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• Is my objective possible using WCF (and is it the right way to do things?)

  - by David

  I'm writing some software that modifies a Windows Server's configuration (things like MS-DNS, IIS, parts of the filesystem). My design has a server process that builds an in-memory object graph of the server configuration state and a client which requests this object graph. The server would then serialize the graph, send it to the client (presumably using WCF), the server then makes changes to this graph and sends it back to the server. The server receives the graph and proceeds to make modifications to the server. However I've learned that object-graph serialisation in WCF isn't as simple as I first thought. My objects have a hierarchy and many have parametrised-constructors and immutable properties/fields. There are also numerous collections, arrays, and dictionaries. My understanding of WCF serialisation is that it requires use of either the XmlSerializer or DataContractSerializer, but DCS places restrictions on the design of my object-graph (immutable data seems right-out, it also requires parameter-less constructors). I understand XmlSerializer lets me use my own classes provided they implement ISerializable and have the de-serializer constructor. That is fine by me. I spoke to a friend of mine about this, and he advocates going for a Data Transport Object-only route, where I'd have to maintain a separate DataContract object-graph for the transport of data and re-implement my server objects on the client. Another friend of mine said that because my service only has two operations ("GetServerConfiguration" and "PutServerConfiguration") it might be worthwhile just skipping WCF entirely and implementing my own server that uses Sockets. So my questions are: Has anyone faced a similar problem before and if so, are there better approaches? Is it wise to send an entire object graph to the client for processing? Should I instead break it down so that the client requests a part of the object graph as it needs it and sends only bits that have changed (thus reducing concurrency-related risks?)? If sending the object-graph down is the right way, is WCF the right tool? And if WCF is right, what's the best way to get WCF to serialise my object graph?

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• Refactoring exercise with generics

  - by Berryl

  I have a variation on a Quantity (Fowler) class that is designed to facilitate conversion between units. The type is declared as: public class QuantityConvertibleUnits<TFactory> where TFactory : ConvertableUnitFactory, new() { ... } In order to do math operations between dissimilar units, I convert the right hand side of the operation to the equivalent Quantity of whatever unit the left hand side is in, and do the math on the amount (which is a double) before creating a new Quantity. Inside the generic Quantity class, I have the following: protected static TQuantity _Add<TQuantity>(TQuantity lhs, TQuantity rhs) where TQuantity : QuantityConvertibleUnits<TFactory>, new() { var toUnit = lhs.ConvertableUnit; var equivalentRhs = _Convert<TQuantity>(rhs.Quantity, toUnit); var newAmount = lhs.Quantity.Amount + equivalentRhs.Quantity.Amount; return _Convert<TQuantity>(new Quantity(newAmount, toUnit.Unit), toUnit); } protected static TQuantity _Subtract<TQuantity>(TQuantity lhs, TQuantity rhs) where TQuantity : QuantityConvertibleUnits<TFactory>, new() { var toUnit = lhs.ConvertableUnit; var equivalentRhs = _Convert<TQuantity>(rhs.Quantity, toUnit); var newAmount = lhs.Quantity.Amount - equivalentRhs.Quantity.Amount; return _Convert<TQuantity>(new Quantity(newAmount, toUnit.Unit), toUnit); } ... same for multiply and also divide I need to get the typing right for a concrete Quantity, so an example of an add op looks like: public static ImperialLengthQuantity operator +(ImperialLengthQuantity lhs, ImperialLengthQuantity rhs) { return _Add(lhs, rhs); } The question is those verbose methods in the Quantity class. The only change between the code is the math operator (+, -, *, etc.) so it seems that there should be a way to refactor them into a common method, but I am just not seeing it. How can I refactor that code? Cheers, Berryl

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• .Net long-running scheduled code execution

  - by Prof Plum

  I am working on a couple of projects now where I really wish there was some sort of component that I could specify a time and date, and then execute some sort of method. DateTime date = new DateTime(x,x,x,x,x,x); ScheduledMethod sMethod = new ScheduledMethod(date, [method delegate of some sort]); \\at the specified date, sMethod invokes [method delegate of some sort] I know that I can do this with Windows Workflow Foundation as a long running process, which is good for certain things, but are there any alternatives? Workflow is not exactly straight forward with the details, and it would be nice to be able to deploy something more simple for light weight tasks. An example would be a method that checks a network folder once a day and deletes any files that are more than 30 days old. I realize that this may be pie in the sky dreaming, but this would be extremely useful for automating certain mundane maintinence tasks (scheduled sql operations, file system cleansing, routine email sending, etc.). It does not necessarily have to be .Net, but that is where I am coming from. Any ideas?

