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  • java RMI connection to server

    - by user85116
    I have a very simple rmi client / server application. I don't use the "rmiregistry" application though, I use this to create the server: server = new RemoteServer(); registry = LocateRegistry.createRegistry(PORT); registry.bind("RemoteServer", server); The client part is: registry = LocateRegistry.getRegistry(IPADDRESS, PORT); remote = (IRemoteServer) registry.lookup("RemoteServer"); Here is the fascinating problem: The application works perfectly when both server and client are running in my (private) local network. As soon as I put the server on a public server, the application hangs for a minute, then gives me the following error: java.rmi.ServerException: RemoteException occurred in server thread; nested exception is: java.rmi.ConnectException: Connection refused to host: 192.168.x.y; nested exception is: java.net.ConnectException: Connection timed out: connect at sun.rmi.server.UnicastServerRef.dispatch(Unknown Source) at sun.rmi.transport.Transport$1.run(Unknown Source) at java.security.AccessController.doPrivileged(Native Method) at sun.rmi.transport.Transport.serviceCall(Unknown Source) at sun.rmi.transport.tcp.TCPTransport.handleMessages(Unknown Source) at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(Unknown Source ... (the rest is truncated) The key I think is that the client (running on my private network) cannot connect to myself (my address is 192.168.x.y where x.y is some other numbers, but the real error message shows my ip address listed there) If I kill the rmi server on the public internet, then I instantly get a "connection refused to host: a.b.c.d") message, so I know that something at the server end is at least working. Any suggestions? EDIT: just to make this a little more clear: 192.168.x.y is the client address, a.b.c.d is the server address. The stacktrace shows the client cannot connect to the client.

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  • "do it all" page structure and things to watch out for?

    - by Andrew Heath
    I'm still getting my feet wet in PHP (my 1st language) and I've reached the competency level where I can code one page that handles all sorts of different related requests. They generally have a structure like this: (psuedo code) <?php include 'include/functions.php'; IF authorized IF submit (add data) ELSE IF update (update data) ELSE IF list (show special data) ELSE IF tab switch (show new area) ELSE display vanilla (show default) ELSE "must be registered/logged-in" ?> <HTML> // snip <?php echo $output; ?> // snip </HTML> and it all works nicely, and quite quickly which is cool. But I'm still sorta feeling my way in the dark... and would like some input from the pros regarding this type of page design... is it a good long-term structure? (it seems easily expanded...) are there security risks particular to this design? are there corners I should avoid painting myself into? Just curious about what lies ahead, really...

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  • handling DATETIME values 0000-00-00 00:00:00 in JDBC

    - by Jason S
    I get an exception (see below) if I try to do resultset.getString("add_date"); for a JDBC connection to a MySQL database containing a DATETIME value of 0000-00-00 00:00:00 (the quasi-null value for DATETIME), even though I'm just trying to get the value as string, not as an object. I got around this by doing SELECT CAST(add_date AS CHAR) as add_date which works, but seems silly... is there a better way to do this? My point is that I just want the raw DATETIME string, so I can parse it myself as is. note: here's where the 0000 comes in: (from http://dev.mysql.com/doc/refman/5.0/en/datetime.html) Illegal DATETIME, DATE, or TIMESTAMP values are converted to the “zero” value of the appropriate type ('0000-00-00 00:00:00' or '0000-00-00'). The specific exception is this one: SQLException: Cannot convert value '0000-00-00 00:00:00' from column 5 to TIMESTAMP. SQLState: S1009 VendorError: 0 java.sql.SQLException: Cannot convert value '0000-00-00 00:00:00' from column 5 to TIMESTAMP. at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1055) at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:956) at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:926) at com.mysql.jdbc.ResultSetImpl.getTimestampFromString(ResultSetImpl.java:6343) at com.mysql.jdbc.ResultSetImpl.getStringInternal(ResultSetImpl.java:5670) at com.mysql.jdbc.ResultSetImpl.getString(ResultSetImpl.java:5491) at com.mysql.jdbc.ResultSetImpl.getString(ResultSetImpl.java:5531)

