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  • No Question mark suddenly É instead. Why?

    - by Xavierjazz
    Windows xp3. This happens occasionally. Today it happened in a calendar item in outlook 2003. As you can see from the title here, the question mark is working here (firefox). I am typing and suddenly the question mark is replaced by this character, É and I have no idea why. Can anyone answer this? I hope this is an appropriate site for this question. Thanks a lot.

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  • Utilize two gateways on the same network same interface with load balancing

    - by RushPL
    My setup is two ISPs on a single interface and single network. I can either set my default gateway to 192.168.0.1 or 192.168.1.250 and either work. My desire is to utilize both of them with some load balancing. I have tried to follow the advice given in here http://serverfault.com/a/96586 #!/bin/sh ip route show table main | grep -Ev '^default' \ | while read ROUTE ; do ip route add table ISP1 $ROUTE done ip route add default via 192.168.1.250 table ISP1 ip route add default via 192.168.0.1 table ISP2 iptables -t mangle -A PREROUTING -j CONNMARK --restore-mark iptables -t mangle -A PREROUTING -m mark ! --mark 0 -j ACCEPT iptables -t mangle -A PREROUTING -j MARK --set-mark 10 iptables -t mangle -A PREROUTING -m statistic --mode random --probability 0.5 -j MARK --set-mark 20 iptables -t mangle -A PREROUTING -j CONNMARK --save-mark Now then I do "traceroute somehost" repeatedly I can only get route through my default route which is 192.168.1.250. Shouldn't the packets change routes in a random manner? How to debug it?

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  • Making a rectangular selection in a RichTextBox with Alt-Left-Mouse sweep?

    - by Harold Bamford
    There are quite a few applications that allow you to select a box or rectangle of text by sweeping with mouse while the Alt key is pressed. Visual Studio 2010 does this in the code editor, for instance. Emacs does it. Winword does it. We've all seen it. It seems like there must be a standard pattern to follow to encode this behavior but I cannot seem to find it. I suspect I am not Googling with the correct keywords as all I am getting are false hits on rectangle, Alt-Left, sweep, selection, etc. I'm sure I can code it up but it would mean disabling the normal selection code used in, say, RichTextBox. And that sounds ugly, error prone and probably more work than it is worth. Anybody have a suggestion (be nice! :-) ) of how to do this or an example of how it is done?

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  • Is Akka a good solution for a concurrent pipeline/workflow problem?

    - by herpylderp
    Disclaimer: I am brand new to Akka and the concept of Actors/Event-Driven Architectures in general. I have to implement a fairly complex problem where users can configure a "concurrent pipeline": Pipeline: consists of 1+ Stages; all Stages execute sequentially Stage: consists of 1+ Tasks; all Tasks execute in parallel Task: essentially a Java Runnable As you can see above, a Task is a Runnable that does some unit of work. Tasks are organized into Stages, which execute their Tasks in parallel. Stages are organized into the Pipeline, which executes its Stages sequentially. Hence if a user specifies the following Pipeline: CrossTheRoadSafelyPipeline Stage 1: Look Left Task 1: Turn your head to the left and look for cars Task 2: Listen for cars Stage 2: Look right Task 1: Turn your head to the right and look for cars Task 2: Listen for cars Then, Stage 1 will execute, and then Stage 2 will execute. However, while each Stage is executing, it's individual Tasks are executing in parallel/at the same time. In reality Pipelines will become very complicated, and with hundreds of Stages, dozens of Tasks per Stage (again, executing at the same time). To implement this Pipeline I can only think of several solutions: ESB/Apache Camel Guava Event Bus Java 5 Concurrency Actors/Akka Camel doesn't seem right because its core competency is integration not synchrony and orchestration across worker threads. Guava is great, but this doesn't really feel like a subscriber/publisher-type of problem. And Java 5 Concurrency (ExecutorService, etc.) just feels too low-level and painful. So I ask: is Akka a strong candidate for this type of problem? If so, how? If not, then why, and what is a good candidate?

