From 2d1ab8c60e43f3e10eb8bd52d62d83734a242e6d Mon Sep 17 00:00:00 2001
From: "armindamon.riess" <armindamon.riess@uzh.ch>
Date: Wed, 7 Dec 2022 12:44:10 +0100
Subject: [PATCH] leapfrog integration done
---
lib/nBodySim.cpp | 14 +++++++++-----
lib/nBodySim.hpp | 4 +++-
2 files changed, 12 insertions(+), 6 deletions(-)
diff --git a/lib/nBodySim.cpp b/lib/nBodySim.cpp
index 181ca15..c47a32f 100644
--- a/lib/nBodySim.cpp
+++ b/lib/nBodySim.cpp
@@ -62,7 +62,9 @@ nBodySim::~nBodySim() {
void nBodySim::runSimulation(double dt, unsigned nSteps) {
for (unsigned i=0; i < nSteps; ++i) {
+ treeCalculateForces();
doTimeStep(dt);
+ updateTree();
}
}
@@ -157,18 +159,20 @@ double nBodySim::calculateMeanForceMagnitude() {
}
void nBodySim::doTimeStep(double dt) {
+ // update velocities, then positions
#pragma omp parallel for
for (unsigned i=0; i < nParticles_; ++i) {
for (unsigned j=0; j < 3; ++j) {
- // TODO
- tree_->kick(dt/2);
- tree_->drift(dt);
- tree_->update();
- tree_->kick(dt/2);
+ velocities_[3*i+j] += 0.5 * forces_[3*i+j] * dt / masses_[i];
+ positions_[3*i+j] += velocities_[3*i+j] * dt;
}
}
}
+void nBodySim::updateTree() {
+ tree_->update();
+}
+
void nBodySim::write2file(const double* array, std::string filename, unsigned dim) const {
// writes array to file, with N rows and dim columns
std::ofstream file(filename);
diff --git a/lib/nBodySim.hpp b/lib/nBodySim.hpp
index cd9fbc8..380bce4 100644
--- a/lib/nBodySim.hpp
+++ b/lib/nBodySim.hpp
@@ -20,8 +20,10 @@ public:
double calculateMeanInterparticleDistance();
// loop over all force vectors and calculate mean force magnitude
double calculateMeanForceMagnitude();
- // updates positions and velocities using the calculated forces
+ // integrate using leapfrog algorithm. doesn't update forces, doesn't update tree
void doTimeStep(double dt);
+ // update tree
+ void updateTree();
// writes data to file, every row is a particle
void write2file(const double* array, std::string filename, unsigned dim) const;
// write current state of simulation to file
--
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