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  • The correct way to Fire-and-Forget an asynchronous delegate

    - by Programming Hero
    Consider me rusty on the subject of asynchronous delegates. If I want to call a method asynchronously, in a fire-and-forget style, is this an appropriate way to do it? Action action = DoSomething; action.BeginInvoke(action.EndInvoke, null); The DoSomething() method catches all exceptions and deals with them internally. Is the call to EndInvoke appropriate? Required? Is there a clearer way to achieve the same behaviour?

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  • Map NHibernate entity to multiple tables based on parent

    - by Programming Hero
    I'm creating a domain model where entities often (but not always) have a member of type ActionLog. ActionLog is a simple class which allows for an audit trail of actions being performed on an instance. Each action is recorded as an ActionLogEntry instance. ActionLog is implemented (approximately) as follows: public class ActionLog { public IEnumerable<ActionLogEntry> Entries { get { return EntriesCollection; } } protected ICollection<ActionLogEntry> EntriesCollection { get; set; } public void AddAction(string action) { // Append to entries collection. } } What I would like is to re-use this class amongst my entities and have the entries map to different tables based on which class they are logged against. For example: public class Customer { public ActionLog Actions { get; protected set; } } public class Order { public ActionLog Actions { get; protected set; } } This design is suitable for me in the application, however I can't see a clear way to map this scenario to a database with NHibernate. I typically use Fluent NHibernate for my configuration, but I'm happy to accept answers in more general HBM xml.

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  • WCF Message Debugging on Custom Binding

    - by Programming Hero
    I've created a custom binding in WCF for a custom MessageEncoder to allow messages to be written as XML using a wider range of encodings than WCF supports out of the box. The encoder appears to be working and I am able to send and receive messages, but I want to verify that the XML message being written is exactly as required by the service I am trying to consume. I've turned on message logging for WCF using the diagnostic trace listeners to output the messages sent and received over the wire to a log file. Unfortunately, for calls using my encoder, the message is displayed as ... stream ... EDIT: I don't think it's anything to do with my custom encoding. I have experimented with my custom binding a little, switching to using the built-in text encoding and http transport. I still don't get a message body logged in the message trace. Is there anything that needs to be specified within a custom binding to enable message logging?

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  • sharing build artifacts between jobs in hudson

    - by programming panda
    Hi I'm trying to set up our build process in hudson. Job 1 will be a super fast (hopefully) continuous integration build job that will be built frequently. Job 2, will be responsible for running a comprehensive test suite, at a regular interval or triggered manually. Job 3 will be responsible for running analysis tools across the codebase (much like Job 2). I tried using the "Advanced Projects Options use custom workspace" feature so that code compiled in Job 1 can be used in Job 2 and 3. However, it seems that all build artifacts remain inside that Job 1 workspace. I'm I doing this right? Is there a better way of doing this? I guess I'm looking for something similar to a build pipeline setup...so that things can be shared and the appropriate jobs can be executed in stages. (I also considered using 'batch tasks'...but it seems like those can't be scheduled? only triggered manually?) Any suggestions are welcomed. Thanks!

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  • WCF Message Debugging on WebHttpBehavior

    - by Programming Hero
    I've created a custom binding in WCF for a custom MessageEncoder to allow messages to be written as XML using a wider range of encodings than WCF supports out of the box. The encoder appears to be working and I am able to send and receive messages, but I want to verify that the XML message being written is exactly as required by the service I am trying to consume. I've turned on message logging for WCF using the diagnostic trace listeners to output the messages sent and received over the wire to a log file. Unfortunately, for calls using my encoder, the message is displayed as ... stream ... EDIT: I don't think it's anything to do with my custom encoding. I have experimented with my custom binding a little, switching to using the built-in text encoding and http transport. I still don't get a message body logged in the message trace. EDIT2: Having done further investigation, the issue looks to be related not to the custom binding, but the custom behaviour. I'm apply the <webHttp/> behaviour. Once this is specified (along with manual addressing), the tracing behaviour shows up. Is this a known issue with WebHttpBehavior? Am I still barking up the wrong tree?

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  • High level vs. low level programming. Do I really have to choose?

    - by EpsilonVector
    Every once in a while I'm asked in interviews which I like the best- low level or high level. It seems to me that the implicit message is that they are both a specialty and they want to know which direction I'm heading. The trouble is, I seem to like both. Low level is extremely challenging and often requires a great deal of esoteric knowledge. High level is where all the sexy things happen: applications that people use directly, results that can be easily demonstrated (showed off) in a way that is accessible to everybody, and you get to work with really advanced tools and interact with new technologies. I would really love to do both, even if it means alternating between them (I doubt there are jobs that will let me do both simultaneously), but I'm guessing that the industry rewards specialists more than generalists. Will it really be problematic career wise if I never choose one over the other? Is it practical to alternate between the two in the sense that if I were to leave a job doing one of them, I should experience no "friction" trying to get a job doing the other (assuming I'm reasonably in the loop)? Are there career opportunities where you get to do both? Do I really have to choose one over the other?