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  • Simultaneous launch of Multiple Kernels using CUDA for a GPU

    - by cudadev
    Is it possible to launch two kernels that do independent tasks, simultaneously. For example if I have this Cuda code // host and device initialization ....... ....... // launch kernel1 myMethod1 <<<.... (params); // launch kernel2 myMethod2 <<<..... (params); Assuming that these kernels are independent, is there a facility to launch them at the same time allocating few grids/blocks for each. Does CUDA/OpenCL have this provision.

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  • Multiple threads or process with threads

    - by sergiobuj
    Hi, this is for an assignment so I'm not looking for code. I have to simulate a game where each player has turns and needs to 'pay attention' to what's going on. So far, i know I'll need two threads for each player, one that will sleep until the player's turn and the other paying attention. My question is: Should I work each player as a 'fork' and the threads on the fork, or just create some threads for the player and associate them somehow? It's the first time I've worked with concurrency, semaphores and threads so I'm not sure about the good practices and programming style. Thanks!

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  • What is the fastest way to send 100,000 HTTP requests in Python?

    - by Igor G.
    Hello, I am opening a file which has 100,000 url's. I need to send an http request to each url and print the status code. I am using Python 2.6, and so far looked at the many confusing ways Python implements threading/concurrency. I have even looked at the python concurrence library, but cannot figure out how to write this program correctly. Has anyone come across a similar problem? I guess generally I need to know how to perform thousands of tasks in Python as fast as possible - I suppose that means 'concurrently'. Thank you, Igor

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  • Using Java Executor on AppEngine causes AccessControlException

    - by Drew
    How do you get java.util.concurrent.Executor or CompletionService to work on Google AppEngine? The classes are all officially white-listed, but I get a runtime security error when trying to submit asynchronous tasks. Code: // uses the async API but this factory makes it so that tasks really // happen sequentially Executor executor = java.util.concurrent.Executors.newSingleThreadExecutor(); // wrap Executor in CompletionService CompletionService<String> completionService = new ExecutorCompletionService<String>(executor); final SomeTask someTask = new SomeTask(); // this line throws exception completionService.submit(new Callable<String>(){ public String call() { return someTask.doNothing("blah"); } }); // alternately, send Runnable task directly to Executor, // which also throws an exception executor.execute(new Runnable(){ public void run() { someTask.doNothing("blah"); } }); } private class SomeTask{ public String doNothing(String message){ return message; } } Exception: java.security.AccessControlException: access denied (java.lang.RuntimePermission modifyThreadGroup) at java.security.AccessControlContext.checkPermission(AccessControlContext.java:323) at java.security.AccessController.checkPermission(AccessController.java:546) at java.lang.SecurityManager.checkPermission(SecurityManager.java:532) at com.google.appengine.tools.development.DevAppServerFactory$CustomSecurityManager.checkPermission(DevAppServerFactory.java:166) at com.google.appengine.tools.development.DevAppServerFactory$CustomSecurityManager.checkAccess(DevAppServerFactory.java:191) at java.lang.ThreadGroup.checkAccess(ThreadGroup.java:288) at java.lang.Thread.init(Thread.java:332) at java.lang.Thread.(Thread.java:565) at java.util.concurrent.Executors$DefaultThreadFactory.newThread(Executors.java:542) at java.util.concurrent.ThreadPoolExecutor.addThread(ThreadPoolExecutor.java:672) at java.util.concurrent.ThreadPoolExecutor.addIfUnderCorePoolSize(ThreadPoolExecutor.java:697) at java.util.concurrent.ThreadPoolExecutor.execute(ThreadPoolExecutor.java:652) at java.util.concurrent.Executors$DelegatedExecutorService.execute(Executors.java:590) at java.util.concurrent.ExecutorCompletionService.submit(ExecutorCompletionService.java:152) This code works fine when run on Tomcat or via command-line JVM. However, it chokes in the AppEngine SDK Jetty container (tried with Eclipse plugin and the maven-gae-plugin). AppEngine is likely designed to not allow potentially dangerous programs to run, so I could see them completely disabling thread creation. However, why would Google allow you to create a class, but not allow you to call methods on it? White-listing java.util.concurrent is misleading. Is there some other way to do parallel/simultaneous/concurrent tasks on GAE?

