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Now integrate() can return the full trajectory and plotted in the Python; improved readablity

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This commit is contained in:
Yohai Meiron 2020-04-12 21:37:03 -04:00
parent a2219af116
commit a624814a0c
5 changed files with 144 additions and 106 deletions
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80
main.cpp
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@ -1,12 +1,16 @@
#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <fstream>
#include <numeric>
#include <gsl/gsl_errno.h>
#include <gsl/gsl_math.h>
#include <gsl/gsl_odeiv2.h>
#include <gsl/gsl_spline.h>
#include <iostream>
#include <numeric>
#include <string>
#include <stdexcept>
#include <vector>
#include "loadtxt.h"
extern "C" const int gsl_success() { return GSL_SUCCESS; } // It's zero, but just for clarity sake.
@ -22,6 +26,7 @@ public:
spline = gsl_spline_alloc(gsl_interp_cspline, x.size());
gsl_spline_init(spline, x.data(), y.data(), x.size());
}
Interp() {}
inline double operator()(double x) const
{
return gsl_spline_eval(spline, x, acc);
@ -54,32 +59,20 @@ class Galaxy {
public:
Galaxy(std::string file_name)
{
std::vector<double> t_data, M_halo_data, b_halo_data;
std::ifstream file(file_name);
std::string line;
while (std::getline(file, line)) {
auto pos = line.find('#');
if (pos != std::string::npos) line = line.substr(0, pos);
pos = line.find_first_not_of(" \t");
if (pos == std::string::npos) continue;
double data[3];
sscanf(line.c_str(), "%*s %lf %lf %lf", &data[0], &data[1], &data[2]);
t_data.push_back(data[0]);
M_halo_data.push_back(data[1]);
b_halo_data.push_back(data[2]); // note, this is not half-mass radius
}
interp_M_halo = new Interp(t_data, M_halo_data);
interp_b_halo = new Interp(t_data, b_halo_data);
auto data = Loadtxt("file.dat", {1, 2, 3}).get_cols();
auto& t_data = data[0];
auto& halo_m_data = data[1];
auto& halo_b_data = data[2];
std::transform(t_data.begin(), t_data.end(), t_data.begin(), [](const double& x){ return x-2.145; });
std::transform(halo_b_data.begin(), halo_b_data.end(), halo_b_data.begin(), [](const double& x){ return x*0.7664209365408798; });
interp_halo_m = Interp(t_data, halo_m_data);
interp_halo_b = Interp(t_data, halo_b_data);
}
int func(double t, const double y[], double f[], void *params)
{
double M_halo = (*interp_M_halo)(t);
double b_halo = (*interp_b_halo)(t);
/*printf("xxxxxxxxx %e, %e msun\n", t, M_halo);
printf("xxxxxxxxx %e, %e kpc\n", t, b_halo);
exit(0);*/
Plummer plummer(M_halo, b_halo);
double halo_m = interp_halo_m(t);
double halo_b = interp_halo_b(t);
Plummer plummer(halo_m, halo_b);
f[0] = y[3]; // vx -> x'
f[1] = y[4]; // vy -> y'
f[2] = y[5]; // vz -> z'
@ -88,27 +81,25 @@ public:
}
private:
Interp *interp_M_halo;
Interp *interp_b_halo;
Interp interp_halo_m;
Interp interp_halo_b;
} galaxy("file.dat");
// Not very nice to have it as a global variable but GSL will have problem otherwise.
int jac(double t, const double y[], double *dfdy, double dfdt[], void *params)
{
return GSL_SUCCESS;
}
int jac(double t, const double y[], double *dfdy, double dfdt[], void *params) { return GSL_SUCCESS; }
int func(double t, const double y[], double f[], void *params)
inline int func(double t, const double y[], double f[], void *params)
{
return galaxy.func(t, y, f, params);
}
extern "C"
int integrate(const double y0[], const double t_max, double y[])
int integrate(const double y0[], const double t_max, const double step_size, double y[])
{
double t = 2.145;
double t = 0;
constexpr double h = 1./4096.;
if (step_size/h - (int)(step_size/h) != 0) throw std::runtime_error("step_size must be a multiple of h");
constexpr double epsabs = 1e-7;
constexpr double epsrel = 0;
const gsl_odeiv2_step_type *T = gsl_odeiv2_step_rk8pd;
@ -118,12 +109,23 @@ int integrate(const double y0[], const double t_max, double y[])
gsl_odeiv2_system sys = {func, jac, 6, nullptr};
gsl_odeiv2_driver *d = gsl_odeiv2_driver_alloc_y_new(&sys, T, h, epsabs, epsrel);
int step = 0;
const int step_max = t_max / step_size;
std::copy(y0, y0+6, y);
int status = gsl_odeiv2_driver_apply(d, &t, t_max, y);
return status;
for (int step=0; step<step_max; step++) {
std::copy(y+step*6, y+(step+1)*6, y+(step+1)*6);
int status = gsl_odeiv2_driver_apply(d, &t, (step+1)*step_size, y+(step+1)*6);
if (status != GSL_SUCCESS) return status;
}
return GSL_SUCCESS;
}
int main()
{
std::cout << "bye" << std::endl;
double y[12];
double y0[] = {80,0,0,0,80,0};
for (int i=0; i<30000; i++)
integrate(y0, 10, 10, y);
return 0;
}