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• Game engine development in C++ [closed]

  - by Chris Cochran

  I am arriving at completion on a multithreaded concurrency framework designed for high-performance computing. Though I am not a gamer, it has occurred to me that this stand-alone software core could be an ideal basis for a multiprocessor game engine (64-bit native C++, 5000+ entry points). Are there any websites I could visit to discuss this technology with programmers and developers who could really benefit from it?

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• Multi Threading - How to split the tasks

  - by Motig

  if I have a game engine with the basic 'game engine' components, what is the best way to 'split' the tasks with a multi-threaded approach? Assuming I have the standard components of: Rendering Physics Scripts Networking And a quad-core, I see two ways of multi-threading: Option A ('Vertical'): Using this approach I can allow one core for each component of the engine; e.g. one core for the Rendering task, one for the Physics, etc. Advantages: I do not need to worry about thread-safety within each component I can take advantage of special optimizations provided for single-threaded access (e.g. DirectX offers a flag that can be set to tell it that you will only use single-threading) Option B ('Horizontal'): Using this approach, each task may be split up into 1 <= n <= numCores threads, and executed simultaneously, one after the other. Advantages: Allows for work-sharing, i.e. each thread can take over work still remaining as the others are still processing I can take advantage of libraries that are designed for multi-threading (i.e. ... DirectX) I think, in retrospect, I would pick Option B, but I wanted to hear you guys' thoughts on the matter.

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• BlockingCollection having issues with byte arrays

  - by MJLaukala

  I am having an issue where an object with a byte[20] is being passed into a BlockingCollection on one thread and another thread returning the object with a byte[0] using BlockingCollection.Take(). I think this is a threading issue but I do not know where or why this is happening considering that BlockingCollection is a concurrent collection. Sometimes on thread2, myclass2.mybytes equals byte[0]. Any information on how to fix this is greatly appreciated. MessageBuffer.cs public class MessageBuffer : BlockingCollection<Message> { } In the class that has Listener() and ReceivedMessageHandler(object messageProcessor) private MessageBuffer RecievedMessageBuffer; On Thread1 private void Listener() { while (this.IsListening) { try { Message message = Message.ReadMessage(this.Stream, this); if (message != null) { this.RecievedMessageBuffer.Add(message); } } catch (IOException ex) { if (!this.Client.Connected) { this.OnDisconnected(); } else { Logger.LogException(ex.ToString()); this.OnDisconnected(); } } catch (Exception ex) { Logger.LogException(ex.ToString()); this.OnDisconnected(); } } } Message.ReadMessage(NetworkStream stream, iTcpConnectClient client) public static Message ReadMessage(NetworkStream stream, iTcpConnectClient client) { int ClassType = -1; Message message = null; try { ClassType = stream.ReadByte(); if (ClassType == -1) { return null; } if (!Message.IDTOCLASS.ContainsKey((byte)ClassType)) { throw new IOException("Class type not found"); } message = Message.GetNewMessage((byte)ClassType); message.Client = client; message.ReadData(stream); if (message.Buffer.Length < message.MessageSize + Message.HeaderSize) { return null; } } catch (IOException ex) { Logger.LogException(ex.ToString()); throw ex; } catch (Exception ex) { Logger.LogException(ex.ToString()); //throw ex; } return message; } On Thread2 private void ReceivedMessageHandler(object messageProcessor) { if (messageProcessor != null) { while (this.IsListening) { Message message = this.RecievedMessageBuffer.Take(); message.Reconstruct(); message.HandleMessage(messageProcessor); } } else { while (this.IsListening) { Message message = this.RecievedMessageBuffer.Take(); message.Reconstruct(); message.HandleMessage(); } } } PlayerStateMessage.cs public class PlayerStateMessage : Message { public GameObject PlayerState; public override int MessageSize { get { return 12; } } public PlayerStateMessage() : base() { this.PlayerState = new GameObject(); } public PlayerStateMessage(GameObject playerState) { this.PlayerState = playerState; } public override void Reconstruct() { this.PlayerState.Poisiton = this.GetVector2FromBuffer(0); this.PlayerState.Rotation = this.GetFloatFromBuffer(8); base.Reconstruct(); } public override void Deconstruct() { this.CreateBuffer(); this.AddToBuffer(this.PlayerState.Poisiton, 0); this.AddToBuffer(this.PlayerState.Rotation, 8); base.Deconstruct(); } public override void HandleMessage(object messageProcessor) { ((MessageProcessor)messageProcessor).ProcessPlayerStateMessage(this); } } Message.GetVector2FromBuffer(int bufferlocation) This is where the exception is thrown because this.Buffer is byte[0] when it should be byte[20]. public Vector2 GetVector2FromBuffer(int bufferlocation) { return new Vector2( BitConverter.ToSingle(this.Buffer, Message.HeaderSize + bufferlocation), BitConverter.ToSingle(this.Buffer, Message.HeaderSize + bufferlocation + 4)); }

