The Java Memory Model (since 1.5) treats final fields differently to non-final fields. In particular, provided the this reference doesn't escape during construction, writes to final fields in the constructor are guaranteed to be visible on other threads even if the object is made available to the other thread via a data race. (Writes to ...
Java 6 API question. Does calling LockSupport.unpark(thread) have a happens-before relationship to the return from LockSupport.park in the just-unparked thread? I strongly suspect the answer is yes, but the Javadoc doesn't seem to mention it explicitly. ...
I'm trying to write some code that has the following behavior: There are many concurrent and random calls to X by various threads (Thread X) At some point in the future, one call is made to Y by one thread (Thread Y) Until Y is called, X should be allowed to pass through unchallenged, with concurrent calls to X perfectly valid Once Y i...
1)My environment is web application, I develop servlet to receive request. A) In some block/method i want to control concurrent to not greater than 5 B) if there are 5 request in that block , the new coming must wait up to 60 second then throws error C) if there are sleep/waiting request more then 30, the 31th request will be throwe...
I would like to implement an observer pattern in Objective-C where the observer implements an interface similar to SKPaymentTransactionObserver and the observable class just extends my base observable. My observable class looks something like what is below. Notice I'm making copies of the observers before enumeration to avoid throwing ...
Anyone thought about how to write a memory manager (in C++) that is completely branch free? I've written a pool, a stack, a queue, and a linked list (allocating from the pool), but I am wondering how plausible it is to write a branch free general memory manager. This is all to help make a really reusable framework for doing solid concur...
Hi I need some help and also some insight. This is a program in Ada-2005 which has 3 tasks. The output is 'z'. If the 3 tasks do not happen in the order of their placement in the program then output can vary from z = 2, z = 1 to z = 0 ( That is easy to see in the program, mutual exclusion is attempted to make sure output is z = 2). WIT...
I have an application that comprises multiple processes each accessing a single Berkeley DB Concurrent Data Store (CDB) database. Each process is single-threaded and does no explicit locking of the database. When each process terminates normally, it calls DB->close() and DB_ENV->close(). When all processes have terminated, there shoul...
Howdy Folks, I have a SQLServer 2008 database in which I have a table for Tags. A tag is just an id and a name. The definition of the tags table looks like: CREATE TABLE [dbo].[Tag]( [ID] [int] IDENTITY(1,1) NOT NULL, [Name] [varchar](255) NOT NULL CONSTRAINT [PK_Tag] PRIMARY KEY CLUSTERED ( [ID] ASC )WITH (PAD_INDEX = ...
I am writing a client-side .NET application which is expected to use a lot of threads. I was warned that .NET performance is very bad when it comes to concurrency. While I am not writing a real-time application, I want to make sure my application is scalable (i.e. allows many threads) and is somehow comparable to an equivalent C++ applic...
We use employees' desktops for CPU-intensive simulation during the night. Desktops run Windows - usually Windows XP. Employees don't log off, they just lock the desktops, switch off their monitors and go. Every employee has a configuration file which he can edit to specify when he is most likely out of office. When that time comes a bac...
Hi, I would like to multi-thread an application, however one library i'm using is not multi-thread capable (i don't know what's the right word ? synchronized ?). What are my options ? As far as i know there's nothing in between threads and processes (Runtime.exec) in java (no abstraction in the jvm to have something like an isolated "...
I have a task that takes a rather long time and should run in the background. According to the documentation, this can be done using an NSOperationQueue. However, I do not want to keep a class-global copy of the NSOperationQueue since I really only use it for that one task. Hence, I just set it to autorelease and hope that it won't get r...
Goetz's Java Concurrency in Practice, page 41, mentions how this reference can escape during construction. A "don't do this" example: public class ThisEscape { public ThisEscape(EventSource source) { source.registerListener( new EventListener() { public void onEvent(Event e) { ...
Hi! all I have an application, that is accessing by number of users at the same time. Those users, who are accessing the application getting the same id. Here what i am doing in the code is, when they are creating new user i am getting a max id from DB and increasing the value to 1. So that they are getting same ID. so that i am facin...
Apologies if I have missed something obvious here but having gone through the documentation, forums and googled for a number of hours, I just can't find a definitive answer to the following questions: How does the WebApplicationContext.GetObject() method handle concurrent requests? Are the requests serialized or executed in parallel? Is...
Has anyone implemented Futures in Objective-C? I (hopefully not naively) assume that it should be reasonably simple to wrap NSInvocations in a nice API? ...
TLDR: What are the pros/cons of using an in-memory database vs locks and concurrent data structures? I am currently working on an application that has many (possibly remote) displays that collect live data from multiple data sources and renders them on screen in real time. One of the other developers have suggested the use of an in mem...
I am writing code that will spawn two thread and then wait for them to sync up using the CyclicBarrier class. Problem is that the cyclic barrier isn't working as expected and the main thread doesnt wait for the individual threads to finish. Here's how my code looks: class mythread extends Thread{ CyclicBarrier barrier; public myt...
I've MS Access db, datagridview that displays items, two checkbox columns that represents Yes/No columns in the db, and refresh/del buttons. When I try to delete a row that its checkboxes hasn't been modified, the row delets just fine, also when I modify the checkbox value, press refresh button, then delete, the row deletes fine too. ...