I am having two threads, where I need to implement a new method run_both which takes two functions as parameters, and calls each of them in a new thread.
The method must return a tuple with the result of the both functions.
Thread t1 = new Thread() {
public void run() {
x = y + z;
}
};
Thread t2 = new Thread() {
public void run() {
y = 1;
z = 2;
}
};
In Github you can find a library which does exactly what you want. The link is here.
The first chapter in the description gives an example. More examples can be found in example-1.cc. Hope this helps!
Related
I have a java thread which is running a path-finding algorithm in a constant while loop. Then, every so often I want to retrieve the most updated path from the thread. However, I am unsure how to do this, and think I might be doing it wrong.
My thread consists of the following code:
public class BotThread extends Thread {
Bot bot;
AStar pathFinder;
Player targetPlayer;
public List<boolean[]> plan;
public BotThread(Bot bot) {
this.bot = bot;
this.plan = new ArrayList<>();
pathFinder = new AStar(bot, bot.getLevelHandler());
}
public void run() {
while (true) {
System.out.println("THREAD RUNNING");
targetPlayer = bot.targetPlayer;
plan = pathFinder.optimise(targetPlayer);
}
}
public boolean[] getNextAction() {
return plan.remove(0);
}
}
I then create an object of BotThread, and call start(). Then when I call getNextAction() on the thread, I seem to receive a null pointer. Is this because I am not able to call another method on the thread whilst it is in the main loop? How should I do this properly?
This is because you are not giving enough time to thread to initialise plan Arraylist. You need to add sleeping time to the threads. Something like this while calling BotThread class from main:
int num_threads = 8;
BotThread myt[] = new BotThread[num_threads];
for (int i = 0; i < num_threads; ++i) {
myt[i] = new BotThread();
myt[i].start();
Thread.sleep(1000);
myt[i].getNextAction();
}
I got JavaFX main thread, there I create new Thread that extends Task and sort and replace bars. Everyhing is good, but I want to make some delays(like 100ms) while replacing to show step by step sorting, maybe with animation. The problem is when I use Thread.sleep() or TranslateTransition() it just sum all delays miliseconds together in one big delay that happens before changing bars. How can I make delay that will work properly in UI thread?
In main class:
Sorting sorting = new Sorting();
sortThread = new Thread(sorting, "sort");
sortThread.start();
sortThread.join();
And my class Sorting extends Task
public class Sorting extends Task<Void> {
//some stuff here
#Override
protected Void call() throws Exception {
taskThread = new Thread(counter, "time");
taskThread.setDaemon(true);
taskThread.start();
int n = array_tmp.length;
int temp;
for (int i = 0; i < n; i++) {
for (int j = 1; j < (n - i); j++) {
if (array_tmp[j - 1] > array_tmp[j]) {
//replacing bars
Node n1 = barChart.getData().get(j-1).getData().get(0).getNode();
Node n2 = barChart.getData().get(j).getData().get(0).getNode();
double x1 = n1.getTranslateX() + ((barChart.getWidth()-69)/array_tmp.length);
double x2 = n2.getTranslateX() - ((barChart.getWidth()-69)/array_tmp.length);
n1.setTranslateX(x1);
n2.setTranslateX(x2);
barChart.getData().get(j-1).getData().get(0).setNode(n2);
barChart.getData().get(j).getData().get(0).setNode(n1);
temp = array_tmp[j - 1];
array_tmp[j - 1] = array_tmp[j];
array_tmp[j] = temp;
}
}
}
}
}
There are two basic rules to threading in JavaFX:
UI components (nodes) that are part of a scene graph that is actually displayed can only be accessed from the JavaFX application thread. Some other operations (such as creating a new Stage) are also subject to this rule.
Any long-running or blocking operation should be run on a background thread (i.e. not the JavaFX application thread). This is because the JavaFX application thread is the one needed to render the UI and respond to user interaction. Consequently, if you block the FX Application Thread, then the UI cannot be rendered and the application will become unresponsive until your operation completes.
The javafx.concurrent API provides facilities for managing code that can be run on background threads and executing callbacks on the FX application thread.
The javafx.animation API additionally provides classes that allow UI code to be executed on the JavaFX application thread at specific times. Note that the animation API avoids creating background threads at all.