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• StringBuffer behavior in LWJGL

  - by Michael Oberlin

  Okay, I've been programming in Java for about ten years, but am entirely new to LWJGL. I have a specific problem whilst attempting to create a text console. I have built a class meant to abstract input polling to it, which (in theory) captures key presses from the Keyboard object and appends them to a StringBuilder/StringBuffer, then retrieves the completed string after receiving the ENTER key. The problem is, after I trigger the String return (currently with ESCAPE), and attempt to print it to System.out, I consistently get a blank line. I can get an appropriate string length, and I can even sample a single character out of it and get complete accuracy, but it never prints the actual string. I could swear that LWJGL slipped some kind of thread-safety trick in while I wasn't looking. Here's my code: static volatile StringBuffer command = new StringBuffer(); @Override public void chain(InputPoller poller) { this.chain = poller; } @Override public synchronized void poll() { //basic testing for modifier keys, to be used later on boolean shift = false, alt = false, control = false, superkey = false; if(Keyboard.isKeyDown(Keyboard.KEY_LSHIFT) || Keyboard.isKeyDown(Keyboard.KEY_RSHIFT)) shift = true; if(Keyboard.isKeyDown(Keyboard.KEY_LMENU) || Keyboard.isKeyDown(Keyboard.KEY_RMENU)) alt = true; if(Keyboard.isKeyDown(Keyboard.KEY_LCONTROL) || Keyboard.isKeyDown(Keyboard.KEY_RCONTROL)) control = true; if(Keyboard.isKeyDown(Keyboard.KEY_LMETA) || Keyboard.isKeyDown(Keyboard.KEY_RMETA)) superkey = true; while(Keyboard.next()) if(Keyboard.getEventKeyState()) { command.append(Keyboard.getEventCharacter()); } if (Framework.isConsoleEnabled() && Keyboard.isKeyDown(Keyboard.KEY_ESCAPE)) { System.out.println("Escape down"); System.out.println(command.length() + " characters polled"); //works System.out.println(command.toString().length()); //works System.out.println(command.toString().charAt(4)); //works System.out.println(command.toString().toCharArray()); //blank line! System.out.println(command.toString()); //blank line! Framework.disableConsole(); } //TODO: Add command construction and console management after that } } Maybe the answer's obvious and I'm just feeling tired, but I need to walk away from this for a while. If anyone sees the issue, please let me know. This machine is running the latest release of Java 7 on Ubuntu 12.04, Mate desktop environment. Many thanks.

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• Multiple readers on FIFO

  - by poly

  I've asked a question here before about multiple writers on a FIFO, and I know now that the write is thread safe as long as I write less than the PIPE_BIF, here is the link for that limit. What about read? what if have two(or more) readers in multiple threads for reading from the same fifo, do I need locks here? or all I need is to read less than the PIPE_BUF? BTW, I'm talking about Linux FIFO, And I'm using C.

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• Write a program using 3 threads, one prints 10 'A's and the second prints 'B's and the third prints 10 'C's with synchrornization

