Search Results

Search found 882 results on 36 pages for 'concurrency coordination'.

facebook twitter digg google delicious technorati stumbleupon myspace wordpress linkedin gmail igoogle windows live tumblr viadeo yahoo buzz yahoo mail yahoo bookmarks favorites email print

Page 14/36 | < Previous Page | 10 11 12 13 14 15 16 17 18 19 20 21  | Next Page >

  • Multi-Threaded Application - Help with some pseudo code!!

    - by HonorGod
    I am working on a multi-threaded application and need help with some pseudo-code. To make it simpler for implementation I will try to explain that in simple terms / test case. Here is the scenario - I have an array list of strings (say 100 strings) I have a Reader Class that reads the strings and passes them to a Writer Class that prints the strings to the console. Right now this runs in a Single Thread Model. I wanted to make this multi-threaded but with the following features - Ability to set MAX_READERS Ability to set MAX_WRITERS Ability to set BATCH_SIZE So basically the code should instantiate those many Readers and Writers and do the work in parallel. Any pseudo code will really be helpful to keep me going!

    Read the article

  • Java: design for using many executors services and only few threads

    - by Guillaume
    I need to run in parallel multiple threads to perform some tests. My 'test engine' will have n tests to perform, each one doing k sub-tests. Each test result is stored for a later usage. So I have n*k processes that can be ran concurrently. I'm trying to figure how to use the java concurrent tools efficiently. Right now I have an executor service at test level and n executor service at sub test level. I create my list of Callables for the test level. Each test callable will then create another list of callables for the subtest level. When invoked a test callable will subsequently invoke all subtest callables test 1 subtest a1 subtest ...1 subtest k1 test n subtest a2 subtest ...2 subtest k2 call sequence: test manager create test 1 callable test1 callable create subtest a1 to k1 testn callable create subtest an to kn test manager invoke all test callables test1 callable invoke all subtest a1 to k1 testn callable invoke all subtest an to kn This is working fine, but I have a lot of new treads that are created. I can not share executor service since I need to call 'shutdown' on the executors. My idea to fix this problem is to provide the same fixed size thread pool to each executor service. Do you think it is a good design ? Do I miss something more appropriate/simple for doing this ?

    Read the article

  • Strange problem with simple multithreading program in Java

    - by Elizabeth
    Hello, I am just starting play with multithreading programming. I would like to my program show alternately character '-' and '+' but it doesn't. My task is to use synchronized keyword. As far I have: class FunnyStringGenerator{ private char c; public FunnyStringGenerator(){ c = '-'; } public synchronized char next(){ if(c == '-'){ c = '+'; } else{ c = '-'; } return c; } } class ThreadToGenerateStr implements Runnable{ FunnyStringGenerator gen; public ThreadToGenerateStr(FunnyStringGenerator fsg){ gen = fsg; } @Override public void run() { for(int i = 0; i < 10; i++){ System.out.print(gen.next()); } } } public class Main{ public static void main(String[] args) throws IOException { FunnyStringGenerator FSG = new FunnyStringGenerator(); ExecutorService exec = Executors.newCachedThreadPool(); for(int i = 0; i < 20; i++){ exec.execute(new ThreadToGenerateStr(FSG)); } } } EDIT: I also testing Thread.sleep in run method instead for loop.

    Read the article

  • Data access strategy for a site like SO - sorted SQL queries and simultaneous updates that affect th

    - by Kaleb Brasee
    I'm working on a Grails web app that would be similar in access patterns to StackOverflow or MyLifeIsAverage - users can vote on entries, and their votes are used to sort a list of entries based on the number of votes. Votes can be placed while the sorted select queries are being performed. Since the selects would lock a large portion of the table, it seems that normal transaction locking would cause updates to take forever (given enough traffic). Has anyone worked on an app with a data access pattern such as this, and if so, did you find a way to allow these updates and selects to happen more or less concurrently? Does anyone know how sites like SO approach this? My thought was to make the sorted selects dirty reads, since it is acceptable if they're not completely up to date all of the time. This is my only idea for possibly improving performance of these selects and updates, but I thought someone might know a better way.

    Read the article

  • 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?

    Read the article

  • Asynchrous calls cause StaleObjectStateException

    - by Mulone
    Hi all, I'm struggling with a Grails service. The service gets AJAX calls from the clients and behaves like a simple local cache for remote objects: void **someCallFromClient**() { // extract params def results = remoteService.queryService(params) results.each{ // try to fetch result object from local DB def obj = SomeClass.findBySomeField(result.someField) if (!obj){ obj = new Result(params) obj.save() } // do stuff on obj } } The service works fine when only one client is connected, but as soon as 2 or more clients start bombing the server with requests, I start getting: 2010-05-24 13:09:49,764 [30893094@qtp-26315919-2] ERROR errors.GrailsExceptionResolver - Row was updated or deleted by another transaction (or unsaved-value mapping was incorrect): [ some object #892901] org.hibernate.StaleObjectStateException: Row was updated or deleted by another transaction (or unsaved-value mapping was incorrect): [ some object #892901] // very long stactrace It probably happens when 2 calls are trying to create the same object concurrently. I suppose this is a rather typical situation to end up in. Could you recommend any pattern/good practice to fix this issue? For example, is there a way to say to one of the service instances to hang on and wait for the other to finish its stuff and try again? Cheers!