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  • I've been hired on as a entry-level game developer at a company and have little/no experience in API programming, what should I expect?

    - by Mr. Geneth
    So, I've been hired on as an entry level game developer with little/no experience working with any API other than Win32. This will be an overall learning experience for me as a person and I have gone over this multiple times with the boss and he has no problem with my inexperience. He says that if I'm not worth it now, I will be later. This gives me confidence, but I still feel that I should know a lot more before tackling this position. I would be stupid to pass it up. This is one of my favorite places to come for advice and help and have tried to just accept this, but it just keeps bothering that I can't go in knowing how to at least do the basics. I want to give the company its money's worth. Ya know? My questions are: What should I expect from the other programmers in this project (In terms of patience with me and working together, and being taught)? Is this normal? Any other advice on this sort of thing would be wonderful. I just want to feel comfortable with it.

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  • Storing website hierarchy in Sql Server 2008

    - by Mika Kolari
    I want to store website page hierarchy in a table. What I would like to achieve is efficiently 1) resolve (last valid) item by path (e.g. "/blogs/programming/tags/asp.net,sql-server", "/blogs/programming/hello-world" ) 2) get ancestor items for breadcrump 3) edit an item without updating the whole tree of children, grand children etc. Because of the 3rd point I thought the table could be like ITEM id type slug title parentId 1 area blogs Blogs 2 blog programming Programming blog 1 3 tagsearch tags 2 4 post hello-world Hello World! 2 Could I use Sql Server's hierarchyid type somehow (especially point 1, "/blogs/programming/tags" is the last valid item)? Tree depth would usually be around 3-4. What would be the best way to achieve all this?

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  • Panel is not displaying in JFrame

    - by mallikarjun
    I created a chat panel and added to Jframe but the panel is not displaying. But my sop in the chat panel are displaying in the console. Any one please let me know what could be the problem My Frame public class MyFrame extends JFrame { MyPanel chatClient; String input; public MyFrame() { input = (String)JOptionPane.showInputDialog(null, "Name:", "Connect to chat server", JOptionPane.QUESTION_MESSAGE, null,null, "Test"); input=input.trim(); chatClient = new MyPanel("localhost",input); setVisible(true); setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); add(chatClient); } public static void main(String...args){ new MyFrame(); } } MyPanel: public class MyPanel extends JPanel{ ChatClient chatClient; public MyPanel(String host, String uid) { chatClient= new ChatClient(host,uid); add(chatClient.getChatPanel()); this.setVisible(true); } } chat panel: public class ChatClient { Client client; String name; ChatPanel chatPanel; String hostid; public ChatClient(String host,String uid){ client = new Client(); client.start(); System.out.println("in constructor"); Network.register(client); client.addListener(new Listener(){ public void connected(Connection connection){ System.out.println("in client connected method"); Network.RegisterName registerName = new Network.RegisterName(); registerName.name=name; client.sendTCP(registerName); } public void received(Connection connection,Object object){ System.out.println("in client received method"); if (object instanceof Network.UpdateNames) { Network.UpdateNames updateNames = (Network.UpdateNames)object; //chatFrame.setNames(updateNames.names); System.out.println("got it message"); return; } if (object instanceof Network.ChatMessage) { Network.ChatMessage chatMessage = (Network.ChatMessage)object; //chatFrame.addMessage(chatMessage.text); System.out.println("send it message"); return; } } }); // end of listner name=uid.trim(); hostid=host.trim(); chatPanel = new ChatPanel(hostid,name); chatPanel.setSendListener(new Runnable(){ public void run(){ Network.ChatMessage chatMessage = new Network.ChatMessage(); chatMessage.chatMessage=chatPanel.getSendText(); client.sendTCP(chatMessage); } }); new Thread("connect"){ public void run(){ try{ client.connect(5000, hostid,Network.port); }catch(IOException e){ e.printStackTrace(); } } }.start(); }//end of constructor static public class ChatPanel extends JPanel{ CardLayout cardLayout; JList messageList,nameList; JTextField sendText; JButton sendButton; JPanel topPanel,bottomPanel,panel; public ChatPanel(String host,String user){ setSize(600, 200); this.setVisible(true); System.out.println("Chat panel "+host+"user: "+user); { panel = new JPanel(new BorderLayout()); { topPanel = new JPanel(new GridLayout(1,2)); panel.add(topPanel); { topPanel.add(new JScrollPane(messageList=new JList())); messageList.setModel(new DefaultListModel()); } { topPanel.add(new JScrollPane(nameList=new JList())); nameList.setModel(new DefaultListModel()); } DefaultListSelectionModel disableSelections = new DefaultListSelectionModel() { public void setSelectionInterval (int index0, int index1) { } }; messageList.setSelectionModel(disableSelections); nameList.setSelectionMode(ListSelectionModel.SINGLE_SELECTION); } { bottomPanel = new JPanel(new GridBagLayout()); panel.add(bottomPanel,BorderLayout.SOUTH); bottomPanel.add(sendText=new JTextField(),new GridBagConstraints(0,0,1,1,1,0,GridBagConstraints.CENTER,GridBagConstraints.BOTH,new Insets(0,0,0,0),0,0)); bottomPanel.add(sendButton=new JButton(),new GridBagConstraints(1,0,1,1,0,0,GridBagConstraints.CENTER,0,new Insets(0,0,0,0),0,0)); } } sendText.addActionListener(new ActionListener(){ public void actionPerformed(ActionEvent e){ sendButton.doClick(); } }); } public void setSendListener (final Runnable listener) { sendButton.addActionListener(new ActionListener() { public void actionPerformed (ActionEvent evt) { if (getSendText().length() == 0) return; listener.run(); sendText.setText(""); sendText.requestFocus(); } }); } public String getSendText () { return sendText.getText().trim(); } public void setNames (final String[] names) { EventQueue.invokeLater(new Runnable(){ public void run(){ DefaultListModel model = (DefaultListModel)nameList.getModel(); model.removeAllElements(); for(String name:names) model.addElement(name); } }); } public void addMessage (final String message) { EventQueue.invokeLater(new Runnable() { public void run () { DefaultListModel model = (DefaultListModel)messageList.getModel(); model.addElement(message); messageList.ensureIndexIsVisible(model.size() - 1); } }); } } public JPanel getChatPanel(){ return chatPanel; } }

