From 98ee5fd73db580a2d2906de366fd8677420b465d Mon Sep 17 00:00:00 2001
From: Sara Gerretsen <sara.gerretsen@student.hku.nl>
Date: Mon, 22 Sep 2025 23:13:19 +0200
Subject: [PATCH] feat: fixed incorrect behaviour on simulation and added
 benchmarking code

---
 src/simulation.cpp | 96 ++++++++++++++++++++++++++++++++++++----------
 1 file changed, 75 insertions(+), 21 deletions(-)

diff --git a/src/simulation.cpp b/src/simulation.cpp
index b324acb..a5efad8 100644
--- a/src/simulation.cpp
+++ b/src/simulation.cpp
@@ -1,4 +1,5 @@
 #include "simulation.h"
+#include "SDL3/SDL_timer.h"
 #include "input.h"
 #include "thread_pool.h"
 #include <SDL3/SDL_log.h>
@@ -77,10 +78,15 @@ static size_t CountNeighbors(Cell const &cell) {
 
 static std::mutex underpopulatedMutex, overpopulatedMutex, bornMutex;
 
-static void FindOverpopulated() {
+static void FindOverpopulated(size_t segment, size_t length) {
 	overpopulatedMutex.lock();
-	overpopulated.clear();
-	std::ranges::copy_if(living, std::back_inserter(overpopulated),
+	std::set<Cell>::iterator begin{ living.begin() };
+	std::set<Cell>::iterator end{ living.begin() };
+
+	std::advance(begin, segment * length);
+	std::advance(end, segment * length + length);
+
+	std::copy_if(begin, end, std::back_inserter(overpopulated),
 	[&](Cell const &c) -> bool {
 		size_t const neighbors{ CountNeighbors(c) };
 		return neighbors > 3;
@@ -88,10 +94,16 @@ static void FindOverpopulated() {
 	overpopulatedMutex.unlock();
 }
 
-static void FindUnderpopulated() {
+static void FindUnderpopulated(size_t segment, size_t length) {
+	uint64_t ns{ SDL_GetTicksNS() };
 	underpopulatedMutex.lock();
-	underpopulated.clear();
-	std::ranges::copy_if(living, std::back_inserter(underpopulated),
+	std::set<Cell>::iterator begin{ living.begin() };
+	std::set<Cell>::iterator end{ living.begin() };
+
+	std::advance(begin, segment * length);
+	std::advance(end, segment * length + length);
+
+	std::copy_if(begin, end, std::back_inserter(underpopulated),
 	[&](Cell const &c) -> bool {
 		size_t const neighbors{ CountNeighbors(c) };
 		return neighbors < 2;
@@ -99,11 +111,17 @@ static void FindUnderpopulated() {
 	underpopulatedMutex.unlock();
 }
 
-static void FindBorn() {
+static void FindBorn(size_t segment, size_t length) {
+	uint64_t ns{ SDL_GetTicksNS() };
 	bornMutex.lock();
-	born.clear();
-	for (Cell const &cell : living) {
-		std::vector<Cell> neighbors{ NeighborSet(cell) };
+	std::set<Cell>::iterator itr{ living.begin() };
+	std::set<Cell>::iterator end{ living.begin() };
+
+	std::advance(itr, segment * length);
+	std::advance(end, segment * length + length);
+
+	for (;itr != end; ++itr) {
+		std::vector<Cell> neighbors{ NeighborSet(*itr) };
 		std::ranges::copy_if(neighbors, std::back_inserter(born),
 		[&](Cell const &c) -> bool {
 			size_t const neighbors{ CountNeighbors(c) };
@@ -113,20 +131,43 @@ static void FindBorn() {
 	bornMutex.unlock();
 }
 
+#define MULTITHREADING 0
+static uint64_t generationTime{ 0 };
+static bool logGenerationTime{ false };
+
 static void PopulateChanges() {
-#if 1
-	threading::tasks.ScheduleTask(&FindOverpopulated);
-	threading::tasks.ScheduleTask(&FindUnderpopulated);
-	threading::tasks.ScheduleTask(&FindBorn);
+	generationTime = SDL_GetTicksNS();
+	logGenerationTime = true;
+#if MULTITHREADING
+	constexpr size_t split{ 2 };
+	size_t const seg_length{ living.size() / split };
+	for (size_t i{ 0 }; i < split; ++i) {
+		threading::tasks.ScheduleTask(std::bind(FindOverpopulated, i, seg_length));
+		threading::tasks.ScheduleTask(std::bind(FindUnderpopulated, i, seg_length));
+		threading::tasks.ScheduleTask(std::bind(FindBorn, i, seg_length));
+	}
 #else
-	FindOverpopulated();
-	FindUnderpopulated();
-	FindBorn();
+	FindOverpopulated(0, living.size());
+	FindUnderpopulated(0, living.size());
+	FindBorn(0, living.size());
 #endif
 }
 
 void InitializeRandom(size_t livingChance, int64_t fillArea) {
+	underpopulatedMutex.lock();
+	underpopulated.clear();
+	underpopulatedMutex.unlock();
+
+	overpopulatedMutex.lock();
+	overpopulated.clear();
+	overpopulatedMutex.unlock();
+
+	bornMutex.lock();
+	born.clear();
+	bornMutex.unlock();
+
 	living.clear();
+
 	Cell itr{ 0, 0 };
 	while (itr.y < fillArea) {
 		if (std::rand() % livingChance == 0	) {
@@ -143,20 +184,28 @@ void InitializeRandom(size_t livingChance, int64_t fillArea) {
 
 void Step() {
 	underpopulatedMutex.lock();
+	overpopulatedMutex.lock();
+	bornMutex.lock();
+
 	for (Cell const &cell : underpopulated) {
 		living.erase(cell);
 	}
-	underpopulatedMutex.unlock();
-	overpopulatedMutex.lock();
+	underpopulated.clear();
+
 	for (Cell const &cell : overpopulated) {
 		living.erase(cell);
 	}
-	overpopulatedMutex.unlock();
-	bornMutex.lock();
+	overpopulated.clear();
+
 	for (Cell const &cell : born) {
 		living.insert(cell);
 	}
+	born.clear();
+
+	underpopulatedMutex.unlock();
+	overpopulatedMutex.unlock();
 	bornMutex.unlock();
+
 	PopulateChanges();
 }
 
@@ -207,6 +256,11 @@ void Draw(SDL_Renderer *renderer, double cellSizePercent) {
 		SDL_RenderRect(renderer, &cellRect);
 	}
 	bornMutex.unlock();
+
+	if (logGenerationTime) {
+		SDL_Log("End Generation %lf", double(SDL_GetTicksNS() - generationTime) * 0.0000000001);
+		logGenerationTime = false;
+	}
 }
 
 void SetSimulationHovered(bool value) {