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  • Can I remove items from a ConcurrentDictionary from within an enumeration loop of that dictionary?

    - by the-locster
    So for example: ConcurrentDictionary<string,Payload> itemCache = GetItems(); foreach(KeyValuePair<string,Payload> kvPair in itemCache) { if(TestItemExpiry(kvPair.Value)) { // Remove expired item. Payload removedItem; itemCache.TryRemove(kvPair.Key, out removedItem); } } Obviously with an ordinary Dictionary this will throw an exception because removing items changes the dictionary's internal state during the life of the enumeration. It's my understanding that this is not the case for a ConcurrentDictionary as the provided IEnumerable handles internal state changing. Am I understanding this right? Is there a better pattern to use?

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  • .Net4 ConcurrentDictionary: Tips & Tricks

    - by SDReyes
    Hi guys, I started to use the new ConcurrentDictionary from .Net4 yesterday to implement a simple caching for a threading project. But I'm wondering what I have to take care of/be careful about when using it? What have been your experiences using it?

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  • ConcurrentLinkedQueue$Node remains in heap after remove()

    - by action8
    I have a multithreaded app writing and reading a ConcurrentLinkedQueue, which is conceptually used to back entries in a list/table. I originally used a ConcurrentHashMap for this, which worked well. A new requirement required tracking the order entries came in, so they could be removed in oldest first order, depending on some conditions. ConcurrentLinkedQueue appeared to be a good choice, and functionally it works well. A configurable amount of entries are held in memory, and when a new entry is offered when the limit is reached, the queue is searched in oldest-first order for one that can be removed. Certain entries are not to be removed by the system and wait for client interaction. What appears to be happening is I have an entry at the front of the queue that occurred, say 100K entries ago. The queue appears to have the limited number of configured entries (size() == 100), but when profiling, I found that there were ~100K ConcurrentLinkedQueue$Node objects in memory. This appears to be by design, just glancing at the source for ConcurrentLinkedQueue, a remove merely removes the reference to the object being stored but leaves the linked list in place for iteration. Finally my question: Is there a "better" lazy way to handle a collection of this nature? I love the speed of the ConcurrentLinkedQueue, I just cant afford the unbounded leak that appears to be possible in this case. If not, it seems like I'd have to create a second structure to track order and may have the same issues, plus a synchronization concern.

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  • Find messages[from-to]

    - by Alfred
    I would like to return all messages from certain key to a certain key. The class should be thread-safe and old keys should be able to be deleted say for example after 30 seconds. I was thinking of using a concurrentskiplistset or concurrentskiplist map. Also I was thinking of deleting the items from inside a newSingleThreadScheduledExecutor. I would like to know how you would implement this or maybe use a library?

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  • How to work threading with ConcurrentQueue<T>.

    - by dboarman
    I am trying to figure out what the best way of working with a queue will be. I have a process that returns a DataTable. Each DataTable, in turn, is merged with the previous DataTable. There is one problem, too many records to hold until the final BulkCopy (OutOfMemory). So, I have determined that I should process each incoming DataTable immediately. Thinking about the ConcurrentQueue<T>...but I don't see how the WriteQueuedData() method would know to dequeue a table and write it to the database. For instance: public class TableTransporter { private ConcurrentQueue<DataTable> tableQueue = new ConcurrentQueue<DataTable>(); public TableTransporter() { tableQueue.OnItemQueued += new EventHandler(WriteQueuedData); // no events available } public void ExtractData() { DataTable table; // perform data extraction tableQueue.Enqueue(table); } private void WriteQueuedData(object sender, EventArgs e) { BulkCopy(e.Table); } } My first question is, aside from the fact that I don't actually have any events to subscribe to, if I call ExtractData() asynchronously will this be all that I need? Second, is there something I'm missing about the way ConcurrentQueue<T> functions and needing some form of trigger to work asynchronously with the queued objects?

