From 843b0fd61b1e31ddb683a8bdd344f28caa46f662 Mon Sep 17 00:00:00 2001
From: Pierce_qiang <2579404335@qq.com>
Date: Mon, 10 Jan 2022 21:27:20 +0800
Subject: [PATCH 1/2] Done!

---
 CMakeLists.txt |   1 +
 main.cpp       | 110 +++++++++++++++++++++++++++++++++----------------
 2 files changed, 75 insertions(+), 36 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 29b152c..030e791 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -7,3 +7,4 @@ if (NOT CMAKE_BUILD_TYPE)
 endif()
 
 add_executable(main main.cpp)
+target_compile_options(main PUBLIC --fast-math -march=native -O3)
\ No newline at end of file
diff --git a/main.cpp b/main.cpp
index cf6369b..df4fbbc 100644
--- a/main.cpp
+++ b/main.cpp
@@ -3,64 +3,102 @@
 #include <vector>
 #include <chrono>
 #include <cmath>
-
+#include <array>
 float frand() {
     return (float)rand() / RAND_MAX * 2 - 1;
 }
-
+const size_t num = 48;
 struct Star {
-    float px, py, pz;
-    float vx, vy, vz;
-    float mass;
+    float px[num], py[num], pz[num];
+    float vx[num], vy[num], vz[num];
+    float mass[num];
 };
 
-std::vector<Star> stars;
+Star stars;
 
 void init() {
-    for (int i = 0; i < 48; i++) {
-        stars.push_back({
-            frand(), frand(), frand(),
-            frand(), frand(), frand(),
-            frand() + 1,
-        });
+    for (int i = 0; i < num; i++) {
+        stars.px[i] = frand();
+        stars.py[i] = frand();
+        stars.pz[i] = frand();
+        stars.vx[i] = frand();
+        stars.vy[i] = frand();
+        stars.vz[i] = frand();
+        stars.mass[i] = frand()+1;
+        // stars[i] = {
+        //     frand(), frand(), frand(),
+        //     frand(), frand(), frand(),
+        //     frand() + 1,
+        // };
     }
 }
 
 float G = 0.001;
 float eps = 0.001;
 float dt = 0.01;
-
+float eps2 = eps * eps;
 void step() {
-    for (auto &star: stars) {
-        for (auto &other: stars) {
-            float dx = other.px - star.px;
-            float dy = other.py - star.py;
-            float dz = other.pz - star.pz;
-            float d2 = dx * dx + dy * dy + dz * dz + eps * eps;
-            d2 *= sqrt(d2);
-            star.vx += dx * other.mass * G * dt / d2;
-            star.vy += dy * other.mass * G * dt / d2;
-            star.vz += dz * other.mass * G * dt / d2;
+    float G_dt = G*dt;
+    // for (auto &star: stars) {
+    //     for (auto &other: stars) {
+    //         float dx = other.px - star.px;
+    //         float dy = other.py - star.py;
+    //         float dz = other.pz - star.pz;
+    //         float d2 = dx * dx + dy * dy + dz * dz + eps2;
+    //         d2 *= std::sqrt(d2);
+    //         float inv_d2 = 1.0f/d2;
+    //         star.vx += dx * other.mass * G_dt * inv_d2;
+    //         star.vy += dy * other.mass * G_dt * inv_d2;
+    //         star.vz += dz * other.mass * G_dt * inv_d2;
+    //     }
+    // }
+    for (size_t i = 0;i<num;i++) {
+        for (size_t j =0;j<num;j++) {
+            float dx = stars.px[j] - stars.px[i];
+            float dy = stars.py[j] - stars.py[i];
+            float dz = stars.pz[j] - stars.pz[i];
+            float d2 = dx * dx + dy * dy + dz * dz + eps2;
+            d2 *= std::sqrt(d2);
+            float inv_d2 = 1.0f/d2;
+            stars.vx[i] += dx * stars.mass[j] * G_dt * inv_d2;
+            stars.vy[i] += dy * stars.mass[j] * G_dt * inv_d2;
+            stars.vz[i] += dz * stars.mass[j] * G_dt * inv_d2;
         }
     }
-    for (auto &star: stars) {
-        star.px += star.vx * dt;
-        star.py += star.vy * dt;
-        star.pz += star.vz * dt;
+    // for (auto &star: stars) {
+    //     star.px += star.vx * dt;
+    //     star.py += star.vy * dt;
+    //     star.pz += star.vz * dt;
+    // }
+    for (size_t i = 0;i<num;i++) {
+        stars.px[i] += stars.vx[i] * dt;
+        stars.py[i] += stars.vy[i] * dt;
+        stars.pz[i] += stars.vz[i] * dt;
     }
 }
 
