Code generation for event functions and ODE solvers

Does MATLAB support code generation for event functions used with ODE solvers like ode45?

From experimenting with MATLAB Coder and from looking at the Extended Capabilities section of the documentation on odeset, I'm inclined to think event functions are currently unsupported, but I'm not positive, because this is my first experience using MATLAB Coder.

When checking my entry-point program (a simulation of a hybrid mechanical system, written as a finite-state machine) for issues with MATLAB Coder, an error arises from the following line of code:

options = odeset('Events', @(t,x) terminal_events(t,x,params));

where params is a struct passed to the entry-point function. The error reported by MATLAB Coder for this line is "All inputs must be constant."

Thank you for any clarification you can provide.

Answer 1

[David Fink]

All odeset inputs must be constant, but the anonymous function (which stores the value of params when the anonymous function is constructed) is not.

You can work around this limitation by storing params somewhere other than the anonymous function. For example, a global or persistent variable.

Here's an example of how you could use a global:

function out = xEntryPoint(params)
    global g
    g = params;
    f = @myFun;
    coder.const(f); % verifies that f is constant
    out = f();
end

function out = myFun
    global g
    out = g;
end

Generate code and verify it works via:

global g;
g = struct('f', 0);
codegen xEntryPoint -args g
s.f = 4;
xEntryPoint_mex(s)

Answer 2

[Guru Kumaresan]

Hello,

It is possible to generate code for event functions but it is necessary that all inputs to the “odeset” inputs must be constant.