Unable to implement ipopt solver for nlp

[Raushan Prabhakar]

I am new to casadi.I am writing the code for the mpc for mobile robots as taking the reference of this(https://www.youtube.com/results?search_query=mpc+casadi). In this video, he implemented on the Matlab but I am writing code in python, but got stuck here. 

Pleae Help

Original exception was:

Traceback (most recent call last):

  File "working.py", line 107, in <module>

    solver=nlpsol('solver','ipopt',nlp_prob,options)

  File "/usr/local/lib/python3.6/dist-packages/casadi/casadi.py", line 16673, in nlpsol

    return _casadi.nlpsol(*args)

RuntimeError: .../casadi/core/function_internal.cpp:144: Error calling IpoptInterface::init for 'solver':

Error in Function::factory for 'nlp' [SXFunction] at .../casadi/core/function.cpp:1634:

Failed to create nlp_grad_f:[x, p]->[f, grad:f:x] with {}:

.../casadi/core/factory.hpp:367: Gradient generation failed:

Error in SX::gradient at .../casadi/core/generic_matrix.hpp:1203:

.../casadi/core/generic_matrix.hpp:1200: Assertion "ex.is_scalar()" failed:

'gradient' only defined for scalar outputs: Use 'jacobian' instead.

Thanks

[Joris Gillis]

Check the shape of your objective.
Apparently it is not scalar, while it should..

Joris

[Raushan Prabhakar]

Thanks a lot, Joris

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[Raushan Prabhakar]

I am trying to solve the nlp,but got this error. Please help me out.

 RuntimeError: .../casadi/core/function_internal.cpp:1821: 'eval_sx' not defined for IpoptInterface

[Joris Gillis]

You are attempting to call an Ipopt solver instance with SX variables, either explictly or implicitly through an 'expand' action (with 'expand' method or with 'expand' option). Don't do that and the error will disappear..

Joris

[Dishan Desai]

I am getting the same error working on a very similar code. I do not recall using any expand method for my code. I am also relatively new to casadi. The error I am getting is:

  Message=.../casadi/core/function_internal.cpp:1832: 'eval_sx' not defined for IpoptInterface

  Source=C:\My drive\thesis_Code\single_shoot_new\single_shoot_new\single_shoot_new.py

  StackTrace:

  File "C:\........\single_shoot_new.py", line 88, in <module>

    sol = solver(x0= au0,lbx = LowerBX, ubx = UpperBX, lbg = LowerG, ubg = UpperG, p = PositionA)

my solver function is:

nlp_prob = {'f':obj,'x':OPT_variables,'g':g,'p':P}

solver = nlpsol('solver','ipopt',nlp_prob)

[Joris Gillis]

Dear Dandes,

Check the type() of au0, LowerBX, UpperBX, LowerG, UpperG, PositionA.

One of these is probably an SX. It should be numeric/DM or MX, not SX.

Best regards,

  Joris

[Prashant lokur]

So is it possible to convert SX to MX as I have a constraint as function of state and state is defined as SX 

[Kamil Etxagibel Begic]

Dear Prashan,

I have the same problem as you, but I have not been able to find a solution anywhere, so if you have managed to solve it please let me know how.

Best regards,

Kamil

El dia dijous, 10 de març de 2022 a les 16:26:49 UTC+1, prashan...@gmail.com va escriure: