Search Results

Search found 956 results on 39 pages for 'synchronization'.

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 2/39 | < Previous Page | 1 2 3 4 5 6 7 8 9 10 11 12  | Next Page >

  • Java consistent synchronization

    - by ring0
    We are facing the following problem in a Spring service, in a multi-threaded environment: three lists are freely and independently accessed for Read once in a while (every 5 minutes), they are all updated to new values. There are some dependencies between the lists, making that, for instance, the third one should not be read while the second one is being updated and the first one already has new values ; that would break the three lists consistency. My initial idea is to make a container object having the three lists as properties. Then the synchronization would be first on that object, then one by one on each of the three lists. Some code is worth a thousands words... so here is a draft private class Sync { final List<Something> a = Collections.synchronizedList(new ArrayList<Something>()); final List<Something> b = Collections.synchronizedList(new ArrayList<Something>()); final List<Something> c = Collections.synchronizedList(new ArrayList<Something>()); } private Sync _sync = new Sync(); ... void updateRunOnceEveryFiveMinutes() { final List<Something> newa = new ArrayList<Something>(); final List<Something> newb = new ArrayList<Something>(); final List<Something> newc = new ArrayList<Something>(); ...building newa, newb and newc... synchronized(_sync) { synchronized(_sync.a) { _synch.a.clear(); _synch.a.addAll(newa); } synchronized(_sync.b) { ...same with newb... } synchronized(_sync.c) { ...same with newc... } } // Next is accessed by clients public List<Something> getListA() { return _sync.a; } public List<Something> getListB() { ...same with b... } public List<Something> getListC() { ...same with c... } The question would be, is this draft safe (no deadlock, data consistency)? would you have a better implementation suggestion for that specific problem? update Changed the order of _sync synchronization and newa... building. Thanks

    Read the article

  • How expensive is synchronization?

    - by someguy
    I am writing a networking application using the java.nio api. My plan is to perform I/O on one thread, and handle events on another. To do this though, I need to synchronize reading/writing so that a race condition is never met. Bearing in mind that I need to handle thousands of connections concurrently, is synchronization worth it, or should I use a single thread for I/O and event handling?

    Read the article

  • SQL Server schema comparison - leaves behind obsolete files on synchronization

    - by b0x0rz
    Directly related to http://stackoverflow.com/questions/2768489/visual-studio-2010-database-project-is-there-a-visual-way/2772205#2772205 I have a problem synchronizing between database project and a database in Visual Studio. Usually I synchronize FROM database TO database project (using the Visual Studio data scheme compare new schema comparison). The synchronization works, BUT when I for example corrected the spelling of a key in the database and synchronized it - the file with the WRONG spelling of a key remains (albeit is commented out inside). the new one is correctly added. This file happens to be in: [project name]/Scheme Objects/Schemas/dbo/Tables/Keys But for sure there are others elsewhere. how to automatically remove such obsolete files when synchronizing? thnx

    Read the article

  • Where to start when programming process synchronization algorithms like clone/fork, semaphores

    - by David
    I am writing a program that simulates process synchronization. I am trying to implement the fork and semaphore techniques in C++, but am having trouble starting off. Do I just create a process and send it to fork from the very beginning? Is the program just going to be one infinite loop that goes back and forth between parent/child processes? And how do you create the idea of 'shared memory' in C++, explicit memory address or just some global variable? I just need to get the overall structure/idea of the flow of the program. Any references would be appreciated.