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• Intermittent asp.net mvc exception: “A public action method ABC could not be found on controller XYZ

  - by Chris Schoon

  Hi, I'm getting an intermittent exception saying that asp.net mvc can’t find the action method. Here’s the exception: A public action method 'Fill' could not be found on controller 'Schoon.Form.Web.Controllers.ChrisController'. I think I have the routing set up correctly because this application works most of the time. Here is the controller’s action method. [ActionName("Fill")] [AcceptVerbs(HttpVerbs.Get | HttpVerbs.Post), UserIdFilter, DTOFilter] public ActionResult Fill(int userId, int subscriberId, DisplayMode? mode) { //… } The route: routes.MapRoute( "SchoonForm", "Form/Fill/{subscriberId}", new { controller = "ChrisController", action = "Fill" }, new { subscriberId = @"\d+" } ); And here is the stack: System.Web.HttpException: A public action method 'Fill' could not be found on controller 'Schoon.Form.Web.Controllers.ChrisController'. at System.Web.Mvc.Controller.HandleUnknownAction(String actionName) in C:\dev\ThirdParty\MvcDev\src\SystemWebMvc\Mvc\Controller.cs:line 197 at System.Web.Mvc.Controller.ExecuteCore() in C:\dev\ThirdParty\MvcDev\src\SystemWebMvc\Mvc\Controller.cs:line 164 at System.Web.Mvc.ControllerBase.Execute(RequestContext requestContext) in C:\dev\ThirdParty\MvcDev\src\SystemWebMvc\Mvc\ControllerBase.cs:line 76 at System.Web.Mvc.ControllerBase.System.Web.Mvc.IController.Execute(RequestContext requestContext) in C:\dev\ThirdParty\MvcDev\src\SystemWebMvc\Mvc\ControllerBase.cs:line 87 at System.Web.Mvc.MvcHandler.ProcessRequest(HttpContextBase httpContext) in C:\dev\ThirdParty\MvcDev\src\SystemWebMvc\Mvc\MvcHandler.cs:line 80 at System.Web.Mvc.MvcHandler.ProcessRequest(HttpContext httpContext) in C:\dev\ThirdParty\MvcDev\src\SystemWebMvc\Mvc\MvcHandler.cs:line 68 at System.Web.Mvc.MvcHandler.System.Web.IHttpHandler.ProcessRequest(HttpContext httpContext) in C:\dev\ThirdParty\MvcDev\src\SystemWebMvc\Mvc\MvcHandler.cs:line 104 at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) Here is an example of my filters they all work the same way: public class UserIdFilter : ActionFilterAttribute { public override void OnActionExecuting(ActionExecutingContext filterContext) { const string Key = "userId"; if (filterContext.ActionParameters.ContainsKey(Key)) { filterContext.ActionParameters[Key] = // get the user id from session or cookie } base.OnActionExecuting(filterContext); } } Thanks, Chris

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• Extracting noun+noun or (adj|noun)+noun from Text

  - by ssuhan

  I would like to query if it is possible to extract noun+noun or (adj|noun)+noun in R package openNLP?That is, I would like to use linguistic filtering to extract candidate noun phrases. Could you direct me how to do? Many thanks. Thanks for the responses. here is the code: library("openNLP") acq <- "Gulf Applied Technologies Inc said it sold its subsidiaries engaged in pipeline and terminal operations for 12.2 mln dlrs. The company said the sale is subject to certain post closing adjustments, which it did not explain. Reuter." acqTag <- tagPOS(acq) acqTagSplit = strsplit(acqTag," ") acqTagSplit qq = 0 tag = 0 for (i in 1:length(acqTagSplit[[1]])){ qq[i] <-strsplit(acqTagSplit[[1]][i],'/') tag[i] = qq[i][[1]][2] } index = 0 k = 0 for (i in 1:(length(acqTagSplit[[1]])-1)) { if ((tag[i] == "NN" && tag[i+1] == "NN") | (tag[i] == "NNS" && tag[i+1] == "NNS") | (tag[i] == "NNS" && tag[i+1] == "NN") | (tag[i] == "NN" && tag[i+1] == "NNS") | (tag[i] == "JJ" && tag[i+1] == "NN") | (tag[i] == "JJ" && tag[i+1] == "NNS")){ k = k +1 index[k] = i } } index Reader can refer index on acqTagSplit to do noun+noun or (adj|noun)+noun extractation. (The code is not optimum but work. If you have any idea, please let me know.) Furthermore, I still have a problem. Justeson and Katz (1995) proposed another linguistic filtering to extract candidate noun phrases: ((Adj|Noun)+|((Adj|Noun)(Noun-Prep)?)(Adj|Noun))Noun I cannot well understand its meaning, could someone do me a favor to explain it or transform such representation into R language

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• How can I SETF an element in a tree by an accessor?

