.net - Update From From Multiple Threads Of The Same Class?
May 31, 2012
I have this class and I have a loop that launches multiple threads from the same class. This is all done from the main form.Now I want to update the richtextbox on the main from these classes.I have tried those begininvokes etc etc and nothing worked, no error but no output as well.Here the code for launching the threads :
Private PingObjects(100000) As Account 'Account is the class and login is the sub in it...
PingObjects(I) = New Account
Threads(I) = New Threading.Thread(AddressOf PingObjects(I).login)
[code]....
And to update the rtb, im using MainForm.log.text = "....." Nothing happens, no error.I have tried using the begin invoker method as well.
Been a while since I did any VB work, and have started a new project that is a Windows Service that will update a database using multiple threads. I am testing this out with a dataset that consists of a "device name" and a "device IP", pinging the device, and attempting to update the device's "status".
I have it working in a single-thread type configuration, but would like to be able to ping and update different records across multiple threads (for obvious reasons).
The problem I'm having is with the logic mainly. When the service is started, I get all the devices from the database and fill a DataSet. From there, I am looping through the dataset's rows, pinging each device and updating the record. I know how to spawn multiple threads, but I do not know how to keep track of updating the correct record and also making sure that all records are checked in some kind of order. Like, if user specifies 5 threads, I need it to get record 1, thread finishes, gets record 6 (while other threads execute), or something like that.
Note: this does no interface updating or anything like that. Only updates a database record's field value.
I am considering a piece of code that will manage access to a collection object from multiple threads - add, update, remove, clear. OK ... so I have put a sync lock within each method, but what is not clear from the MS documentation is exactly how the sync lock is behaving. Is it locking the piece of code it wraps? Or is it locking the object? And if it is locking the object a private static object should lock out any code locked on the object within all instances of the object? i.e. if an add operation is underway, an update, delete or clear will wait for the lock to be released.
Finally, if I have multiple threads contending for the sync lock, how is the release managed? First come, first serve? random (from my p.o.v)? Is there a chance that two separate threads could blunder into 'locked' code simulataneously?
I just had a new, last-minute idea on to take on a task, so I am running to StackExchange for quick help.
What I want to do is execute a series of methods right in a row, each in their own threads. I want the application to wait until all of these threads are completed, after which the program will resume. It also has to use managed threading (thread pool).
What quick examples could you provide to help me along the way? If it's too complex, what things should I know about so that I can Google it on my own?
I have a web app that I'm writing in asp.net, with vb code behind. The threads were working well when I had all my code in the aspx.vb code behind files, but after I moved the code into a seperate Class.vb file, the threads don't seem to be working in parallel any more. Below is a small section of my code.
It used to be that when the "botThread.Start()" method was called, the page would redirect to success.aspx, and work on the SQL query (RunBots()) thread in the background. Now when botThread.Start() is called, the page doesn't redirect to success.aspx until AFTER the RunBots() sub has been completed.
I am writing a project in Visual Basic where I need to run several instances of the same method in parallel. I can do this using BackgrooundWorker by having several (4) copies of my code module (modules 1, 2, 3 and 4) with a call to background worker in each. I then have a Main form which invoke the 4 modules which setup 4 simultaneous background threads. Seeing as the code is the same I want to simply invoke the same module 4 times.
However when I do this I get an error from Backgroounworker that it is already busy. As I understand it this means that it is being shared. However, I have specifically instantiated it as "private" (private with events worker as new backgroundworker). I have tried running the same code in a Class instead of a Module but unless I make it public I have no way of invoking it from Main. I need to be able to pass each thread data from main for it to work on and if the class is private I cant invoke it.
how to convert videos files using vb.net and ffmpeg. But as far as i know we cannot use multiple threads to run same exe file to convert files. Do you know how i can convert multiple videos using one external exe file (ffmpeg)?
I have not tried because my computer time was over. So iam just asking a general doubt whether if we attach it to one process then wouldn't the process get locked? Then can we multi-thread this application or not ?
I'm testing here something, but i don't know what's the best way to do this.I have a var that tells the application the number of threads that will be started, inside the thread/function that i call i need to return/get two values i have two sub functions, each one returns an integer.Then in the end i need to sum the values.
After all threads are over, i get the SF1Total = 2 + 1 and SF2Total = 3 + 5.
I'm thinking in using shared vars, and inside the function/subfunctions update the values. It's this a correct way to do it? Other question, the threads are assync, but i need to know when the last one finishes. How do i control this? The order they finish doesn't need to be the order they were called....
I want to launch a bunch of threads, each performing the same task, and know in main() when each finishs and it if it was successful or failed.The solution offered was to use a ConcurrentQueue, but other posts have recommended using a BackgroundWorker Class, or a thread pool.Is there a definitive answer?Again, all threads perform the same code and have a pass/fail result. I want to run more than there are available threads so as soon as one thread finishes I will launch another asap - I want tehm to stress a remote systems as much as possible (reather than stressing my local PC with too many threads, so I will need to experiment to determine the optimal number of threads).