 float calc() {
     float energy = 0;
-    for (auto &star: stars) {
-        float v2 = star.vx * star.vx + star.vy * star.vy + star.vz * star.vz;
-        energy += star.mass * v2 / 2;
-        for (auto &other: stars) {
-            float dx = other.px - star.px;
-            float dy = other.py - star.py;
-            float dz = other.pz - star.pz;
-            float d2 = dx * dx + dy * dy + dz * dz + eps * eps;
-            energy -= other.mass * star.mass * G / sqrt(d2) / 2;
+    // for (auto &star: stars) {
+    //     float v2 = star.vx * star.vx + star.vy * star.vy + star.vz * star.vz;
+    //     energy += star.mass * v2 * 0.5;
+    //     for (auto &other: stars) {
+    //         float dx = other.px - star.px;
+    //         float dy = other.py - star.py;
+    //         float dz = other.pz - star.pz;
+    //         float d2 = dx * dx + dy * dy + dz * dz + eps;
+    //         energy -= other.mass * star.mass * G / std::sqrt(d2) * 0.5;
+    //     }
+    // }
+    for (size_t i = 0;i<num;i++) {
+        float v2 = stars.vx[i] * stars.vx[i] + stars.vy[i] * stars.vy[i] + stars.vz[i] * stars.vz[i];
+        energy += stars.mass[i] * v2 * 0.5;
+        for (size_t j =0;j<num;j++) {
+            float dx = stars.px[j] - stars.px[i];
+            float dy = stars.py[j] - stars.py[i];
+            float dz = stars.pz[j] - stars.pz[i];
+            float d2 = dx * dx + dy * dy + dz * dz + eps2;
+            energy -= stars.mass[j] * stars.mass[i] * G / std::sqrt(d2) * 0.5;
         }
     }
     return energy;

From 5d6c22f4a5175cf5da47670de01c25c9cfe51614 Mon Sep 17 00:00:00 2001
From: Pierce_qiang <2579404335@qq.com>
Date: Mon, 10 Jan 2022 21:39:38 +0800
Subject: [PATCH 2/2] done!

---
 main.cpp | 34 ----------------------------------
 1 file changed, 34 deletions(-)

diff --git a/main.cpp b/main.cpp
index df4fbbc..d028124 100644
--- a/main.cpp
+++ b/main.cpp
@@ -25,11 +25,6 @@ void init() {
         stars.vy[i] = frand();
         stars.vz[i] = frand();
         stars.mass[i] = frand()+1;
-        // stars[i] = {
-        //     frand(), frand(), frand(),
-        //     frand(), frand(), frand(),
-        //     frand() + 1,
-        // };
     }
 }
 
@@ -39,19 +34,6 @@ float dt = 0.01;
 float eps2 = eps * eps;
 void step() {
     float G_dt = G*dt;
-    // for (auto &star: stars) {
-    //     for (auto &other: stars) {
-    //         float dx = other.px - star.px;
-    //         float dy = other.py - star.py;
-    //         float dz = other.pz - star.pz;
-    //         float d2 = dx * dx + dy * dy + dz * dz + eps2;
-    //         d2 *= std::sqrt(d2);
-    //         float inv_d2 = 1.0f/d2;
-    //         star.vx += dx * other.mass * G_dt * inv_d2;
-    //         star.vy += dy * other.mass * G_dt * inv_d2;
-    //         star.vz += dz * other.mass * G_dt * inv_d2;
-    //     }
-    // }
     for (size_t i = 0;i<num;i++) {
         for (size_t j =0;j<num;j++) {
             float dx = stars.px[j] - stars.px[i];
@@ -65,11 +47,6 @@ void step() {
             stars.vz[i] += dz * stars.mass[j] * G_dt * inv_d2;
         }
     }
-    // for (auto &star: stars) {
-    //     star.px += star.vx * dt;
-    //     star.py += star.vy * dt;
-    //     star.pz += star.vz * dt;
-    // }
     for (size_t i = 0;i<num;i++) {
         stars.px[i] += stars.vx[i] * dt;
         stars.py[i] += stars.vy[i] * dt;
@@ -79,17 +56,6 @@ void step() {
 
 float calc() {
     float energy = 0;
-    // for (auto &star: stars) {
-    //     float v2 = star.vx * star.vx + star.vy * star.vy + star.vz * star.vz;
-    //     energy += star.mass * v2 * 0.5;
-    //     for (auto &other: stars) {
-    //         float dx = other.px - star.px;
-    //         float dy = other.py - star.py;
-    //         float dz = other.pz - star.pz;
-    //         float d2 = dx * dx + dy * dy + dz * dz + eps;
-    //         energy -= other.mass * star.mass * G / std::sqrt(d2) * 0.5;
-    //     }
-    // }
     for (size_t i = 0;i<num;i++) {
         float v2 = stars.vx[i] * stars.vx[i] + stars.vy[i] * stars.vy[i] + stars.vz[i] * stars.vz[i];
         energy += stars.mass[i] * v2 * 0.5;