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  • Iphone memory leak with malloc

    - by Icky
    Hello. I have memory leak, found by instruments and it is supposed to be in this line of code: indices = malloc( sizeof(indices[0]) * totalQuads * 6); This is actually a code snippet from a tutorial, something which i think is leak-free so to say. Now I reckon, the error is somewhere else, but I do not know, where. These are the last trackbacks: 5 ColorRun -[EAGLView initWithCoder:] /Users/thomaskopinski/programming/colorrun_3.26/Classes/EAGLView.m:98 4 ColorRun -[EAGLView initGame] /Users/thomaskopinski/programming/colorrun_3.26/Classes/EAGLView.m:201 3 ColorRun -[SpriteSheet initWithImageNamed:spriteWidth:spriteHeight:spacing:imageScale:] /Users/thomaskopinski/programming/colorrun_3.26/SpriteSheet.m:68 2 ColorRun -[Image initWithImage:scale:] /Users/thomaskopinski/programming/colorrun_3.26/Image.m:122 1 ColorRun -[Image initImpl] /Users/thomaskopinski/programming/colorrun_3.26/Image.m:158 0 libSystem.B.dylib malloc Does anyone know how to approach this?

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  • Routing redirection decision

    - by programming late night
    I have really no idea why I'm asking this as this a really completely irrelevant question for which I should have figured out an answer within milliseconds, yet I'm doing it. So in my project I have a Router class which splits up the request and selects the right page to be loaded. Fine so far. Now I have a page displayed when the user requests a page that doesn't exist, you know, 404. So theoretically, if the user entered mydomain.com/404 (I use mod_rewrite with a requests collector via index.php?req=*) the 404 error would be shown to him, but in fact there was no error - the 404 page would be displayed as a perfectly normal page. So if someone would try out requesting the 404 page via /404, he would be shown the page but he can't tell if the 404 page he requested doesn't exist and he is actually getting a, you guessed it, 404 error or if he actually found some flaw in the system that makes him able to see an error page when there is no error. I don't know how dumb this whole thing here is but I'm sure some of you have in fact ran into this problem already. Short version: If the user enters mydomain.com/404 the 404 page is shown even though there is no 404 error. I know this is a completely irrelevant question, please don't tell me, but I just spontaneously wanted to hear your thoughts on it. Strange eh? Should I redirect direct access to my 404-page to the home page? Should I do nothing? Should I just go to bed and stop asking irrelevant stuff?

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  • In China. Want to set up my own private proxy. Already have website/webhosting. Help please! n00b with respect to coding/programming, go easy on me [closed]

    - by user1725461
    I am in China and have used freegate in the past -- http://en.wikipedia.org/wiki/Freegate Recently I've been having too many problems with that and some other web-based proxies I usually use. I have a website that is hosted in the US which I can access from China. Is there an easy way for me to setup my own secure private proxy? I'm sick of all my internet problems and looking for a new workable solution. Thank you! PS: and I really hope this is the right place for such a question...

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  • What is the benefits and drawbacks of using header files?

    - by vodkhang
    I had some experience on programming languages like Java, C#, Scala as well as some lower level programming language like C, C++, Objective - C. My observation is that low level languages separate out header files and implementation files while other higher level programming language never separate it out. They use some identifiers like public, private, protected to do the jobs of header files. I saw one benefit of using header file (in some book like Code Complete), they talk about that using header files, people can never look at our implementation file and it helps with encapsulation. A drawback is that it creates too many files for me. Sometimes, it looks like verbose. It is just my thought and I don't know if there are any other benefits and drawbacks that people ever see and work with header file This question may not relate directly to programming but I think that if I can understand better about programming to interface, design software.