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  • Merging: hg/git vs. svn

    - by stmax
    I often read that hg (and git and...) are better at merging than svn but I have never seen practical examples of where hg/git can merge something where svn fails (or where svn needs manual intervention). Could you post a few step-by-step lists of branch/modify/commit/...-operations that show where svn would fail while hg/git happily moves on? Practical, not highly exceptional cases please... Some background: we have a few dozen developers working on projects using svn, with each project (or group of similar projects) in its own repo. We know how to apply release- and feature-branches so we don't run into problems very often (i.e. we've been there, but we've learned to overcome joel's problems of "one programmer causing trauma to the whole team" or "needing six developers for two weeks to reintegrate a branch"). We have release-branches that are very stable and only used to apply bugfixes. We have trunks that should be stable enough to be able to create a release within one week. And we have feature-branches that single developers or groups of developers can work on. Yes, they are deleted after reintegration so they don't clutter up the repository. ;) So I'm still trying to find the advantages of hg/git over svn. I'd love to get some hands-on experience, but there aren't any bigger projects we could move to hg/git yet, so I'm stuck with playing with small artifical projects that only contain a few made up files. And I'm looking for a few cases where you can feel the impressive power of hg/git, since so far I have often read about them but failed to find them myself.

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  • How to avoid using this in a constructor

    - by Paralife
    I have this situation: interface MessageListener { void onMessageReceipt(Message message); } class MessageReceiver { MessageListener listener; public MessageReceiver(MessageListener listener, other arguments...) { this.listener = listener; } loop() { Message message = nextMessage(); listener.onMessageReceipt(message); } } and I want to avoid the following pattern: (Using the this in the Client constructor) class Client implements MessageListener { MessageReceiver receiver; MessageSender sender; public Client(...) { receiver = new MessageReceiver(this, other arguments...); sender = new Sender(...); } . . . @Override public void onMessageReceipt(Message message) { if(Message.isGood()) sender.send("Congrtulations"); else sender.send("Boooooooo"); } } The reason why i need the above functionality is because i want to call the sender inside the onMessageReceipt() function, for example to send a reply. But I dont want to pass the sender into a listener, so the only way I can think of is containing the sender in a class that implements the listener, hence the above resulting Client implementation. Is there a way to achive this without the use of 'this' in the constructor? It feels bizare and i dont like it, since i am passing myself to an object(MessageReceiver) before I am fully constructed. On the other hand, the MessageReceiver is not passed from outside, it is constructed inside, but does this 'purifies' the bizarre pattern? I am seeking for an alternative or an assurance of some kind that this is safe, or situations on which it might backfire on me.

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  • Any book on designing and implementing a CRPG engine?

    - by Fabzter
    Hi! First, let me tell you, I am not really interested in making my own rpg engine (at least not in the near future, hehe), but I do feel like I want to understand the internals of how a rpg engine works. Why? Well, because I like to read about programming and design, It keeps me motivated and excited, and because I know I will learn a lot, for, even when I have been programming for some years now, I never stop considering myself an ignorant... there are simply SO many things involving a game engine (specially rpg ones, like branching storylines, and items and economics!) I'm eager to know. I've been searching (and thus, finding) lots of info online, but it is never focused in what I'm interested (most of it talks about the mathematics and AI algorithms implementation, which I know quite well), which is the design of overall structure, patterns, scripting engine, decision engine... damn, so many things I can't even imagine, since I've never done any game programming. I hope you know have an idea of how I feel, and how I want to learn for the sake of learning, and why would I want you to tell me if you know if there exist books touching the topics that interest me the most.

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  • Should I learn VB.NET or C#?

    - by Ravi
    Background I have decided to do my graduation project (yet to start) in .NET. Regarding it, I am bit confused about: what language should I learn: VB.NET or C#? What I have learnt from those who know it that both VB.NET and C# have: The same concepts VB.NET is simpler as it is more like English statements but also C# is simple too if you already know C (Which I do know) Question So considering some factors, e.g. career point of view, newness, challenging and beneficial, etc., what language should I choose? Please help me out. And clearly do justify your answer (whatever reason you have.) References (Extra) A little information about what project I am doing: It is a database file system. Technologies I'll be using are SQL Server, WPF, etc. I just love the concept of Database file system.So those who want to know more about Database file system, here are the links DBFS (This one is really good.Serves as primary reference for me) Towards A Single Folder Filesystem stackoverflow-What is a database file system? UPDATE1 : After some really good explained answers (actually all are good at their place), I have finally decided to go with C# for myself. Thank you all. Still, you are requested to put your opinion (Once it is reopened,of course) UPDATE2 : Question reopened and made community wiki.Thank you all.

