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Subject: [boost] Interest in a library for building simulations of dynamical systems?
From: Jay Graham (jaycgraham_at_[hidden])
Date: 20090129 20:05:31
Is there interest in a library for building simulations of dynamical
systems represented by timebased differential equations?
The proposed library would implement ideas found in the C++ Model Developer
(CMD) library developed by Ray Sells, but in a more generic way. For
example,
the proposed library would support the use of user defined data types when
defining states and their derivatives. Other CMD features to be
included in the proposed library are:
1. The ability to mix both continuous and discrete events.
2. Support for a simulation structure that makes it easy to go from a
mathematical description of a system to code.
3. Support for timevarying system topologies (e.g., multistage missiles).
4. User extendable set of numerical integration algorithms.
For more information on CMD see:
http://www.dtic.mil/srch/doc?collection=t2&id=ADA433836
and
http://rocket.itsc.uah.edu/u/education/files/R/IPT_Producer/AIAA/Sells/Sells.ppt
Code snippet:
// Define states and their derivatives
struct x_pos : state<
double, // state type
double // derivative type
> {};
struct y_pos : state< double, double > {};
// Define a simulation object
struct Ball: obj<
rk4, // fourthorder RungeKutta numerical integration algorithm
mpl::vector< x_pos, y_pos > // State vector
>
{
Ball(double x, double y, double vx, double vy)
{
// Initial state
s_<x_pos>().value = x;
s_<y_pos>().value = y;
this>vx = vx;
this>vy = vy;
// Integrators
add_integrator<x_pos>(this>vx);
add_integrator<y_pos>(this>vy);
}
template< typename S, typename C >
inline void update(S &sim, C &clock)
{
// Update the derivatives
vx = 0.8*vx;
vy = 0.8*vy;
// Use a discrete event to stop the simulation
// after 10 seconds
if (clock.event(10.0))
{
sim.halt();
}
}
template< typename C >
void report(C &clock)
{
// Report current state at 1 second intervals
if (clock.sample(1.0))
{
std::cout << "Ball"
<< clock.t << " "
<< s_<x_pos>().value << " "
<< s_<y_pos>().value << "\n";
}
}
double vx;
double vy;
};
// Define the integration timestep
struct dts
{
typedef double time_type;
static time_type value() { return 0.01; }
};
// Define a simulation stage
struct stage_1 : stage< dts, mpl::vector<Ball> > {};
main()
{
// Create a simulation object
Ball ball(0.0, 0.0, 10.0, 5.0);
// Create the simulation execution object
sim< mpl::vector< stage_1 > > sim();
// Initialize the simulation stage
sim.stage_<stage_1>().obj_<Ball>() = &ball;
// Run the simulation
run(sim);
}
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