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• image analysis and 64bit OS

  - by picciopiccio

  I developed a C# application that makes use of Congex vision library (VPro). My application is developed with Visual Studio 2008 Pro on a 32bit Windows PC with 3GB of RAM. During the startup of application I see that a large amount of memory is allocated. So far so good, but when I add many and many vision elaboration the memory allocation increases and a part of application (only Cognex OCX) stops working well. The rest of application stills to work (working threads, com on socket....) I did whatever I could to save memory, but when the memory allocated is about 700MB I begin to have the problems. A note on the documentation of Cognex library tells that /LARGEADDRESSWARE is not supported. Anyway I'm thinking to try the migration of my app on win64 but what do I have to do? Can I simply use a processor with 64bit and windows 64bit without recompiling my application that would remain a 32bit application to take advantage of 64bit ? Or I should recompile my application ? If I don't need to recompile my application, can I link it with 64bit Congnex library? If I have to recompile my application, is it possible to cross compile the application so that my develop suite is on a 32bit PC? Every help will be very appreciated!! Thank in advance

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• Cassandra random read speed

  - by Jody Powlette

  We're still evaluating Cassandra for our data store. As a very simple test, I inserted a value for 4 columns into the Keyspace1/Standard1 column family on my local machine amounting to about 100 bytes of data. Then I read it back as fast as I could by row key. I can read it back at 160,000/second. Great. Then I put in a million similar records all with keys in the form of X.Y where X in (1..10) and Y in (1..100,000) and I queried for a random record. Performance fell to 26,000 queries per second. This is still well above the number of queries we need to support (about 1,500/sec) Finally I put ten million records in from 1.1 up through 10.1000000 and randomly queried for one of the 10 million records. Performance is abysmal at 60 queries per second and my disk is thrashing around like crazy. I also verified that if I ask for a subset of the data, say the 1,000 records between 3,000,000 and 3,001,000, it returns slowly at first and then as they cache, it speeds right up to 20,000 queries per second and my disk stops going crazy. I've read all over that people are storing billions of records in Cassandra and fetching them at 5-6k per second, but I can't get anywhere near that with only 10mil records. Any idea what I'm doing wrong? Is there some setting I need to change from the defaults? I'm on an overclocked Core i7 box with 6gigs of ram so I don't think it's the machine. Here's my code to fetch records which I'm spawning into 8 threads to ask for one value from one column via row key: ColumnPath cp = new ColumnPath(); cp.Column_family = "Standard1"; cp.Column = utf8Encoding.GetBytes("site"); string key = (1+sRand.Next(9)) + "." + (1+sRand.Next(1000000)); ColumnOrSuperColumn logline = client.get("Keyspace1", key, cp, ConsistencyLevel.ONE); Thanks for any insights

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• Asynchronous crawling F#

  - by jlezard

  When crawling on webpages I need to be careful as to not make too many requests to the same domain, for example I want to put 1 s between requests. From what I understand it is the time between requests that is important. So to speed things up I want to use async workflows in F#, the idea being make your requests with 1 sec interval but avoid blocking things while waiting for request response. let getHtmlPrimitiveAsyncTimer (uri : System.Uri) (timer:int) = async{ let req = (WebRequest.Create(uri)) :?> HttpWebRequest req.UserAgent<-"Mozilla" try Thread.Sleep(timer) let! resp = (req.AsyncGetResponse()) Console.WriteLine(uri.AbsoluteUri+" got response") use stream = resp.GetResponseStream() use reader = new StreamReader(stream) let html = reader.ReadToEnd() return html with | _ as ex -> return "Bad Link" } Then I do something like: let uri1 = System.Uri "http://rue89.com" let timer = 1000 let jobs = [|for i in 1..10 -> getHtmlPrimitiveAsyncTimer uri1 timer|] jobs |> Array.mapi(fun i job -> Console.WriteLine("Starting job "+string i) Async.StartAsTask(job).Result) Is this alright ? I am very unsure about 2 things: -Does the Thread.Sleep thing work for delaying the request ? -Is using StartTask a problem ? I am a beginner (as you may have noticed) in F# (coding in general actually ), and everything envolving Threads scares me :) Thanks !!