  - by Willi Ballenthin

  We've been using Lisp in my AI course. The assignments I've received have involved searching and generating tree-like structures. For each assignment, I've ended up writing something like: (defun initial-state () (list 0 ; score nil ; children 0 ; value 0)) ; something else and building my functions around these "states", which are really just nested lists with some loosely defined structure. To make the structure more rigid, I've tried to write accessors, such as: (defun state-score ( state ) (nth 2 state)) This works for reading the value (which should be all I need to do in a nicely functional world. However, as time crunches, and I start to madly hack, sometimes I want a mutable structure). I don't seem to be able to SETF the returned ...thing (place? value? pointer?). I get an error with something like: (setf (state-score *state*) 10) Sometimes I seem to have a little more luck writing the accessor/mutator as a macro: (defmacro state-score ( state ) `(nth 2 ,state)) However I don't know why this should be a macro, so I certainly shouldn't write it as a macro (except that sometimes it works. Programming by coincidence is bad). What is an appropriate strategy to build up such structures? More importantly, where can I learn about whats going on here (what operations affect the memory in what way)?

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• .NET multithreading, volatile and memory model

  - by fedor-serdukov

  Assume that we have the following code: class Program { static volatile bool flag1; static volatile bool flag2; static volatile int val; static void Main(string[] args) { for (int i = 0; i < 10000 * 10000; i++) { if (i % 500000 == 0) { Console.WriteLine("{0:#,0}",i); } flag1 = false; flag2 = false; val = 0; Parallel.Invoke(A1, A2); if (val == 0) throw new Exception(string.Format("{0:#,0}: {1}, {2}", i, flag1, flag2)); } } static void A1() { flag2 = true; if (flag1) val = 1; } static void A2() { flag1 = true; if (flag2) val = 2; } } } It's fault! The main quastion is Why... I suppose that CPU reorder operations with flag1 = true; and if(flag2) statement, but variables flag1 and flag2 marked as volatile fields...

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• Visual Studio crashes consistently on web-related projects

  - by Traveling Tech Guy

  Hi, I have a brand new VS2010 installed on a Win2008R2 machine. I started getting this error when debugging a WCF service project: "Attempted to read or write protected memory. This is often an indication that other memory is corrupt." When I started developing a web site a week later, this became consistent - I can't debug it. The stack dump reads: at Microsoft.VisualStudio.WebHost.Host.ProcessRequest(Connection conn) at Microsoft.VisualStudio.WebHost.Server.OnSocketAccept(Object acceptedSocket) at System.Threading.QueueUserWorkItemCallback.WaitCallback_Context(Object state) at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean ignoreSyncCtx) at System.Threading.QueueUserWorkItemCallback.System.Threading.IThreadPoolWorkItem.ExecuteWorkItem() at System.Threading.ThreadPoolWorkQueue.Dispatch() at System.Threading._ThreadPoolWaitCallback.PerformWaitCallback() I tried searching online, and some recommend turning off the "Suppress JIT Optimizations" in the Debugging options - this dos not seem to make a difference. Clearly the problem is with the built in web server. But am I doing something wrong? Is there something I can do? Or is this a known bug? Thanks for your time, Guy Update 12/31: Today I tried using CassiniDev as a replacement to the original VS2010 WebServer - exact same result. My suspicion is that there's some internal conflict between VS2010, Windows Server 2008R2 and maybe the fact that it's a 64 bit OS. I switched to using IIS as my debug server - and that seems to work, with some annoying side effects. My conclusion: do not use a 64 bit server system as your dev machine. Develop on 32bit - deploy to 64bit. Side conclusion: there are some scenarios Microsoft's QA doesn't test.

