsAttached { get { return PropertyChanging != null; } } public void Detach() { if (IsAttached) { PropertyChanged = null; PropertyChanging = null; Transaction.Detach(); } } #endregion } Every time I do a DAL operation in my repository I "detach" when I'm done with the object (and it should theoretically detach from any child objects) to remove the DataContext's context. Like I said, this works pretty well, but there are some edge cases that seem to be a big pain in the ass. For instance, my Transaction object has many PaymentDetails. Even when there are no PaymentDetails in that collection it's still attached to the DataContext's context! Thus, if I try to update (I update by Attach()ing to the object and then SubmitChanges()) I get that dreaded "An attempt has been made to Attach or Add an entity that is not new, perhaps having been loaded from another DataContext. This is not supported." message. Anyway, I'm starting to doubt that this technology was a good gamble. Has anyone got a decent architecture that they're willing to share? I'd really love to use this technology but I feel like I spend 1/3 of my time just debugging is retarded quirks!

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  • Merging k sorted linked lists - analysis

    - by Kotti
    Hi! I am thinking about different solutions for one problem. Assume we have K sorted linked lists and we are merging them into one. All these lists together have N elements. The well known solution is to use priority queue and pop / push first elements from every lists and I can understand why it takes O(N log K) time. But let's take a look at another approach. Suppose we have some MERGE_LISTS(LIST1, LIST2) procedure, that merges two sorted lists and it would take O(T1 + T2) time, where T1 and T2 stand for LIST1 and LIST2 sizes. What we do now generally means pairing these lists and merging them pair-by-pair (if the number is odd, last list, for example, could be ignored at first steps). This generally means we have to make the following "tree" of merge operations: N1, N2, N3... stand for LIST1, LIST2, LIST3 sizes O(N1 + N2) + O(N3 + N4) + O(N5 + N6) + ... O(N1 + N2 + N3 + N4) + O(N5 + N6 + N7 + N8) + ... O(N1 + N2 + N3 + N4 + .... + NK) It looks obvious that there will be log(K) of these rows, each of them implementing O(N) operations, so time for MERGE(LIST1, LIST2, ... , LISTK) operation would actually equal O(N log K). My friend told me (two days ago) it would take O(K N) time. So, the question is - did I f%ck up somewhere or is he actually wrong about this? And if I am right, why doesn't this 'divide&conquer' approach can't be used instead of priority queue approach?

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  • ruby on rails delajed_job failing with rvm

    - by mottalrd
    I have delayed_job installed and I start the daemon to run the jobs with this ruby script require 'rubygems' require 'daemon_spawn' $: << '.' RAILS_ROOT = File.expand_path(File.join(File.dirname(__FILE__), '..')) class DelayedJobWorker < DaemonSpawn::Base def start(args) ENV['RAILS_ENV'] ||= args.first || 'development' Dir.chdir RAILS_ROOT require File.join('config', 'environment') Delayed::Worker.new.start end def stop system("kill `cat #{RAILS_ROOT}/tmp/pids/delayed_job.pid`") end end DelayedJobWorker.spawn!(:log_file => File.join(RAILS_ROOT, "log", "delayed_job.log"), :pid_file => File.join(RAILS_ROOT, 'tmp', 'pids', 'delayed_job.pid'), :sync_log => true, :working_dir => RAILS_ROOT) If I run the command with rvmsudo it works perfectly If I simply use the ruby command without rvm it fails and this is the output, but I have no idea why this happens. Could you give me some clue? Thank you user@mysystem:~/redeal.it/application$ ruby script/delayed_job start production /usr/local/rvm/gems/ruby-1.9.3-p194/gems/daemon-spawn-0.4.2/lib/daemon_spawn.rb:16:in `kill': Operation not permitted (Errno::EPERM) from /usr/local/rvm/gems/ruby-1.9.3-p194/gems/daemon-spawn-0.4.2/lib/daemon_spawn.rb:16:in `alive?' from /usr/local/rvm/gems/ruby-1.9.3-p194/gems/daemon-spawn-0.4.2/lib/daemon_spawn.rb:125:in `alive?' from /usr/local/rvm/gems/ruby-1.9.3-p194/gems/daemon-spawn-0.4.2/lib/daemon_spawn.rb:176:in `block in start' from /usr/local/rvm/gems/ruby-1.9.3-p194/gems/daemon-spawn-0.4.2/lib/daemon_spawn.rb:176:in `select' from /usr/local/rvm/gems/ruby-1.9.3-p194/gems/daemon-spawn-0.4.2/lib/daemon_spawn.rb:176:in `start' from /usr/local/rvm/gems/ruby-1.9.3-p194/gems/daemon-spawn-0.4.2/lib/daemon_spawn.rb:165:in `spawn!' from script/delayed_job:37:in `<main>'