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• Blocking on DBCP connection pool (open and close connnection). Is database connection pooling in OpenEJB pluggable?

  - by topchef

  We use OpenEJB on Tomcat (used to run on JBoss, Weblogic, etc.). While running load tests we experience significant performance problems with handling JMS messages (queues). Problem was localized to blocking on database connection pool getting or releasing connection to the pool. Blocking prevented concurrent MDB instances (threads) from running hence performance suffered 10-fold and worse. The same code used to run on application servers (with their respective connection pool implementations) with no blocking at all. Example of thread blocked: Name: JMS Resource Adapter-worker-23 State: BLOCKED on org.apache.commons.pool.impl.GenericObjectPool@1ea6b4a owned by: JMS Resource Adapter-worker-19 Total blocked: 18,426 Total waited: 0 Stack trace: org.apache.commons.pool.impl.GenericObjectPool.returnObject(GenericObjectPool.java:916) org.apache.commons.dbcp.PoolableConnection.close(PoolableConnection.java:91) - locked org.apache.commons.dbcp.PoolableConnection@1bcba8 org.apache.commons.dbcp.managed.ManagedConnection.close(ManagedConnection.java:147) com.xxxxx.persistence.DbHelper.closeConnection(DbHelper.java:290) .... Couple of questions. I am almost certain that some transactional attributes and properties contribute to this blocking, but MDBs are defined as non-transactional (we use both annotations and ejb-jar.xml). Some EJBs do use container-managed transactions though (and we can observe blocking there as well). Are there any DBCP configurations that may fix blocking? Is DBCP connection pool implementation replaceable in OpenEJB? How easy (difficult) to replace it with another library? Just in case this is how we define data source in OpenEJB (openejb.xml): <Resource id="MyDataSource" type="DataSource"> JdbcDriver oracle.jdbc.driver.OracleDriver JdbcUrl ${oracle.jdbc} UserName ${oracle.user} Password ${oracle.password} JtaManaged true InitialSize 5 MaxActive 30 ValidationQuery SELECT 1 FROM DUAL TestOnBorrow true </Resource>

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• Why am I getting an error on Heroku that suggests I need to migrate my app to Bamboo?

  - by user242065

  When I type: git push heroku master, this is what happens @68-185-86-134:sample_app git push heroku master Counting objects: 110, done. Delta compression using up to 2 threads. Compressing objects: 100% (94/94), done. Writing objects: 100% (110/110), 87.48 KiB, done. Total 110 (delta 19), reused 0 (delta 0) -----> Heroku receiving push -----> Rails app detected ! This version of Rails is only supported on the Bamboo stack ! Please migrate your app to Bamboo and push again. ! See http://docs.heroku.com/bamboo for more information ! Heroku push rejected, incompatible Rails version error: hooks/pre-receive exited with error code 1 To [email protected]:blazing-frost-89.git ! [remote rejected] master -> master (pre-receive hook declined) error: failed to push some refs to '[email protected]:blazing-frost-89.git' My .gems file: rails --version 2.3.8 My .git/config file: [core] repositoryformatversion = 0 filemode = true bare = false logallrefupdates = true ignorecase = true [remote "origin"] url = [email protected]:csmeder/sample_app.git fetch = +refs/heads/*:refs/remotes/origin/* [remote "heroku"] url = [email protected]:blazing-frost-89.git fetch = +refs/heads/*:refs/remotes/heroku/*

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• eventmachine and external scripts via backticks

  - by Maciek

  I have a small HTTP server script I've written using eventmachine which needs to call external scripts/commands and does so via backticks (``). When serving up requests which don't run backticked code, everything is fine, however, as soon as my EM code executes any backticked external script, it stops serving requests and stops executing in general. I noticed eventmachine seems to be sensitive to sub-processes and/or threads, and appears to have the popen method for this purpose, but EM's source warns that this method doesn't work under Windows. Many of the machines running this script are running Windows, so I can't use popen. Am I out of luck here? Is there a safe way to run an external command from an eventmachine script under Windows? Is there any way I could fire off some commands to be run externally without blocking EM's execution? edit: the culprit that seems to be screwing up EM the most is my usage of the Windows start command, as in: start java myclass. The reason I'm using start is because I want those external scripts to start running and keep running after the EM request is served