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• Accelerometer gravity components

  - by Dvd

  Hi, I know this question is definitely solved somewhere many times already, please enlighten me if you know of their existence, thanks. Quick rundown: I want to compute from a 3 axis accelerometer the gravity component on each of these 3 axes. I have used 2 axes free body diagrams to work out the accelerometer's gravity component in the world X-Z, Y-Z and X-Y axes. But the solution seems slightly off, it's acceptable for extreme cases when only 1 accelerometer axis is exposed to gravity, but for a pitch and roll of both 45 degrees, the combined total magnitude is greater than gravity (obtained by Xa^2+Ya^2+Za^2=g^2; Xa, Ya and Za are accelerometer readings in its X, Y and Z axis). More detail: The device is a Nexus One, and have a magnetic field sensor for azimuth, pitch and roll in addition to the 3-axis accelerometer. In the world's axis (with Z in the same direction as gravity, and either X or Y points to the north pole, don't think this matters much?), I assumed my device has a pitch (P) on the Y-Z axis, and a roll (R) on the X-Z axis. With that I used simple trig to get: Sin(R)=Ax/Gxz Cos(R)=Az/Gxz Tan(R)=Ax/Az There is another set for pitch, P. Now I defined gravity to have 3 components in the world's axis, a Gxz that is measurable only in the X-Z axis, a Gyz for Y-Z, and a Gxy for X-Y axis. Gxz^2+Gyz^2+Gxy^2=2*G^2 the 2G is because gravity is effectively included twice in this definition. Oh and the X-Y axis produce something more exotic... I'll explain if required later. From these equations I obtained a formula for Az, and removed the tan operations because I don't know how to handle tan90 calculations (it's infinity?). So my question is, anyone know whether I did this right/wrong or able to point me to the right direction? Thanks! Dvd

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• Finding Palindromes in an Array

  - by Jack L.

  For this assignemnt, I think that I got it right, but when I submit it online, it doesn't list it as correct even though I checked with Eclipse. The prompt: Write a method isPalindrome that accepts an array of Strings as its argument and returns true if that array is a palindrome (if it reads the same forwards as backwards) and /false if not. For example, the array {"alpha", "beta", "gamma", "delta", "gamma", "beta", "alpha"} is a palindrome, so passing that array to your method would return true. Arrays with zero or one element are considered to be palindromes. My code: public static void main(String[] args) { String[] input = new String[6]; //{"aay", "bee", "cee", "cee", "bee", "aay"} Should return true input[0] = "aay"; input[1] = "bee"; input[2] = "cee"; input[3] = "cee"; input[4] = "bee"; input[5] = "aay"; System.out.println(isPalindrome(input)); } public static boolean isPalindrome(String[] input) { for (int i=0; i<input.length; i++) { // Checks each element if (input[i] != input[input.length-1-i]){ return false; // If a single instance of non-symmetry } } return true; // If symmetrical, only one element, or zero elements } As an example, {"aay", "bee", "cee", "cee", "bee", "aay"} returns true in Eclipse, but Practice-It! says it returns false. What is going on?

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• WinForms programing - Modal and Non-Modal forms problem

  - by Povilas

  I have a problem with modality of the forms under C#.NET. Let's say I have main form #0 (see the image below). This form represents main application form, where user can perform various operations. However, from time to time, there is a need to open additional non-modal form to perform additional main application functionality supporting tasks. Let's say this is form #1 in the image. On this #1 form there might be opened few additional modal forms on top of each other (#2 form in the image), and at the end, there is a progress dialog showing a long operation progress and status, which might take from few minutes up to few hours. The problem is that the main form #0 is not responsive until you close all modal forms (#2 in the image). I need that the main form #0 would be operational in this situation. However, if you open a non-modal form in form #2, you can operate with both modal #2 form and newly created non modal form. I need the same behavior between the main form #0 and form #1 with all its child forms. Is it possible? Or am I doing something wrong? Maybe there is some kind of workaround, I really would not like to change all ShowDialog calls to ShowDialog...

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• Java Process.waitFor() and IO streams

  - by lynks

  I have the following code; String[] cmd = { "bash", "-c", "~/path/to/script.sh" }; Process p = Runtime.getRuntime().exec(cmd); PipeThread a = new PipeThread(p.getInputStream(), System.out); PipeThread b = new PipeThread(p.getErrorStream(), System.err); p.waitFor(); a.die(); b.die(); The PipeThread class is quite simple so I will include it in full; public class PipeThread implements Runnable { private BufferedInputStream in; private BufferedOutputStream out; public Thread thread; private boolean die = false; public PipeThread(InputStream i, OutputStream o) { in = new BufferedInputStream(i); out = new BufferedOutputStream(o); thread = new Thread(this); thread.start(); } public void die() { die = true; } public void run() { try { byte[] b = new byte[1024]; while(!die) { int x = in.read(b, 0, 1024); if(x > 0) out.write(b, 0, x); else die(); out.flush(); } } catch(Exception e) { e.printStackTrace(); } try { in.close(); out.close(); } catch(Exception e) { } } } My problem is this; p.waitFor() blocks endlessly, even after the subprocess has terminated. If I do not create the pair of PipeThread instances, then p.waitFor() works perfectly. What is it about the piping of io streams that is causing p.waitFor() to continue blocking? I'm confused as I thought the IO streams would be passive, unable to keep a process alive, or to make Java think the process is still alive.