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  • Single Form with Multiple Dynamic Buttons

    - by John Reilly
    I've spent hours/days trying to figure this out and now I'm completely perplexed so I thought I'd give stackoverflow a try. I'm (a newb) working in Java/JSP using Eclipse hosting on Google App Engine trying to develop an app for a volunteer organization I'm a member of. Rather than embarrass myself by showing my current code I'd love just a nudge in the right direction. I have a form (which doubles as a report basically) showing "people" grouped under the "task" they are currently working on. I would like to select multiple people from multiple tasks and reassign them to another task e.g. Bill and Jane are Gardening, Jeff is Painting. I want to select Jane and Jeff (all people have an associated checkbox in the form) and re-assign them to Sweeping (which is a task on the form but has no people assigned to it yet). Ideally, the re-assignment to Sweeping would be via a Sweeping button (each task would have a dynamically-created task button) that would pass the "Sweeping" value to a servlet along with an array or list of people whose checkbox has been checked. The servlet would handle the request (creating an Assignment "object/entity" with timeStamp, personId, taskId) and then re-direct back to the form/report which would then repaint with the current tasks/people generated from the Assignments class in the datastore. All the tasks are user-defined and retrieved from the database when building the form. Ditto the people. I've been trying to keep the jsp for presentation and the servlets for the processing but I'm no purist and would just like to get unstuck. Many thanks in advance for your assistance.

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  • Why does this cast to Base class in virtual function give a segmentation fault?

    - by dehmann
    I want to print out a derived class using the operator<<. When I print the derived class, I want to first print its base and then its own content. But I ran into some trouble (see segfault below): class Base { public: friend std::ostream& operator<<(std::ostream&, const Base&); virtual void Print(std::ostream& out) const { out << "BASE!"; } }; std::ostream& operator<<(std::ostream& out, const Base& b) { b.Print(out); return out; } class Derived : public Base { public: virtual void Print(std::ostream& out) const { out << "My base: "; //((const Base*)this)->Print(out); // infinite, calls this fct recursively //((Base*)this)->Print(out); // segfault (from infinite loop?) ((Base)*this).Print(out); // OK out << " ... and myself."; } }; int main(int argc, char** argv){ Derived d; std::cout << d; return 0; } Why can't I cast in one of these ways? ((const Base*)this)->Print(out); // infinite, calls this fct recursively ((Base*)this)->Print(out); // segfault (from infinite loop?)

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  • T-SQL Table Joins - Unique Situation

    - by Dimitri
    Hello Everyone. This is my first time encountering the case like this and don't quite know how to handle. Situation: I have one table tblSettingsDefinition, with fields: ID, GroupID, Name, typeID, DefaultValue. Then I have tblSettingtypes with fields TypeID, Name. And I have final table, tblUserSettings with fields SettingID, SettingDefinitionID, UserID, Value. The whole point of this is to have customizable settings. Setting can be defined for a Group or as global setting (if GroupID is NULL). It will have a default value, but if user modifies the setting, an entry is added to tblUserSettings that stores new value. I want to have a query that grabs user settings by first looking at the tblUserSettings, and if it has records for the given user, grabs them, if not retrieves default settings. But the trick is that no matter if user has settings or not, I need to have fields from other two table retrieved to know the setting's Type, Name etc... (which are stored in those other tables). I'm writing query something like this: SELECT * FROM tblSettingDefinition SD LEFT JOIN tblUserSettings US ON SD.SettingID = US.SettingDefinitionID JOIN tblSettingTypes ST ON SD.TypeID=ST.ID WHERE US.UserID=@UserID OR ((SD.GroupID IS NULL) OR (SD.GroupID=(SELECT GroupID FROM tblUser WHERE ID=@UserID))) but it retrieves settings for all users from tblUserSettings instead of just ones that match current @UserID. And if @UserID has no records in tblUserSettings, still, all user settings are retrieved instead of the defaults from tblSettingDefinition. Hope I made myself clear. Any help would be highly appreciated. Thank you.

