simulation is on different thread

CMakeLists.txt

@@ -8,10 +8,11 @@ set(CMAKE_AUTOUIC ON)
 
 find_package(Qt6 COMPONENTS OpenGLWidgets REQUIRED)
 find_package(Eigen3 REQUIRED)
+find_package(OpenMP REQUIRED)
 
 file(GLOB_RECURSE SOURCE_FILES src/**.cpp)
 add_executable(Pendulum WIN32 ${SOURCE_FILES} icons/icons.qrc)
 
 include_directories(${EIGEN3_INCLUDE_DIR})
 
-target_link_libraries(Pendulum Qt6::OpenGLWidgets)
+target_link_libraries(Pendulum Qt6::OpenGLWidgets OpenMP::OpenMP_CXX)

src/GLWidget.cpp

@@ -33,8 +33,9 @@ void GLWidget::timerEvent(QTimerEvent *e) {
 
 void GLWidget::updateFPS() {
 	auto thisFrame = high_resolution_clock::now();
-	auto diff = duration_cast<milliseconds>(thisFrame - previousFrame).count();
+	auto diff = (int)duration_cast<milliseconds>(thisFrame - previousFrame).count();
 	currentFPS = 1000 / (diff == 0 ? 1 : diff);
+	// std::cout << currentFPS << std::endl;
 	previousFrame = thisFrame;
 }
 

src/MainWindow.cpp

@@ -14,9 +14,15 @@
 #include <QCoreApplication>
 #include "Pendulum.h"
 #include "Button.h"
+#include <QThread>
+#include <QCloseEvent>
+#include <QTimer>
 
 MainWindow::MainWindow() {
+	simulationThread = new QThread(this);
 	simulation = new Simulation;
+	simulation->moveToThread(simulationThread);
+	simulationThread->start();
 
 	masses = std::vector<double>(MaxSegments);
 	lengths = std::vector<double>(MaxSegments);
@@ -291,7 +297,7 @@ QWidget * MainWindow::buildAddUI() {
 	removeBtn->setStyleSheet("background-color: #ffaaaa");
 
 	connect(addBtn, &QPushButton::clicked, this, &MainWindow::add);
-	connect(removeBtn, &QPushButton::clicked, this, &MainWindow::remove);
+	connect(removeBtn, &QPushButton::clicked, simulation, &Simulation::clearPendula);
 
 	btnLyt->addWidget(addBtn);
 	btnLyt->addWidget(removeBtn);
@@ -420,10 +426,6 @@ void MainWindow::add() {
 	}
 }
 
-void MainWindow::remove() {
-	simulation->clearPendula();
-}
-
 void MainWindow::resetSimulationControl() {
 	gravitySlider->setValue(981);
 	timescaleSlider->setValue(100);
@@ -433,3 +435,9 @@ void MainWindow::resetSimulationControl() {
 void MainWindow::toggleSimulation() {
 	simulation->isPlaying = !simulation->isPlaying;
 }
+
+void MainWindow::closeEvent(QCloseEvent *e) {
+	simulationThread->quit();
+	simulationThread->wait();
+	e->accept();
+}

src/MainWindow.h

@@ -11,11 +11,14 @@ enum Property {Angle, Mass, Length};
 class MainWindow : public QWidget {
 public:
 	explicit MainWindow();
+protected:
+	void closeEvent(QCloseEvent*) override;
 private:
 	void buildUI();
 	QWidget * buildAddUI();
 	QWidget * buildSimulationUI();
 	Simulation * simulation;
+	QThread * simulationThread;
 
 	GLWidget * glWidget = nullptr;
 
@@ -42,7 +45,6 @@ public slots:
 	void resetLengths();
 	void normalizeLengths();
 	void add();
-	void remove();
 
 	void resetSimulationControl();
 	void toggleSimulation();

src/Simulation.cpp

@@ -2,12 +2,16 @@
 #include "Pendulum.h"
 #include <QPainter>
 #include <QTimer>
+#include <QThread>
+#include <omp.h>
+#include <iostream>
 
 Simulation::Simulation() {
 	timer = new QTimer(this);
 	QTimer::connect(timer, &QTimer::timeout, this, &Simulation::update);
 	timer->setInterval(updateInterval);
 	timer->start();
+	lastUpdate = high_resolution_clock::now();
 };
 
 void Simulation::draw(QPainter *p, int screenSize) const {
@@ -18,6 +22,11 @@ void Simulation::draw(QPainter *p, int screenSize) const {
 }
 
 void Simulation::update() {
+	auto thisUpdate = high_resolution_clock::now();
+	auto ms = (int)duration_cast<milliseconds>(thisUpdate - lastUpdate).count();
+	// std::cout << ms << std::endl;
+	lastUpdate = thisUpdate;
+
 	if (!isPlaying)
 		return;
 
@@ -25,8 +34,9 @@ void Simulation::update() {
 
 	h /= substeps;
 
-	for (int i = 0; i < substeps; i++)
-		for (const auto pendulum : pendula)
+	#pragma omp parallel for
+	for (const auto pendulum : pendula)
+		for (int i = 0; i < substeps; i++)
 			pendulum->update(h, gravity);
 }
 
@@ -35,3 +45,4 @@ void Simulation::clearPendula() {
 		delete p;
 	pendula.clear();
 }
+

src/Simulation.h

@@ -1,6 +1,9 @@
 #include <vector>
 #include <cstdint>
 #include <QObject>
+#include <chrono>
+
+using namespace std::chrono;
 
 class Pendulum;
 class QPainter;
@@ -12,20 +15,23 @@ public:
 
 	double size = 50;
 
-	double gravity;
-	double timescale;
-	int substeps;
+	double gravity {};
+	double timescale {};
+	int substeps {};
 
 	int updateInterval = 17;
 
 	bool isPlaying = false;
 
 	std::vector<Pendulum *> pendula;
-	void clearPendula();
 
 	QTimer * timer;
 
 	void draw(QPainter*, int) const;
+public slots:
+	void clearPendula();
 private slots:
 	void update();
+private:
+	time_point<system_clock> lastUpdate;
 };

src/main.cpp

@@ -1,6 +1,11 @@
 #include <QApplication>
 #include <QSurfaceFormat>
 #include "MainWindow.h"
+#include <omp.h>
+#include <chrono>
+#include <iostream>
+
+using namespace std::chrono;
 
 int main(int argc, char* argv[]) {
 	QApplication app(argc, argv);
@@ -12,5 +17,29 @@ int main(int argc, char* argv[]) {
 	MainWindow w;
 	w.show();
 
+	for (int threads = 1; threads <= 16; threads++){
+		int num_steps = 100'000;
+		double step = 1.0 / double(num_steps);
+
+		omp_set_num_threads(threads);
+		double pi = 0;
+		auto t = high_resolution_clock ::now();
+		#pragma omp parallel
+		{
+			int numThreads = omp_get_num_threads();
+			int threadId = omp_get_thread_num();
+			int i;
+			double localSum = 0;
+			for (i = threadId; i < num_steps; i += numThreads){
+				double x = (i + 0.5) * step;
+				localSum += 4.0 / (1.0 + x * x);
+			}
+			#pragma omp atomic
+			pi += localSum * step;
+		}
+		std::cout << threads << " " << duration_cast<microseconds>(high_resolution_clock::now() - t).count() << " ";
+		std::cout << pi << std::endl;
+	}
+
 	return QApplication::exec();
 }