[SCIP] Does SCIP use Ipopt as NLP local solver?

[Angel Manuel Gonzalez Rueda]

Hello,

I want to solve a Non-Linear Programming Problem with SCIP and I would like
to know what is the default Non-Linear Local solver that SCIP calls at each
step in order to obtain upper bounds during the branch and bound procedure.

We have installed the SCIP Optimization Suite version 7.0.2 using the
source code for LINUX. It seems that by default the Ipopt solver is
installed (I am not sure about this), so I suppose that this is the one
that SCIP used by default.

However, I have reviewed the list of all scip parameters, and I have found
the following parameter:

# solver to use for solving NLPs; leave empty to select NLPI with
highest priority
# [type: string, advanced: FALSE, default: ""]
nlp/solver = ""


Thus, I do not have clear if it is mandatory to specify in this parameter
"Ipopt". Furthermore, in case Ipopt is not installed (even any NLPs
solver), how does SCIP to obtain upper bounds?

Thank you in advance,
Ángel M. González Rueda
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