Reaches max iteration although within tolerance

User Questions
1

Hi,

I’m using python interface and I’m running into an error of Exception: acados acados_ocp_solver returned status 2, which I read to have something to do with reaching maximum number of iteration. Here’s the stats printed out:

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where my tolerances are set to be:

ocp.solver_options.levenberg_marquardt = 1e-2
    ocp.solver_options.regularize_method = 'PROJECT'
    ocp.solver_options.nlp_solver_type = 'SQP'
    ocp.solver_options.nlp_solver_max_iter = 50
    ocp.solver_options.qp_solver = 'PARTIAL_CONDENSING_HPIPM'
    ocp.solver_options.qp_solver_iter_max = 50
    ocp.solver_options.hessian_approximation = 'GAUSS_NEWTON'
    ocp.solver_options.integrator_type = 'ERK'  
    ocp.solver_options.sim_method_num_stages = 4
    ocp.solver_options.sim_method_newton_iter = 3
    ocp.solver_options.qp_solver_tol_stat = 1e-3
    ocp.solver_options.qp_solver_tol_eq = 1e-3
    ocp.solver_options.qp_solver_tol_ineq = 1e-6
    ocp.solver_options.qp_solver_tol_comp = 1e-3
    
    ocp.solver_options.print_level = 2  
    ocp.solver_options.warm_start = 1

    ocp.solver_options.nlp_solver_step_length = 0.9 # Smaller steps
    ocp.solver_options.globalization = 'MERIT_BACKTRACKING'
    ocp.solver_options.alpha_min = 0.2
    ocp.solver_options.alpha_reduction = 0.7

It seems like I’m not violating the tolerance, it there any reason I’m not able to exit the iterations?

2

Hi,

It seems that you only set the QP solver tolerances.
The acados SQP method checks the NLP solver tolerances, see e.g. Python Interface — acados documentation
The QP solver tolerances are used in the QP solver only.

Best,
Jonathan