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  • .NET threading solution for long queries

    - by Eddie
    Senerio We have an application that records incidents. An external database needs to be queried when an incident is approved by a supervisor. The queries to this external database are sometimes taking a while to run. This lag is experienced through the browser. Possible Solution I want to use threading to eliminate the simulated hang to the browser. I have used the Thread class before and heard about ThreadPool. But, I just found BackgroundWorker in this post. MSDN states: The BackgroundWorker class allows you to run an operation on a separate, dedicated thread. Time-consuming operations like downloads and database transactions can cause your user interface (UI) to seem as though it has stopped responding while they are running. When you want a responsive UI and you are faced with long delays associated with such operations, the BackgroundWorker class provides a convenient solution. Is BackgroundWorker the way to go when handling long running queries? What happens when 2 or more BackgroundWorker processes are ran simultaneously? Is it handled like a pool?

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  • How close can I get C# to the performance of C++ for small intensive tasks?

    - by SLC
    I was thinking about the speed difference of C++ to C# being mostly about C# compiling to byte-code that is taken in by the JIT compiler (is that correct?) and all the checks C# does. I notice that it is possible to turn a lot of these functions off, both in the compile options, and possibly through using the unsafe keyword as unsafe code is not verifiable by the common language runtime. Therefore if you were to write a simple console application in both languages, that flipped an imaginary coin an infinite number of times and displayed the results to the screen every 10,000 or so iterations, how much speed difference would there be? I chose this because it's a very simple program. I'd like to test this but I don't know C++ or have the tools to compile it. This is my C# version though: static void Main(string[] args) { unsafe { Random rnd = new Random(); int heads = 0, tails = 0; while (true) { if (rnd.NextDouble() > 0.5) heads++; else tails++; if ((heads + tails) % 1000000 == 0) Console.WriteLine("Heads: {0} Tails: {1}", heads, tails); } } } Is the difference enough to warrant deliberately compiling sections of code "unsafe" or into DLLs that do not have some of the compile options like overflow checking enabled? Or does it go the other way, where it would be beneficial to compile sections in C++? I'm sure interop speed comes into play too then. To avoid subjectivity, I reiterate the specific parts of this question as: Does C# have a performance boost from using unsafe code? Do the compile options such as disabling overflow checking boost performance, and do they affect unsafe code? Would the program above be faster in C++ or negligably different? Is it worth compiling long intensive number-crunching tasks in a language such as C++ or using /unsafe for a bonus? Less subjectively, could I complete an intensive operation faster by doing this?

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  • Google App Engine - Caching generated HTML

    - by Alexander
    I have written a Google App Engine application that programatically generates a bunch of HTML code that is really the same output for each user who logs into my system, and I know that this is going to be in-efficient when the code goes into production. So, I am trying to figure out the best way to cache the generated pages. The most probable option is to generate the pages and write them into the database, and then check the time of the database put operation for a given page against the time that the code was last updated. Then, if the code is newer than the last put to the database (for a particular HTML request), new HTML will be generated and served, and cached to the database. If the code is older than the last put to the database, then I will just get the HTML direct from the database and serve it (therefore avoiding all the CPU wastage of generating the HTML). I am not only looking to minimize load times, but to minimize CPU usage. However, one issue that I am having is that I can't figure out how to programatically check when the version of code uploaded to the app engine was updated. I am open to any suggestions on this approach, or other approaches for caching generated html. Note that while memcache could help in this situation, I believe that it is not the final solution since I really only need to re-generate html when the code is updated (as opposed to every time the memcache expires). Kind Regards, and thank you in advance for any suggestions you may be able to offer. -Alex

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  • Can I compare a template variable to an integer in App Engine templates?