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  • Python - List and Loop in one def

    - by Dunwitch
    I'm trying to get the def wfsc_pod1 and wfsc_ip into the same def. I'm not quite sure how to approach the problem. I want wfsc_pod1 to display all the information for name, subnet and gateway. Then wfsc_ip shows the ip addresses below it. I also get a None value when I run it as it. Not sure why. Anything more pythonic is more appreciated. class OutageAddress: subnet = ["255.255.255.0", "255.255.255.1"] # Gateway order is matched with names gateway = ["192.168.1.1", "192.168.1.2", "192.168.1.3", "192.168.1.4", "192.168.1.5", "192.168.1.6", "192.168.1.7", "192.168.1.8", "192.168.1.9"] name = ["LOC1", "LOC2", "LOC3", "LOC4", "LOC5", "LOC6", "LOC7", "LOC8", "LOC9"] def wfsc_pod1(self): wfsc_1 = "%s\t %s\t %s\t" % (network.name[0],network.subnet[0],network.gateway[0]) return wfsc_1 def wfsc_ip(self): for ip in range(100,110): ip = "192.168.1."+str(ip) print ip network = OutageAddress() print network.wfsc_pod1() print network.wfsc_ip()

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  • LINQ to SQL - database relationships won't update after submit

    - by Quantic Programming
    I have a Database with the tables Users and Uploads. The important columns are: Users -> UserID Uploads -> UploadID, UserID The primary key in the relationship is Users -> UserID and the foreign key is Uploads -> UserID. In LINQ to SQL, I do the following operations: Retrieve files var upload = new Upload(); upload.UserID = user.UserID; upload.UploadID = XXX; db.Uploads.InsertOnSubmit(upload) db.SubmitChanges(); If I do that and rerun the application (and the db object is re-built, of course) - if do something like this: foreach(var upload in user.Uploads) I get all the uploads with that user's ID. (like added in the previous example) The problem is, that my application, after adding an upload an submitting changes, doesn't update the user.Uploads collection. i.e - I don't get the newly added uploads. The user object is stored in the Session object. At first, I though that the LINQ to SQL Framework doesn't update the reference of the object, therefore I should simply "reset" the user object from a new SQL request. I mean this: Session["user"] = db.Users.Where(u => u.UserID == user.UserID).SingleOrDefault(); (Where user is the previous user) But it didn't help. Please note: After rerunning the application, user.Uploads does have the new upload! Did anyone experience this type of problem, or is it normal behavior? I am a newbie to this framework. I would gladly take any advice. Thank you!

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  • GPGPU

    WhatGPU obviously stands for Graphics Processing Unit (the silicon powering the display you are using to read this blog post). The extra GP in front of that stands for General Purpose computing.So, altogether GPGPU refers to computing we can perform on GPU for purposes beyond just drawing on the screen. In effect, we can use a GPGPU a bit like we already use a CPU: to perform some calculation (that doesn’t have to have any visual element to it). The attraction is that a GPGPU can be orders of magnitude faster than a CPU.WhyWhen I was at the SuperComputing conference in Portland last November, GPGPUs were all the rage. A quick online search reveals many articles introducing the GPGPU topic. I'll just share 3 here: pcper (ignoring all pages except the first, it is a good consumer perspective), gizmodo (nice take using mostly layman terms) and vizworld (answering the question on "what's the big deal").The GPGPU programming paradigm (from a high level) is simple: in your CPU program you define functions (aka kernels) that take some input, can perform the costly operation and return the output. The kernels are the things that execute on the GPGPU leveraging its power (and hence execute faster than what they could on the CPU) while the host CPU program waits for the results or asynchronously performs other tasks.However, GPGPUs have different characteristics to CPUs which means they are suitable only for certain classes of problem (i.e. data parallel algorithms) and not for others (e.g. algorithms with branching or recursion or other complex flow control). You also pay a high cost for transferring the input data from the CPU to the GPU (and vice versa the results back to the CPU), so the computation itself has to be long enough to justify the overhead transfer costs. If your problem space fits the criteria then you probably want to check out this technology.HowSo where can you get a graphics card to start playing with all this? At the time of writing, the two main vendors ATI (owned by AMD) and NVIDIA are the obvious players in this industry. You can read about GPGPU on this AMD page and also on this NVIDIA page. NVIDIA's website also has a free chapter on the topic from the "GPU Gems" book: A Toolkit for Computation on GPUs.If you followed the links above, then you've already come across some of the choices of programming models that are available today. Essentially, AMD is offering their ATI Stream technology accessible via a language they call Brook+; NVIDIA offers their CUDA platform which is accessible from CUDA C. Choosing either of those locks you into the GPU vendor and hence your code cannot run on systems with cards from the other vendor (e.g. imagine if your CPU code would run on Intel chips but not AMD chips). Having said that, both vendors plan to support a new emerging standard called OpenCL, which theoretically means your kernels can execute on any GPU that supports it. To learn more about all of these there is a website: gpgpu.org. The caveat about that site is that (currently) it completely ignores the Microsoft approach, which I touch on next.On Windows, there is already a cross-GPU-vendor way of programming GPUs and that is the DirectX API. Specifically, on Windows Vista and Windows 7, the DirectX 11 API offers a dedicated subset of the API for GPGPU programming: DirectCompute. You use this API on the CPU side, to set up and execute the kernels that run on the GPU. The kernels are written in a language called HLSL (High Level Shader Language). You can use DirectCompute with HLSL to write a "compute shader", which is the term DirectX uses for what I've been referring to in this post as a "kernel". For a comprehensive collection of links about this (including tutorials, videos and samples) please see my blog post: DirectCompute.Note that there are many efforts to build even higher level languages on top of DirectX that aim to expose GPGPU programming to a wider audience by making it as easy as today's mainstream programming models. I'll mention here just two of those efforts: Accelerator from MSR and Brahma by Ananth. Comments about this post welcome at the original blog.