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• Vim: yank and replace -- the same yanked input -- multiple times, and two other questions

  - by Hassan Syed

  Now that I am using vim for everything I type, rather then just for configuring servers, I wan't to sort out the following trivialities. I tried to formulate Google search queries but the results didn't address my questions :D. Question one: How do I yank and replace multiple times ? Once I have something in the yank history (if that is what its called) and then highlight and use the 'p' char in command mode the replaced text is put at the front of the yank history; therefore subsequent replace operations do not use the the text I intended. I imagine this to be a usefull feature under certain circumstances but I do not have a need for it in my workflow. Question two: How do I type text without causing the line to ripple forward ? I use hard-tab stops to allign my code in a certain way -- e.g., FunctionNameX ( lala * land ); FunctionNameProto ( ); When I figure out what needs to go into the second function, how do I insert it without move the text up ? Question three Is there a way of having a uniform yank history across gvim instances on the same machine ? I have 1 monitors. Just wondering, atm I am using highlight + mouse middle click.

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• How to efficiently store and update binary data in Mongodb?

  - by Rocketman

  I am storing a large binary array within a document. I wish to continually add bytes to this array and sometimes change the value of existing bytes. I was looking for some $append_bytes and $replace_bytes type of modifiers but it appears that the best I can do is $push for arrays. It seems like this would be doable by performing seek-write type operations if I had access somehow to the underlying bson on disk, but it does not appear to me that there is anyway to do this in mongodb (and probably for good reason). If I were instead to just query this binary array, edit or add to it, and then update the document by rewriting the entire field, how costly will this be? Each binary array will be on the order of 1-2MB, and updates occur once every 5 minutes and across 1000s of documents. Worse, yet there is no easy way to spread these out (in time) and they will usually be happening close to one another on the 5 minute intervals. Does anyone have a good feel for how disastrous this will be? Seems like it would be problematic. An alternative would be to store this binary data as separate files on disk, implement a thread pool to efficiently manipulate the files on disk, and reference the filename from my mongodb document. (I'm using python and pymongo so I was looking at pytables). I'd prefer to avoid this though if possible. Is there any other alternative that I am overlooking here? Thanks in advnace.

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• Java OO design confusion: how to handle actions modified by states modified by actions...

  - by Arvanem

  Hi folks, Given an entity, whose action is potentially modified by states (of the entity and other entities) in turn potentially modified by other actions (of the entity and other entities) , what is the best way to code or design to handle the potential existence of the modifiers? Speaking metaphorically, I am coding a Java application representing a piano. As you know a piano has keys (which, when pressed, emit sound) and pedals (which, when pressed, modify the keys' sounds). My base class structure is as follows: Entity (for keys and pedals) State (this holds each entity's states, e.g. name such as "soft pedal", and boolean "Pressed"), Action (this holds each entity's actions, e.g. play sound when pressed, or modify others sounds). By composition, the Entity class has a copy of each of State and Action inside it. e.g.: public class Entity { State entityState = new State(); Action entityAction = new Action(); Thus I have coded a "C-Sharp" key Entity. When I "press" that entity (set its "Pressed" state to true), its action plays a "C-Sharp" sound and then sets its "Pressed" state to false. At the same time, if the "C-Sharp" key entity is not "tuned", its sound deviates from "C-Sharp". Meanwhile I have coded a "soft pedal" Entity. When that entity is "pressed", no sound plays but its action is to make softer the sound of the "C-Sharp" and other key entities. I have also coded a "sustain pedal" Entity. When that entity is "pressed", no sound plays but its action is to enable reverberation of the sound of the "C-Sharp" and other key entities. Both the "soft" and "sustain pedals" can be pressed at the same time with the result that keys entities become both softened and reverberating. In short, I do not understand how to make this simultaneous series of states and actions modify each other in a sensible OO way. I am wary of coding a massive series of "if" statements or "switches". Thanks in advance for any help or links you can offer.

