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/*
dsp/Lorenz.h
Copyright 2001-4 Tim Goetze <tim@quitte.de>
http://quitte.de/dsp/
Lorenz fractal.
*/
/*
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
02111-1307, USA or point your web browser to http://www.gnu.org.
*/
#ifndef _DSP_LORENZ_H_
#define _DSP_LORENZ_H_
namespace DSP {
class Lorenz
{
public:
double x[2], y[2], z[2];
double h, a, b, c;
int I;
public:
Lorenz()
{
h = 0.001;
a = 10.0;
b = 28.0;
c = 8.0 / 3.0;
}
/* rate is normalized (0 .. 1) */
void set_rate (double r)
{
h = max (.0000001, r * .015);
}
void init (double _h = .001, double seed = .0)
{
I = 0;
x[0] = .1 + seed - frandom() * .1;
y[0] = 0;
z[0] = 0;
/* progress quickly to get a 'stable' system */
h = .001;
int n = 10000 + min ((int) (10000 * seed), 10000);
for (int i = 0; i < n; ++i)
step();
h = _h;
}
d_sample get()
{
step();
return .5 * get_y() + get_z();
}
void step()
{
int J = I ^ 1;
x[J] = x[I] + h * a * (y[I] - x[I]);
y[J] = y[I] + h * (x[I] * (b - z[I]) - y[I]);
z[J] = z[I] + h * (x[I] * y[I] - c * z[I]);
I = J;
}
double get_x()
{
return .024 * (x[I] - .172);
}
double get_y()
{
return .018 * (y[I] - .172);
}
double get_z()
{
return .019 * (z[I] - 25.43);
}
};
} /* namespace DSP */
#endif /* _DSP_LORENZ_H_ */
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