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  • The long road to bug-free software

    - by Tony Davis
    The past decade has seen a burgeoning interest in functional programming languages such as Haskell or, in the Microsoft world, F#. Though still on the periphery of mainstream programming, functional programming concepts are gradually seeping into the imperative C# language (for example, Lambda expressions have their root in functional programming). One of the more interesting concepts from functional programming languages is the use of formal methods, the lofty ideal behind which is bug-free software. The idea is that we write a specification that describes exactly how our function (say) should behave. We then prove that our function conforms to it, and in doing so have proved beyond any doubt that it is free from bugs. All programmers already use one form of specification, specifically their programming language's type system. If a value has a specific type then, in a type-safe language, the compiler guarantees that value cannot be an instance of a different type. Many extensions to existing type systems, such as generics in Java and .NET, extend the range of programs that can be type-checked. Unfortunately, type systems can only prevent some bugs. To take a classic problem of retrieving an index value from an array, since the type system doesn't specify the length of the array, the compiler has no way of knowing that a request for the "value of index 4" from an array of only two elements is "unsafe". We restore safety via exception handling, but the ideal type system will prevent us from doing anything that is unsafe in the first place and this is where we start to borrow ideas from a language such as Haskell, with its concept of "dependent types". If the type of an array includes its length, we can ensure that any index accesses into the array are valid. The problem is that we now need to carry around the length of arrays and the values of indices throughout our code so that it can be type-checked. In general, writing the specification to prove a positive property, even for a problem very amenable to specification, such as a simple sorting algorithm, turns out to be very hard and the specification will be different for every program. Extend this to writing a specification for, say, Microsoft Word and we can see that the specification would end up being no simpler, and therefore no less buggy, than the implementation. Fortunately, it is easier to write a specification that proves that a program doesn't have certain, specific and undesirable properties, such as infinite loops or accesses to the wrong bit of memory. If we can write the specifications to prove that a program is immune to such problems, we could reuse them in many places. The problem is the lack of specification "provers" that can do this without a lot of manual intervention (i.e. hints from the programmer). All this might feel a very long way off, but computing power and our understanding of the theory of "provers" advances quickly, and Microsoft is doing some of it already. Via their Terminator research project they have started to prove that their device drivers will always terminate, and in so doing have suddenly eliminated a vast range of possible bugs. This is a huge step forward from saying, "we've tested it lots and it seems fine". What do you think? What might be good targets for specification and verification? SQL could be one: the cost of a bug in SQL Server is quite high given how many important systems rely on it, so there's a good incentive to eliminate bugs, even at high initial cost. [Many thanks to Mike Williamson for guidance and useful conversations during the writing of this piece] Cheers, Tony.

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  • The long road to bug-free software

    - by Tony Davis
    The past decade has seen a burgeoning interest in functional programming languages such as Haskell or, in the Microsoft world, F#. Though still on the periphery of mainstream programming, functional programming concepts are gradually seeping into the imperative C# language (for example, Lambda expressions have their root in functional programming). One of the more interesting concepts from functional programming languages is the use of formal methods, the lofty ideal behind which is bug-free software. The idea is that we write a specification that describes exactly how our function (say) should behave. We then prove that our function conforms to it, and in doing so have proved beyond any doubt that it is free from bugs. All programmers already use one form of specification, specifically their programming language's type system. If a value has a specific type then, in a type-safe language, the compiler guarantees that value cannot be an instance of a different type. Many extensions to existing type systems, such as generics in Java and .NET, extend the range of programs that can be type-checked. Unfortunately, type systems can only prevent some bugs. To take a classic problem of retrieving an index value from an array, since the type system doesn't specify the length of the array, the compiler has no way of knowing that a request for the "value of index 4" from an array of only two elements is "unsafe". We restore safety via exception handling, but the ideal type system will prevent us from doing anything that is unsafe in the first place and this is where we start to borrow ideas from a language such as Haskell, with its concept of "dependent types". If the type of an array includes its length, we can ensure that any index accesses into the array are valid. The problem is that we now need to carry around the length of arrays and the values of indices throughout our code so that it can be type-checked. In general, writing the specification to prove a positive property, even for a problem very amenable to specification, such as a simple sorting algorithm, turns out to be very hard and the specification will be different for every program. Extend this to writing a specification for, say, Microsoft Word and we can see that the specification would end up being no simpler, and therefore no less buggy, than the implementation. Fortunately, it is easier to write a specification that proves that a program doesn't have certain, specific and undesirable properties, such as infinite loops or accesses to the wrong bit of memory. If we can write the specifications to prove that a program is immune to such problems, we could reuse them in many places. The problem is the lack of specification "provers" that can do this without a lot of manual intervention (i.e. hints from the programmer). All this might feel a very long way off, but computing power and our understanding of the theory of "provers" advances quickly, and Microsoft is doing some of it already. Via their Terminator research project they have started to prove that their device drivers will always terminate, and in so doing have suddenly eliminated a vast range of possible bugs. This is a huge step forward from saying, "we've tested it lots and it seems fine". What do you think? What might be good targets for specification and verification? SQL could be one: the cost of a bug in SQL Server is quite high given how many important systems rely on it, so there's a good incentive to eliminate bugs, even at high initial cost. [Many thanks to Mike Williamson for guidance and useful conversations during the writing of this piece] Cheers, Tony.