  - by user132967

  Iam try to implement this questions using threads and mutex this is my code : include include include include include define Num_thread 3 pthread_mutex_t lett[Num_thread]; void Sleep_rand(double max) { struct timespec delai; delai.tv_sec=max; delai.tv_nsec=0; nanosleep(&delai,NULL); } void *Print_Sequence(); int main() { int i; pthread_t tid[Num_thread];// this is threads identifier for(i=0;i<Num_thread;i++) pthread_mutex_init(&lett[i],0); for(i=0;i<Num_thread;i++) { printf("i=%d\n",i); /* create the threads / pthread_create(&tid[i], / This variable will have the thread is after successful creation / NULL, / send the thread attributes / Print_Sequence, / the function the thread will run / &i/ send the parameter's address to the function */); } /* Wait till threads are complete and join before main continues */ for (i = 0; i pthread_join(tid[i], NULL); } return 0; } /* The thread will begin control in this function */ void Print_Sequence(void param) { int i,j=(int)param; printf("j=%d\n",(*j)); int max; pthread_mutex_lock(&lett[0]); pthread_mutex_lock(&lett[1]); for (i = 1; i <= 10; i++) { max=(int) (8*rand()/(RAND_MAX+1.0)); Sleep_rand( max); printf("A"); } pthread_mutex_unlock(&lett[0]); pthread_mutex_lock(&lett[2]); for (i = 1; i <= 10; i++) { max=(int) (2*rand()/(RAND_MAX+1.0)); Sleep_rand( max); printf("B"); } for (i = 1; i <= 10; i++) { max=(int) (15*rand()/(RAND_MAX+1.0)); Sleep_rand( max); printf("C"); } pthread_mutex_unlock(&lett[1]); pthread_mutex_unlock(&lett[2]); pthread_exit(0); } and the o/p is like : AAAAAAAAAABBBBBBBBBBCCCCCCCCCCAAAAAAAAAABBBBBBBBBBCCCCCCCCCCAAAAAAAAAABBBBBBBBBBCCCCCCCCCC COULD ANYONE PLEASE EXPLAIN WHAT IS THE WRONG WITH CODE ??

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• Optimising news fetching

  - by aceBox

  I have a web scraper for scraping news from different sources in wp7. My current appraoch for doing this is: load newspapers information from xml file. go to the specified sections and fetch the urls of the news items. go to each url and fetch headline, image, publisher. display using a MVVM architecture of windows phone. The whole thing takes place asynchronously...meaning as soon as url from a section of a newspaper is fetched it is added to the queue, and the second stage consisting of fetching headline, image etc starts... and as soon this is fetched even for one article, it is displayed. Later on as more articles are fetched, they are added on to the list. For the fetching purpose I am using a SmartThreadPool(http://www.codeproject.com/Articles/7933/Smart-Thread-Pool) for windows phone. My problem is that...even for fetching around 80 items (in total) from 9 publications, it is taking more than a minute. How can i speed up the procedure? Note: I have a two stage approach because many times the images are not available with headlines, and are only found in the article.

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• How can I designed multi-threaded application for larger user base

  - by rokonoid

  Here's my scenario, I need to develop a scalable application. My user base may be over 100K, every user has 10 or more small tasks. Tasks check every minute with a third party application through web services, retrieving data which is written in the database, then the data is forwarded to it's original destination. So here's the processing of a small task: while(true){ Boolean isNewInformationAvailable = checkWhetherInformationIsAvailableOrNot(); If(isNewInformationAvailable ==true){ fetchTheData(); writeToDatabase(); findTheDestination(); deliverTheData(); isAvailable =false; } } Here is the question: as the application is large, how should I approach designing this. I'm going to use Java to write it. Should I use concurrency, and how would you manage the concurrency?

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• Barrier implementation with mutex and condition variable

  - by kkp

  I would like to implement a barrier using mutex locks and conditional variables. Please let me know whether my implementation below is fine or not? static int counter = 0; static int Gen = 999; void* thread_run(void*) { pthread_mutex_lock(&lock); int g = Gen; if (++counter == nThreads) { counter = 0; Gen++; pthread_cond_broadcast(&cond_var); } else { while (Gen == g) pthread_cond_wait(&cond_var, &lock); } pthread_mutex_unlock(&lock); return NULL; }

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• Multi-threaded JOGL Problem