    - by matt b
    Using Django templates in Google App Engine (on Python), is it possible to compare a template variable to an integer in an {% if %} block? views.py: class MyHandler(webapp.RequestHandler): def get(self): foo_list = db.GqlQuery(...) ... template_values['foos'] = foo_list template_values['foo_count'] = len(foo_list) handler.response.out.write(template.render(...)) My template: {% if foo_count == 1 %} There is one foo. {% endif %} This blows up with 'if' statement improperly formatted. What I was attempting to do in my template was build a simple if/elif/else tree to be grammatically correct to be able to state #foo_count == 0: There are no foos. #foo_count == 1: There is one foo. #else: There are {{ foos|length }} foos. Browsing the Django template documents (this link provided in the GAE documentation appears to be for versions of Django far newer than what is supported on GAE), it appears as if I can only actually use boolean operators (if in fact boolean operators are supported in this older version of Django) with strings or other template variables. Is it not possible to compare variables to integers or non-strings with Django templates? I'm sure there is an easy way to workaround this - built up the message string on the Python side rather than within the template - but this seems like such a simple operation you ought to be able to handle in a template. It sounds like I should be switching to a more advanced templating engine, but as I am new to Django (templates or any part of it), I'd just like some confirmation first.

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  • Emailing smtp with Python error

    - by jakecar
    I can't figure out why this isn't working. I'm trying to send an email from my school email address with this code I got online. The same code works for sending from my GMail address. Does anyone know what this error means? The error occurs after waiting for about one and a half minutes. import smtplib FROMADDR = "FROM_EMAIL" LOGIN = "USERNAME" PASSWORD = "PASSWORD" TOADDRS = ["TO_EMAIL"] SUBJECT = "Test" msg = ("From: %s\r\nTo: %s\r\nSubject: %s\r\n\r\n" % (FROMADDR, ", ".join(TOADDRS), SUBJECT) ) msg += "some text\r\n" server = smtplib.SMTP('OUTGOING_SMTP', 587) server.set_debuglevel(1) server.ehlo() server.starttls() server.login(LOGIN, PASSWORD) server.sendmail(FROMADDR, TOADDRS, msg) server.quit() And here's the error I get: Traceback (most recent call last): File "emailer.py", line 13, in server = smtplib.SMTP('OUTGOING_SMTP', 587) File "/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/smtplib.py", line 239, in init (code, msg) = self.connect(host, port) File "/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/smtplib.py", line 295, in connect self.sock = self._get_socket(host, port, self.timeout) File "/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/smtplib.py", line 273, in _get_socket return socket.create_connection((port, host), timeout) File "/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/socket.py", line 514, in create_connection raise error, msg socket.error: [Errno 60] Operation timed out

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  • Time complexity with bit cost

    - by Keyser
    I think I might have completely misunderstood bit cost analysis. I'm trying to wrap my head around the concept of studying an algorithm's time complexity with respect to bit cost (instead of unit cost) and it seems to be impossible to find anything on the subject. Is this considered to be so trivial that no one ever needs to have it explained to them? Well I do. (Also, there doesn't even seem to be anything on wikipedia which is very unusual). Here's what I have so far: The bit cost of multiplication and division of two numbers with n bits is O(n^2) (in general?) So, for example: int number = 2; for(int i = 0; i < n; i++ ){ number = i*i; } has a time complexity with respect to bit cost of O(n^3), because it does n multiplications (right?) But in a regular scenario we want the time complexity with respect to the input. So, how does that scenario work? The number of bits in i could be considered a constant. Which would make the time complexity the same as with unit cost except with a bigger constant (and both would be linear). Also, I'm guessing addition and subtraction can be done in constant time, O(1). Couldn't find any info on it but it seems reasonable since it's one assembler operation.

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