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• ASP.NET lock thread method

  - by Peter

  Hello, I'm developing an ASP.NET forms webapplication using C#. I have a method which creates a new Order for a customer. It looks similar to this; private string CreateOrder(string userName) { // Fetch current order Order order = FetchOrder(userName); if (order.OrderId == 0) { // Has no order yet, create a new one order.OrderNumber = Utility.GenerateOrderNumber(); order.Save(); } return order; } The problem here is, it is possible that 1 customer in two requests (threads) could cause this method to be called twice while another thread is also inside this method. This can cause two orders to be created. How can I properly lock this method, so it can only be executed by one thread at a time per customer? I tried; Mutex mutex = null; private string CreateOrder(string userName) { if (mutex == null) { mutex = new Mutex(true, userName); } mutex.WaitOne(); // Code from above mutex.ReleaseMutex(); mutex = null; return order; } This works, but on some occasions it hangs on WaitOne and I don't know why. Is there an error, or should I use another method to lock? Thanks

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• Thread Message Loop Hangs in Delphi

  - by erikjw

  Hello all. I have a simple Delphi program that I'm working on, in which I am attempting to use threading to separate the functionality of the program from its GUI, and to keep the GUI responsive during more lengthy tasks, etc. Basically, I have a 'controller' TThread, and a 'view' TForm. The view knows the controller's handle, which it uses to send the controller messages via PostThreadMessage. I have had no problem in the past using this sort of model for forms which are not the main form, but for some reason, when I attempt to use this model for the main form, the message loop of the thread just quits. Here is my code for the threads message loop: procedure TController.Execute; var Msg : TMsg; begin while not Terminated do begin if (Integer(GetMessage(Msg, hwnd(0), 0, 0)) = -1) then begin Synchronize(Terminate); end; TranslateMessage(Msg); DispatchMessage(Msg); case Msg.message of // ...call different methods based on message end; end; To set up the controller, I do this: Controller := TController.Create(true); // Create suspended Controller.FreeOnTerminate := True; Controller.Resume; For processing the main form's messages, I have tried using both Application.Run and the following loop (immediately after Controller.Resume) while not Application.Terminated do begin Application.ProcessMessages; end; I've run stuck here - any help would be greatly appreciated.

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• unable to place breakpoints in eclipse

  - by anjanb

  I am using eclipse europa (3.5) on windows vista home premium 64-bit using JDK 1.6.0_18 (32 BIT). Normally, I am able to put breakpoints just fine; However, for a particular class which is NOT part of the project (this class is inside a .JAR file (.JAR file is part of the project) ), although I have attached a source directory to this .JAR file, I am unable to place a breakpoint in this class. If I double-click on the breakpoint pane(left border), I notice that a class breakpoint is placed. I was wondering if there was NO debug info; However, found that this particular class was compiled using ant/javac task using debug="true" and debuglevel="lines,vars,source". I even ran jad on this class to confirm that it indeed contained the debug info. So, why is eclipse preventing me from placing a breakpoint ? EDIT : Just so everyone understands the context, this is a webapp running under tomcat 6.0. I am remote debugging the application from eclipse after having started tomcat outside. The application is working just fine. I am trying to understand the behavior of the above class which I'm unable to do since eclipse is not letting me set a BP. P.S : I saw a few threads here talking about BPs not being hit but in my case, I am unable to place the BP! P.P.S : I tried JDK 1.6.0_16 before trying out 1.6.0_18. Thanks for any pointers.

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• Using pthread to perform matrix multiplication