    Read the article

  • 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.

    Read the article

  • Inconsistency in java.util.concurrent.Future?

    - by loganj
    For the sake of argument, let's say I'm implementing Future for a task which is not cancelable. The Java 6 API doc says: After [cancel()] returns, subsequent calls to isDone() will always return true. [cancel()] returns false if the task could not be cancelled, typically because it has already completed normally It also says: [isDone()] returns true if this task completed. But what if my cancellation fails not because the task is already completed, but because it simply cannot be cancelled? Is there a way out of this contradiction (other than making my uncancelable task cancelable and sidestepping it altogether)?

    Read the article

  • Is PetraVM Jinx Beta 1 good?

    - by Brian T Hannan
    PetraVM recently came out with a Beta release of their Jinx product. Has anyone checked it out yet? Any feedback? By good, I mean: 1) easy to use 2) intuitive 3) useful 4) doesn't take a lot of code to integrate ... those kinds of things. Thanks guys!

    Read the article

  • How does one SELECT block another?

    - by Krip
    I'm looking at output of SP_WhoIsActive on SQL Server 2005, and it's telling me one session is blocking another - fine. However they both are running a SELECT. How does one SELECT block another? Shouldn't they both be acquiring shared locks (which are compatible with one another)? Some more details: Neither session has an open transaction count - so they are stand-alone. The queries join a view with a table. They are complex queries which join lots of tables and results in 10,000 or so reads. Any insight much appreciated.

    Read the article

  • What Use are Threads Outside of Parallel Problems on MultiCore Systesm?

    - by Robert S. Barnes
    Threads make the design, implementation and debugging of a program significantly more difficult. Yet many people seem to think that every task in a program that can be threaded should be threaded, even on a single core system. I can understand threading something like an MPEG2 decoder that's going to run on a multicore cpu ( which I've done ), but what can justify the significant development costs threading entails when you're talking about a single core system or even a multicore system if your task doesn't gain significant performance from a parallel implementation? Or more succinctly, what kinds of non-performance related problems justify threading? Edit Well I just ran across one instance that's not CPU limited but threads make a big difference: TCP, HTTP and the Multi-Threading Sweet Spot Multiple threads are pretty useful when trying to max out your bandwidth to another peer over a high latency network connection. Non-blocking I/O would use significantly less local CPU resources, but would be much more difficult to design and implement.

    Read the article

  • Would this prevent the row from being read during the transaction?

    - by acidzombie24
    I remember an example where reads in a transaction then writing back the data is not safe because another transaction may read/write to it in the time between. So i would like to check the date and prevent the row from being modified or read until my transaction is finish. Would this do the trick? and are there any sql variants that this will not work on? update tbl set id=id where date>expire_date and id=@id Note: dateexpire_date happens to be my condition. It could be anything. Would this prevent other transaction from reading the row until i commit or rollback?

    Read the article

  • Using ManualResetEvent to wait for multiple Image.ImageOpened events

    - by umlgorithm
    Dictionary<Image, ManualResetEvent> waitHandleMap = new Dictionary<Image, ManualResetEvent>(); List<Image> images = GetImagesWhichAreAlreadyInVisualTree(); foreach (var image in images) { image.Source = new BitmapImage(new Uri("some_valid_image_url")); waitHandleMap.Add(image, new ManualResetEvent(false)); image.ImageOpened += delegate { waitHandleMap[image].Set(); }; image.ImageFailed += delegate { waitHandleMap[image].Set(); }; } WaitHandle.WaitAll(waitHandleMap.Values.ToArray()); WaitHandle.WaitAll blocks the current UI thread, so ImageOpened/ImageFailed events would never get fired. Could you suggest me an easy workaround to wait for the multiple ui events?

    Read the article

  • Is there any point in using a volatile long?