  - by moeabdol

  I'm writing a simple OpenGL application in Java that implements the Monte Carlo method for estimating the value of PI. The method is pretty easy. Simply, you draw a circle inside a unit square and then plot random points over the scene. Now, for each point that is inside the circle you increment the counter for in points. After determining for all the random points wither they are inside the circle or not you divide the number of in points over the total number of points you have plotted all multiplied by 4 to get an estimation of PI. It goes something like this PI = (inPoints / totalPoints) * 4. This is because mathematically the ratio of a circle's area to a square's area is PI/4, so when we multiply it by 4 we get PI. My problem doesn't lie in the algorithm itself; however, I'm having problems trying to plot the points as they are being generated instead of just plotting everything at once when the program finishes executing. I want to give the application a sense of real-time display where the user would see the points as they are being plotted. I'm a beginner at OpenGL and I'm pretty sure there is a multi-threading feature built into it. Non the less, I tried to manually create my own thread. Each worker thread plots one point at a time. Following is the psudo-code: /* this part of the code exists in display() method in MyCanvas.java which extends GLCanvas and implements GLEventListener */ // main loop for(int i = 0; i < number_of_points; i++){ RandomGenerator random = new RandomGenerator(); float x = random.nextFloat(); float y = random.nextFloat(); Thread pointThread = new Thread(new PointThread(x, y)); } gl.glFlush(); /* this part of the code exists in run() method in PointThread.java which implements Runnable */ void run(){ try{ gl.glPushMatrix(); gl.glBegin(GL2.GL_POINTS); if(pointIsIn) gl.glColor3f(1.0f, 0.0f, 0.0f); // red point else gl.glColor3f(0.0f, 0.0f, 1.0f); // blue point gl.glVertex3f(x, y, 0.0f); // coordinates gl.glEnd(); gl.glPopMatrix(); }catch(Exception e){ } } I'm not sure if my approach to solving this issue is correct. I hope you guys can help me out. Thanks.

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• How can I tell if I am overusing multi-threading?

  - by exhuma

  NOTE: This is a complete re-write of the question. The text before was way too lengthy and did not get to the point! If you're interested in the original question, you can look it up in the edit history. I currently feel like I am over-using multi-threading. I have 3 types of data, A, B and C. Each A can be converted to multiple Bs and each B can be converted to multiple Cs. I am only interested in treating Cs. I could write this fairly easily with a couple of conversion functions. But I caught myself implementing it with threads, three queues (queue_a, queue_b and queue_c). There are two threads doing the different conversions, and one worker: ConverterA reads from queue_a and writes to queue_b ConverterB reads from queue_b and writes to queue_c Worker handles each element from queue_c The conversions are fairly mundane, and I don't know if this model is too convoluted. But it seems extremely robust to me. Each "converter" can start working even before data has arrived on the queues, and at any time in the code I can just "submit" new As or Bs and it will trigger the conversion pipeline which in turn will trigger a job by the worker thread. Even the resulting code looks simpler. But I still am unsure if I am abusing threads for something simple.

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• Do threads delete themselves?

  - by Prog

  Let's say I was working on a Swing application. Most of it is run on the EDT using SwingUtilities.invokeLater() inside the main method, because I heard (please correct me if I'm wrong) that that's what you need to do with Swing. However, some parts of it shouldn't run on the EDT. These parts are parts that take long to complete (I assume that this is because long tasks on the EDT will interfere with GUI stuff the EDT should be doing, and thus these kinds of tasks should be run on parallel, on a different thread. Is this assumption correct?) To do this, when I need to perform a task that takes long to complete and thus can't be run on the EDT like the rest of the program, I create a new thread and run that task inside it. My question is: When the run() method of that new thread finishes, aka the thread finished it's job. Does it delete itself? Or does it keep existing in the memory?

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• Application that provides unique keys to multiple threads

  - by poly

  Thanks all for your help before. So, this is what I came up with so far, the requirements are, application has two or more threads and each thread requires a unique session/transaction ID. is the below considered thread safe? thread 1 will register itself with get_id by sending it's pid thread 2 will do the same then thread 1 & 2 will call the function to get a unique ID function get_id(bool choice/*register thread or get id*/, pid_t pid) { static int pid[15][1]={0};//not sure if this work, anyway considor any it's been set to 0 by any other way than this static int total_threads = 0; static int i = 0; int x=0,y=0; if (choice) // thread registeration part { for(x=0;x<15;x++) { if (pid[x][0]==0); { pid[x][0] = (int) pid; pid[x][1] = (x & pidx[x][1]) << 24;//initiate counter for this PID by shifting x to the 25th bit, it could be any other bit, it's just to set a range. //so the range will be between 0x0000000 and 0x0ffffff, the second one will be 0x1000000 and 0x1ffffff, break; } total_threads++; } } //search if pid exist or not, if yes return transaction id for(x=0;x<15;x++) { if (pid[x][0]==pid); { pid[x][1]++;//put some test here to reset the number to 0 if it reaches 0x0ffffff return pid[x][1]; break; } } }