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  • Hibernate Lazy init exception in spring scheduled job

    - by Noam Nevo
    I have a spring scheduled job (@Scheduled) that sends emails from my system according to a list of recipients in the DB. This method is annotated with the @Scheduled annotation and it invokes a method from another interface, the method in the interface is annotated with the @Transactional annotation. Now, when i invoke the scheduled method manually, it works perfectly. But when the method is invoked by spring scheduler i get the LazyInitFailed exception in the method implementing the said interface. What am I doing wrong? code: The scheduled method: @Component public class ScheduledReportsSender { public static final int MAX_RETIRES = 3; public static final long HALF_HOUR = 1000 * 60 * 30; @Autowired IScheduledReportDAO scheduledReportDAO; @Autowired IDataService dataService; @Autowired IErrorService errorService; @Scheduled(cron = "0 0 3 ? * *") // every day at 2:10AM public void runDailyReports() { // get all daily reports List<ScheduledReport> scheduledReports = scheduledReportDAO.getDaily(); sendScheduledReports(scheduledReports); } private void sendScheduledReports(List<ScheduledReport> scheduledReports) { if(scheduledReports.size()<1) { return; } //check if data flow ended its process by checking the report_last_updated table in dwh int reportTimeId = scheduledReportDAO.getReportTimeId(); String todayTimeId = DateUtils.getTimeid(DateUtils.getTodayDate()); int yesterdayTimeId = Integer.parseInt(DateUtils.addDaysSafe(todayTimeId, -1)); int counter = 0; //wait for time id to update from the daily flow while (reportTimeId != yesterdayTimeId && counter < MAX_RETIRES) { errorService.logException("Daily report sender, data not ready. Will try again in one hour.", null, null, null); try { Thread.sleep(HALF_HOUR); } catch (InterruptedException ignore) {} reportTimeId = scheduledReportDAO.getReportTimeId(); counter++; } if (counter == MAX_RETIRES) { MarketplaceServiceException mse = new MarketplaceServiceException(); mse.setMessage("Data flow not done for today, reports are not sent."); throw mse; } // get updated timeid updateTimeId(); for (ScheduledReport scheduledReport : scheduledReports) { dataService.generateScheduledReport(scheduledReport); } } } The Invoked interface: public interface IDataService { @Transactional public void generateScheduledReport(ScheduledReport scheduledReport); } The implementation (up to the line of the exception): @Service public class DataService implements IDataService { public void generateScheduledReport(ScheduledReport scheduledReport) { // if no recipients or no export type - return if(scheduledReport.getRecipients()==null || scheduledReport.getRecipients().size()==0 || scheduledReport.getExportType() == null) { return; } } } Stack trace: ERROR: 2012-09-01 03:30:00,365 [Scheduler-15] LazyInitializationException.<init>(42) | failed to lazily initialize a collection of role: com.x.model.scheduledReports.ScheduledReport.recipients, no session or session was closed org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: com.x.model.scheduledReports.ScheduledReport.recipients, no session or session was closed at org.hibernate.collection.AbstractPersistentCollection.throwLazyInitializationException(AbstractPersistentCollection.java:383) at org.hibernate.collection.AbstractPersistentCollection.throwLazyInitializationExceptionIfNotConnected(AbstractPersistentCollection.java:375) at org.hibernate.collection.AbstractPersistentCollection.readSize(AbstractPersistentCollection.java:122) at org.hibernate.collection.PersistentBag.size(PersistentBag.java:248) at com.x.service.DataService.generateScheduledReport(DataService.java:219) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:616) at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:309) at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:183) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:150) at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:110) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172) at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:202) at $Proxy208.generateScheduledReport(Unknown Source) at com.x.scheduledJobs.ScheduledReportsSender.sendScheduledReports(ScheduledReportsSender.java:85) at com.x.scheduledJobs.ScheduledReportsSender.runDailyReports(ScheduledReportsSender.java:38) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:616) at org.springframework.util.MethodInvoker.invoke(MethodInvoker.java:273) at org.springframework.scheduling.support.MethodInvokingRunnable.run(MethodInvokingRunnable.java:65) at org.springframework.scheduling.support.DelegatingErrorHandlingRunnable.run(DelegatingErrorHandlingRunnable.java:51) at org.springframework.scheduling.concurrent.ReschedulingRunnable.run(ReschedulingRunnable.java:81) at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471) at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:334) at java.util.concurrent.FutureTask.run(FutureTask.java:166) at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$101(ScheduledThreadPoolExecutor.java:165) at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:266) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603) at java.lang.Thread.run(Thread.java:636) ERROR: 2012-09-01 03:30:00,366 [Scheduler-15] MethodInvokingRunnable.run(68) | Invocation of method 'runDailyReports' on target class [class com.x.scheduledJobs.ScheduledReportsSender] failed org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: com.x.model.scheduledReports.ScheduledReport.recipients, no session or session was closed at org.hibernate.collection.AbstractPersistentCollection.throwLazyInitializationException(AbstractPersistentCollection.java:383) at org.hibernate.collection.AbstractPersistentCollection.throwLazyInitializationExceptionIfNotConnected(AbstractPersistentCollection.java:375) at org.hibernate.collection.AbstractPersistentCollection.readSize(AbstractPersistentCollection.java:122) at org.hibernate.collection.PersistentBag.size(PersistentBag.java:248) at com.x.service.DataService.generateScheduledReport(DataService.java:219) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:616) at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:309) at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:183) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:150) at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:110) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172) at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:202) at $Proxy208.generateScheduledReport(Unknown Source) at com.x.scheduledJobs.ScheduledReportsSender.sendScheduledReports(ScheduledReportsSender.java:85) at com.x.scheduledJobs.ScheduledReportsSender.runDailyReports(ScheduledReportsSender.java:38) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:616) at org.springframework.util.MethodInvoker.invoke(MethodInvoker.java:273) at org.springframework.scheduling.support.MethodInvokingRunnable.run(MethodInvokingRunnable.java:65) at org.springframework.scheduling.support.DelegatingErrorHandlingRunnable.run(DelegatingErrorHandlingRunnable.java:51) at org.springframework.scheduling.concurrent.ReschedulingRunnable.run(ReschedulingRunnable.java:81) at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471) at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:334) at java.util.concurrent.FutureTask.run(FutureTask.java:166) at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$101(ScheduledThreadPoolExecutor.java:165) at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:266) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603) at java.lang.Thread.run(Thread.java:636)