So for your use case, if you want to animate the swapping of two bars in the bar chart, you can do so with the animation API. A general method that creates an animation that performs such a swap might look like this:
private <T> Animation createSwapAnimation(Data<?, T> first, Data<?, T> second) {
double firstX = first.getNode().getParent().localToScene(first.getNode().getBoundsInParent()).getMinX();
double secondX = first.getNode().getParent().localToScene(second.getNode().getBoundsInParent()).getMinX();
double firstStartTranslate = first.getNode().getTranslateX();
double secondStartTranslate = second.getNode().getTranslateX();
TranslateTransition firstTranslate = new TranslateTransition(Duration.millis(500), first.getNode());
firstTranslate.setByX(secondX - firstX);
TranslateTransition secondTranslate = new TranslateTransition(Duration.millis(500), second.getNode());
secondTranslate.setByX(firstX - secondX);
ParallelTransition translate = new ParallelTransition(firstTranslate, secondTranslate);
translate.statusProperty().addListener((obs, oldStatus, newStatus) -> {
if (oldStatus == Animation.Status.RUNNING) {
T temp = first.getYValue();
first.setYValue(second.getYValue());
second.setYValue(temp);
first.getNode().setTranslateX(firstStartTranslate);
second.getNode().setTranslateX(secondStartTranslate);
}
});
return translate;
}
The basic idea here is pretty simple: we measure the distance in the x-coordinates between the two nodes; make a note of their current translateX properties, and then create two transitions which move the nodes so they take each others positions. Those two transitions are executed in parallel. When the transitions are complete (indicated by the status of the transition changing from RUNNING to something else), the values in the chart are exchanged and the translateX properties reset to their previous values (the effect of these will cancel out visually, but now the chart data will reflect the fact that the two have been exchanged).
If you want to perform a sort algorithm which animates the exchanges in the sorting, pausing between each step of the algorithm, you can do this using a background thread (you may be able to do this with an animation too - but this seems simple enough and is perhaps more instructional).
The idea here is to create a Task whose call() method performs the sort algorithm, pausing at various points to allow the use to see what is happening. Because we are pausing (blocking), this cannot be run on the FX Application Thread, as the blocking would prevent the UI being updated until the entire process was complete.
Here is an implementation of a bubble sort (for simplicity). On each iteration of the sort, we:
highlight the two bars to be compared in green*
pause so the user can see that
if the values need to be exchanged:
get the animation defined above and run it*
pause again, and
reset the colors*.
Steps marked * in the above psuedocode change the UI, so they must be executed on the FX Application thread, so they need to be wrapped in a call to Platform.runLater(...), which causes the provided code to be executed on the FX Application Thread.
The last tricky part here (and this is unusually tricky) is that the animation, of course, takes some time to execute. So we must arrange for our background thread to wait until the animation is complete. We do this by creating a CountDownLatch with a count of 1. When the animation is complete, we count the latch down. Then after submitting the animation to Platform.runLater(..), our background thread just waits for the latch to count down before proceeding, by calling latch.await(). It is quite unusual for a background thread to need to wait for something to run on the FX Application Thread, but this is one technique to do that in a case where you do need it.
The implementation of the bubble sort thus looks like
private Task<Void> createSortingTask(Series<String, Number> series) {
return new Task<Void>() {
#Override
protected Void call() throws Exception {
ObservableList<Data<String, Number>> data = series.getData();
for (int i = data.size() - 1; i >= 0; i--) {
for (int j = 0 ; j < i; j++) {
Data<String, Number> first = data.get(j);
Data<String, Number> second = data.get(j + 1);
Platform.runLater(() -> {
first.getNode().setStyle("-fx-background-color: green ;");
second.getNode().setStyle("-fx-background-color: green ;");
});
Thread.sleep(500);
if (first.getYValue().doubleValue() > second.getYValue().doubleValue()) {
CountDownLatch latch = new CountDownLatch(1);
Platform.runLater(() -> {
Animation swap = createSwapAnimation(first, second);
swap.setOnFinished(e -> latch.countDown());
swap.play();
});
latch.await();
}
Thread.sleep(500);
Platform.runLater(() -> {
first.getNode().setStyle("");
second.getNode().setStyle("");
});
}
}
return null;
}
};
}
Here is a complete demo. Since the sort algorithm, with its pauses, is encapsulated as a Task, we can leverage its callbacks and state properties if we need. As an example, we disable the buttons before starting the task, and use the onSucceeded handler to enable them again when it completes. It would be easy to add a "cancel" option too.
