[Ipopt] Problem has too few degrees of freedom

[Novalio Daratha]

Hi guys,

I am trying to solve a NLP problem.

min f(x)
s.t.

g(x,p_i)=0  \forall i=1...N_s
h(x)>=0

where x represents control variables and p_i represents the i-th set of
parameters.
for N_s<=4, Ipopt can solve the problem. Otherwise, IPOPT gave the
following message:


******************************************************************************
This program contains Ipopt, a library for large-scale nonlinear
optimization.
 Ipopt is released as open source code under the Common Public License
(CPL).
         For more information visit http://projects.coin-or.org/Ipopt
******************************************************************************

NOTE: You are using Ipopt by default with the MUMPS linear solver.
      Other linear solvers might be more efficient (see Ipopt
documentation).


This is Ipopt version 3.8.0, running with linear solver mumps.

Number of nonzeros in equality constraint Jacobian...:  1743324
Number of nonzeros in inequality constraint Jacobian.:   225000
Number of nonzeros in Lagrangian Hessian.............:   540888

Exception of type: TOO_FEW_DOF in file
"f:\stefan\nbBuildDir\Ipopt\releases-3.8.0\Ipopt\src\Interfaces\IpIpoptApplication.cpp"
at line 788:
 Exception message: status != TOO_FEW_DEGREES_OF_FREEDOM evaluated false:
Too few degrees of freedom (rethrown)!

EXIT: Problem has too few degrees of freedom.


Is there anyway to avoid this problem?

Thank you very much for your kind attention.

I look forward for your favorable reply.


SIncerely Yours,

Novalio Daratha
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