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  • ExecutorService that interrupts tasks after a timeout

    - by scompt.com
    I'm looking for an ExecutorService implementation that can be provided with a timeout. Tasks that are submitted to the ExecutorService are interrupted if they take longer than the timeout to run. Implementing such a beast isn't such a difficult task, but I'm wondering if anybody knows of an existing implementation.

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  • Efficient algorithm to distribute work?

    - by Zwei Steinen
    It's a bit complicated to explain but here we go. We have problems like this (code is pseudo-code, and is only for illustrating the problem. Sorry it's in java. If you don't understand, I'd be glad to explain.). class Problem { final Set<Integer> allSectionIds = { 1,2,4,6,7,8,10 }; final Data data = //Some data } And a subproblem is: class SubProblem { final Set<Integer> targetedSectionIds; final Data data; SubProblem(Set<Integer> targetedSectionsIds, Data data){ this.targetedSectionIds = targetedSectionIds; this.data = data; } } Work will look like this, then. class Work implements Runnable { final Set<Section> subSections; final Data data; final Result result; Work(Set<Section> subSections, Data data) { this.sections = SubSections; this.data = data; } @Override public void run(){ for(Section section : subSections){ result.addUp(compute(data, section)); } } } Now we have instances of 'Worker', that have their own state sections I have. class Worker implements ExecutorService { final Map<Integer,Section> sectionsIHave; { sectionsIHave = {1:section1, 5:section5, 8:section8 }; } final ExecutorService executor = //some executor. @Override public void execute(SubProblem problem){ Set<Section> sectionsNeeded = fetchSections(problem.targetedSectionIds); super.execute(new Work(sectionsNeeded, problem.data); } } phew. So, we have a lot of Problems and Workers are constantly asking for more SubProblems. My task is to break up Problems into SubProblem and give it to them. The difficulty is however, that I have to later collect all the results for the SubProblems and merge (reduce) them into a Result for the whole Problem. This is however, costly, so I want to give the workers "chunks" that are as big as possible (has as many targetedSections as possible). It doesn't have to be perfect (mathematically as efficient as possible or something). I mean, I guess that it is impossible to have a perfect solution, because you can't predict how long each computation will take, etc.. But is there a good heuristic solution for this? Or maybe some resources I can read up before I go into designing? Any advice is highly appreciated!

