use std::list for local particle indices

lib/node.cpp

@@ -48,7 +48,7 @@ void Node::update(List localParticles, unsigned nLocalParticles) {
     // for each local particle, determine which octant it is in
     // get the mass in this node while we're at it
     for (unsigned i=0; i<8; ++i) {
-        childParticles_[i] = List{};
+        childParticles_[i] = {};
     }
     for (unsigned i : localParticles) {
         childParticles_[getOctant(i)].push_back(i);
@@ -169,7 +169,7 @@ Vector Node::multipole(Vector y, double ynorm) const {
             double qij = 0;
             // go through every local particle
             for (unsigned c=0; c<8; ++c) {
-                for (auto k : childParticles_[c]) {
+                for (unsigned k : childParticles_[c]) {
                     // calculate using the formula from page 17 of the pdf for lecture 7
                     qij += 3*(centerOfMass_[i] - positions_[3*k+i])*(centerOfMass_[j] - positions_[3*k+j]);
                     if (i!=j) continue;

lib/node.hpp

@@ -2,11 +2,12 @@
 #define NODE_HPP
 
 #include <vector>
+#include <list>
 #include <fstream>
 
 using Vector = std::vector<double>;
 using Matrix = std::vector<Vector>;
-using List = std::vector<unsigned>;
+using List = std::list<unsigned>;
 
 class Node {
 public:

lib/tree.cpp

@@ -14,8 +14,8 @@ Tree::Tree(double mass, double* positions, double* forces, double softening, uns
     center_ = Vector(3);
     for (unsigned i=0; i < 3; ++i) center_[i] = center[i];
 
-    allParticles_ = List(nParticles_);
-    for (unsigned i=0; i < nParticles_; ++i) allParticles_[i] = i;
+    allParticles_ = {};
+    for (unsigned i=0; i < nParticles_; ++i) allParticles_.push_back(i);
 
     root_ = new Node(mass_, positions_, nParticles_, softening_, 0, size_, center_, allParticles_, nParticles_);
 }