  - by shadyabhi

  I have both matrices containing only ones and each array has 500 rows and columns. So, the resulting matrix should be a matrix of all elements having value 500. But, I am getting res_mat[0][0]=5000. Even other elements are also 5000. Why? #include<stdio.h> #include<pthread.h> #include<unistd.h> #include<stdlib.h> #define ROWS 500 #define COLUMNS 500 #define N_THREADS 10 int mat1[ROWS][COLUMNS],mat2[ROWS][COLUMNS],res_mat[ROWS][COLUMNS]; void *mult_thread(void *t) { /*This function calculates 50 ROWS of the matrix*/ int starting_row; starting_row = *((int *)t); starting_row = 50 * starting_row; int i,j,k; for (i = starting_row;i<starting_row+50;i++) for (j=0;j<COLUMNS;j++) for (k=0;k<ROWS;k++) res_mat[i][j] += (mat1[i][k] * mat2[k][j]); return; } void fill_matrix(int mat[ROWS][COLUMNS]) { int i,j; for(i=0;i<ROWS;i++) for(j=0;j<COLUMNS;j++) mat[i][j] = 1; } int main() { int n_threads = 10; //10 threads created bcos we have 500 rows and one thread calculates 50 rows int j=0; pthread_t p[n_threads]; fill_matrix(mat1); fill_matrix(mat2); for (j=0;j<10;j++) pthread_create(&p[j],NULL,mult_thread,&j); for (j=0;j<10;j++) pthread_join(p[j],NULL); printf("%d\n",res_mat[0][0]); return 0; }

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• Python Socket Getting Connection Reset

  - by Ian

  I created a threaded socket listener that stores newly accepted connections in a queue. The socket threads then read from the queue and respond. For some reason, when doing benchmarking with 'ab' (apache benchmark) using a concurrency of 2 or more, I always get a connection reset before it's able to complete the benchmark (this is taking place locally, so there's no external connection issue). class server: _ip = '' _port = 8888 def __init__(self, ip=None, port=None): if ip is not None: self._ip = ip if port is not None: self._port = port self.server_listener(self._ip, self._port) def now(self): return time.ctime(time.time()) def http_responder(self, conn, addr): httpobj = http_builder() httpobj.header('HTTP/1.1 200 OK') httpobj.header('Content-Type: text/html; charset=UTF-8') httpobj.header('Connection: close') httpobj.body("Everything looks good") data = httpobj.generate() sent = conn.sendall(data) def http_thread(self, id): self.log("THREAD %d: Starting Up..." % id) while True: conn, addr = self.q.get() ip, port = addr self.log("THREAD %d: responding to request: %s:%s - %s" % (id, ip, port, self.now())) self.http_responder(conn, addr) self.q.task_done() conn.close() def server_listener(self, host, port): self.q = Queue.Queue(0) sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM) sock.bind( (host, port) ) sock.listen(5) for i in xrange(4): #thread count thread.start_new(self.http_thread, (i+1, )) while True: self.q.put(sock.accept()) sock.close() server('', 9999) When running the benchmark, I get totally random numbers of good requests before it errors out, usually between 4 and 500. Edit: Took me a while to figure it out, but the problem was in sock.listen(5). Because I was using apache benchmark with a higher concurrency (5 and up) it was causing the backlog of connections to pile up, at which point the connections started getting dropped by the socket.

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• sh: dot: command not found + doxygen + Lion

  - by Salil

  MacOS version : 10.7.2 ( lion ) Doxygen version : 1.7.5.1 Graphviz version : 2.29 Doxygen configuration - DOT_PATH = ../../../../Applications/Contents/MacOS/Graphviz HAVE_DOT = YES SHORT_NAMES = YES From the log console - First line it gives a warning - warning: the dot tool could not be found at ../../../../Applications/Contents/MacOS/Graphviz - I have tried various combinations but the warning does not go , although it generates the images. Generating dot graphs using 9 parallel threads... Running dot for graph 1/68 sh: dot: command not found Problems running dot: exit code=127, command='dot', arguments='"/Users/salilk/Documents/project/DoxygenDocs/html/a00033.dot" -Tpng -o "/Users/salilk/Documents/project/DoxygenDocs/html/a00033.png"' In the html directory the .dot files have been generated but no .png. Now if I execute the same command from the Terminal the .png file gets generated and is displayed in its .html file. Another error from the console is - error: problems opening map file /Users/salilk/Documents/A2O Collaborate/DoxygenDocs/html/a00032.map for inclusion in the docs! If you installed Graphviz/dot after a previous failing run, try deleting the output directory and rerun doxygen. - Is this related to the above problem ? I have used Doxygen before on a Windows machine and didn't have these errors , do we need to do any configurations specific for Mac ? - Salil.