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• Python C API from C++ app - know when to lock

  - by Alex

  Hi Everyone, I am trying to write a C++ class that calls Python methods of a class that does some I/O operations (file, stdout) at once. The problem I have ran into is that my class is called from different threads: sometimes main thread, sometimes different others. Obviously I tried to apply the approach for Python calls in multi-threaded native applications. Basically everything starts from PyEval_AcquireLock and PyEval_ReleaseLock or just global locks. According to the documentation here when a thread is already locked a deadlock ensues. When my class is called from the main thread or other one that blocks Python execution I have a deadlock. Python Cfunc1() - C++ func that creates threads internally which lead to calls in "my class", It stuck on PyEval_AcquireLock, obviously the Python is already locked, i.e. waiting for C++ Cfunc1 call to complete... It completes fine if I omit those locks. Also it completes fine when Python interpreter is ready for the next user command, i.e. when thread is calling funcs in the background - not inside of a native call I am looking for a workaround. I need to distinguish whether or not the global lock is allowed, i.e. Python is not locked and ready to receive the next command... I tried PyGIL_Ensure, unfortunately I see hang. Any known API or solution for this ? (Python 2.4)

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• What can cause my code to run slower when the server JIT is activated?

  - by durandai

  I am doing some optimizations on an MPEG decoder. To ensure my optimizations aren't breaking anything I have a test suite that benchmarks the entire codebase (both optimized and original) as well as verifying that they both produce identical results (basically just feeding a couple of different streams through the decoder and crc32 the outputs). When using the "-server" option with the Sun 1.6.0_18, the test suite runs about 12% slower on the optimized version after warmup (in comparison to the default "-client" setting), while the original codebase gains a good boost running about twice as fast as in client mode. While at first this seemed to be simply a warmup issue to me, I added a loop to repeat the entire test suite multiple times. Then execution times become constant for each pass starting at the 3rd iteration of the test, still the optimized version stays 12% slower than in the client mode. I am also pretty sure its not a garbage collection issue, since the code involves absolutely no object allocations after startup. The code consists mainly of some bit manipulation operations (stream decoding) and lots of basic floating math (generating PCM audio). The only JDK classes involved are ByteArrayInputStream (feeds the stream to the test and excluding disk IO from the tests) and CRC32 (to verify the result). I also observed the same behaviour with Sun JDK 1.7.0_b98 (only that ist 15% instead of 12% there). Oh, and the tests were all done on the same machine (single core) with no other applications running (WinXP). While there is some inevitable variation on the measured execution times (using System.nanoTime btw), the variation between different test runs with the same settings never exceeded 2%, usually less than 1% (after warmup), so I conclude the effect is real and not purely induced by the measuring mechanism/machine. Are there any known coding patterns that perform worse on the server JIT? Failing that, what options are available to "peek" under the hood and observe what the JIT is doing there?

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• Collision of dot and line in 2D space

  - by Anderiel

  So i'm trying to make my first game on android. The thing is i have a small moving ball and i want it to bounce from a line that i drew. For that i need to find if the x,y of the ball are also coordinates of one dot from the line. I tried to implement these equations about lines x=a1 + t*u1 y=a2 + t*u2 = (x-a1)/u1=(y-a2)/u2 (t=t which has to be if the point is on the line) where x and y are the coordinates im testing, dot[a1,a2] is a dot that is on the line and u(u1,u2) is the vector of the line. heres the code: public boolean Collided() { float u1 =Math.abs(Math.round(begin_X)-Math.round(end_X)); float u2 =Math.abs(Math.round(begin_Y)-Math.round(end_Y)); float t_x =Math.round((elect_X - begin_X)/u1); float t_y =Math.round((elect_Y - begin_Y)/u2); if(t_x==t_y) { return true; } else { return false; } } points [begin_X,end_X] and [begin_Y,end_Y] are the two points from the line and [elect_X,elect_Y] are the coordinates of the ball theoreticaly it should work, but in the reality the ball most of the time just goes straigth through the line or bounces somewhere else where it shouldnt

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• Node & Redis: Crucial Design Issues in Production Mode

  - by Ali

  This question is a hybrid one, being both technical and system design related. I'm developing the backend of an application that will handle approx. 4K request per second. We are using Node.js being super fast and in terms of our database struction we are using MongoDB, with Redis being a layer between Node and MongoDB handling volatile operations. I'm quite stressed because we are expecting concurrent requests that we need to handle carefully and we are quite close to launch. However I do not believe I've applied the correct approach on redis. I have a class Student, and they constantly change stages(such as 'active', 'doing homework','in lesson' etc. Thus I created a Redis DB for each state. (1 for being 'active', 2 for being 'doing homework'). Above I have the structure of the 'active' students table; xa5p - JSON stringified object #1 pQrW - JSON stringified object #2 active_student_table - {{studentId:'xa5p'}, {studentId:'pQrW'}} Since there is no 'select all keys method' in Redis, I've been suggested to use a set such that when I run command 'smembers' I receive the keys and later on do 'get' for each id in order to find a specific user (lets say that age older than 15). I've been also suggested that in fact I used never use keys in production mode. My question is, no matter how 'conceptual' it is, what specific things I should avoid doing in Node & Redis in production stage?. Are they any issues related to my design? Students must be objects and I sure can list them in a list but I haven't done yet. Is it that crucial in production stage?

