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Code Issues Releases Wiki Activity

nisot:: parallel_transport now also uses RK4

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Zeno Rogue
2020-04-11 15:28:22 +02:00
parent e4a8b73819
commit 825a8aba82
1 changed files with 25 additions and 5 deletions
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30
nonisotropic.cpp
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@@ -1987,7 +1987,6 @@ EX namespace nisot {
} }
EX int rk_steps = 20; EX int rk_steps = 20;
EX int pt_steps = 100;
EX hyperpoint numerical_exp(hyperpoint v) { EX hyperpoint numerical_exp(hyperpoint v) {
hyperpoint at = point31(0, 0, 0); hyperpoint at = point31(0, 0, 0);
@@ -2014,13 +2013,34 @@ EX namespace nisot {
} }
else h = Pos * h; else h = Pos * h;
int steps = 100; int steps = rk_steps;
h /= steps; h /= steps;
auto& at = tPos[3];
auto& vel = h;
for(int i=0; i<steps; i++) { for(int i=0; i<steps; i++) {
for(int j=0; j<3; j++) auto acc1 = get_acceleration(at, vel);
tPos[j] += christoffel(tPos[3], h, tPos[j]); auto at1 = at + vel/2; auto vel1 = vel + acc1/2;
geodesic_step(tPos[3], h); auto acc2 = get_acceleration(at1, vel1);
auto at2 = at1 + acc1/4; auto vel2 = vel + acc2/2;
auto acc3 = get_acceleration(at2, vel2);
auto at3 = at + vel + acc2/2; auto vel3 = vel + acc3;
auto acc4 = get_acceleration(at3, vel3);
for(int j=0; j<3; j++) {
auto& tra = tPos[j];
auto tacc1 = christoffel(at, vel, tra);
auto tacc2 = christoffel(at1, vel1, tra + tacc1/2);
auto tacc3 = christoffel(at2, vel2, tra + tacc2/2);
auto tacc4 = christoffel(at3, vel3, tra + tacc3);
tra += (tacc1+tacc2*2+tacc3*2+tacc4) / 6;
}
at += vel + (acc1+acc2+acc3)/6;
vel += (acc1+2*acc2+2*acc3+acc4)/6;
} }
if(sl2) { if(sl2) {