I've read a lot of different questions on SO about multithreaded applications and how to split work up between them, but none really seem to fit what I need for this. Here's how my program currently basically works:
Module Module1 'string X declared out here Sub Main()
[Code]....
This is only a rough outline of what actually happens in my code by the way.
My problem being that if multiple threads start running Main2(), they're dealing with the same X value as in the other threads. The loop inside of main2 executes multiple times per millisecond, so I can't just stagger the loops. There is often duplication of work done.
How can I properly divide up the work so that the two threads running simultaneously never have the same work to run?
I need help to implement multiple threads in application.Assume ds.table(0) has 5 and sometime 6 rows rows for i=0 to ds.tables(0).rows.count-1.I have to apply multiple threads, means all five/six rows should start at once using thead and "Process 1" .."Process 4" should also handled by threads.This is hierarchy that I have to apply with threads, how can I do it. It is requested to put piece of code so I can understand better.
I know a little about threading and delegates, as well as socket programming. I'm working with a VB.NET-compatible SDK called TrueVision3D to create a small online game for me and my friends. The problem is that I cannot for the life of me figure out how to pass data from one thread to another. I've created 2 seperate threads on seperate forms.
The first thread is created on a form titled FrmLogin, and it contains all the socket code. I need to be able to update variables in the second thread, which mainly consists of a render loop. The second thread is created on a form titled FrmMain. I'm not quite sure if it matters what forms the threads are created on, I'm just trying to give as much information about the issue as I can. I've tried using delegates and events to pass information from the thread back to the form it was created on, which works fine, but how do I pass data to the second thread from the first?
I have an application that needs to perform a series of different actions at specific points in time.To do this I have a timer with various actions that occur in its tick event.One possible action is to send out a few messages via a serial port and then wait (between 1- 300 mins typically) for the next timer tick.Another possible action is to continuously toggle one of the control lines on the serial port until the next tick (again 1-300 mins).
In most instances, i'm happy for everything to run on the main thread, but in the case of toggling the line endlessly, I thought it better to give it its own thread.My problem is that for the new thread to use the Serial Port, it must open the port. Likewise, it must close it before the main thread can have it back.
Here are 2 code snippets
Private Sub activityTimer_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles activityTimer.Tick Dim some variables here activityTimer.Stop() If speedThread.ThreadState = ThreadState.Running Then
I have a map image with data associated with the map indicated by RGB index. The data has been populated into an MS Access database. I imported the information in the database into my program as an array and sorted them to go in the order I want the program to run.
I want the program to find the nearest pixel that has a different color from the incumbent pixel being compared. (Colors are stored as string attributes of object Pixel)
First question: Should I use integers to represent my colors instead of string? Would this make the comparison function run significantly faster?
In order to find the nearest pixel of different color, the program begins with all 8 adjacent pixels around the incumbent. If a nonMatch is not found, it then continues onto the next "degree", and in this fashion, it spirals out from the incumbent pixel until it hits a nonMatch. When found, the color of the nonMatch is saved as an attribute of incumbent. After I find the nonMatch for each of the Pixels, the data is re-inserted into the database
The program accomplishes what I want in the manner I've written it, but it is very very slow. After 24 hours, I am only about 3% through with execution.
Question Two: Does my program behavior sound about right? Is this algorithm you would use if you had to accomplish this task?
Question Three: Would it be appropriate for me to use threads in order to finish execution of the program faster? How exactly does that work?
Question Four: Would it be more "intelligent" for my program to find the nonMatch for each pixel and insert it into the database immediately after finding it? (I'm making a guess that this would be good in multi-threading, because while one record is accessing the database (to insert), another record is accessing the array of pixels (shared global variable in program).
Question Five: If threading is a good idea, I'm guessing I would split the records up into more manageable chunks (i.e. quarters), and have each thread run the same functions for their specified number of records? Am I close at all?
In the same line of this thread Now i have a problem with the control of the ending threads. This is my
vb.net threadsEnded = 0 For j As Integer = 0 To numThreads - 1
[Code]...
Some times the application doesn't finish and if i pause the application i see that the threadEnded var doesn't have the correct value, seems like some thread doesn't update the value of the var.
I have a created a class, which contains a sub routine.This sub routine, should ideally be accessable by objects which are not members of the class, so I would like to make the sub, a 'shared sub' (call it Sub1).
Question: I am using many threads and there will be possibly 100s of 1000s of threads all wanting to use Sub1 (which is at present, is not shared).At present Sub1 , is not a shared sub, so every time a thread wishes to use Sub1 , I am creating a (dummy) instance of the class and then applying Sub1, to that instance.
My program works flawlessly using the above technique.Question: If I were to turn Sub1 (which is not currently shared) into a shared sub, and directly had various threads calling Sub1, would there be any issues with locking, ie. would it possible for 2 threads to enter that thread and start overwriting variables, which another thread has written to?
NOTE: there are no shared variables/properties in Sub1 and all variables used in Sub1 are declared within the sub itself.