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• Using Qt signals/slots instead of a worker thread

  - by Rob

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

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• Eclipse CDT: cannot debug or terminate application

  - by Paul Lammertsma

  I have Eclipse set up fairly nicely to run the G++ compiler through Cygwin. Even the character encoding is set up correctly! There still seems to be something wrong with my configuration: I can't debug. The pause button in the debug view is simply disabled, and no threads appear in my application tree. It seems that gdb is simply not communicating with Eclipse. Presently, I have the debug settings as follows: Debugger: "Cygwin gdb Debugger" GDB debugger: gdb GDB command file: .gdbinit Protocol: Default I should mention here that I have no idea what .gdbinit does; in my project it is merely an empty file. What is wrong with my configuration? Debugging When attempting to terminate the application in debug mode, Eclipse displays the following error: Target request failed: failed to interrupt. I can't kill the process, either; I have to kill its parent gdb.exe, which in turn kills my application. Running When running it normally, a bunch of kill.exes are called, doing nothing, while Eclipse displays the following error: Terminate failed. I can kill FaceDetector.exe from the task manager. Process Explorer This is what it looks like in Process Explorer (debugging left, running right):

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• How to correctly relay TCP traffic between sockets?

  - by flukes1

  I'm trying to write some Python code that will establish an invisible relay between two TCP sockets. My current technique is to set up two threads, each one reading and subsequently writing 1kb of data at a time in a particular direction (i.e. 1 thread for A to B, 1 thread for B to A). This works for some applications and protocols, but it isn't foolproof - sometimes particular applications will behave differently when running through this Python-based relay. Some even crash. I think that this is because when I finish performing a read on socket A, the program running there considers its data to have already arrived at B, when in fact I - the devious man in the middle - have yet to send it to B. In a situation where B isn't ready to receive the data (whereby send() blocks for a while), we are now in a state where A believes it has successfully sent data to B, yet I am still holding the data, waiting for the send() call to execute. I think this is the cause of the difference in behaviour that I've found in some applications, while using my current relaying code. Have I missed something, or does that sound correct? If so, my real question is: is there a way around this problem? Is it possible to only read from socket A when we know that B is ready to receive data? Or is there another technique that I can use to establish a truly 'invisible' two-way relay between [already open & established] TCP sockets?

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• Deadlock in ThreadPoolExecutor

  - by Vitaly

  Encountered a situation when ThreadPoolExecutor is parked in execute(Runnable) function while all the ThreadPool threads are waiting in getTask func, workQueue is empty. Does anybody have any ideas? The ThreadPoolExecutor is created with ArrayBlockingQueue, corePoolSize == maximumPoolSize = 4 [Edit] To be more precise, the thread is blocked in ThreadPoolExecutor.exec(Runnable command) func. It has the task to execute, but doesn't do it. [Edit2] The executor is blocked somewhere inside the working queue (ArrayBlockingQueue). [Edit3] The callstack: thread = front_end(224) at sun.misc.Unsafe.park(Native methord) at java.util.concurrent.locks.LockSupport.park(LockSupport.java:158) at java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:747) at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireQueued(AbstractQueuedSynchronizer.java:778) at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquire(AbstractQueuedSynchronizer.java:1114) at java.util.concurrent.locks.ReentrantLock$NonfairSync.lock(ReentrantLock.java:186) at java.util.concurrent.locks.ReentrantLock.lock(ReentrantLock.java:262) at java.util.concurrent.ArrayBlockingQueue.offer(ArrayBlockingQueue.java:224) at java.util.concurrent.ThreadPoolExecutor.execute(ThreadPoolExecutor.java:653) at net.listenThread.WorkersPool.execute(WorkersPool.java:45) at the same time the workQueue is empty (checked using remote debug) [Edit4] Code working with ThreadPoolExecutor: public WorkersPool(int size) { pool = new ThreadPoolExecutor(size, size, IDLE_WORKER_THREAD_TIMEOUT, TimeUnit.SECONDS, new ArrayBlockingQueue<Runnable>(WORK_QUEUE_CAPACITY), new ThreadFactory() { @NotNull private final AtomicInteger threadsCount = new AtomicInteger(0); @NotNull public Thread newThread(@NotNull Runnable r) { final Thread thread = new Thread(r); thread.setName("net_worker_" + threadsCount.incrementAndGet()); return thread; } }, new RejectedExecutionHandler() { public void rejectedExecution(@Nullable Runnable r, @Nullable ThreadPoolExecutor executor) { Verify.warning("new task " + r + " is discarded"); } }); } public void execute(@NotNull Runnable task) { pool.execute(task); } public void stopWorkers() throws WorkersTerminationFailedException { pool.shutdownNow(); try { pool.awaitTermination(THREAD_TERMINATION_WAIT_TIME, TimeUnit.SECONDS); } catch (InterruptedException e) { throw new WorkersTerminationFailedException("Workers-pool termination failed", e); } } }