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• Timer Service in ejb 3.1 - schedule calling timeout problem

  - by Greg

  Hi Guys, I have created simple example with @Singleton, @Schedule and @Timeout annotations to try if they would solve my problem. The scenario is this: EJB calls 'check' function every 5 secconds, and if certain conditions are met it will create single action timer that would invoke some long running process in asynchronous fashion. (it's sort of queue implementation type of thing). It then continues to check, but as long as long running process is there it won't start another one. Below is the code I came up with, but this solution does not work, because it looks like asynchronous call I'm making is in fact blocking my @Schedule method. @Singleton @Startup public class GenerationQueue { private Logger logger = Logger.getLogger(GenerationQueue.class.getName()); private List<String> queue = new ArrayList<String>(); private boolean available = true; @Resource TimerService timerService; @Schedule(persistent=true, minute="*", second="*/5", hour="*") public void checkQueueState() { logger.log(Level.INFO,"Queue state check: "+available+" size: "+queue.size()+", "+new Date()); if (available) { timerService.createSingleActionTimer(new Date(), new TimerConfig(null, false)); } } @Timeout private void generateReport(Timer timer) { logger.info("!!--timeout invoked here "+new Date()); available = false; try { Thread.sleep(1000*60*2); // something that lasts for a bit } catch (Exception e) {} available = true; logger.info("New report generation complete"); } What am I missing here or should I try different aproach? Any ideas most welcome :) Testing with Glassfish 3.0.1 latest build - forgot to mention

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• Sparse (Pseudo) Infinite Grid Data Structure for Web Game

  - by Ming

  I'm considering trying to make a game that takes place on an essentially infinite grid. The grid is very sparse. Certain small regions of relatively high density. Relatively few isolated nonempty cells. The amount of the grid in use is too large to implement naively but probably smallish by "big data" standards (I'm not trying to map the Internet or anything like that) This needs to be easy to persist. Here are the operations I may want to perform (reasonably efficiently) on this grid: Ask for some small rectangular region of cells and all their contents (a player's current neighborhood) Set individual cells or blit small regions (the player is making a move) Ask for the rough shape or outline/silhouette of some larger rectangular regions (a world map or region preview) Find some regions with approximately a given density (player spawning location) Approximate shortest path through gaps of at most some small constant empty spaces per hop (it's OK to be a bad approximation often, but not OK to keep heading the wrong direction searching) Approximate convex hull for a region Here's the catch: I want to do this in a web app. That is, I would prefer to use existing data storage (perhaps in the form of a relational database) and relatively little external dependency (preferably avoiding the need for a persistent process). Guys, what advice can you give me on actually implementing this? How would you do this if the web-app restrictions weren't in place? How would you modify that if they were? Thanks a lot, everyone!

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• java annotations - problem with calling a locator class from a Vaadin Project

  - by George

  Hello, I'm not sure how to explain this without writing several pages so I hope the actual code is more expressive. I've made a jar containing multiple annotation declaration similar to the following: @Target(ElementType.PACKAGE) @Retention(RetentionPolicy.RUNTIME) public @interface MarkedPackage { } then I have made a test jar containing several classes in several packages and marked just one package with the above annotation (with package-info.java) like below: @myPackage.MarkedPackage package package.test.jar; this jar had in its build path the jar containing the annotations. then I made a static class that has a method (LoadPlugins) that retrieves a list with all the jars of a directory. Then it searches through the jars for the 'package-info' class and checks if that classes package contains the MarkedPackage annotation. by calling this: if (checkPackageAnnotation(thisClass.getPackage())) where thisClass is the package-info class retrieved via a classloader. and: public static boolean checkPackageAnnotation(AnnotatedElement elem) { System.out.println(elem.getAnnotations().length); if (elem == null || !elem.isAnnotationPresent(MarkedPackage.class)) return false; return true; } the elem.getAnnotatios().length is there for debug purposes. And the problem appears when I call the method from the static class: if I call it from a main function: public class MyMain { public static void main(String[] args){ PluginUtils.LoadPlugins(); } } everything works perfectly it displays '1' from that System.out.println(elem.getAnnotations().length); But if I call it from a button from my Vaadin project: header.addComponent(new Button("CallThat", new Button.ClickListener() { public void buttonClick(ClickEvent event) { PluginUtils.LoadPlugins(); } })); It displays '0' from that System.out.println(elem.getAnnotations().length); Also I should mention that I created the main inside my Vaadin project so it would have the exact same build path and resources. Is there a problem with web applications and that "@Retention(RetentionPolicy.RUNTIME)" ? hope I was clear enough... Hope someone has a solution for me... If you need more information - let me know. Thank you.

