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4th_order_system_poisson.cpp
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4th_order_system_poisson.cpp
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#include <iostream>
#include <fstream>
#include <vector>
#include <string>
using namespace std;
#include <boost/numeric/ublas/matrix.hpp>
#include <boost/numeric/ublas/io.hpp>
#include <mpreal.h>
using namespace mpfr;
#include <sys/time.h>
typedef boost::numeric::ublas::matrix<mpreal> matrix;
typedef boost::numeric::ublas::vector<mpreal> vector_col;
typedef boost::numeric::ublas::matrix<double> matrix_double;
// Точность по степенному ряду
#define eps_pw "1e-20"
// Количество бит под мантиссу вещественного числа
#define b_m 128
// Шаг по времени для отслеживания устойчивости по Пуассону
#define Delta_tau 1e-7
int m;
matrix A;
vector<matrix> Q;
double mu, sum_nA_2mu, sum_nA_mu;
// Функция возвращает длину отрезка сходимости степенного ряда
mpreal get_delta_t(const vector_col &Upsilon0)
{
mpreal h1 = boost::numeric::ublas::norm_1(Upsilon0);
mpreal h2 = h1 > 1 ? mu * h1 * h1 + sum_nA_2mu * h1 : sum_nA_mu;
return 1 / (h2 + "1e-10");
}
// Функция вычисления значений фазовых координат в конечный момент времени
// T - длина отрезка интегрирования;
// way - направление поиска решений: 1 - вперед по времени, -1 - назад по времени
void calc(vector_col &X, const mpreal &T, int way = 1)
{
mpreal t = 0, delta_t, L, pr;
bool fl_rp;
vector_col Psi(m);
do
{
delta_t = get_delta_t(X);
t += delta_t;
if(t < T)
fl_rp = true;
else if(t > T)
{
delta_t -= t-T;
fl_rp = false;
}
else
fl_rp = false;
vector<vector_col> Upsilon;
Upsilon.push_back(X);
L = boost::numeric::ublas::norm_1(X);
int i = 0;
pr = way * delta_t;
while(L > eps_pw)
{
// Вычисляем новые коэффициенты степенного ряда
mpreal sum_prod;
for(int p = 0; p < m; p++)
{
sum_prod = 0;
for(int j = 0; j <= i; j++)
{
vector_col prod_matrix_vector = prod(Q[p], Upsilon[j]);
sum_prod += inner_prod(prod_matrix_vector, Upsilon[i - j]);
}
Psi(p) = sum_prod;
}
Upsilon.push_back((prod(A, Upsilon[i]) + Psi) / (i + 1));
i++;
X += Upsilon[i] * pr;
L = fabs(pr) * boost::numeric::ublas::norm_1(Upsilon[i]);
pr *= way * delta_t;
}
}
while(fl_rp);
}
inline mpreal dist(vector_col &X, vector_col &X0)
{
return boost::numeric::ublas::norm_2(X - X0);
}
unsigned long GetTickCount()
{
timeval tv;
gettimeofday(&tv, NULL);
return tv.tv_sec * 1000 + tv.tv_usec / 1000;
}
int main()
{
mpreal::set_default_prec(b_m);
cout << "Машинный эпсилон = " << machine_epsilon() << endl;
mpreal T;
cout << "\nВведите длину отрезка времени > ";
cin >> T;
ifstream f_ini_val("initial_vals.txt");
if(!f_ini_val)
throw "Input File initial_vals.txt is not opened\n";
f_ini_val >> m;
vector_col X(m);
string s;
for(int p = 0; p < m; p++)
{
f_ini_val >> s;
X(p) = s;
}
f_ini_val.close();
ifstream matrix_A("A.txt");
if(!matrix_A)
throw "Input File A.txt is not opened\n";
matrix_double A_double;
matrix_A >> A_double;
matrix_A.close();
A = A_double;
ifstream matrices_Q("Q.txt");
if(!matrices_Q)
throw "Input File Q.txt is not opened\n";
double maxnormQ, normQ;
for(int p = 0; p < m; p++)
{
matrix_double Qp;
matrices_Q >> Qp;
Q.push_back(Qp);
if(!p)
maxnormQ = boost::numeric::ublas::norm_1(Qp);
else
{
normQ = norm_1(Qp);
if(normQ > maxnormQ)
maxnormQ = normQ;
}
}
double nA = boost::numeric::ublas::norm_1(A_double);
mu = m * maxnormQ;
sum_nA_mu = nA + mu;
sum_nA_2mu = sum_nA_mu + mu;
mpreal t = 3 * Delta_tau;
vector_col X0 = X;
calc(X, Delta_tau);
vector_col X1 = X;
calc(X, Delta_tau);
vector_col X2 = X;
calc(X, Delta_tau);
vector_col X3 = X;
unsigned long t1 = GetTickCount();
mpreal eps1 = dist(X1, X0), eps2 = dist(X2, X0), eps3 = dist(X3, X0);
ofstream points("points.txt");
while(t <= T)
{
if(eps1 > eps2 && eps2 < eps3 && eps2 < 1)
{
points << "t = " << t - Delta_tau << endl;
points << "eps = " << eps2 << endl;
points << "X(t) = " << X2 << endl << endl;
cout << "t = " << t - Delta_tau << endl;
cout << "eps = " << eps2 << endl;
cout << "X(t) = " << X2 << endl << endl;
}
X1 = X2;
eps1 = eps2;
X2 = X3;
eps2 = eps3;
calc(X3, Delta_tau);
eps3 = dist(X3, X0);
t += Delta_tau;
}
cout << "\nTime = " << (GetTickCount() - t1) / 60000.0 << " min.\n\n";
points << "Time = " << (GetTickCount() - t1) / 60000.0 << " min.\n\n";
points.close();
return 0;
}