"Error: Argument 1(i1) is not symbolic." when calling qpsol

[Stuart]

I've had this error in different situations, and so far I've always been able to solve it. This time though, I'm stumped. Can't tell why the argument is not symbolic. The error appears when calling qpsol.

Code snippet here: 
https://gist.github.com/StuartShanks/a16a7a163e12a586883d38a5600791c0

I thought the error might be with the function F which is called in the above code, however I have tested the function with dummy values and it evaluates fine. As far as I understand it, 'x', 'g', 'f', 'p' should be symbolic, but the bounds 'ubg', 'lbg', etc don't have to be symbolic (bound of 0 for example). Tried to follow those rules when constructing the qp.

As an aside, how should I interpret "Argument 1(i1)" in this situation? How do I know which argument specifically it's referring to? (and also, where that argument is in the code) .

Thank you!

[Bruno M L]

Hi!

I could not run your code from the source you provided.

But I did some digging, and "Argument 1(i1)" is related to 'p', so there is some error in your parameters.

[Stuart]

Hi!

Thank you, you're right, there was a problem with the parameters which I've now fixed :)

What digging did you do to find out that "Argument 1(i1)" is related to 'p'? Would be super useful for the future to know which arguments correspond to which inputs!

[Bruno M L]

Hi!

When you create a Function without names for inputs and outputs, such as:

Function('name', [x, u], [out1, out2])

Then, if you print the Function, you get something like this:

Function(name:(i0,i1)->(o0,o1) MXFunction)

These are the default names for the inputs and outputs. 

After that, I created qpsol solver and printed the solver, since this kind of object is also a Function in Casadi. The result is something like:

Function(solver:(x0[80],p[],lbx[80],ubx[80],lbg[40],ubg[40],lam_x0[80],lam_g0[40])->(x[80],f,g[40],lam_x[80],lam_g[40],lam_p[]) MXFunction)

I noticed that 'p' is the second argument (i1). After that, I put a float as a parameter and it resulted in the same error as yours. =)

Good luck with your work!

PS: I'm not a developer

[Stuart]

Ahh, thanks so much for your help! Good to know, will make debugging much easier in the future :D