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• Threads slowing down application and not working properly

  - by Belgin

  I'm making a software renderer which does per-polygon rasterization using a floating point digital differential analyzer algorithm. My idea was to create two threads for rasterization and have them work like so: one thread draws each even scanline in a polygon and the other thread draws each odd scanline, and they both start working at the same time, but the main application waits for both of them to finish and then pauses them before continuing with other computations. As this is the first time I'm making a threaded application, I'm not sure if the following method for thread synchronization is correct: First of all, I use two global variables to control the two threads, if a global variable is set to 1, that means the thread can start working, otherwise it must not work. This is checked by the thread running an infinite loop and if it detects that the global variable has changed its value, it does its job and then sets the variable back to 0 again. The main program also uses an empty while to check when both variables become 0 after setting them to 1. Second, each thread is assigned a global structure which contains information about the triangle that is about to be rasterized. The structures are filled in by the main program before setting the global variables to 1. My dilemma is that, while this process works under some conditions, it slows down the program considerably, and also it fails to run properly when compiled for Release in Visual Studio, or when compiled with any sort of -O optimization with gcc (i.e. nothing on screen, even SEGFAULTs). The program isn't much faster by default without threads, which you can see for yourself by commenting out the #define THREADS directive, but if I apply optimizations, it becomes much faster (especially with gcc -Ofast -march=native). N.B. It might not compile with gcc because of fscanf_s calls, but you can replace those with the usual fscanf, if you wish to use gcc. Because there is a lot of code, too much for here or pastebin, I created a git repository where you can view it. My questions are: Why does adding these two threads slow down my application? Why doesn't it work when compiling for Release or with optimizations? Can I speed up the application with threads? If so, how? Thanks in advance.

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• Relationship between "Task Parallel Library" and "Task-based Asynchronous Pattern"?

  - by Sid

  In the context of C#, .NET 4/4.5 used for an application running on a web-server, what is the relationship between "Task Parallel Library" and "Task-based Asynchronous Pattern"? I understand one is a library and the other is a pattern. But to dig deeper, is it like "The library is used by the pattern to enforce good practices". I'm also not clear if both are supported in .NET 4.0 (with awake and async keywords) Edit: Seems that awake and async are only in .NET 4.5 ...

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• Massive vehicular network simulator

  - by IvanK

  I am interested in making a vehicular network simulator (vehicular network as in vehicles can be equipped with radios and when they come in range they can talk with each other). I want to be able to scale to 1000s of nodes if not more. I am quite frankly torn on how to do, or even which language to use or whether I should instead be using some other piece of software/code. I know that this should depend on a lot of design decisions that I may have, but it would be great if somebody can point me towards the right direction. I was planning to use a multi-threaded architecture, but not sure whether it will add to the complication or make it easier. Also if I go for a multi-threaded architecutre, do you think that 'Go' language will be a good choice?

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• shared transaction ID function among multiple threads

  - by poly

  I'm writing an application in C that requires multiple threads to request a unique transaction ID from a function as shown below; struct list{ int id; struct list *next }; function generate_id() { linked-list is built here to hold 10 millions } my concern is how to sync between two or more threads so that transaction id can be unique among them without using mutex, is this possible? Please share anything even if I need to change linked list to something else.

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• process monitoring in c under linux

  - by poly

  I'm trying to write a multi threaded/processes application and it need to know how to monitor a process from another process all the time. So here is what I have, I have a 2 processes, each with multiple threads that handle the network part, then another 2 process also with multiple threads that interact with DB and with the network processes, what I need to do is that if for example one of the network processes goes down the DB process start sending to the live network process until the second one is up again. I'm using fifo between the DB and the network process. I was thinking of sending messages with message passing all the time but not sure whether this is a good idea or I need to use some other IPC for this issue, or probably neither is good and I need to use entirely something else? Thanks,

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• When creating a library for a simple program, what must I do to protect others from its lack of thread safety?

