Error status 3: ACADOS_MINSTEP. Any configuration to alleviate it?

FreyJo · October 1, 2021, 8:28am

Hi Angel,

In RTI, a single QP is solved within every solver call.
However, the QP solver itself (here HPIPM) is also an iterative method.
Error status 3 in HPIPM corresponds to “NaN in solution detected”.

github.com

giaf/hpipm/blob/8fbddb7e9bee0befbe1915e0651bf23cf99c841b/include/hpipm_common.h#L62


      
          	SPEED, // focus on speed, relative IPM formulation
          	BALANCE, // balanced mode, relative IPM formulation
          	ROBUST, // focus on robustness, relative IPM formulation
          	};
          
          enum hpipm_status
          	{
          	SUCCESS, // found solution satisfying accuracy tolerance
          	MAX_ITER, // maximum iteration number reached
          	MIN_STEP, // minimum step length reached
          	NAN_SOL, // NaN in solution detected
          	INCONS_EQ, // unconsistent equality constraints
          	};
          
          
          
          #ifdef __cplusplus
          } /* extern "C" */
          #endif

I am not really sure why this happens and don’t know your problem formulation.
Maybe regularizing the Hessian can help.
https://docs.acados.org/python_api/#acados_template.acados_ocp.AcadosOcpOptions.levenberg_marquardt

Best,
Jonathan