symengine | SymEngine is a fast symbolic manipulation library | Math library

Following the TimeSynth library's example, the import statement of OP

I was running on bash of MINGW64 where the errors were coming. Running on sh (installed from MSYS) was successful.

No, it's not the the dimension problem. Although we can not reproduce the error due to incomplete code, the error message is clear:

Supplied objective function must return a scalar value.

Tyr call F with a static vector and check the size of its results. It should return a single value.

But there are also warnings about upper/lower bounds:

The fun takes only one argument, which is a vector with nvars elements. From particleswarm doc:

x = particleswarm(fun,nvars) attempts to find a vector x that achieves a local minimum of fun. nvars is the dimension (number of design variables) of fun.

So you need to declare a new objective function that only takes 1 argument:

As the comments unveiled, your problem eventually boiled down to this:

step_on_discontinuities assumes delays that are small with respect to the integration time and performs steps that are placed on those times where the delayed components points to the integration start (0 in your case). This way initial discontinuities are handled.

However, implementing an input with a delayed dummy variable introduces a large delay into the system, totT in your case. The respective step for step_on_discontinuities would be at totT itself, i.e., after the desired integration time. Thus when you reach for time in np.arange(DDE.t, DDE.t+totT, 1): in your code, DDE.t is totT. Therefore you have made a big step before you actually start integrating and observing which may seem like a discontinuity and lead to weird results, in particular you do not see the effect of your input, because it has already “ended” at this point. To avoid this, use adjust_diff or integrate_blindly instead of step_on_discontinuities.