  - by DeveloperDon

  When creating a library for a simple program, is it more cost effective to make it thread safe or is there a way to detect the program's use in a multithreaded program and ASSERT() or otherwise determine (preferably at compile or link time) that it may create problems. Related help for this question would be automated tool support for finding potential problems with thread safety, programming language features that enforce it,

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• Scalability of multi-threading in game server

  - by Taylor Hill

  What is a reasonable number of threads for a simple 2D mmo in Java? Is it reasonable to have two threads per connection, one for the input stream and one for the output stream? The reason I ask is because I use a blocking method on the input stream, and a workaround seems unnecessarily complex if I were to try to get around it without adding threads. This is mostly for my own edification; I don't expect to have 5 million people playing it ever, or even 5, but I'm wondering what a good scalable solution is, and if this is reasonable for a small server (<30 connections).

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• multi-thread in mmorpg server

  - by jean

  For MMORPG, there is a tick function to update every object's state in a map. The function was triggered by a timer in fixed interval. So each map's update can be dispatch to different thread. At other side, server handle player incoming package have its own threads also: I/O threads. Generally, the handler of the corresponding incoming package run in I/O threads. So there is a problem: thread synchronization. I have consider two methods: Synchronize with mutex. I/O thread lock a mutex before execute handler function and map thread lock same mutex before it execute map's update. Execute all handler functions in map's thread, I/O thread only queue the incoming handler and let map thread to pop the queue then call handler function. These two have a disadvantage: delay. For method 1, if the map's tick function is running, then all clients' request need to waiting the lock release. For method 2, if map's tick function is running, all clients' request need to waiting for next tick to be handle. Of course, there is another method: add lock to functions that use data which will be accessed both in I/O thread & map thread. But this is hard to maintain and easy to goes incorrect. It needs carefully check all variables whether or not accessed by both two kinds thread. My problem is: is there better way to do this? Notice that I said map is logic concept means no interactions can happen between two map except transport. I/O thread means thread in 3rd part network lib which used to handle client request.

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• how to serialize function depending on what instance of object calls it, if same instance call in a thread then do serialize else not

  - by LondonDreams

  I have a function which fetches and updates some record from db and I am trying to make sure each if the function is called by same instance of object(same Or different thread) then function should behave synchronized else its a call from different object instance function need not to be synchronized. I have tried it use a lock per client. That is, instead of synchronizing the method directly using explicit locking through lock objects using Map. function is like :- getAndUpdateMyHitCount(myObjId){ //go to db and get unique record by myObjId //fetch value , increment , save update } And this function may get call is same thread by different Or same object instance But as fetching and matching from Map is slow , Is there other optimized way to do this ? Found similar at this Question but dont feel that is optimized

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• Communication between Box2D and libGDX Stage (Scene2D) running in separate threads

  - by atok

  I'm making a physics based 2D game using libGDX and Box2D. I want to move the execution of the simulation out of render thread. I use immutable messages and the BlockingQueue to pass the information about player actions. The Box2D applies forces and runs a frame of simulation. In the next step I would like to sync back the changes and update Scene2D Actors accordingly. Making an immutable copy of the state of the game world and sending it back using Gdx.app.postRunnable() is one option but it seems inefficient. Is there any other option?

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• If I use locks, can my algorithm still be lock-free?

  - by Joe Pension

  A common definition of lock-free is that at least one process makes progress. 1 If I have a simple data structure such as a queue, protected by a lock, then one process can always make progress, as one process can acquire the lock, do what it wants, and release it. So does it meet the definition of lock-free? 1 See eg M. Herlihy, V. Luchangco, and M. Moir. Obstruction-free synchronization: Double-ended queues as an example. In Distributed Computing, 2003. "It is lock-free if it ensures only that some thread always makes progress".

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• Shared memory multiprocesses

  - by poly

  I'm building an multi processes application and I need to save session ID, the sessions ID is 32 bit, and of course it can't be used twice in its lifetime, I'm currently using DB that saves all the ID in a table, and I do the following, ID table is (int key, char used(1)) //1 is used, 0 is not 1. lock table 2. get one key for one sessions 3. update used field in it to used 4. unlock After the session is finished the process use below to free key, 1. lock table 2. update used field in it to not used 4. unlock I'm really wondering whether this is a good/fast implementation. and please note it's multi processes application.

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