    Read the article

  • linux thread synchronization

    - by johnnycrash
    I am new to linux and linux threads. I have spent some time googling to try to understand the differences between all the functions available for thread synchronization. I still have some questions. I have found all of these different types of synchronizations, each with a number of functions for locking, unlocking, testing the lock, etc. gcc atomic operations futexes mutexes spinlocks seqlocks rculocks conditions semaphores My current (but probably flawed) understanding is this: semaphores are process wide, involve the filesystem (virtually I assume), and are probably the slowest. Futexes might be the base locking mechanism used by mutexes, spinlocks, seqlocks, and rculocks. Futexes might be faster than the locking mechanisms that are based on them. Spinlocks dont block and thus avoid context swtiches. However they avoid the context switch at the expense of consuming all the cycles on a CPU until the lock is released (spinning). They should only should be used on multi processor systems for obvious reasons. Never sleep in a spinlock. The seq lock just tells you when you finished your work if a writer changed the data the work was based on. You have to go back and repeat the work in this case. Atomic operations are the fastest synch call, and probably are used in all the above locking mechanisms. You do not want to use atomic operations on all the fields in your shared data. You want to use a lock (mutex, futex, spin, seq, rcu) or a single atomic opertation on a lock flag when you are accessing multiple data fields. My questions go like this: Am I right so far with my assumptions? Does anyone know the cpu cycle cost of the various options? I am adding parallelism to the app so we can get better wall time response at the expense of running fewer app instances per box. Performances is the utmost consideration. I don't want to consume cpu with context switching, spinning, or lots of extra cpu cycles to read and write shared memory. I am absolutely concerned with number of cpu cycles consumed. Which (if any) of the locks prevent interruption of a thread by the scheduler or interrupt...or am I just an idiot and all synchonization mechanisms do this. What kinds of interruption are prevented? Can I block all threads or threads just on the locking thread's CPU? This question stems from my fear of interrupting a thread holding a lock for a very commonly used function. I expect that the scheduler might schedule any number of other workers who will likely run into this function and then block because it was locked. A lot of context switching would be wasted until the thread with the lock gets rescheduled and finishes. I can re-write this function to minimize lock time, but still it is so commonly called I would like to use a lock that prevents interruption...across all processors. I am writing user code...so I get software interrupts, not hardware ones...right? I should stay away from any functions (spin/seq locks) that have the word "irq" in them. Which locks are for writing kernel or driver code and which are meant for user mode? Does anyone think using an atomic operation to have multiple threads move through a linked list is nuts? I am thinking to atomicly change the current item pointer to the next item in the list. If the attempt works, then the thread can safely use the data the current item pointed to before it was moved. Other threads would now be moved along the list. futexes? Any reason to use them instead of mutexes? Is there a better way than using a condition to sleep a thread when there is no work? When using gcc atomic ops, specifically the test_and_set, can I get a performance increase by doing a non atomic test first and then using test_and_set to confirm? *I know this will be case specific, so here is the case. There is a large collection of work items, say thousands. Each work item has a flag that is initialized to 0. When a thread has exclusive access to the work item, the flag will be one. There will be lots of worker threads. Any time a thread is looking for work, they can non atomicly test for 1. If they read a 1, we know for certain that the work is unavailable. If they read a zero, they need to perform the atomic test_and_set to confirm. So if the atomic test_and_set is 500 cpu cycles because it is disabling pipelining, causes cpu's to communicate and L2 caches to flush/fill .... and a simple test is 1 cycle .... then as long as I had a better ratio of 500 to 1 when it came to stumbling upon already completed work items....this would be a win.* I hope to use mutexes or spinlocks to sparilngly protect sections of code that I want only one thread on the SYSTEM (not jsut the CPU) to access at a time. I hope to sparingly use gcc atomic ops to select work and minimize use of mutexes and spinlocks. For instance: a flag in a work item can be checked to see if a thread has worked it (0=no, 1=yes or in progress). A simple test_and_set tells the thread if it has work or needs to move on. I hope to use conditions to wake up threads when there is work. Thanks!