    - by Adamski
    I occasionally use a volatile instance variable in cases where I have two threads reading from / writing to it and don't want the overhead (or potential deadlock risk) of taking out a lock; for example a timer thread periodically updating an int ID that is exposed as a getter on some class: public class MyClass { private volatile int id; public MyClass() { ScheduledExecutorService execService = Executors.newScheduledThreadPool(1); execService.scheduleAtFixedRate(new Runnable() { public void run() { ++id; } }, 0L, 30L, TimeUnit.SECONDS); } public int getId() { return id; } } My question: Given that the JLS only guarantees that 32-bit reads will be atomic is there any point in ever using a volatile long? (i.e. 64-bit). Caveat: Please do not reply saying that using volatile over synchronized is a case of pre-optimisation; I am well aware of how / when to use synchronized but there are cases where volatile is preferable. For example, when defining a Spring bean for use in a single-threaded application I tend to favour volatile instance variables, as there is no guarantee that the Spring context will initialise each bean's properties in the main thread.

    Read the article

  • Standard term for a thread I/O reorder buffer?

    - by Crashworks
    I have a case where many threads all concurrently generate data that is ultimately written to one long, serial file. I need to somehow serialize these writes so that the file gets written in the right order. ie, I have an input queue of 2048 jobs j0..jn, each of which produces a chunk of data oi. The jobs run in parallel on, say, eight threads, but the output blocks have to appear in the file in the same order as the corresponding input blocks — the output file has to be in the order o0o1o2... The solution to this is pretty self evident: I need some kind of buffer that accumulates and writes the output blocks in the correct order, similar to a CPU reorder buffer in Tomasulo's algorithm, or to the way that TCP reassembles out-of-order packets before passing them to the application layer. Before I go code it, I'd like to do a quick literature search to see if there are any papers that have solved this problem in a particularly clever or efficient way, since I have severe realtime and memory constraints. I can't seem to find any papers describing this though; a Scholar search on every permutation of [threads, concurrent, reorder buffer, reassembly, io, serialize] hasn't yielded anything useful. I feel like I must just not be searching the right terms. Is there a common academic name or keyword for this kind of pattern that I can search on?

    Read the article

  • Can fields of the class and arguments of the method interfere?

    - by Roman
    I have a class with a fields called "a". In the class I have a method and in the list of arguments of this method I also have "a". So, which "a" I will see inside of the method? Will it be the field or it will be the argument of the method? public class myClass { private String a; // Method which sets the value of the field "a". public void setA(String a) { a = a; } } By the way, there is a similar situation. A method has some local (for method) variables whose names coincide with the names of the fields. What will the "see" the method if I refer to such a method-local variable inside the method (the field or the local variable)?

    Read the article

  • PHP thread pool?

    - by embedded
    I have scheduled a CRON job to run every 4 hours which needs to gather user accounts information. Now I want to speed things up and to split the work between several processes and to use one process to update the MySQL DB with the retrieved data from other processes. In JAVA I know that there is a thread pool which I can dedicate some threads to accomplish some work. how do I do it in PHP? Any advice is welcome. Thank

    Read the article

  • Java: serial thread confinement question

    - by denis
    Assume you have a Collection(ConcurrentLinkedQueue) of Runnables with mutable state. Thread A iterates over the Collection and hands the Runnables to an ExecutorService. The run() method changes the Runnables state. The Runnable has no internal synchronization. The above is a repetitive action and the worker threads need to see the changes made by previous iterations. So a Runnable gets processed by one worker thread after another, but is never accessed by more than one thread at a time - a case of serial thread confinement(i hope ;)). The question: Will it work just with the internal synchronization of the ConcurrentLinkedQueue/ExecutorSerivce? To be more precise: If Thread A hands Runnable R to worker thread B and B changes the state of R, and then A hands R to worker thread C..does C see the modifications done by B?

    Read the article

  • Generating different randoms valid for a day on different independent devices?

    - by Pentium10
    Let me describe the system. There are several mobile devices, each independent from each other, and they are generating content for the same record id. I want to avoid generating the same content for the same record on different devices, for this I though I would use a random and make it so too cluster the content pool based on these randoms. Suppose you have choices from 1 to 100. Day 1 Device#1 will choose for the record#33 between 1-10 Device#2 will choose for the record#33 between 40-50 Device#3 will choose for the record#33 between 50-60 Device#1 will choose for the record#55 between 40-50 Device#2 will choose for the record#55 between 1-10 Device#3 will choose for the record#55 between 10-20 Device#1 will choose for the record#11 between 1-10 Device#2 will choose for the record#22 between 1-10 Device#3 will choose for the record#99 between 1-10 Day 2 Device#1 will choose for the record#33 between 90-100 Device#2 will choose for the record#33 between 1-10 Device#3 will choose for the record#33 between 50-60 They don't have access to a central server. Data available for each of them: IMEI (unique per mobile) Date of today (same on all devices) Record id (same on all devices) What do you think, how is it possible? ps. tags can be edited

    Read the article

facebook twitter digg google delicious technorati stumbleupon myspace wordpress linkedin gmail igoogle windows live tumblr viadeo yahoo buzz yahoo mail yahoo bookmarks favorites email print

< Previous Page | 10 11 12 13 14 15 16 17 18 19 20 21  | Next Page >