priority-queue

As you know from the title, I'm trying to use PriorityQueue with multiprocessing. More precisely, I wanted to make shared PriorityQueue, wrote some code and it doesn't run as I expected. Look at the code: import time from multiprocessing import Process, Lock from Queue import PriorityQueue def worker(queue): lock = Lock() with lock: for i in range(100): queue.put(i) print "worker", queue.qsize() pr_queue = PriorityQueue() worker_process = Process(target = worker, args = (pr_queue,)) worker_process.start() time.sleep(5) # nope, race condition, you shall not pass (probably) print "main", pr

I need a data structure that always holds the n largest items inserted so far (in no particular order). So, if n is 3, we could have the following session where I insert a few numbers and the content of the container changes: [] // now insert 1 [1] // now insert 0 [1,0] // now insert 4 [1,0,4] // now insert 3 [1,4,3] // now insert 0 [1,4,3] // now insert 3 [4,3,3] You get the idea. What's the name of the data structure? What's the best way to implement this? Or is this in some library? I am thinking to use a container that has a priority_queue for its elements (delegation), which uses the

Is there a concurrent mutable priority queue? Ideally, I'm looking for a C++ implementation, but, for starters, a pointer to an algorithm would be very helpful. To be clear, I'm looking for a priority queue where I can adjust the priorities of the elements. In particular, TBB's concurrent_priority_queue doesn't provide the necessary functionality. (For that matter, neither does STL's priority_queue , even if we ignore the concurrency.) Boost.Heap library provides serial functionality that I want, but without concurrency. Naturally, I'm looking for something finer grained than just locking the

I am implementing a small queue to handle which process gets to run first. I am using a table in a database to do this. Here is the structure of the table (I'm mocking it up in SQLite): "id" INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL , "identifier" VARCHAR NOT NULL , "priority_number" INTEGER DEFAULT 15, "timestamp" DATETIME DEFAULT CURRENT_TIMESTAMP, "description" VARCHAR I am trying to write SQL to give me the row of which process can run next. Here is some sample data: id identifier priority_number timestamp description 1 test1 15 2009-01-20 17:14:49 NULL 2 test2 15 2009-01-20 17:14:56 NULL

When using a min/max-heap algorithm, priorities may change. One way to handle this is to removal and insert the element to update the queue order. For priority queues implemented using arrays, this can be a performance bottleneck that seems avoidable, especially for cases when the change to priority is small. Even if this is not a standard operation for a priority queue , this is a custom implementation which can be modified for my needs. Are there well known best-practice methods for updating elements in the min/max-heap? Background Info: I'm no expert in binary-trees, I inherited some code

I have implemented a compression algorithm (using huffman coding) which uses a priority queue of nodes (a struct i defined). Now, when i just run the code in linux or in visual studio, everything works fine. When I check for memory leaks in visual studio, none are given. The problem now is, when I use valgrind to analyse my program, it terminates with signal 11 (sigsegv). The first error encountered is an 'invalid read of size 4' in the method delete min. Other errors after that are: Adress is 0 bytes inside a block of size 453 freed, invalid write of size 4, invalid free,delete or realloc.

I am trying to implement A* search in Scala (version 2.10), but I've ran into a brick wall - I can't figure out how to use Scala's Priority Queue. It seems like a simple task, but searching on Google didn't turn up anything (except for a single code sample that stopped working back in version 2.8) I have a set of squares, represented by (Int, Int) s, and I need to insert them with priorities represented by Int s. In Python it's pretty simple, since you just have a list of key, value pairs and use the heapq functions to sort it. But it appears that Scala's tuples aren't even comparable. So how

I'm still confused about priority queue in STL. Here is the objective I wanna achieve, say: I have a structure called Record, which contains a string word and a int counter. For example: I have many records of these (in the sample program, only 5), now I want to keep top N records(in sample, 3). I know now that I could overload operator < in Record, and put all records in a vector, and then initialize the priority_queue like: priority_queue< Record, vector<Record>, less<Record> > myQ (myVec.begin(),myVec.end()); However, as I understood, it's not easy to control the size of vector myVec