    Read the article

  • Dropbox takes hours? to sync & shows diff. modified times (coincidentially in the future)

    - by user10580
    Dropbox is taking hours to sync, I can't tell exactly how long because the time stamps on the website make no sense - they say the files were modified. . . tomorrow. Actually my netbook (windows xp) says they're last modified tomorrow in windows explorer as well. It's bizarre. The time and date on both computers are correct. The files in question are in a symlinked directory on the laptop (which are synced fine, with the correct timestamps). I have looked for an option to force dropbox to sync, but haven't located one. (There might be a command line method, but I haven't had the time to explore). thanks

    Read the article

  • Remote synchronization

    - by Tomas Mysik
    Hi all, today we would like to show you another improvement we have prepared for NetBeans 7.2. Today, let's talk a little bit about remote synchronization. If you already use our simple (S)FTP client, this enhancement could be useful for you. Simply right click on Source Files and select Synchronize. Please notice that the remote synchronization works better only on the whole project (it means that the Source Files must be selected). The Synchronize action is also available on individual files (more files can be selected at once) but the suggested operation (download, upload etc.) does not work so precisely. Also please notice that the suggested operations are not 100% reliable since the timestamps provided by FTP servers are not exact. Once the remote files (their names and paths only, of course) are fetched, the main dialog appears: As you can see, NetBeans tries to suggest you operations (upload, download etc.) which should be done for each individual file of your project. If you are interested only in some particular changes, you can simply filter the list: Since we have a file conflict, we need to resolve it first. Fortunately this is very easy because we just select the desired file and click the Diff button . The remote version of our file is downloaded and compared with the local version. The resut is displayed in the dialog where you can easily apply and/or refuse the remote changes or even simply type manually to the local version of the selected file: Once we are done with our changes, the operation for the selected file changes to Upload and the file is marked with * (since we made some changes). Please notice that if you now click the Cancel button, in fact no changes are done in our local file. As you can see, if we have one or more files selected, we can change their operation to: no operation (file won't be synchronized) download upload delete (both local and remote file) reset (the operation is resetted to the original one suggested by NetBeans and also all changes done via Diff action are discarded) Now we are ready to synchronize our project. NetBeans will show us the synchronization summary (this dialog can be omitted, see the Show Summary checkbox on the previous image). The synchronization itself starts and we can see its progress and of course its result. As always, all the operations can be reviewed in the Output window. That's all for today, as always, please test it and report all the issues or enhancements you find in NetBeans BugZilla (component php, subcomponent FTP support).

    Read the article

  • Use Thread-local Storage to Reduce Synchronization

    Synchronization is often an expensive operation that can limit the performance of a multithreaded program. Using thread-local data structures instead of data structures shared by the threads can reduce synchronization in certain cases, allowing a program to run faster.

    Read the article

  • C# ThreadPool QueueUserWorkItem Synchronization

    - by ikurtz
    Greetings, I am employing ThreadPool.QueueUserWorkItem to play some sound files and not hanging up the GUI while doing so. It is working but has an undesirable side effect. While the QueueUserWorkItem CallBack Proc is being executed there is nothing to stop it from starting a new thread. This causes the samples in the threads to overlap. How can I make it so that it waits for the already running thread to finish running and only then run the next request? Thanks in advance :)

    Read the article

  • Java RMI method synchronization

    - by James Moore
    Hello, I have a class that is stored on the 'server' and multiple clients can call this method. This method returns a class. Now when clients call accessor methods within this class for example a set accessor method. I want the object on the server to be updated and synchronized across all the other clients. How do I use: public synchronized setStatus(String s) { this.status = s; } within java to achieve this. Thanks

    Read the article

  • .NET ThreadPool QueueUserWorkItem Synchronization

    - by ikurtz
    I am employing ThreadPool.QueueUserWorkItem to play some sound files and not hanging up the GUI while doing so. It is working but has an undesirable side effect. While the QueueUserWorkItem CallBack Proc is being executed there is nothing to stop it from starting a new thread. This causes the samples in the threads to overlap. How can I make it so that it waits for the already running thread to finish running and only then run the next request? EDIT: I did: Thread t = new Thread(FireAttackProc(fireResult)); t.Start(); but it gave me some errors. How do I specify a thread method with parameters?