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  • New to web development - backend questions

    - by James
    I'm new to web development although I'm confident in the roadmap for the front-end. I need direction on two things: Basic architecture Back-end technologies For architecture, what do I need to get started? From what I know, its: Get a domain name registered (godaddy?) Find a web host ??? anything else? or start developing the site? I don't think its that easy, there must be something I'm missing, right? For the back-end technologies, I have application development experience with Java and Python, but how likely is it to find a back-end hosting site that supports these languages over PHP? Is PHP a better choice? If I stick with what I know for the back-end, am I sabotaging myself later on? If I need help, how is the market for a python/java developer vs. a php developer? What do I need to know about databases? I have some basic SQL experience. Do hosting sites have limitations on the type of databases or bandwidth I need to worry about? I'm working through some of the common sites: StackOverflow, Sitepoint forums, Google, etc...are there other resources I should use?

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  • Architecture Guidance Needed?

    - by vijay
    We are about to automate number of process for our reporting team. (The reports are like daily reports, weekly reports, monthly reports, etc..) Mostly the process is like pulling some data from the oracle and then fill them in particular excel template files. Each reports and so their templates are different from each other. Except the excel file manipulation, there are hardly any business logic behind these. Client wanted an integrated tool and all the automated processes are placed as menus/submenus. Right now roughly there are around 30 process waiting to be automated. And we are expecting more new reports in the next quarter. I am nowhere to near having any practical experience when comes to architecuring. Already i have been maintaining two or three systems(they are more than 4yrs old.) for this prestegious client.The possiblity of the above mentioned tool will be manintained for another 3 yrs is very likely. From my past experience i've been through the pain of implmenting change requests to the rigd & undocumented code base resulting in the break down of the system and then eventually myself. So My main and top most concern is the maintainablity. When i was searching for these i came across this link, Smart Clients Using CAB and SCSF is the above link appropriate for my requirement? Also Should i place each automated processes in separate forms under a single project, or place them in separate projects under a single solution.. Please correct me if have missed any other important information. Thx.

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  • Python: OSX Library for fast full screen jpg/png display

    - by Parand
    Frustrated by lack of a simple ACDSee equivalent for OS X, I'm looking to hack one up for myself. I'm looking for a gui library that accommodates: Full screen image display High quality image fit-to-screen (for display) Low memory usage Fast display Reasonable learning curve (the simpler the better) Looks like there are several choices, so which is the best? Here are some I've run across: PyOpenGL PyGame PyQT wxpython I don't have any particular experience with any of these, nor any strong desire to become an expert - I'm looking for the simplest solution. What do you recommend? [Update] For those not familiar with ACDSee, here's what it does that I care about: Simple list/thubmnail display of images in a directory Sort by name/size/type Ability to view images full screen Single-key delete while viewing full screen Move to next/previous image while viewing full screen Ability to select a group of images for: move to / copy to directory delete resize ACDSee has a bunch of niceties as well, such as remembering directories you've moved images to in the past, remembering your resize settings, displaying the total size of the images you've selected, etc. I've tried most of the options I could find (including Xee) and none of them quite get there. Please keep in mind that this is a programming/library question, not a criticism of any of the existing tools.

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  • Qt moc failure without an error message

    - by Robert Parker
    So I'm pretty new to Qt, and I've just inherited a project from someone else who is also new to Qt. He isn't around this week btw. We are using Visual Studio 2008, and have the latest version of Qt installed(4.6.2). The project builds on my coworker's machine fine, and I can get the project from svn and build it directly. But under any other circumstances it refuses to build on my machine, and it doesn't give me much of an explanation why. Even if I just do a 'build clean' and then a 'build' it doesn't work. Any slight modification will make it fail. When I try to build the entire project I get the error message: 1Moc'ing MatrixTypeInterface.h... 1moc: Cannot create .\GeneratedFiles\Debug\moc_MatrixTypeInterface.cpp;.\GeneratedFiles\Debug\moc_matrixtypeinterface.cpp 1Project : error PRJ0019: A tool returned an error code from "Moc'ing MatrixTypeInterface.h..." The moc tool doesn't give any sort of error message as to why it isn't working, and I wasted most of yesterday trying to figure out why. I got the command that VS was using to call moc, and I entered in the command line myself. It didn't write anything to the screen. Any ideas?