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  • Problem with "write" function in linux

    - by Dumitru Catalin
    I am trying to write 2 server/client programs under Linux, in which they communicate through named pipes. The problem is that sometimes when I try to write from the server into a pipe that doesn't exist anymore (the client has stopped), I get a "Resource temporarily unavailable" error and the server stops completely. I understand that this is caused by using a O_NONBLOCK parameter when opening the fifo chanel, indicating the point where the program would usually wait until it could write again in the file, but is there a way to stop this behavior, and not halt the entire program if a problem occurs (shouldn't the write command return -1 ad the program continue normally)? And another strange thing is that this error only occurs when running the programs outside the ide (eclipse). If I run both programs inside eclipse, on error the write function just returns -1 and the programs continues normally.

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  • ScheduledThreadPoolExecutor executing a wrong time because of CPU time discrepancy

    - by richs
    I'm scheduling a task using a ScheduledThreadPoolExecutor object. I use the following method: public ScheduledFuture<?> schedule(Runnable command, long delay,TimeUnit unit) and set the delay to 30 seconds (delay = 30,000 and unit=TimeUnit.MILLISECONDS). Sometimes my task occurs immediately and other times it takes 70 seconds. I believe the ScheduledThreadPoolExecutor uses CPU specific clocks. When i run tests comparing System.currentTimeMillis(), System.nanoTime() [which is CPU specific] i see the following schedule: 1272637682651ms, 7858346157228410ns execute: 1272637682667ms, 7858386270968425ns difference is 16ms but 4011374001ns (or 40,113ms) so it looks like there is discrepancy between two CPU clocks of 40 seconds How do i resolve this issue in java code? Unfortunately this is a clients machine and i can't modify their system.

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  • Java Executor: Small tasks or big ones?

    - by Arash Shahkar
    Consider one big task which could be broken into hundreds of small, independently-runnable tasks. To be more specific, each small task is to send a light network request and decide upon the answer received from the server. These small tasks are not expected to take longer than a second, and involve a few servers in total. I have in mind two approaches to implement this using the Executor framework, and I want to know which one's better and why. Create a few, say 5 to 10 tasks each involving doing a bunch of send and receives. Create a single task (Callable or Runnable) for each send & receive and schedule all of them (hundreds) to be run by the executor. I'm sorry if my question shows that I'm lazy to test these and see for myself what's better (at least performance-wise). My question, while looking after an answer to this specific case, has a more general aspect. In situations like these when you want to use an executor to do all the scheduling and other stuff, is it better to create lots of small tasks or to group those into a less number of bigger tasks?

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  • Invalid Cross-Thread Operations from BackgroundWorker2_RunWorkerCompleted in C#