    Read the article

  • JTable's and DefaultTableModel's row indexes lose their synchronization after I sort JTable

    - by Stefanos Kargas
    JAVA NETBEANS // resultsTable, myModel JTable resultsTable; DefaultTableModel myModel; //javax.swing.table.DefaultTableModel myModel = (DefaultTableModel) resultsTable.getModel(); // event of clicking on item of table String value = (String) myModel.getValueAt(resultsTable.getSelectedRow(), columnIndex) I use JTable and DefaultTableModel to view a table of various info and I want to get a value of a certain column of the selected index of the table. The code I wrote above works fine except when: I use the sort of the GUI (click on the field name I want to sort on the table) The table is properly sorted but after that when I select a row, it gets the value of the row that was there before the sort. This means that after sorting (using the JTable's GUI) the 'myModel' and 'resultsTable' objects have different row indexes. How do I synchronize those two?

    Read the article

  • Simplest possible voting/synchronization algorithm

    - by Domchi
    What would be a simplest algorithm one or more people could use to decide who of them should perform some task? There is one task, which needs to be done only once, and one or more people. People can speak, that is, send messages one to another. Communication must be minimal, and all people use the exact same algorithm. One person saying "I'm doing it" is not good enough since two persons may say it at a same time. Simplest that comes to my mind is that each person says a number and waits a bit. If somebody responds in that time, the person with lower number "wins" and does the task. If nobody responds, person says that she's doing it and does it. When she says that she does it, everybody else backs off. This should be enough to avoid two persons doing the task in the same time (since there is wait/handhake period), but might need a "second round" if both persons say the same number. Is there something simpler? For those curious, I'm trying to synchronize several copies of SecondLife LSL script to do something only once.

    Read the article

  • Synchronization of Nested Data Structures between Threads in Java

    - by Dominik
    I have a cache implementation like this: class X { private final Map<String, ConcurrentMap<String, String>> structure = new HashMap...(); public String getValue(String context, String id) { // just assume for this example that there will be always an innner map final ConcurrentMap<String, String> innerStructure = structure.get(context); String value = innerStructure.get(id); if(value == null) { synchronized(structure) { // can I be sure, that this inner map will represent the last updated // state from any thread? value = innerStructure.get(id); if(value == null) { value = getValueFromSomeSlowSource(id); innerStructure.put(id, value); } } } return value; } } Is this implementation thread-safe? Can I be sure to get the last updated state from any thread inside the synchronized block? Would this behaviour change if I use a java.util.concurrent.ReentrantLock instead of a synchronized block, like this: ... if(lock.tryLock(3, SECONDS)) { try { value = innerStructure.get(id); if(value == null) { value = getValueFromSomeSlowSource(id); innerStructure.put(id, value); } } finally { lock.unlock(); } } ... I know that final instance members are synchronized between threads, but is this also true for the objects held by these members? Maybe this is a dumb question, but I don't know how to test it to be sure, that it works on every OS and every architecture.

    Read the article

  • database schema eligible for delta synchronization

    - by WilliamLou
    it's a question for discussion only. Right now, I need to re-design a mysql database table. Basically, this table contains all the contract records I synchronized from another database. The contract record can be modified, deleted or users can add new contract records via GUI interface. At this stage, the table structure is exactly the same as the Contract info (column: serial number, expiry date etc.). In that case, I can only synchronize the whole table (delete all old records, replace with new ones). If I want to delta(only synchronize with modified, new, deleted records) synchronize the table, how should I change the database schema? here is the method I come up with, but I need your suggestions because I think it's a common scenario in database applications. 1)introduce a sequence number concept/column: for each sequence, mark the new added records, modified records, deleted records with this sequence number. By recording the last synchronized sequence number, only pass those records with higher sequence number; 2) because deleted contracts can be added back, and the original table has primary key constraints, should I create another table for those deleted records? or add a flag column to indicate if this contract has been deleted? I hope I explain my question clearly. Anyway, if you know any articles or your own suggestions about this, please let me know. Thanks!

    Read the article

  • Is this a correct Interlocked synchronization design?