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  • What is your workflow when designing HTML/CSS layouts?

    - by DMin
    I have been working with PHP/MySQL as a hobby for close to a couple of years now, I have been working with photoshop for a very long time, I know CSS & HTML well enough to write without any reference, so, I would not consider myself someone who's very new at this. I have recently started developing websites professionally - (only person working on the project). I have seen the power of Joomla and how you can make a website ready for your customer in a matter of hours(if not minutes). I find it very hard to make layouts that remotely look like the themes on joomla. I find making even simple layouts a very cumbersome process and takes a lot of time to get a good enough output. I have a feeling I may not be using the right tools or workflow for the job. What I wanted to findout was, as part of the industry : How do, you, make your website when you do it from scratch? What are the tools that you use? What is your workflow? Just noted a few things I know already, for your reference(You can skip this if you like) I have seen the export for web for Photoshop that exports CSS - but (as far as I know) exports only absolutely positioned webpages so they need to be beaten and fixed if you want to use them for example for joomla. I have used the SiteGrinder plugin for Photoshop that exports HTML/CSS. It looks promising but haven't tried it extensively. One of the tools that save loads of time is FireBug. This makes it easy to edit html and css on the fly and get the page looking exactly as you want it. Recently stumbled upon fireworks. But haven't explored it much. Thanks! :)

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  • Building a News-feed that comprises posts "created by user's connections" && "on the topics user is following"

    - by aklin81
    I am working on a project of Questions & Answers website that allows a user to follow questions on certain topics from his network. A user's news-feed wall comprises of only those questions that have been posted by his connections and tagged on the topics that he is following(his expertise topics). I am confused what database's datamodel would be most fitting for such an application. The project needs to consider the future provisions for scalability and high performance issues. I have been looking at Cassandra and MySQL solutions as of now. After my study of Cassandra I realized that Simple news-feed design that shows all the posts from network would be easy to design using Cassandra by executing fast writes to all followers of a user about the post from user. But for my kind of application where there is an additional filter of 'followed topics', (ie, the user receives posts "created by his network" && "on topics user is following"), I could not convince myself with a good schema design in Cassandra. I hope if I missed something because of my short understanding of cassandra, perhaps, can you please help me out with your suggestions of how this news-feed could be implemented in Cassandra ? Looking for a great project with Cassandra ! Edit: There are going to be maximum 5 tags allowed for tagging the question (ie, max 5 topics can be tagged on a question).

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  • Are there any ASP.NET MVC subscription-based starter kits or examples?

    - by Wayne M
    Basically something that handles the low-level "plumbing" code for a subscription-based service. I see a lot of things dealing with basic membership, but nothing that handles the subscription aspect (recurring billing, automated jobs for setting up billing, notification for billing, etc). This might be the one thing that keeps me from using ASP.NET MVC for my SaaS idea, since it would take a fair amount of development time to write my own; if I go with my other option, Ruby on Rails, I can buy a kit that does all of this for $250. I haven't found anything even remotely close to this for .NET - all of the SaaS sample apps I've seen are more like StackOverflow et all where you have one site that multiple people log on to, not the web application model where you have subscribers who are billed monthly, each of whom has users and other entities (e.g. Customers, Tasks, etc) for their own site. Is there anything similar for ASP.NET, or some kind of guidelines for writing my own if I have to, so I don't waste too much time? As a startup that means that I'm doing all the coding myself. I've found this, but it seems to only be for billing and didn't seem to have much (any?) documentation on exactly how to set it up.

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  • Delegate OpenID to Google (NOT Google Apps)

    - by Rio
    OK, I searched this question on SO but no good answer. After spent some time I figured out how to do it. I'm going to answer this myself as a way to share it. Not sure if this is the correct way to use SO, but here it goes: Now it is possible delegate OpenID to your Google account (not Google Apps). No, this is not using the demo OpenID provider using App Engine. This is your REAL Google account! First you need to enable your Google Profiles. Try to view your profile and edit it, there should be an option to set your Profile URL. You have two choices there: either use your Gmail account name (without the @gmail.com part) as your profile id, or a random number assigned to you. It's up to you to decide which one to use. Either way, that id is your profile id below. Now add the following HTML code to your delegating page: <link rel="openid2.provider" href="https://www.google.com/accounts/o8/ud?source=profiles" > <link rel="openid2.local_id" href="http://www.google.com/profiles/[YOUR PROFILE ID]" > And it's done. Now try login SO with your custom url!

