lorenz.cc
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////////////////////////////////////////////////////////////////////////////
// Model lorenz.cc SIMLIB/C++
//
// Lorenz equation:
//
// dx1/dt = sigma * (x2 - x1)
// dx2/dt = (1 + lambda - x3) * x1 - x2
// dx3/dt = x1 * x2 - b * x3
//
// where: sigma=10, lambda=24 and b=2 are parameters
// initial conditions: xi(0) = 1.0
//
// Source: SimPack
//
#include "simlib.h"
#include <stdlib.h> // atoi()
const double StepPrn = 0.01; // output period
struct Lorenz {
Integrator x1, x2, x3;
Lorenz(double sigma, double lambda, double b) :
x1(sigma*(x2 - x1), 1), // dx1/dt = sigma * (x2 - x1)
x2((1 + lambda - x3)*x1 - x2, 1), // dx2/dt = (1 + lambda - x3) * x1 - x2
x3(x1*x2 - b*x3, 1) {} // dx3/dt = x1 * x2 - b * x3
};
Lorenz L(10, 24, 2); // model
// output:
void Sample() {
Print("%6.2f %g %g\n", T.Value(), L.x1.Value(), L.x2.Value());
}
Sampler S(Sample, StepPrn);
int main(int argc, char *argv[]) { // experiment
if(argc!=2) {
_Print("\nUsage: %s maxtime \n\n", argv[0]);
return 1;
}
SetOutput("lorenz.dat");
_Print("# LORENZ - Lorenz equation \n");
Init(0,atoi(argv[1]));
SetAccuracy(1e-3); // required accuracy
Run(); // simulation
}
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![[result1]](lorenz1.png)
![[result2]](lorenz2.png)
Last modification:
21. March 2002
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