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  • VirtualBox - Public Static IP for a Debian Guest on a Dedicated Server

    - by user86296
    Goal: I want to run a Debian-squeeze-Guest in VirtualBox and it's own public static ip. I found tons of threads about this topic, but all in all I'm now trying for 10 hours (reading the manual, the forums, trying to learn about networking concepts & commands) to give a Guest his own public static ip (so that the Guest is similar to a vServer you can order from a hosting company), but wasn't able to. Since I'm a big noob as far as networking stuff is concerned, I'm probably doing something wrong.(please bear with me :-) ) Situation: VirtualBox 4.0.10 (headless no gui) is running on a dedicated Debian-Server, the Guest OS is Debian as well. The server has a static ip and I ordered an additional ip for a VM. Problem description: Upto now I was able to use NAT to access the VM from the outside and to setup an internal network between several Guests and all of this worked very well. When setting NIC 1 to bridged and configuring a public static ip on the guest, the guest was unpingable. (neither from outside, nor from the host) I could connect to the guest via the internal network, from another vm, though. ( VBoxManage controlvm VMGuest nic1 bridged eth0 ) ( configuration attempt of static-ip on the guest '/etc/network/interfaces' is below) Please let me know what I'm doing wrong, or what I can try to get it to work, or if you need more info. I think I've read that with a current VirtualBox-version for bridged networking no special host-configuration is necessary, is that accurate, or might that be the problem? Additional Info Info I got from the hosting company about the additional IP Please note that you can use the IP address only for this server. IP: 46.4.xx.xx Gateway: 46.4.xx.xx Mask: 255.255.255.248 VBoxManage showvminfo VMGuest |less ... NIC 1: MAC: 080027D72F7B, Attachment: Bridged Interface 'eth0', Cable connected: on, Trace: off (file: none), Type: 82540EM, Reported speed: 0 Mbps, Boot priority: 0 NIC 2: MAC: 080027B03B75, Attachment: Internal Network 'InternalNet1', Cable connected: on, Trace: off (file: none), Type: Am79C973, Reported speed: 0 Mbps, Boot priority: 0 NIC 3: disabled (...rest is disabled) cat /etc/network/interfaces on the Host-machine # Loopback device: auto lo iface lo inet loopback # device: eth0 auto eth0 iface eth0 inet static address 46.4.xx.xx broadcast 46.4.xx.xx netmask 255.255.255.224 gateway 46.4.xx.xx post-up mii-tool -F 100baseTx-FD eth0 # default route to access subnet up route add -net 46.4.xx.xx netmask 255.255.255.224 gw 46.4.xx.xx eth0 cat /etc/network/interfaces on the Guest-VM # This file describes the network interfaces available on your system # and how to activate them. For more information, see interfaces(5). # The loopback network interface auto lo iface lo inet loopback # The primary network interface allow-hotplug eth0 auto eth0 iface eth0 inet static address 46.4.xx.xx netmask 255.255.255.248 gateway 46.4.xx.xx auto eth1 iface eth1 inet dhcp ifconfig -a on the Guest shows the correct static ip for eth0 but the Guest is unreachable "over eth0" eth0 Link encap:Ethernet HWaddr 08:00:27:d7:2f:7b inet addr:46.4.xx.xx Bcast:46.4.xx.xx Mask:255.255.255.248 inet6 addr: fe80::a00:27ff:fed7:2f7b/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:21 errors:0 dropped:0 overruns:0 frame:0 TX packets:69 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:1260 (1.2 KiB) TX bytes:3114 (3.0 KiB) eth1 Link encap:Ethernet HWaddr 08:00:27:b0:3b:75 inet addr:192.168.10.3 Bcast:192.168.10.255 Mask:255.255.255.0 inet6 addr: fe80::a00:27ff:feb0:3b75/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:142 errors:0 dropped:0 overruns:0 frame:0 TX packets:92 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:15962 (15.5 KiB) TX bytes:14540 (14.1 KiB) Interrupt:16 Base address:0xd240 lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:123 errors:0 dropped:0 overruns:0 frame:0 TX packets:123 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:25156 (24.5 KiB) TX bytes:25156 (24.5 KiB)

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  • Which Stroustrup book should I use?

