Search code examples
c#multithreadingblockingcollection

Multithreading BlockingCollection same value

I am using two threads in a C# application that access the same BlockingCollection. This works fine, but I want to retrieve the first value twice so the two threads retrieve the same value *.

After a few seconds I want to poll the currentIndex of both threads and delete every value < index. So for example the lowest currentIndex of a thread is 5, the application deletes the items at index 0 -5 in the queue. Another solution is to delete the value in the queue if all threads processed the value.

How can I accomplish this? I think I need another type of buffer..?

Thank you in advance!

*If .Take() is called by thread1, the item is removed in the collection and thread2 can't get the same item again.

Update:

I want to store data in a buffer, so for example thread1 saves the data to a HDD and thread2 analyzes the (same) data (concurrent).

Solution

  • Use a producer-consumer to add Value1 to two separate ConcurrentQueues. Have the threads dequeue then process them from their own queue.

    Edit 7/4/14: Here's a, hazy, hacky, and half thought out solution: Create a custom object that is buffered. It could include space for both the information you're trying to buffer in thread 1 and the analysis results in thread 2.

    Add the objects to a buffer in thread 1 and a BlockingCollection. Use thread 2 to analyse the results and update the objects with the results. The blocking collection shouldn't get too big, and since it's only dealing with references shouldn't hit your memory. This assumes that you won't be modifying the info in the buffer at the same time on both threads.

    Another, also half thought out solution is to feed the info into the buffer and a blocking collection simultaneously. Analyse the data from the BlockingCollection, feed it into an output collection and match them up with the buffer again. This option can handle concurrent modification if you do it right, but is probably more work.

    I think option one is better. As I've pointed out, these are only half-formed, but they might help you find something that suits your specific needs. Good luck.