On the iPhone, I would like to do some operations on an image in a separate thread. Rather than dealing with semiphores, locking, etc., I'd like to use the 'One Object, One Thread' method of safely writing this concurrent operation. I'm not sure what is the correct way to copy my object into a new thread so that the object is not acces...
Suppose that I've queued a work item in a ThreadPool, but the work item blocks if there is no data to process (reading from a BlockingQueue). If the queue is empty and there will be no more work going into the queue, then I must call the Thread.Interrupt method if I want to interrupt the blocking task, but how does one do the same thing...
I have a native Visual C++ COM object and I need to make it completely thread-safe to be able to legally mark it as "free-threaded" in th system registry. Specifically I need to make sure that no more than one thread ever accesses any member variable of the object simultaneously. The catch is I'm almost sure that no sane consumer of my ...
The problem is this: I have multiple competing threads (100+) that need to access one database table Each thread will pass a String name - where that name exists in the table, the database should return the id for the row, where the name doesn't already exist, the name should be inserted and the id returned. There can only ever be one ...
I have a Pylons web application served by Apache (mod_wsgi, prefork). Because of Apache, there are multiple separate processes running my application code concurrently. Some of the non-critical tasks that the application does I want to defer for processing in background to improve "live" response times. So I'm thinking of task queue, man...
In an asp.net web application, say everytime the user makes the request, and the page loads, a thread is fired off that uses thread.join() to block execution until it's finished. Say this thread takes 10 seconds to complete. Does this mean that if 5 totally seperate users make a request to this page, mere miliseconds after the last, do...
I have a web application that synchronizes with a central database four times per hour. The process usually takes 2 minutes. I would like to run this process as a thread at X:55, X:10, X:25, and X:40 so that the users knows that at X:00, X:15, X:30, and X:45 they have a clean copy of the database. It is just about managing expectation...
Say a website on my localhost takes about 3 seconds to do each request. This is fine, and as expected (as it is doing some fancy networking behind the scenes). However, if i open the same url in tabs (in firefox), then reload them all at the same time, it appears to load each page sequentially rather than all at the same time. What is t...
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". ...
Hi, I have a homework task to prove whether or not a particular variation on the dining philosophers problem suffers from deadlock or starvation. I suspect that the situation does not suffer at all from either but I'm finding this tricky to prove and I don't really know where to start. Is there a general strategy for attacking this so...
(note that this question is not about CAS, it's about the "May fail spuriously" Javadoc). The only difference in the Javadoc between these two methods from the AtomicInteger class is that the weakCompareAndSet contains the comment: "May fail spuriously". Now unless my eyes are cheated by some spell, both method do look to be doing exac...
I'm scraping data from the web, and I have several processes of my scraper running in parallel. I want the output of each of these processes to end up in the same file. As long as lines of text remain intact, I the order of the lines does not matter. In UNIX, can I just pipe the output of each process to the same file using the >> ope...
All the examples I've seen of sock.listen(5) in the python documentation suggest I should set the max backlog number to be 5. This is causing a problem for my app since I'm expecting some very high volume (many concurrent connections). I set it to 200 and haven't seen any problems on my system, but was wondering how high I can set it bef...
Hi I have implemented optimistic locking for concurrency situations. I have used the version property in the mapping files to link to a integer. My aim is that if a user tried to save an out-of-date object, she will be given the option to overwrite changes. I have easily managed to get the SaveOrUpdate to throw an exception, but how...
I need to implement a statistics reporter - an object that prints to screen bunch of statistic. This info is updated by 20 threads. The reporter must be a thread itself that wakes up every 1 sec, read the info and prints it to screen. My design so far: InfoReporterElement - one element of info. has two function, PrintInfo and UpdateDat...
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! ...
I need a sequence of numbers for an application, and I am hoping to leverage the abilities of SQL Server to do it. I have created the following table and procedure (in SQL Server 2005): CREATE TABLE sequences ( seq_name varchar(50) NOT NULL, seq_value int NOT NULL ) CREATE PROCEDURE nextval @seq_name varchar(50) AS BEGIN DECLAR...
I'm writing a small web server for testing purposes using python, BasicHTTPServer and SimpleHTTPServer. It looks like it's processing one request at a time. Is there any way to make it a little faster without messing around too deeply? Basicly my code looks as the following and I'd like to keep it this simple ;) os.chdir(webroot) httpd ...
Hi, I'm working on a legacy Java 1.4 project, and I have a factory that instantiates a csv file parser as a singleton. In my csv file parser, however, I have a HashSet that will store objects created from each line of my CSV file. All that will be used by a web application, and users will be uploading CSV files, possibly concurrently. ...
This is some sample code from an example. What I need to know is when call() gets called on the callable? What triggers it? public class CallableExample { public static class WordLengthCallable implements Callable { private String word; public WordLengthCallable(String word) { this.word = word; } public Intege...