    - by Chris Simmons
    I'm a C# programmer that is looking to branch out. I'm bored of writing business software and want to start getting into graphics programming and games/simulators. So I figured, although writing that stuff isn't impossible in managed code, the "right" way to do that would be to look to C++, of course focussing on the language first, then getting into OpenGL or DirectX (or whatever). Way way back ('98? '99?) I had tried and failed to really grasp Stroustrup's The C++ Programming Language. I know that this book is often not recommended for the beginner. Anyway, I picked it back up (in a much more recent printing) and I'm actually getting it and enjoying it. I also have a copy of his textbook, Programming: Principles and Practice Using C++, which, as I understand it, is really geared toward teaching programming, not necessarily C++. I'm certainly not arrogant enough to claim I don't have anything more to learn about programming, data structures, algoriths, etc., however I'm not a novice there either. So my question is, with the goal of gaining the broader and more real-world-useful understanding of C++ and given my background, on which should I focus? The denser (as I perceive it) TCPPPL or the gentler Programming? EDIT: I thank everyone for the responses. However, I've got a personal choice here to make between these two books. Granted there are other very good books out there, but I'm already a good length into both of the books I mention and I'd like to finish one. So, can anyone respond on which would be the better and why? Time is not an issue; I'm not looking (at this point) at an "accelerated" read.

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  • What does it mean when ARP shows <incomplete> on eth1

    - by Geoff Dalgas
    We have been using HAProxy along with heartbeat from the Linux-HA project. We are using two linux instances to provide a failover. Each server has with their own public IP and a single IP which is shared between the two using a virtual interface (eth1:1) at IP: 69.59.196.211 The virtual interface (eth1:1) IP 69.59.196.211 is configured as the gateway for the windows servers behind them and we use ip_forwarding to route traffic. We are experiencing an occasional network outage on one of our windows servers behind our linux gateways. HAProxy will detect the server is offline which we can verify by remoting to the failed server and attempting to ping the gateway: Pinging 69.59.196.211 with 32 bytes of data: Reply from 69.59.196.220: Destination host unreachable. Running arp -a on this failed server shows that there is no entry for the gateway address (69.59.196.211): Interface: 69.59.196.220 --- 0xa Internet Address Physical Address Type 69.59.196.161 00-26-88-63-c7-80 dynamic 69.59.196.210 00-15-5d-0a-3e-0e dynamic 69.59.196.212 00-21-5e-4d-45-c9 dynamic 69.59.196.213 00-15-5d-00-b2-0d dynamic 69.59.196.215 00-21-5e-4d-61-1a dynamic 69.59.196.217 00-21-5e-4d-2c-e8 dynamic 69.59.196.219 00-21-5e-4d-38-e5 dynamic 69.59.196.221 00-15-5d-00-b2-0d dynamic 69.59.196.222 00-15-5d-0a-3e-09 dynamic 69.59.196.223 ff-ff-ff-ff-ff-ff static 224.0.0.22 01-00-5e-00-00-16 static 224.0.0.252 01-00-5e-00-00-fc static 225.0.0.1 01-00-5e-00-00-01 static On our linux gateway instances arp -a shows: peak-colo-196-220.peak.org (69.59.196.220) at <incomplete> on eth1 stackoverflow.com (69.59.196.212) at 00:21:5e:4d:45:c9 [ether] on eth1 peak-colo-196-215.peak.org (69.59.196.215) at 00:21:5e:4d:61:1a [ether] on eth1 peak-colo-196-219.peak.org (69.59.196.219) at 00:21:5e:4d:38:e5 [ether] on eth1 peak-colo-196-222.peak.org (69.59.196.222) at 00:15:5d:0a:3e:09 [ether] on eth1 peak-colo-196-209.peak.org (69.59.196.209) at 00:26:88:63:c7:80 [ether] on eth1 peak-colo-196-217.peak.org (69.59.196.217) at 00:21:5e:4d:2c:e8 [ether] on eth1 Why would arp occasionally set the entry for this failed server as <incomplete>? Should we be defining our arp entries statically? I've always left arp alone since it works 99% of the time, but in this one instance it appears to be failing. Are there any additional troubleshooting steps we can take help resolve this issue? THINGS WE HAVE TRIED I added a static arp entry for testing on one of the linux gateways which still didn't help. root@haproxy2:~# arp -a peak-colo-196-215.peak.org (69.59.196.215) at 00:21:5e:4d:61:1a [ether] on eth1 peak-colo-196-221.peak.org (69.59.196.221) at 00:15:5d:00:b2:0d [ether] on eth1 stackoverflow.com (69.59.196.212) at 00:21:5e:4d:45:c9 [ether] on eth1 peak-colo-196-219.peak.org (69.59.196.219) at 00:21:5e:4d:38:e5 [ether] on eth1 peak-colo-196-209.peak.org (69.59.196.209) at 00:26:88:63:c7:80 [ether] on eth1 peak-colo-196-217.peak.org (69.59.196.217) at 00:21:5e:4d:2c:e8 [ether] on eth1 peak-colo-196-220.peak.org (69.59.196.220) at 00:21:5e:4d:30:8d [ether] PERM on eth1 root@haproxy2:~# arp -i eth1 -s 69.59.196.220 00:21:5e:4d:30:8d root@haproxy2:~# ping 69.59.196.220 PING 69.59.196.220 (69.59.196.220) 56(84) bytes of data. --- 69.59.196.220 ping statistics --- 7 packets transmitted, 0 received, 100% packet loss, time 6006ms Rebooting the windows web server solves this issue temporarily with no other changes to the network but our experience shows this issue will come back. Swapping network cards and switches I noticed the link light on the port of the switch for the failed windows server was running at 100Mb instead of 1Gb on the failed interface. I moved the cable to several other open ports and the link indicated 100Mb for each port that I tried. I also swapped the cable with the same result. I tried changing the properties of the network card in windows and the server locked up and required a hard reset after clicking apply. This windows server has two physical network interfaces so I have swapped the cables and network settings on the two interfaces to see if the problem follows the interface. If the public interface goes down again we will know that it is not an issue with the network card. (We also tried another switch we have on hand, no change) Changing network hardware driver versions We've had the same problem with the latest Broadcom driver, as well as the built-in driver that ships in Windows Server 2008 R2. Replacing network cables As a last ditch effort we remembered another change that occurred was the replacement of all of the patch cords between our servers / switch. We had purchased two sets, one green of lengths 1ft - 3ft for the private interfaces and another set of red cables for the public interfaces. We swapped out all of the public interface patch cables with a different brand and ran our servers without issue for a full week ... aaaaaand then the problem recurred. Disable checksum offload, remove TProxy We also tried disabling TCP/IP checksum offload in the driver, no change. We're now pulling out TProxy and moving to a more traditional x-forwarded-for network arrangement without any fancy IP address rewriting. We'll see if that helps.