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• Does HttpListener work well on Mono?

  - by billpg

  Hi everyone. I'm looking to write a small web service to run on a small Linux box. I prefer to code in C#, so I'm looking to use Mono. I don't want the overhead of running a full web server or Mono's version of ASP.NET. I'm thinking of having a single process with a thread dealing with each client connection. Shared memory between threads instead of a database. I've read a little on Microsoft's version of HttpListener and how it works with the Http.sys driver. Alas, Mono's documentation on this class is just the automated class interface with no discussion of how it works under the hood. (Linux doesn't have Http.sys, so I imagine it's implemented substantially differently.) Could anyone point me towards some resources discussing this module please? Many thanks, Bill, billpg.com (A little background to my question for the interested.) Some time ago, I asked this question, interested in keeping a long conversation open with lots of back-and-forth. I had settled on designing my own ad-hoc protocol, but people I spoke to really wanted a REST interface, even at the cost of the "Okay, send your command now" signal. So, I wondered about running ASP.NET on a Linux/Mono server, but stumbled upon HttpListener. This seemed ideal, as each "conversation" could run in a separate thread. The thread that calls HttpListener in a loop can look for which thread each incomming connection is for and pass the reference to that thread. The alternative for an ASP.NET driven service, would be to have the ASPX code pick up the state from a database, and write back the new state when it finishes. Yes, it would work, but that's a lot of overhead.

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• Java Performance measurement

  - by portoalet

  Hi, I am doing some Java performance comparison between my classes, and wondering if there is some sort of Java Performance Framework to make writing performance measurement code easier? I.e, what I am doing now is trying to measure what effect does it have having a method as "synchronized" as in PseudoRandomUsingSynch.nextInt() compared to using an AtomicInteger as my "synchronizer". So I am trying to measure how long it takes to generate random integers using 3 threads accessing a synchronized method looping for say 10000 times. I am sure there is a much better way doing this. Can you please enlighten me? :) public static void main( String [] args ) throws InterruptedException, ExecutionException { PseudoRandomUsingSynch rand1 = new PseudoRandomUsingSynch((int)System.currentTimeMillis()); int n = 3; ExecutorService execService = Executors.newFixedThreadPool(n); long timeBefore = System.currentTimeMillis(); for(int idx=0; idx<100000; ++idx) { Future<Integer> future = execService.submit(rand1); Future<Integer> future1 = execService.submit(rand1); Future<Integer> future2 = execService.submit(rand1); int random1 = future.get(); int random2 = future1.get(); int random3 = future2.get(); } long timeAfter = System.currentTimeMillis(); long elapsed = timeAfter - timeBefore; out.println("elapsed:" + elapsed); } the class public class PseudoRandomUsingSynch implements Callable<Integer> { private int seed; public PseudoRandomUsingSynch(int s) { seed = s; } public synchronized int nextInt(int n) { byte [] s = DonsUtil.intToByteArray(seed); SecureRandom secureRandom = new SecureRandom(s); return ( secureRandom.nextInt() % n ); } @Override public Integer call() throws Exception { return nextInt((int)System.currentTimeMillis()); } } Regards

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• How to switch from Core Data automatic lightweight migration to manual?