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  • bash: function + source + declare = boom

    - by Chen Levy
    Here is a problem: In my bash scripts I want to source several file with some checks, so I have: if [ -r foo ] ; then source foo else logger -t $0 -p crit "unable to source foo" exit 1 fi if [ -r bar ] ; then source bar else logger -t $0 -p crit "unable to source bar" exit 1 fi # ... etc ... Naively I tried to create a function that do: function save_source() { if [ -r $1 ] ; then source $1 else logger -t $0 -p crit "unable to source $1" exit 1 fi } safe_source foo safe_source bar # ... etc ... But there is a snag there. If one of the files foo, bar, etc. have a global such as -- declare GLOBAL_VAR=42 -- it will effectively become: function save_source() { # ... declare GLOBAL_VAR=42 # ... } thus a global variable becomes local. The question: An alias in bash seems too weak for this, so must I unroll the above function, and repeat myself, or is there a more elegant approach? ... and yes, I agree that Python, Perl, Ruby would make my file easier, but when working with legacy system, one doesn't always have the privilege of choosing the best tool.

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  • Drupal workflow action access integrated with taxonomy access control?

    - by groovehunter
    hi, I am building a DMS for our intranet and use a taxonomy hierarchy because we need access control that way. All company locations manage (upload,edit) their own documents but should be able to access all. This is inherited to the child terms and works fine. Additionally we want simple 3-step workflow (draft,published,archived). So i introduced roles for editor, publisher and docadmin and set permissions for the transitions. Also triggers to effectivly (un)publish documents. But (of course) a user of role publisher can do the transition for ALL documents. But we want publisher for each company location (top taxonomy level, see above). Could this be achieved? Do i have to set it up by myself (i guess "rules" is appropriate to do this) or is there another module helping. role inheritance was a guess, but that is only about roles (naturally). "module grants" i use and checked first option. That way my thoughts are going. I hope you get my idea resp. problem. drupal 6.16 current edit: I reread the docs and found ie. http://drupal.org/node/408018 Revisioning for categorized content. Will reread that.

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  • Code Own Socket Server or Use Red5/ElectroServer on Amazon EC2?

    - by Travis
    I've been thinking for a long time about working on a multiplayer game in Flash. I need updates frequently enough that ajax requests won't work so I need to use a socket server. The system will eventually have enough objects/players that I would consider it an MMO. I would like to set up a scalable system on Amazon's EC2. (Which probably effects my choice of server) This architecture would hopefully allow the game to grow without many changes over time. (Using a domain decomposition technique or something similar) Heres my internal debate: Should I a. Code my own socket server in C++ or Java? b. Use the free and open source Red5 socket server for Flash? or c. Pay the licensing fees and go for Electroserver? I consider myself a decent developer, but am at an impasse as to what road to go down. I'm not sure if I, could develop/would need, the features of one of the prepackaged socket servers. I'm also not sure if the prepackaged servers would work well in an Amazon EC2 environment and take full advantage of its features. Any help or guidance would be greatly appreciated.

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  • notify listener inside or outside inner synchronization

    - by Jary Zeels
    Hello all, I am struggling with a decision. I am writing a thread-safe library/API. Listeners can be registered, so the client is notified when something interesting happens. Which of the two implementations is most common? class MyModule { protected Listener listener; protected void somethingHappens() { synchronized(this) { ... do useful stuff ... listener.notify(); } } } or class MyModule { protected Listener listener; protected void somethingHappens() { Listener l = null; synchronized(this) { ... do useful stuff ... l = listener; } l.notify(); } } In the first implementation, the listener is notified inside the synchronization. In the second implementation, this is done outside the synchronization. I feel that the second one is advised, as it makes less room for potential deadlocks. But I am having trouble to convince myself. A downside of the second imlementation is that the client might receive 'incorrect' notifications, which happens if it accessed the module prior to the l.notify() statement. thanks a lot

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  • Neural Network with softmax activation