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  • Gnome 3 freezes on logon on samsung RV 509

    - by Noufal
    I have a Samsung NP-RV509 A0FIN and I tried to install GNU/Linux with gnome 3.2 on it. I tried Fedora 16, Ubuntu 11.10 and Linux Mint 12 RC, but with no success. All of these freezes upon login into gnome shell. I think it is the problem with graphics driver, so I tried xorg-edgers ppa on my last installation, ie., Linux Mint. I also tried various intel graphics packages listed on Synaptic package manager, but no success again. My device configuration is as follows(obtained from windows 7): More details about my computer Component Details Subscore Base score Processor Intel(R) Pentium(R) CPU P6200 @ 2.13GHz 5.6 4.6 Memory (RAM) 4.00 GB 7.2 Graphics Intel(R) HD Graphics 4.6 Gaming graphics 1562 MB Total available graphics memory 5.2 Primary hard disk 12GB Free (50GB Total) 5.9 Windows 7 Ultimate System -------------------------------------------------------------------------------- Manufacturer SAMSUNG ELECTRONICS CO., LTD. Model RV409/RV509/RV709 Total amount of system memory 4.00 GB RAM System type 32-bit operating system Number of processor cores 2 64-bit capable Yes Storage -------------------------------------------------------------------------------- Total size of hard disk(s) 418 GB Disk partition (C:) 12 GB Free (50 GB Total) Media drive (D:) CD/DVD Disk partition (E:) 526 MB Free (191 GB Total) Disk partition (F:) 101 GB Free (177 GB Total) Graphics -------------------------------------------------------------------------------- Display adapter type Intel(R) HD Graphics Total available graphics memory 1562 MB Dedicated graphics memory 64 MB Dedicated system memory 0 MB Shared system memory 1498 MB Display adapter driver version 8.15.10.2202 Primary monitor resolution 1366x768 DirectX version DirectX 10 Network -------------------------------------------------------------------------------- Network Adapter Realtek PCIe GBE Family Controller Network Adapter Broadcom 802.11n Network Adapter Network Adapter Microsoft Virtual WiFi Miniport Adapter Notes -------------------------------------------------------------------------------- The gaming graphics score is based on the primary graphics adapter. If this system has linked or multiple graphics adapters, some software applications may see additional performance benefits. Any help is appreciated, and thanks in advance.

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  • Ubuntu 12.04 Beta 2 takes over 2 minutes to boot up! [closed]

    - by oshirowanen
    Possible Duplicate: There's an issue with an Alpha/Beta Release of Ubuntu, what should I do? I've installed Ubuntu 12.04 Beta 2 for testing purposes. When I power on the computer now, I get the following message beneath the ubuntu logo: Waiting for network configuration About a minute later I get this message: Waiting up to 60 more seconds for network configuration About a minute later I get this message: Booting system without full network configuation About 10 seconds later I get the ubuntu login screen. Why is this happening?

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