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• How to handle dynamic role or username changes in JSF?

  - by roadrunner

  I have a JSF application running on glassfish 2.1 with a EJB 3 backend. For authentication I use a custom realm. The user authenticates using the e-mail-address and password he specified on registration. Everything is working quite well. Now I have two related problems: 1) The user can edit his profile and -- naturally -- he can also change his e-mail-address. Unfortunately when I perform operations based on the current user's identity using ExternalContext.getUserPrincipal().getName(), I will receive the previous e-mail-address the user used on login. At the moment I handle this by forcing the user to reauthenticate after he changed his e-mail-address, but is there another more graceful possibility? 2) Same for user roles. E.g. I have the user roles MEMBER and PREMIUM_MEMBER. A MEMBER may become a PREMIUM_MEMBER during his current session. Unfortunately the role seems to be only determined at login. Is there any possibility, that JSF and EJB recognize the new user role without the need for the user to re-authenticated?

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• need help about process........

  - by adeel amin

  when i start process like process= Runtime.getRuntime().exec("gnome-terminal");, it start shell execution, i want to stop shell execution and want to redirect I/O from process, can anybody tell how i can do this? my code is: public void start_process() { try { process= Runtime.getRuntime().exec("bash"); pw= new PrintWriter(process.getOutputStream(),true); br=new BufferedReader(new InputStreamReader(process.getInputStream())); err=new BufferedReader(new InputStreamReader(process.getErrorStream())); } catch (Exception ioe) { System.out.println("IO Exception-> " + ioe); } } public void execution_command() { if(check==2) { try { boolean flag=thread.isAlive(); if(flag==true) thread.stop(); Thread.sleep(30); thread = new MyReader(br,tbOutput,err,check); thread.start(); }catch(Exception ex){ JOptionPane.showMessageDialog(null, ex.getMessage()+"1"); } } else { try { Thread.sleep(30); thread = new MyReader(br,tbOutput,err,check); thread.start(); check=2; }catch(Exception ex){ JOptionPane.showMessageDialog(null, ex.getMessage()+"1"); } } } private void jButton3ActionPerformed(java.awt.event.ActionEvent evt) { // TODO add your handling code here: command=tfCmd.getText().toString().trim(); pw.println(command); execution_command(); } when i enter some command in textfield and press execute button, nothing displayed on my output textarea, how i can stop shellexecution and can redirect Input and output?

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• SL3 Nav framework + MVVM ligh

  - by Murari

  Hi All, Thanks for taking time to read through my question. Any guidance is really appreciated. I am using SL3 Navigation framework in my LOB application. I m currently using MVVM Light as the framework guidance. I have a datagrid consisting of employees and when the "user" clicks on "employee id link" in the datagrid, i am transferring the user to "Edit Page". I would like to transfer the "employee id" as query parameter to "edit page". The issue here is: I can access the query parameter in the EditStaffView.xaml.cs - which i don't want to do. protected override void OnNavigatedTo(NavigationEventArgs e) { if (this.NavigationContext.QueryString.ContainsKey("staffcode")) { string title = this.NavigationContext.QueryString["staffcode"]; } } I would like to retrieve the query parameter in my viewmodel and based on the query parameter, i will perform certain operations. When the constructor is called I would like the "view" to pass the staffid as shown below public EditStaffViewModel(int staffId) { LoadData(staffId); } I am constructing my hyperlink buttons in the datagrid dyanmically as shown below: staffListingModel.HyperlinkNavigationUri = string.Format("{0}{1}", NavigationUri.DataEntryEditStaff,"?staffcode={" + staffListingModel.StaffCode + "}"); and XAML looks HyperlinkButton Content="{Binding StaffCode,Mode=TwoWay}" NavigateUri="{Binding HyperlinkNavigationUri}" HyperlinkButton Any idea how to do this ?? Thanks for the help. Murari

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