import java.util.Random;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import javafx.animation.Animation;
import javafx.animation.ParallelTransition;
import javafx.animation.TranslateTransition;
import javafx.application.Application;
import javafx.application.Platform;
import javafx.collections.ObservableList;
import javafx.concurrent.Task;
import javafx.geometry.Insets;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.chart.BarChart;
import javafx.scene.chart.CategoryAxis;
import javafx.scene.chart.NumberAxis;
import javafx.scene.chart.XYChart.Data;
import javafx.scene.chart.XYChart.Series;
import javafx.scene.control.Button;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.HBox;
import javafx.stage.Stage;
import javafx.util.Duration;
public class AnimatedBubbleSort extends Application {
private Random rng = new Random();
private ExecutorService exec = Executors.newCachedThreadPool(runnable -> {
Thread t = new Thread(runnable);
t.setDaemon(true);
return t;
});
#Override
public void start(Stage primaryStage) {
BarChart<String, Number> chart = new BarChart<>(new CategoryAxis(), new NumberAxis());
chart.setAnimated(false);
Series<String, Number> series = generateRandomIntegerSeries(10);
chart.getData().add(series);
Button sort = new Button("Sort");
Button reset = new Button("Reset");
reset.setOnAction(e -> chart.getData().set(0, generateRandomIntegerSeries(10)));
HBox buttons = new HBox(5, sort, reset);
buttons.setAlignment(Pos.CENTER);
buttons.setPadding(new Insets(5));
sort.setOnAction(e -> {
Task<Void> animateSortTask = createSortingTask(chart.getData().get(0));
buttons.setDisable(true);
animateSortTask.setOnSucceeded(event -> buttons.setDisable(false));
exec.submit(animateSortTask);
});
BorderPane root = new BorderPane(chart);
root.setBottom(buttons);
Scene scene = new Scene(root);
primaryStage.setScene(scene);
primaryStage.show();
}
private Task<Void> createSortingTask(Series<String, Number> series) {
return new Task<Void>() {
#Override
protected Void call() throws Exception {
ObservableList<Data<String, Number>> data = series.getData();
for (int i = data.size() - 1; i >= 0; i--) {
for (int j = 0 ; j < i; j++) {
Data<String, Number> first = data.get(j);
Data<String, Number> second = data.get(j + 1);
Platform.runLater(() -> {
first.getNode().setStyle("-fx-background-color: green ;");
second.getNode().setStyle("-fx-background-color: green ;");
});
Thread.sleep(500);
if (first.getYValue().doubleValue() > second.getYValue().doubleValue()) {
CountDownLatch latch = new CountDownLatch(1);
Platform.runLater(() -> {
Animation swap = createSwapAnimation(first, second);
swap.setOnFinished(e -> latch.countDown());
swap.play();
});
latch.await();
}
Thread.sleep(500);
Platform.runLater(() -> {
first.getNode().setStyle("");
second.getNode().setStyle("");
});
}
}
return null;
}
};
}
private <T> Animation createSwapAnimation(Data<?, T> first, Data<?, T> second) {
double firstX = first.getNode().getParent().localToScene(first.getNode().getBoundsInParent()).getMinX();
double secondX = first.getNode().getParent().localToScene(second.getNode().getBoundsInParent()).getMinX();
double firstStartTranslate = first.getNode().getTranslateX();
double secondStartTranslate = second.getNode().getTranslateX();
TranslateTransition firstTranslate = new TranslateTransition(Duration.millis(500), first.getNode());
firstTranslate.setByX(secondX - firstX);
TranslateTransition secondTranslate = new TranslateTransition(Duration.millis(500), second.getNode());
secondTranslate.setByX(firstX - secondX);
ParallelTransition translate = new ParallelTransition(firstTranslate, secondTranslate);
translate.statusProperty().addListener((obs, oldStatus, newStatus) -> {
if (oldStatus == Animation.Status.RUNNING) {
T temp = first.getYValue();
first.setYValue(second.getYValue());
second.setYValue(temp);
first.getNode().setTranslateX(firstStartTranslate);
second.getNode().setTranslateX(secondStartTranslate);
}
});
return translate;
}
private Series<String, Number> generateRandomIntegerSeries(int n) {
Series<String, Number> series = new Series<>();
for (int i = 1; i <= n; i++) {
series.getData().add(new Data<>(Integer.toString(i), rng.nextInt(90) + 10));
}
return series;
}
public static void main(String[] args) {
launch(args);
}
}
i have a class in a cs file:
public class ThreadData
{
private int index;
public ThreadData(int index)
{
this.index = index;
}
public static ThreadDataOutput DoWork(ThreadDataInput input)
{
return new ThreadDataOutput();
}
}
now, i have c++ code that tries to init a new task and to us the above function:
int numOfThread = 2;
array<Task^>^ taskArr = gcnew array<Task^>(numOfThread);
for (int i = 0; i < numOfThread; i++)
{
ThreadData^ td = gcnew ThreadData(i);
ThreadDataInput^ input = gcnew ThreadDataInput(i);
Task<ThreadDataOutput^>^ task = gcnew Task<ThreadDataOutput^>(td->DoWork, input);
taskArr[i] = task;
taskArr[i]->Start();
}
Task::WaitAll(taskArr, 300 * 1000);
the following code return 2 errors at compile time:
can't take address of 'ThreadData::DoWork' unless creating delegate instance
cannot convert argument 1 from 'AmadeusWS::ThreadDataOutput ^(__clrcall *)(AmadeusWS::ThreadDataInput ^)' to 'System::Func ^
i also tried to declare a delegate like this in the cs file:
public static Func<ThreadDataInput, ThreadDataOutput> DoWork2 = delegate(ThreadDataInput taskDataInput)
{
return new ThreadDataOutput();
};
but i don't know how to call it from the c++\cli code
can anyone assist me to understand how to define cli delegate that can take parametr ?
thanks
In order to create a delegate instance in C++/CLI, you need to construct it explicitly, and specify the object that it will be called on separately from the class & method to be called.
gcnew Func<TInput, TOutput>(theObject, &TheClass::MethodToInvoke)
Note that the method to be called is specified in the C++ style.