    - by Dan Bryant
    I have a system that takes Samples. I have multiple client threads in the application that are interested in these Samples, but the actual process of taking a Sample can only occur in one context. It's fast enough that it's okay for it to block the calling process until Sampling is done, but slow enough that I don't want multiple threads piling up requests. I came up with this design (stripped down to minimal details): public class Sample { private static Sample _lastSample; private static int _isSampling; public static Sample TakeSample(AutomationManager automation) { //Only start sampling if not already sampling in some other context if (Interlocked.CompareExchange(ref _isSampling, 0, 1) == 0) { try { Sample sample = new Sample(); sample.PerformSampling(automation); _lastSample = sample; } finally { //We're done sampling _isSampling = 0; } } return _lastSample; } private void PerformSampling(AutomationManager automation) { //Lots of stuff going on that shouldn't be run in more than one context at the same time } } Is this safe for use in the scenario I described?

    Read the article

  • Linux synchronization with FIFO waiting queue

    - by EpsilonVector
    Are there locks in Linux where the waiting queue is FIFO? This seems like such an obvious thing, and yet I just discovered that pthread mutexes aren't FIFO, and semaphores apparently aren't FIFO either (I'm working on kernel 2.4 (homework))... Does Linux have a lock with FIFO waiting queue, or is there an easy way to make one with existing mechanisms?

    Read the article

  • Efficient synchronization of querying an array of resources

    - by Erel Segal Halevi
    There is a list of N resources, each of them can be queried by at most a single thread at a time. There are serveral threads that need to do the same thing at approximately the same time: query each of the resources (each thread has a different query), in arbitrary order, and collect the responses. If each thread loops over the resources in the same order, from 0 to N-1, then they will probably have to wait for each other, which is not efficient. I thought of letting the threads loop over the resources in a random permutation, but this seems too complex and also not so efficient, for example, for 2 resources and 2 threads, in half the cases they will choose the same order and wait for each other. Is there a simple and more efficient way to solve this?

    Read the article

  • Microsoft Access to SQL Server - synchronization

    - by David Pfeffer
    I have a client that uses a point-of-sale solution involving an Access database for its back-end storage. I am trying to provide this client with a service that involves, for SLA reasons, the need to copy parts of this Access database into tables in my own database server which runs SQL Server 2008. I need to do this on a periodic basis, probably about 5 times a day. I do have VPN connectivity to the client. Is there an easy programmatic way to do this, or an available tool? I don't want to handcraft what I assume is a relatively common task.

    Read the article

  • GWT synchronization

    - by hdantas
    i'm doing a function in gwt it sends an IQ stanza into a server and has to wait for the server answer in the function i make the handler that waits for the answer from the server to that IQ stanza so what i need is for the function to wait until i get the response from the server and after that do other stuff i'm a beginner in gwt so any thoughts would be great thanks public void getServices() { IQ iq = new IQ(IQ.Type.get); iq.setAttribute("to", session.getDomainName()); iq.addChild("query", "http://jabber.org/protocol/disco#items"); session.addResponseHandler(iq, new ResponseHandler() { public void onError(IQ iq, ErrorType errorType, ErrorCondition errorCondition, String text) { <do stuff> } public void onResult(IQ iq) { <do stuff> } }); session.send(iq); <after receiving answer do stuff> }

    Read the article

  • Java Thread - Synchronization issue

    - by Yatendra Goel
    From Sun's tutorial: Synchronized methods enable a simple strategy for preventing thread interference and memory consistency errors: if an object is visible to more than one thread, all reads or writes to that object's variables are done through synchronized methods. (An important exception: final fields, which cannot be modified after the object is constructed, can be safely read through non-synchronized methods, once the object is constructed) This strategy is effective, but can present problems with liveness, as we'll see later in this lesson. Q1. Is the above statements mean that if an object of a class is going to be shared among multiple threads, then all instance methods of that class (except getters of final fields) should be made synchronized, since instance methods process instance variables?

    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 | 1 2 3 4 5 6 7 8 9 10 11 12  | Next Page >