    - by Cambium
    This is more or less a research project for a course, and my understanding of NN is very/fairly limited, so please be patient :) ============== I am currently in the process of building a neural network that attempts to examine an input dataset and output the probability/likelihood of each classification (there are 5 different classifications). Naturally, the sum of all output nodes should add up to 1. Currently, I have two layers, and I set the hidden layer to contain 10 nodes. I came up with two different types of implementations 1) Logistic sigmoid for hidden layer activation, softmax for output activation 2) Softmax for both hidden layer and output activation I am using gradient descent to find local maximums in order to adjust the hidden nodes' weights and the output nodes' weights. I am certain in that I have this correct for sigmoid. I am less certain with softmax (or whether I can use gradient descent at all), after a bit of researching, I couldn't find the answer and decided to compute the derivative myself and obtained softmax'(x) = softmax(x) - softmax(x)^2 (this returns an column vector of size n). I have also looked into the MATLAB NN toolkit, the derivative of softmax provided by the toolkit returned a square matrix of size nxn, where the diagonal coincides with the softmax'(x) that I calculated by hand; and I am not sure how to interpret the output matrix. I ran each implementation with a learning rate of 0.001 and 1000 iterations of back propagation. However, my NN returns 0.2 (an even distribution) for all five output nodes, for any subset of the input dataset. My conclusions: o I am fairly certain that my gradient of descent is incorrectly done, but I have no idea how to fix this. o Perhaps I am not using enough hidden nodes o Perhaps I should increase the number of layers Any help would be greatly appreciated! The dataset I am working with can be found here (processed Cleveland): http://archive.ics.uci.edu/ml/datasets/Heart+Disease

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  • Save has_and_belongs_to_many link in basic RoR app

    - by Stéphane V
    I try to learn the has_and_belongs_to_many relationship between my 2 fresh new and simple models Product and Author, where a Product can have many authors and where author can have a lots of products. I wrote this : class Author < ActiveRecord::Base has_and_belongs_to_many :products end class Product < ActiveRecord::Base has_and_belongs_to_many :authors end In the partial form of view for the products, I have : <p>Products</p> <%= collection_select(:product, :author_ids, @authors, :id, :name, :prompt => " ", :multiple => true) %> but when I hit the update button, I get this strange message I can't resolve myself : NoMethodError in ProductsController#update undefined method `reject' for "1":String Rails.root: /home/stephane/www/HABTM Application Trace | Framework Trace | Full Trace app/controllers/products_controller.rb:63:in block in update' app/controllers/products_controller.rb:62:inupdate' Request Parameters: {"utf8"="✓", "_method"="put", "authenticity_token"="2GlTssOFjTVZ9BikrIFgx22cdTOIJuAB70liYhhLf+4=", "product"={"title"="Le trésor des Templiers", "original_title"="", "number"="1", "added_by"="", "author_ids"="1"}, "commit"="Update Product", "id"="1"} What's wrong ? Is there a problem with :product_ids... I saw on internet I had to pu a "s" but I'm not sure of what it represents.... How can I link the table authors_products to the key which is given back by the drop-down menu ? (here "author_ids"="1") Thx !

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  • PostgreSQL insert on primary key failing with contention, even at serializable level

    - by Steven Schlansker
    I'm trying to insert or update data in a PostgreSQL db. The simplest case is a key-value pairing (the actual data is more complicated, but this is the smallest clear example) When you set a value, I'd like it to insert if the key is not there, otherwise update. Sadly Postgres does not have an insert or update statement, so I have to emulate it myself. I've been working with the idea of basically SELECTing whether the key exists, and then running the appropriate INSERT or UPDATE. Now clearly this needs to be be in a transaction or all manner of bad things could happen. However, this is not working exactly how I'd like it to - I understand that there are limitations to serializable transactions, but I'm not sure how to work around this one. Here's the situation - ab: => set transaction isolation level serializable; a: => select count(1) from table where id=1; --> 0 b: => select count(1) from table where id=1; --> 0 a: => insert into table values(1); --> 1 b: => insert into table values(1); --> ERROR: duplicate key value violates unique constraint "serial_test_pkey" Now I would expect it to throw the usual "couldn't commit due to concurrent update" but I'm guessing since the inserts are different "rows" this does not happen. Is there an easy way to work around this?

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