I have this application that users can make exams that contain exercises of different ... whatever. Anyway when student takes the exam he chooses it from a list and then all exercises are loaded from database. I wanted to make loading process faster by loading only first exercise data and putting others in background thread.
Actually in other parts of this application something like that is done but not by me. Basicaly an api class is built around BackgroudWorker and i can use this class to put certain functions of objects to be executed in background. The idea sounds great but in real life there are some problems with it. For example for historical reasons this application uses global functions and reader and uses global connection to Access database which means if in background something is being fectched from data base and you try to fetch from database in main thread then a „reader is already open" error occurs. To avoid this error if im doing something in main thread and want to fetch some data i have to move my function from main thread into background worker function list. And basically this in my opinion stinks cuz you end up with many delegātes, invoked checking and thre result... I was just thinking that there maybe is another way to allow (maybe with events) not put everything in background in case something is happening in bakcground but rather allow bgworker to finsih current thing, then do my thing and then resume bgWorker and not create havoc in code.
Basically i have to classes - exam and exercise that each implement many interfaces (like IExercise, IExerciseResult, IExerciseYesNo, IExerciseMultipleChoise etc.)And then i have DataBase classes like ExerciseDB, ExerciseResult etc. That have functions that preparē the sql params and call sqlHelper functions.And for example when i load up exam i go throug all exercises and call LoadData function that in turn calls ExerciseDB function selectData and then i put the returned data in Exercise object. And this type of thing of course would producē error if i at the same time would try to register the answer in database for another exercise. Ofcourse i could always check and put this in background... but as i said i'd rather want to work with database from both threads.
In the past few weeks, to speed up our database freshening process, I've created a couple of extra programs, basically copies of the exe file. The program itself, accesses web pages, images etc and uses threads to do so. The second program uses LIMIT 300,100 and the third LIMIT 600,100, to make sure they don't work on the same records.
Before the last few weeks, one occurrence of the program used to run without problem, from the task scheduler all through the day. Only one occurrence of each exe can run at a time.Since theres now three programs running, .net 2.0, on xp, the program often seems to get stuck and never ends. I have to kill it from task manager.
It runs fine in the IDE I just wonder if there would be any benefit from upgrading to vb.net 2010 ?
I've used mutiple threads in a VB.NET program but I don't know if I did it right.I would like to start about 3 threads.Can they all use the same methods?Will a separate instance of each method automatically be created for each thread?If not, how do you make sure that the data within the method that is used by one thread is not used by another thread?I would like some data to be shared by all threads.How is data shared among threads?What is the protocol for changing the data and checking for changed data?Is there a good tutorial / website that explains how to handle methods and data when using multiple threads?
I have a application that use threadpool, and each thread stores data in the same textfile. I now want to have each thread store the data in the same array instead and use a timer to store all current data in the array into the text file after every couple of minutes.
So what I want to do is:
1. All threads store data in one array that they all have access to
2. After every couple of minutes the data in the array is stored into the text file.
I know number 2 can be done with a timer, but is the first one possible? If so how do I accomplish this task?
I've created a news ticker control, which reads from RSS feeds and scrolls the text Horizontally. The plan is to have 3 of these on my Windows form, which will each display their own information.
The control is created as a label, which is populated with the text, and then scrolls right to left using a timer, once the label gets to the end of the text, and disappears of the left side, the rss is re-read, and then the cycle resumes. The problem is that with multiple copies of this controls on my form, once one gets to the end of it's run, all three freeze while the rss is reread, rather than just the control that needs to do it.
Is there a way to run each of these controls independently (threading?)? Or is there a glitch in my code causing this? (below - some elements not included, but it should be fairly obvious what is happening!)
How to I run multiple threads in VB.NET? Say I need 2 threads - one that prints 100 numbers in a loop and the second one that asks for the user's name and prints it inside a message box.
I have a sub-procedure which I want to run a different process, depending on what is currently running. I thought the easiest way to do this was by using an ArrayList of each of the campaign details & adding an 'Inuse' field to check to see if the Inuse field is set to 0 or 1. The problem that I have is that when running the process it is all happening at once & the integer hasn't been changed before the next thread kicks in so my threads are running the same campaigns. I tried to avoid the problem by adding a Thread.Sleep(100) delay inbetween starting threads but this led to exactly the same problem.
Here's an example of what I am trying to do: Imports System.Threading Public Class Form1 Private Campaigns As New ArrayList Private ProcessRunning As Boolean = False Friend StopProcess As Boolean = False [Code] .....
I'm using the following flavor of threading to create n number of worker threads. These threads all have a bit of latency as they interrogate devices that have strict temporal/physical limits.
[Code]...
I'm looking for a pattern that will let me start the worker threads then wait patiently for completion. Sounds simple ("Just raise an event!") but there seem to be timing landmines. Since the completion EventHandler is single threaded, collisions can occur that destroy the EventHandler data.
Is there a straight forward way for 1 of n threads to report an "I'm done" condition?I've literally got lists of these for c++ but vb.net/CLR is giving me brain freeze.