  - by Jaanus

  My situation is similar to this question. I am using lightweight migration with the following code, fairly vanilla from Apple docs and other SO threads. It runs upon app startup when initializing the Core Data stack. NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys: [NSNumber numberWithBool:YES], NSMigratePersistentStoresAutomaticallyOption, [NSNumber numberWithBool:YES], NSInferMappingModelAutomaticallyOption, nil]; NSError *error = nil; NSString *storeType = nil; if (USE_SQLITE) { // app configuration storeType = NSSQLiteStoreType; } else { storeType = NSBinaryStoreType; } persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]]; // the following line sometimes crashes on app startup if (![persistentStoreCoordinator addPersistentStoreWithType:storeType configuration:nil URL:[self persistentStoreURL] options:options error:&error]) { // handle the error } For some users, especially with slower devices, I have crashes confirmed by logs at the indicated line. I understand that a fix is to switch this to manual mapping and migration. What is the recipe to do that? The long way for me would be to go through all Apple docs, but I don't recall there being good examples and tutorials specifically for schema migration.

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• Pthread Queue System

  - by Wallace

  Hi. I'm working on my assignment on pthreads. I'm new and never touched on pthreads before. Is there any sample codes or resources out there that anyone of you have, that might aid me in my assignment? Here are my assignment details. A pthread program about queue system: Write a C/C++ Pthread program for a Dental clinic’s queuing system that declares an array of integers of size N, where N is the maximum number of queue for the day. The pthread program uses two threads. Whenever there is a new dental appointment, the first thread (the creator) puts the queue numbers in the array, one after the other. The second thread (the remover) removes the queue numbers from the array whenever the dentist has seen the patient. This is done in a FIFO fashion (First In First Out). The algorithm of the creator is as follows: • If the array is not full then put a new number in it (the numbers start at 1 and are incremented by one each time, so the creator create queue number 1, 2, 3 etc.) • sleep for 1 to 10 seconds, randomly • repeat The algorithm of the remover is as follows: • If the array is not empty then remove its smallest queue number • sleep for 1 to 10 seconds, randomly • repeat You should use mutex locks to protect things that must be protected. Each thread should print on the screen what it is doing (eg: "number 13 is added into the queue", "number 7 is removed from the queue", etc.). The program should run forever. Any help will be appreciated. Thanks.

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• C# COM Cross Thread problem

  - by user364676

  Hi, we're developing a software to control a scientific measuring device. it provides a COM-Interface defines serveral functions to set measurement parameters and fires an event when it measured data. in order to test our software, i'm implementing a simulation of that device. the com-object runs a loop which periodically fires the event. another loop in the client app should now setup up the com-simulator using the given functions. i created a class for measuring parameters which will be instanciated when setting up a new measurement. // COM-Object public class MeasurementParams { public double Param1; public double Param2; } public class COM_Sim : ICOMDevice { public MeasurementParams newMeasurement; IClient client; public int NewMeasurement() { newMeasurment = new MeasurementParam(); } public int SetParam1(double val) { // why is newMeasurement null when method is called from client loop newMeasurement.Param1 = val; } void loop() { while(true) { // fire event client.HandleEvent; } } } public class Client : IClient { ICOMDevice server; public int HandleEvent() { // handle this event server.NewMeasurement(); server.SetParam1(0.0); } void loop() { while(true) { // do some stuff... server.NewMeasurement(); server.SetParam1(0.0); } } } both of the loops run in independent threads. when server.NewMeasurement() is called, the object on the server is set to a new instance. but in the next function, the object is null again. do the same when handling the server-event, it works perfectly, because the method runs in the servers thread. how to make it work from client-thread as well. as the client is meant to be working with the real device, i cannot modify the interfaces given by the manufactor. also i need to setup measurements independent from the event-handler, which will be fired not regulary. i assume this problem related to multithreaded-COM behavior but i found nothing on this topic.

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• How do I print an HTML document from a web service?

  - by Chris Marasti-Georg

  I want to print HTML from a C# web service. The Web Browser control is overkill, and does not function well in a service-environment, nor does it function well on a system with very tight security constraints. Is there any sort of free .NET library that will support the printing of a basic HTML page? Here is the code I have so far, that is not running properly. public void PrintThing(string document) { if (Thread.CurrentThread.GetApartmentState() != ApartmentState.STA) { Thread thread = new Thread((ThreadStart) delegate { PrintDocument(document); }); thread.SetApartmentState(ApartmentState.STA); thread.Start(); } else { PrintDocument(document); } } protected void PrintDocument(string document) { WebBrowser browser = new WebBrowser(); browser.DocumentText = document; while (browser.ReadyState != WebBrowserReadyState.Complete) { Application.DoEvents(); } browser.Print(); } This works fine when called from UI-type threads, but nothing happens when called from a service-type thread. Changing Print() to ShowPrintPreviewDialog() yields the following IE script error: Error: 'dialogArguments.___IE_PrintType' is null or not an object URL: res://ieframe.dll/preview.dlg And a small empty print preview dialog appears.