    - by Jim Fell
    Hello. I'm getting an error that does not make sense. Cross-thread operation not valid: Control 'buttonOpenFile' accessed from a thread other than the thread it was created on. In my application, the UI thread fires off backgroundWorker1, which when almost complete fires off backgroundWorker2 and waits for it to complete. backgroundWorker1 waits for backgroundWorker2 to complete, before it completes. AutoResetEvent variables are used to flag when each of the workers complete. In backgroundWorker2_RunWorkerComplete a function is called that resets the form controls. It is in this ResetFormControls() function where the exception is thrown. I thought it was safe to modify form controls in the RunWorkerCompleted function. Both background workers are instantiated from the UI thread. Here is a greatly summarized version of what I am doing: AutoResetEvent evtProgrammingComplete_c = new AutoResetEvent(false); AutoResetEvent evtResetComplete_c = new AutoResetEvent(false); private void ResetFormControls() { toolStripProgressBar1.Enabled = false; toolStripProgressBar1.RightToLeftLayout = false; toolStripProgressBar1.Value = 0; buttonInit.Enabled = true; buttonOpenFile.Enabled = true; // Error occurs here. buttonProgram.Enabled = true; buttonAbort.Enabled = false; buttonReset.Enabled = true; checkBoxPeripheryModule.Enabled = true; checkBoxVerbose.Enabled = true; comboBoxComPort.Enabled = true; groupBoxToolSettings.Enabled = true; groupBoxNodeSettings.Enabled = true; } private void buttonProgram_Click(object sender, EventArgs e) { while (backgroundWorkerProgram.IsBusy) backgroundWorkerProgram.CancelAsync(); backgroundWorkerProgram.RunWorkerAsync(); } private void backgroundWorkerProgram_DoWork(object sender, DoWorkEventArgs e) { // Does a bunch of stuff... if (tProgramStat_c == eProgramStat_t.DONE) { tProgramStat_c = eProgramStat_t.RESETTING; while (backgroundWorkerReset.IsBusy) backgroundWorkerReset.CancelAsync(); backgroundWorkerReset.RunWorkerAsync(); evtResetComplete_c.WaitOne(LONG_ACK_WAIT * 2); if (tResetStat_c == eResetStat_t.COMPLETED) tProgramStat_c = eProgramStat_t.DONE; } } private void backgroundWorkerProgram_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e) { // Updates form to report complete. No problems here. evtProgrammingComplete_c.Set(); backgroundWorkerProgram.Dispose(); } private void backgroundWorkerReset_DoWork(object sender, DoWorkEventArgs e) { // Does a bunch of stuff... if (tResetStat_c == eResetStat_t.COMPLETED) if (tProgramStat_c == eProgramStat_t.RESETTING) evtProgrammingComplete_c.WaitOne(); } private void backgroundWorkerReset_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e) { CloseAllComms(); ResetFormControls(); evtResetComplete_c.Set(); backgroundWorkerReset.Dispose(); } Any thoughts or suggestions you may have would be appreciated. I am using Microsoft Visual C# 2008 Express Edition. Thanks.

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  • ArrayBlockingQueue exceeds given capacity

    - by Wojciech Reszelewski
    I've written program solving bounded producer & consumer problem. While constructing ArrayBlockingQueue I defined capacity 100. I'm using methods take and put inside threads. And I've noticed that sometimes I see put 102 times with any take's between them. Why does it happen? Producer run method: public void run() { Object e = new Object(); while(true) { try { queue.put(e); } catch (InterruptedException w) { System.out.println("Oj, nie wyszlo, nie bij"); } System.out.println("Element added"); } } Consumer run method: public void run() { while(true) { try { queue.take(); } catch (InterruptedException e) { e.printStackTrace(); } System.out.println("Element removed"); } } Part of uniq -c on file with output: 102 Element removed 102 Element added 102 Element removed 102 Element added 102 Element removed 102 Element added 102 Element removed 102 Element added 102 Element removed 102 Element added 102 Element removed 102 Element added 2 Element removed 2 Element added 102 Element removed 102 Element added

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  • Find messages from certain key till certain key while being able to remove stale keys.

    - by Alfred
    My problem Let's say I add messages to some sort of datastructure: 1. "dude" 2. "where" 3. "is" 4. "my" 5. "car" Asking for messages from index[4,5] should return: "my","car". Next let's assume that after a while I would like to purge old messages because they aren't useful anymore and I want to save memory. Let's say at time x messages[1-3] became stale. I assume that it would be most efficient to just do the deletion once every x seconds. Next my datastructure should contain: 4. "my" 5. "car" My solution? I was thinking of using a concurrentskiplistset or concurrentskiplist map. Also I was thinking of deleting the old messages from inside a newSingleThreadScheduledExecutor. I would like to know how you would implement(efficiently/thread-safe) this or maybe use a library?

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