Substituting that in to your task creation, I believe this statement will work for you:
Task<ThreadDataOutput^>^ task = gcnew Task<ThreadDataOutput^>(
gcnew Func<ThreadDataInput^, ThreadDataOutput^>(td, &ThreadData::DoWork),
input);
Edit
In the code you posted in your comment, you missed the object to invoke the delegate on.
gcnew Func<Object^, Object^>(td, &ThreadData::DoWork)
^^
I am getting started with Haxe and OpenFl, and have some experience with Javascript and Lua.
It was going pretty well, till I got to a point where I needed a function similar to wait() in Lua, etc, which stops the script until the number of seconds you set is over.
How would I go about doing this?
EDIT: To clarify, I am building to Flash.
Although this is old, I wanted to add another point for reference. The OP mentioned in a comment this was for a game. One method I often use is (and could probably be put in a library):
var timerCount:Float = 0;
var maxTimerCounter:Float = 5;
function update () {
timerCounter += elapsedTime;
if (timerCounter > maxTimerCounter){
onTimerComplete();
timerCount = 0;
}
}
In SYS you are looking for:
static function sleep( seconds : Float ) : Void
Suspend the current execution for the given time (in seconds).
Example: Sys.sleep(.5);
http://haxe.org/api/sys/
Edit: User is porting to flash.
So the suggestion is to use Timer
http://haxe.org/api/haxe/timer
In Timer the suggestion is to use
static function delay( f : Void -> Void, time_ms : Int ) : Timer
Someone on stack overflow has an example that looks like this: haxe.Timer.delay(callback(someFunction,"abc"), 10); located here... Pass arguments to a delayed function with Haxe
For the Flash compile target, the best you can do is use a timer, and something like this setTimeout() function.
This means slicing your function into two - everything before the setTimeout(), and everything after that, which is in a separate function that the timeout can call.
so somethine like, eg:
tooltipTimerId = GlobalTimer.setTimeout(
Tooltip.TOOLTIP_DELAY_MS,
handleTooltipAppear,
tootipParams
);
[...]
class GlobalTimer {
private static var timerList:Array<Timer>;
public static function setTimeout(milliseconds:Int, func:Dynamic, args:Array<Dynamic>=null):Int {
var timer:Timer = new Timer(milliseconds);
var id = addTimer(timer, timerList);
timer.run = function() {
Reflect.callMethod(null, func, args);
clearTimeout(id);
}
return id;
}
private static function addTimer(timer:Timer, arr:Array<Timer>):Int {
for (i in 0...arr.length) {
if (null == arr[i]) {
arr[i] = timer;
return i;
}
}
arr.push(timer);
return arr.length -1;
}
public static function clearTimeout(id:Int) {
var timers:Array<Timer> = GlobalTimer.getInstance().timerList;
try {
timers[id].stop();
timers[id] = null;
} catch(e:Error) {/* Nothing we can do if it fails, really. */}
}
}
How can I distribute the operations, say duplicate the items\actions sent in one pipe to various different pipes which can access the original pipe?
Say I have Parent thread is "Pthread", I want to link it to 4 or 5 child threads, Just like a binary tree. Any operations performed on "Pthread" should be distributed to all the child threads(Something similar to what ESB does in the SOA architecture).
Like A+B should be sent in all the 5 threads\pipes at the same time and processed.
Is there a way to do this?
public class MainThreadEntry {
public void ThreadCreationMethod()
{
List<Future<Object>> listOfResult = null; // listOfResult is list of Integer objects as a result of computation by different threads
ExecutorService executor = Executors.newFixedThreadPool(5); // no of threads to create from main thread
List<EachThreadComputation> list = new ArrayList<MainThreadEntry .EachThreadComputation>();
for (int i = 0; i < 5; i++) {
EachThreadComputation separeateComputaionInnerClass = new EachThreadComputation(1,2); // innerClass Created For Ecah Thread 1,2 parameter can be dynamic
list.add(separeateComputaionInnerClass);
}
try {
listOfResult = executor.invokeAll(list); // call on different threads with 5 separate executionpath for computation
} catch (InterruptedException e) {
}
}
private class EachThreadComputation implements Callable<Object>{
private int A;
private int B;
EachThreadComputation(int A,int B) {
this.A = A;
this.B = B;
}
#Override
public Object call() throws Exception {
return (Integer)A+B
}
}}