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• Pattern for limiting number of simultaneous asynchronous calls

  - by hitch

  I need to retrieve multiple objects from an external system. The external system supports multiple simultaneous requests (i.e. threads), but it is possible to flood the external system - therefore I want to be able to retrieve multiple objects asynchronously, but I want to be able to throttle the number of simultaneous async requests. i.e. I need to retrieve 100 items, but don't want to be retrieving more than 25 of them at once. When each request of the 25 completes, I want to trigger another retrieval, and once they are all complete I want to return all of the results in the order they were requested (i.e. there is no point returning the results until the entire call is returned). Are there any recommended patterns for this sort of thing? Would something like this be appropriate (pseudocode, obviously)? private List<externalSystemObjects> returnedObjects = new List<externalSystemObjects>; public List<externalSystemObjects> GetObjects(List<string> ids) { int callCount = 0; int maxCallCount = 25; WaitHandle[] handles; foreach(id in itemIds to get) { if(callCount < maxCallCount) { WaitHandle handle = executeCall(id, callback); addWaitHandleToWaitArray(handle) } else { int returnedCallId = WaitHandle.WaitAny(handles); removeReturnedCallFromWaitHandles(handles); } } WaitHandle.WaitAll(handles); return returnedObjects; } public void callback(object result) { returnedObjects.Add(result); }

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• Usability for content editors: Drupal or PHP framework?

  - by Jim

  Greetings: I am going to develop a basic Web site that supports some custom content types, is multilingual, and has content moderation workflow for a restricted group of content editors. This seems like an obvious choice for Drupal, except... the content editors will have little computer experience. In my opinion, that is a show-stopper for Drupal. For example, placing arbitrary inline images in content is a task that WordPress does well. I find Drupal's alternatives (IMCE, img_assist, etc.) clunky and not well integrated, and that will be a problem for this group of content editors. Also, none of the Drupal content workflow modules I tried seemed well-integrated; they all had a "tacked on" feel to them. As an admin I can understand why an "Accessible content" menu item (via Module Grants module) is necessary to view draft content (fixed in D7 but I can't wait for all the modules to be ported), but I'm pretty sure it'll confuse the content editors. An alternative is to use a PHP framework. I've read a few threads suggesting that it will take roughly the same amount of time using a good framework as it will to bend Drupal to my willing... maybe wishful thinking? I'm looking at Symfony, which gives me a basic auto-generated back-end, but which I believe I can customize to my heart's content. How do you make Drupal accessible to non-savvy content editors? If you recommend a PHP framework, which one? TIA!

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• Sharing session variables from http and https versio

  - by tangurena

  I am trying to fix an ASP.NET site that a friend had botched converting from older technologies. To the user, the site appears to have public and secured sections. Behind the scenes, the public and private sites are separate web applications with separate app pools. The difficulty arises because it appears that the applications share the same session IDs (when going from the public to the secured pages, the session ID remains the same), yet none of the (InProc) session variables are getting passed from the public site to the private one. Basically, the workflow consists of the user checking a checkbox ("I agree" type of stuff) on the public site (let's call that page http://www.boring.gov/iAgree.aspx), then logging in on the secured site (let's call that page https://www.boring.gov/login.aspx). The commandments from the parent agency in DC are that the user may not bookmark the login page, the user has to click "I agree" every time they log in, and that the "I agree" stuff has to be on a separate page. What am I missing? How would you do it? Notes: 1 - This is getting hosted on a single Windows 2003 server. 2 - Yes, it is a government agency. 3 - I would have done things very differently if I was doing the conversion, but I wasn't brought in until the poop hit the fan, and it is too late to redo things. 4 - Two previous SO threads that appear to be related, yet don't apply are this and that

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